Cisco Nexus 9000 NX-OS Routing Configuration Configuration Guide

Cisco Nexus 9000 Series NX-OS Unicast
Routing Configuration Guide, Release 6.x
November 2014
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Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
©2013-2014 Cisco Systems, Inc. All rights reserved.
CONTENTS
iii
New and Changed Information
Preface
xxiii
19
Audience
19
Document Conventions
19
Related Documentation
20
Documentation Feedback
21
Obtaining Documentation and Submitting a Service Request
CHAPTER
1
Overview
21
1-1
About Layer 3 Unicast Routing 1-1
Routing Fundamentals 1-2
Packet Switching 1-2
Routing Metrics 1-3
Path Length 1-4
Reliability 1-4
Routing Delay 1-4
Bandwidth 1-4
Load 1-4
Communication Cost 1-4
Router IDs 1-5
Autonomous Systems 1-5
Convergence 1-6
Load Balancing and Equal Cost Multipath
Route Redistribution 1-6
Administrative Distance 1-7
Stub Routing 1-7
1-6
Routing Algorithms 1-8
Static Routes and Dynamic Routing Protocols
Interior and Exterior Gateway Protocols 1-8
Distance Vector Protocols 1-9
Link-State Protocols 1-9
Layer 3 Virtualization
1-8
1-10
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Cisco NX-OS Fowarding Architecture 1-10
Unicast RIB 1-10
Adjacency Manager 1-11
Unicast Forwarding Distribution Module
FIB 1-12
Hardware Forwarding 1-12
Software Forwarding 1-12
1-11
Summary of Layer 3 Unicast Routing Features 1-12
IPv4 and IPv6 1-13
IP Services 1-13
OSPF 1-13
EIGRP 1-13
IS-IS 1-14
BGP 1-14
RIP 1-14
Static Routing 1-14
Layer 3 Virtualization 1-14
Route Policy Manager 1-14
Policy-Based Routing 1-15
First Hop Redundancy Protocols 1-15
Object Tracking 1-15
Related Topics
CHAPTER
2
Configuring IPv4
1-15
2-1
About IPv4 2-1
Multiple IPv4 Addresses 2-2
LPM Routing Modes 2-2
Address Resolution Protocol 2-3
ARP Caching 2-4
Static and Dynamic Entries in the ARP Cache
Devices That Do Not Use ARP 2-4
Reverse ARP 2-4
Proxy ARP 2-5
Local Proxy ARP 2-6
Gratuitous ARP 2-6
Glean Throttling 2-6
Path MTU Discovery 2-6
ICMP 2-6
Virtualization Support 2-7
2-4
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Licensing Requirements for IPv4
Prerequisites for IPv4
2-7
Guidelines and Limitations for IPv4
Default Settings
2-7
2-7
2-7
Configuring IPv4 2-7
Configuring IPv4 Addressing 2-8
Configuring Multiple IP Addresses 2-9
Configuring Max-Host Routing Mode (Cisco Nexus 9500 Series Switches Only) 2-10
Configuring Nonhierarchical Routing Mode (Cisco Nexus 9500 Series Switches Only) 2-11
Configuring 64-Bit ALPM Routing Mode (Cisco Nexus 9500 Series Switches Only) 2-12
Configuring a Static ARP Entry 2-13
Configuring Proxy ARP 2-14
Configuring Local Proxy ARP 2-15
Configuring Gratuitous ARP 2-16
Configuring Path MTU Discovery 2-17
Configuring IP Directed Broadcasts 2-17
Configuring IP Glean Throttling 2-18
Configuring the Hardware IP Glean Throttle Maximum 2-18
Configuring a Hardware IP Glean Throttle Timeout 2-19
Configuring the Interface IP Address for the ICMP Source IP Field 2-20
Verifying the IPv4 Configuration
CHAPTER
3
Configuring IPv6
2-20
3-1
About IPv6 3-1
IPv6 Address Formats 3-2
IPv6 Unicast Addresses 3-3
Aggregatable Global Addresses 3-3
Link-Local Addresses 3-4
IPv4-Compatible IPv6 Addresses 3-5
Unique Local Addresses 3-5
Site-Local Address 3-6
IPv6 Anycast Addresses 3-6
IPv6 Multicast Addresses 3-7
IPv4 Packet Header 3-8
Simplified IPv6 Packet Header 3-8
DNS for IPv6 3-11
Path MTU Discovery for IPv6 3-11
CDP IPv6 Address Support 3-12
LPM Routing Modes 3-12
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Virtualization Support
3-13
Licensing Requirements for IPv6
Prerequisites for IPv6
3-13
3-13
Guidelines and Limitations for IPv6
3-13
Configuring IPv6 3-13
Configuring IPv6 Addressing 3-14
Configuring Max-Host Routing Mode (Cisco Nexus 9500 Series Switches Only) 3-16
Configuring Nonhierarchical Routing Mode (Cisco Nexus 9500 Series Switches Only) 3-17
Configuring 64-Bit ALPM Routing Mode (Cisco Nexus 9500 Series Switches Only) 3-18
CHAPTER
4
Verifying the IPv6 Configuration
3-19
Configuration Examples for IPv6
3-19
Configuring DNS
4-1
About DNS Clients 4-1
DNS Client Overview 4-1
Name Servers 4-2
DNS Operation 4-2
High Availability 4-2
Virtualization Support 4-2
Licensing Requirements for DNS Clients
Prerequisites for DNS Clients
4-3
Guidelines and Limitations for DNS
Default Settings
4-3
4-3
4-3
Configuring DNS Clients 4-3
Configuring the DNS Client 4-4
Configuring Virtualization 4-5
Verifying the DNS Client Configuration
4-7
Configuration Examples for the DNS Client
CHAPTER
5
Configuring OSPFv2
4-7
5-1
About OSPFv2 5-1
Hello Packet 5-2
Neighbors 5-3
Adjacency 5-3
Designated Routers 5-3
Areas 5-4
Link-State Advertisements
LSA Types 5-5
5-5
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Link Cost 5-6
Flooding and LSA Group Pacing 5-6
Link-State Database 5-7
Opaque LSAs 5-7
OSPFv2 and the Unicast RIB 5-7
Authentication 5-7
Simple Password Authentication 5-8
MD5 Authentication 5-8
Advanced Features 5-8
Stub Area 5-8
Not-So-Stubby Area 5-9
Virtual Links 5-9
Route Redistribution 5-10
Route Summarization 5-10
High Availability and Graceful Restart 5-11
OSPFv2 Stub Router Advertisements 5-12
Multiple OSPFv2 Instances 5-12
SPF Optimization 5-12
BFD 5-12
Virtualization Support 5-12
Licensing Requirements for OSPFv2
Prerequisites for OSPFv2
5-13
Guidelines and Limitations for OSPFv2
Default Settings
5-13
5-13
5-14
Configuring Basic OSPFv2 5-14
Enabling OSPFv2 5-15
Creating an OSPFv2 Instance 5-16
Configuring Optional Parameters on an OSPFv2 Instance
Configuring Networks in OSPFv2 5-18
Configuring Authentication for an Area 5-20
Configuring Authentication for an Interface 5-21
5-17
Configuring Advanced OSPFv2 5-23
Configuring Filter Lists for Border Routers 5-24
Configuring Stub Areas 5-25
Configuring a Totally Stubby Area 5-27
Configuring NSSA 5-27
Configuring Virtual Links 5-29
Configuring Redistribution 5-31
Limiting the Number of Redistributed Routes 5-33
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Configuring Route Summarization 5-35
Configuring Stub Route Advertisements 5-36
Configuring the Administrative Distance of Routes
Modifying the Default Timers 5-40
Configuring Graceful Restart 5-42
Restarting an OSPFv2 Instance 5-44
Configuring OSPFv2 with Virtualization 5-44
Verifying the OSPFv2 Configuration
Monitoring OSPFv2
5-46
5-47
Configuration Examples for OSPFv2 5-47
OSPF RFC Compatibility Mode Example
5-47
Additional References 5-48
Related Documents 5-48
MIBs 5-48
CHAPTER
6
Configuring OSPFv3
6-1
About OSPFv3 6-1
Comparison of OSPFv3 and OSPFv2 6-2
Hello Packet 6-2
Neighbors 6-3
Adjacency 6-3
Designated Routers 6-4
Areas 6-5
Link-State Advertisement 6-5
LSA Types 6-6
Link Cost 6-6
Flooding and LSA Group Pacing 6-7
Link-State Database 6-7
Multi-Area Adjacency 6-7
OSPFv3 and the IPv6 Unicast RIB 6-8
Address Family Support 6-8
Advanced Features 6-8
Stub Area 6-9
Not-So-Stubby Area 6-10
Virtual Links 6-10
Route Redistribution 6-11
Route Summarization 6-11
High Availability and Graceful Restart
Multiple OSPFv3 Instances 6-12
6-12
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Contents
SPF Optimization 6-13
Virtualization Support 6-13
Licensing Requirements for OSPFv3
Prerequisites for OSPFv3
6-13
Guidelines and Limitations for OSPFv3
Default Settings
6-13
6-14
6-14
Configuring Basic OSPFv3 6-15
Enabling OSPFv3 6-15
Creating an OSPFv3 Instance 6-16
Configuring Networks in OSPFv3 6-19
Configuring Advanced OSPFv3 6-21
Configuring Filter Lists for Border Routers 6-22
Configuring Stub Areas 6-23
Configuring a Totally Stubby Area 6-24
Configuring NSSA 6-25
Configuring Multi-Area Adjacency 6-27
Configuring Virtual Links 6-28
Configuring Redistribution 6-30
Limiting the Number of Redistributed Routes 6-32
Configuring Route Summarization 6-34
Configuring the Administrative Distance of Routes 6-35
Modifying the Default Timers 6-38
Configuring Graceful Restart 6-40
Restarting an OSPFv3 Instance 6-42
Configuring OSPFv3 with Virtualization 6-42
Verifying the OSPFv3 Configuration
Monitoring OSPFv3
6-45
Configuration Examples for OSPFv3
Related Topics
7
Configuring EIGRP
6-45
6-45
Additional References
MIBs 6-46
CHAPTER
6-44
6-45
7-1
About EIGRP 7-1
EIGRP Components 7-2
Reliable Transport Protocol 7-2
Neighbor Discovery and Recovery
Diffusing Update Algorithm 7-2
7-2
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EIGRP Route Updates 7-3
Internal Route Metrics 7-3
Wide Metrics 7-4
External Route Metrics 7-4
EIGRP and the Unicast RIB 7-5
Advanced EIGRP 7-5
Address Families 7-5
Authentication 7-6
Stub Routers 7-6
Route Summarization 7-6
Route Redistribution 7-7
Load Balancing 7-7
Split Horizon 7-7
BFD 7-8
Virtualization Support 7-8
Graceful Restart and High Availability
Multiple EIGRP Instances 7-9
Licensing Requirements for EIGRP
Prerequisites for EIGRP
7-9
7-9
Guidelines and Limitations for EIGRP
Default Settings
7-8
7-9
7-10
Configuring Basic EIGRP 7-10
Enabling the EIGRP Feature 7-11
Creating an EIGRP Instance 7-12
Restarting an EIGRP Instance 7-14
Shutting Down an EIGRP Instance 7-14
Configuring a Passive Interface for EIGRP 7-15
Shutting Down EIGRP on an Interface 7-15
Configuring Advanced EIGRP 7-15
Configuring Authentication in EIGRP 7-16
Configuring EIGRP Stub Routing 7-18
Configuring a Summary Address for EIGRP 7-18
Redistributing Routes into EIGRP 7-19
Limiting the Number of Redistributed Routes 7-21
Configuring Load Balancing in EIGRP 7-23
Configuring Graceful Restart for EIGRP 7-24
Adjusting the Interval Between Hello Packets and the Hold Time
Disabling Split Horizon 7-26
Enabling Wide Metrics 7-27
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Contents
Tuning EIGRP
7-27
Configuring Virtualization for EIGRP
Verifying the EIGRP Configuration
Monitoring EIGRP
7-31
7-31
Configuration Examples for EIGRP
Related Topics
7-29
7-31
7-32
Additional References 7-32
Related Documents 7-33
MIBs 7-33
CHAPTER
8
Configuring IS-IS
8-1
About IS-IS 8-1
IS-IS Overview 8-2
IS-IS Areas 8-2
NET and System ID 8-3
Designated Intermediate System 8-3
IS-IS Authentication 8-3
Mesh Groups 8-4
Overload Bit 8-4
Route Summarization 8-4
Route Redistribution 8-5
Load Balancing 8-5
BFD 8-5
Virtualization Support 8-5
High Availability and Graceful Restart 8-5
Multiple IS-IS Instances 8-6
Licensing Requirements for IS-IS
Prerequisites for IS-IS
8-6
Guidelines and Limitations for IS-IS
Default Settings
8-6
8-6
8-7
Configuring IS-IS 8-7
IS-IS Configuration Modes 8-8
Router Configuration Mode 8-8
Router Address Family Configuration Mode
Enabling the IS-IS Feature 8-9
Creating an IS-IS Instance 8-9
Restarting an IS-IS Instance 8-12
Shutting Down IS-IS 8-12
8-8
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Configuring IS-IS on an Interface 8-12
Shutting Down IS-IS on an Interface 8-14
Configuring IS-IS Authentication in an Area 8-14
Configuring IS-IS Authentication on an Interface 8-15
Configuring a Mesh Group 8-17
Configuring a Designated Intermediate System 8-17
Configuring Dynamic Host Exchange 8-17
Setting the Overload Bit 8-17
Configuring the Attached Bit 8-18
Configuring the Transient Mode for Hello Padding 8-18
Configuring a Summary Address 8-18
Configuring Redistribution 8-20
Limiting the Number of Redistributed Routes 8-21
Disabling Strict Adjacency Mode 8-23
Configuring a Graceful Restart 8-24
Configuring Virtualization 8-26
Tuning IS-IS 8-28
Verifying the IS-IS Configuration
Monitoring IS-IS
8-31
Configuration Examples for IS-IS
Related Topics
CHAPTER
9
8-30
8-32
8-32
Configuring Basic BGP
9-1
About Basic BGP 9-1
BGP Autonomous Systems 9-2
4-Byte AS Number Support 9-2
Administrative Distance 9-2
BGP Peers 9-3
BGP Sessions 9-3
Dynamic AS Numbers for Prefix Peers 9-3
BGP Router Identifier 9-3
BGP Path Selection 9-4
Step 1—Comparing Pairs of Paths 9-4
Step 2—Determining the Order of Comparisons 9-6
Step 3—Determining the Best-Path Change Suppression
BGP and the Unicast RIB 9-7
BGP Prefix Independent Convergence Core 9-7
BGP Virtualization 9-7
Licensing Requirements for Basic BGP
9-7
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Contents
Prerequisites for BGP
9-7
Guidelines and Limitations for BGP
Default Settings
9-8
9-8
CLI Configuration Modes 9-9
Global Configuration Mode 9-9
Address Family Configuration Mode 9-9
Neighbor Configuration Mode 9-10
Neighbor Address Family Configuration Mode
9-10
Configuring Basic BGP 9-10
Enabling BGP 9-11
Creating a BGP Instance 9-12
Restarting a BGP Instance 9-14
Shutting Down BGP 9-14
Configuring BGP Peers 9-14
Configuring Dynamic AS Numbers for Prefix Peers
Clearing BGP Information 9-18
Verifying the Basic BGP Configuration
Monitoring BGP Statistics
9-24
Additional References
MIBs 9-24
10
9-23
9-23
Where to Go Next
CHAPTER
9-21
9-23
Configuration Examples for Basic BGP
Related Topics
9-16
9-24
Configuring Advanced BGP
10-1
About Advanced BGP 10-1
Peer Templates 10-2
Authentication 10-2
Route Policies and Resetting BGP Sessions
eBGP 10-3
iBGP 10-3
AS Confederations 10-4
Route Reflector 10-5
Capabilities Negotiation 10-6
Route Dampening 10-6
Load Sharing and Multipath 10-6
BGP Additional Paths 10-7
Route Aggregation 10-8
10-3
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BGP Conditional Advertisement 10-8
BGP Next-Hop Address Tracking 10-8
Route Redistribution 10-9
BFD 10-9
Tuning BGP 10-10
BGP Timers 10-10
Tuning the Best-Path Algorithm 10-10
Multiprotocol BGP 10-10
Graceful Restart and High Availability 10-11
Low Memory Handling 10-11
Virtualization Support 10-12
Licensing Requirements for Advanced BGP
Prerequisites for Advanced BGP
10-12
10-12
Guidelines and Limitations for Advanced BGP
Default Settings for Advanced BGP
10-12
10-13
Configuring Advanced BGP 10-13
Configuring BGP Session Templates 10-14
Configuring BGP Peer-Policy Templates 10-17
Configuring BGP Peer Templates 10-19
Configuring Prefix Peering 10-21
Configuring BGP Authentication 10-22
Resetting a BGP Session 10-23
Modifying the Next-Hop Address 10-23
Configuring BGP Next-Hop Address Tracking 10-24
Configuring Next-Hop Filtering 10-24
Shrinking Next-Hop Groups When A Session Goes Down 10-25
Disabling Capabilities Negotiation 10-25
Disabling Policy Batching 10-25
Configuring BGP Additional Paths 10-26
Advertising the Capability of Sending and Receiving Additional Paths
Configuring the Sending and Receiving of Additional Paths 10-27
Configuring Advertised Paths 10-27
Configuring Additional Path Selection 10-28
Configuring eBGP 10-28
Disabling eBGP Single-Hop Checking 10-29
Configuring eBGP Multihop 10-29
Disabling a Fast External Fallover 10-29
Limiting the AS-path Attribute 10-30
Configuring Local AS Support 10-30
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Contents
Configuring AS Confederations 10-30
Configuring Route Reflector 10-31
Configuring Next Hops on Reflected Routes Using an Outbound Route Map
Configuring Route Dampening 10-35
Configuring Load Sharing and ECMP 10-36
Configuring Maximum Prefixes 10-36
Configuring Dynamic Capability 10-37
Configuring Aggregate Addresses 10-37
Suppressing BGP Routes 10-37
Configuring BGP Conditional Advertisement 10-38
Configuring Route Redistribution 10-40
Advertising the Default Route 10-41
Configuring Multiprotocol BGP 10-43
Tuning BGP 10-44
Configuring a Graceful Restart 10-48
Configuring Virtualization 10-50
Verifying the Advanced BGP Configuration
Monitoring BGP Statistics
Configuration Examples
Related Topics
11
Configuring RIP
10-52
10-53
10-54
10-54
Additional References
MIBs 10-54
CHAPTER
10-33
10-54
11-1
About RIP 11-1
RIP Overview 11-2
RIPv2 Authentication 11-2
Split Horizon 11-2
Route Filtering 11-3
Route Summarization 11-3
Route Redistribution 11-3
Load Balancing 11-3
High Availability 11-4
Virtualization Support 11-4
Licensing Requirements for RIP
Prerequisites for RIP
11-4
Guidelines and Limitations
Default Settings
11-4
11-4
11-4
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Configuring RIP 11-5
Enabling RIP 11-5
Creating a RIP Instance 11-6
Restarting a RIP Instance 11-8
Configuring RIP on an Interface 11-8
Configuring RIP Authentication 11-9
Configuring a Passive Interface 11-11
Configuring Split Horizon with Poison Reverse 11-11
Configuring Route Summarization 11-11
Configuring Route Redistribution 11-11
Configuring Cisco NX-OS RIP for Compatibility with Cisco IOS RIP
Configuring Virtualization 11-14
Tuning RIP 11-17
Verifying the RIP Configuration
Displaying RIP Statistics
11-18
Configuration Examples for RIP
Related Topics
CHAPTER
12
11-18
11-19
11-19
Configuring Static Routing
12-1
About Static Routing 12-1
Administrative Distance 12-2
Directly Connected Static Routes 12-2
Fully Specified Static Routes 12-2
Floating Static Routes 12-2
Remote Next Hops for Static Routes 12-3
BFD 12-3
Virtualization Support 12-3
Licensing Requirements for Static Routing
Prerequisites for Static Routing
Default Settings
12-3
12-3
12-4
Configuring Static Routing 12-4
Configuring a Static Route 12-4
Configuring a Static Route over a VLAN
Configuring Virtualization 12-7
Verifying the Static Routing Configuration
Configuration Example for Static Routing
12-5
12-8
12-9
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Contents
CHAPTER
13
Configuring Layer 3 Virtualization
13-1
About Layer 3 Virtualization 13-1
VRF and Routing 13-2
Route Leaking and Importing Routes from the Default VRF
VRF-Aware Services 13-2
Reachability 13-3
Filtering 13-4
Combining Reachability and Filtering 13-4
Licensing Requirements for VRFs
13-5
Guidelines and Limitations for VRFs
13-5
Guidelines and Limitations for VRF Route Leaking
Default Settings
13-2
13-5
13-5
Configuring VRFs 13-6
Creating a VRF 13-6
Assigning VRF Membership to an Interface 13-7
Configuring VRF Parameters for a Routing Protocol
Configuring a VRF-Aware Service 13-10
Setting the VRF Scope 13-11
Verifying the VRF Configuration
13-12
Configuration Examples for VRF
13-12
13-9
Additional References 13-15
Related Documents 13-15
Standards 13-15
CHAPTER
14
Managing the Unicast RIB and FIB
14-1
About the Unicast RIB and FIB 14-1
Layer 3 Consistency Checker 14-2
Licensing Requirements for the Unicast RIB and FIB
14-2
Managing the Unicast RIB and FIB 14-2
Displaying Module FIB Information 14-3
Configuring Load Sharing in the Unicast FIB 14-3
Displaying Routing and Adjacency Information 14-5
Triggering the Layer 3 Consistency Checker 14-7
Clearing Forwarding Information in the FIB 14-8
Configuring Maximum Routes for the Unicast RIB 14-8
Estimating Memory Requirements for Routes 14-9
Clearing Routes in the Unicast RIB 14-9
Verifying the Unicast RIB and FIB
14-10
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Additional References 14-11
Related Documents 14-11
CHAPTER
15
Configuring Route Policy Manager
15-1
About Route Policy Manager 15-1
Prefix Lists 15-1
Route Maps 15-2
Match Criteria 15-2
Set Changes 15-3
Access Lists 15-3
AS Numbers for BGP 15-3
AS-Path Lists for BGP 15-3
Community Lists for BGP 15-3
Extended Community Lists for BGP 15-4
Route Redistribution and Route Maps 15-4
Licensing Requirements for Route Policy Manager
Guidelines and Limitations
Default Settings
15-5
15-5
Configuring Route Policy Manager 15-6
Configuring IP Prefix Lists 15-6
Configuring AS-Path Lists 15-8
Configuring Community Lists 15-9
Configuring Extended Community Lists
Configuring Route Maps 15-11
16
15-10
Verifying the Route Policy Manager Configuration
15-18
Configuration Examples for Route Policy Manager
15-18
Related Topics
CHAPTER
15-5
15-18
Configuring Policy-Based Routing
16-1
About Policy-Based Routing 16-1
Policy Route Maps 16-2
Set Criteria for Policy-Based Routing 16-2
Route-Map Processing Logic 16-3
Policy-Based Routing Filtering Options 16-3
Licensing Requirements for Policy-Based Routing
Prerequisites for Policy-Based Routing
Guidelines and Limitations
Default Settings
16-4
16-4
16-4
16-5
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Configuring Policy-Based Routing 16-5
Enabling the Policy-Based Routing Feature
Configuring a Route Policy 16-6
Verifying the Policy-Based Routing Configuration
16-8
Configuration Examples for Policy-Based Routing
16-8
Related Documents
CHAPTER
17
16-5
Configuring HSRP
16-9
17-1
Information About HSRP 17-1
HSRP Overview 17-2
HSRP Versions 17-3
HSRP for IPv4 17-4
HSRP for IPv6 17-4
HSRP IPv6 Addresses 17-5
HSRP Authentication 17-5
HSRP Messages 17-5
HSRP Load Sharing 17-6
Object Tracking and HSRP 17-6
vPC and HSRP 17-7
vPC Peer Gateway and HSRP 17-7
BFD 17-7
High Availability and Extended Nonstop Forwarding
Virtualization Support 17-8
Licensing Requirements for HSRP
Prerequisites for HSRP
17-8
17-8
Guidelines and Limitations for HSRP
Default Settings
17-7
17-8
17-9
Configuring HSRP 17-9
Enabling HSRP 17-10
Configuring the HSRP Version 17-10
Configuring an HSRP Group for IPv4 17-11
Configuring an HSRP Group for IPv6 17-12
Configuring the HSRP Virtual MAC Address
Authenticating HSRP 17-15
Authenticating HSRP 17-16
Configuring HSRP Object Tracking 17-18
Configuring the HSRP Priority 17-20
Customizing HSRP 17-21
Configuring Extended Hold Timers for HSRP
17-14
17-22
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Contents
Verifying the HSRP Configuration
17-23
Configuration Examples for HSRP
17-23
Additional References 17-24
Related Documents 17-24
MIBs 17-24
CHAPTER
18
Configuring VRRP
18-1
Information About VRRP 18-1
VRRP Operation 18-2
VRRP Benefits 18-3
Multiple VRRP Groups 18-3
VRRP Router Priority and Preemption
vPC and VRRP 18-5
VRRP Advertisements 18-5
VRRP Authentication 18-5
VRRP Tracking 18-5
BFD 18-6
High Availability
18-6
Virtualization Support
18-6
Licensing Requirements for VRRP
18-6
Guidelines and Limitations for VRRP
Default Settings
18-4
18-7
18-7
Configuring VRRP 18-7
Enabling the VRRP Feature 18-8
Configuring VRRP Groups 18-8
Configuring VRRP Priority 18-9
Configuring VRRP Authentication 18-11
Configuring Time Intervals for Advertisement Packets
Disabling Preemption 18-14
Configuring VRRP Interface State Tracking 18-15
Verifying the VRRP Configuration
Monitoring VRRP Statistics
18-16
18-17
Configuration Examples for VRRP
18-17
Additional References 18-18
Related Documents 18-18
CHAPTER
19
Configuring Object Tracking
19-1
Information About Object Tracking
19-1
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18-12
Contents
Object Tracking Overview 19-1
Object Track List 19-2
High Availability 19-3
Virtualization Support 19-3
Licensing Requirements for Object Tracking
Guidelines and Limitations
Default Settings
19-3
19-3
19-3
Configuring Object Tracking 19-4
Configuring Object Tracking for an Interface 19-4
Deleting a Tracked Object 19-5
Configuring Object Tracking for Route Reachability 19-6
Configuring an Object Track List with a Boolean Expression 19-7
Configuring an Object Track List with a Percentage Threshold 19-8
Configuring an Object Track List with a Weight Threshold 19-9
Configuring an Object Tracking Delay 19-11
Configuring Object Tracking for a Nondefault VRF 19-13
Verifying the Object Tracking Configuration
19-14
Configuration Examples for Object Tracking
19-14
Related Topics
19-15
Additional References 19-15
Related Documents 19-15
APPENDIX
A
IETF RFCs Supported by Cisco NX-OS Unicast Features
BGP RFCs A-1
First-Hop Redundancy Protocol RFCs A-2
IP Services RFCs A-2
IPv6 RFCs A-2
IS-IS RFCs A-3
OSPF RFCs A-3
RIP RFCs A-3
APPENDIX
B
Configuration Limits for Cisco NX-OS Layer 3 Unicast Features
A-1
B-1
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Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
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New and Changed Information
This chapter provides release-specific information for each new and changed feature in the Cisco Nexus
9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x. The latest version of this
document is available at the following Cisco website:
http://www.cisco.com/en/US/docs/switches/datacenter/nexus9000/sw/6.x/unicast/configuration/guide/l
3_cli_nxos.html
To check for additional information about Cisco NX-OS Release 6.x, see the Cisco Nexus 9000 Series
NX-OS Release Notes available at the following Cisco website:
http://www.cisco.com/en/US/docs/switches/datacenter/nexus9000/sw/6.x/release/notes/61-nxos-rn.htm
l
Table 1 summarizes the new and changed features for the Cisco Nexus 9000 Series NX-OS Unicast
Routing Configuration Guide, Release 6.x and tells you where they are documented.
Table 1
New and Changed Features for Release 6.x
Feature
Description
Changed in
Release
64-bit ALPM routing
mode
Introduced this feature.
6.1(2)I3(2)
Chapter 2, “Configuring IPv4” and
Chapter 3, “Configuring IPv6”
BGP
Added the ability to disable policy batching.
6.1(2)I3(2)
Chapter 10, “Configuring
Advanced BGP”
Policy-based ACLs
(PBACLs)
Introduced this feature.
6.1(2)I3(2)
Chapter 16, “Configuring
Policy-Based Routing” and Cisco
Nexus 9000 Series NX-OS Security
Configuration Guide
Policy-based routing
Introduced this feature.
6.1(2)I3(1)
Chapter 16, “Configuring
Policy-Based Routing”
BGP
Added the ability to enable or disable
neighbor status change messages for a
specific neighbor in the Cisco NX-OS
6.1(2)I2.x software train.
6.1(2)I2(2b) Chapter 10, “Configuring
Advanced BGP”
Nonhierarchical routing
mode
Introduced this feature.
6.1(2)I2(2a) Chapter 2, “Configuring IPv4” and
Chapter 3, “Configuring IPv6”
BGP
Added the ability to advertise newly learned 6.1(2)I2(2a) Chapter 10, “Configuring
Advanced BGP”
BGP routes only after these routes are
confirmed by the Forwarding Information
Base (FIB) and programmed in the hardware.
Where Documented
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Table 1
New and Changed Features for Release 6.x (continued)
Changed in
Release
Feature
Description
BGP
Added the ability to configure BGP to
pre-shrink next-hop groups when a session
goes down.
6.1(2)I2(2a) Chapter 10, “Configuring
Advanced BGP”
FIB
Added the rotate and concatenation options
to the ip load-sharing address command.
6.1(2)I2(1)
Chapter 14, “Managing the Unicast
RIB and FIB”
Hardware IP glean
throttling
Introduced this feature.
6.1(2)I2(1)
Chapter 2, “Configuring IPv4”
HSRP
Introduced this feature.
6.1(2)I2(1)
Chapter 17, “Configuring HSRP”
Max-host routing mode
Introduced this feature.
6.1(2)I2(1)
Chapter 2, “Configuring IPv4” and
Chapter 3, “Configuring IPv6”
Object tracking
Introduced this feature.
6.1(2)I2(1)
Chapter 19, “Configuring Object
Tracking”
OSPFv2 and OSPFv3
Added vPC support.
6.1(2)I2(1)
Chapter 5, “Configuring OSPFv2”
and Chapter 6, “Configuring
OSPFv3”
Route policy manager
Added VLAN support.
6.1(2)I2(1)
Chapter 15, “Configuring Route
Policy Manager”
VRRP
Introduced this feature.
6.1(2)I2(1)
Chapter 18, “Configuring VRRP”
BGP
Added the ability to enable or disable
neighbor status change messages for a
specific neighbor in the Cisco NX-OS
6.1(2)I1.x software train.
6.1(2)I1(3)
Chapter 10, “Configuring
Advanced BGP”
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Where Documented
Preface
This preface describes the audience, organization, and conventions of the Cisco Nexus 9000 Series
NX-OS Unicast Routing Configuration Guide. It also provides information on how to obtain related
information.
This preface includes the following sections:
•
Audience, page 19
•
Document Conventions, page 19
•
Related Documentation, page 20
•
Documentation Feedback, page 21
•
Obtaining Documentation and Submitting a Service Request, page 21
Audience
To use this guide, you must be familiar with IP and routing technology.
Document Conventions
Command descriptions use these conventions:
Convention
Description
boldface font
Commands and keywords are in boldface.
italic font
Arguments for which you supply values are in italics.
[ ]
Elements in square brackets are optional.
[x|y|z]
Optional alternative keywords are grouped in brackets and separated by vertical
bars.
string
A nonquoted set of characters. Do not use quotation marks around the string or
the string will include the quotation marks.
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
19
Screen examples use these conventions:
screen font
Terminal sessions and information that the switch displays are in screen font.
boldface screen
font
Information that you must enter is in boldface screen font.
italic screen font
Arguments for which you supply values are in italic screen font.
< >
Nonprinting characters, such as passwords, are in angle brackets.
[ ]
Default responses to system prompts are in square brackets.
!, #
An exclamation point (!) or a pound sign (#) at the beginning of a line of code
indicates a comment line.
This document uses the following conventions:
Note
Caution
Means reader take note. Notes contain helpful suggestions or references to material not covered in the
manual.
Means reader be careful. In this situation, you might do something that could result in equipment
damage or loss of data.
Related Documentation
Cisco NX-OS includes the following documents:
Release Notes
Cisco Nexus 9000 Series NX-OS Release Notes
Cisco Nexus 9000 Series FPGA/EPLD Upgrade Release Notes
Cisco NX-OS Configuration Guides
Cisco Nexus 2000 Series NX-OS Fabric Extender Software Configuration Guide for Cisco Nexus 9000
Series Switches
Cisco Nexus 9000 Series NX-OS Fundamentals Configuration Guide
Cisco Nexus 9000 Series NX-OS High Availability and Redundancy Guide
Cisco Nexus 9000 Series NX-OS Interfaces Configuration Guide
Cisco Nexus 9000 Series NX-OS Layer 2 Switching Configuration Guide
Cisco Nexus 9000 Series NX-OS Multicast Routing Configuration Guide
Cisco Nexus 9000 Series NX-OS Quality of Service Configuration Guide
Cisco Nexus 9000 Series NX-OS Security Configuration Guide
Cisco Nexus 9000 Series NX-OS System Management Configuration Guide
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide
Cisco Nexus 9000 Series NX-OS Verified Scalability Guide
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
20
Cisco Nexus 9000 Series Virtual Machine Tracker Configuration Guide
Cisco Nexus 9000 Series NX-OS VXLAN Configuration Guide
Other Software Documents
Cisco Nexus 7000 Series and 9000 Series NX-OS MIB Quick Reference
Cisco Nexus 9000 Series NX-OS Programmability Guide
Cisco Nexus 9000 Series NX-OS Software Upgrade and Downgrade Guide
Cisco Nexus 9000 Series NX-OS System Messages Reference
Cisco Nexus 9000 Series NX-OS Troubleshooting Guide
Cisco NX-OS Licensing Guide
Cisco NX-OS XML Interface User Guide
Documentation Feedback
To provide technical feedback on this document, or to report an error or omission, please send your
comments to [email protected]. We appreciate your feedback.
Obtaining Documentation and Submitting a Service Request
For information on obtaining documentation, using the Cisco Bug Search Tool (BST), submitting a
service request, and gathering additional information, see What’s New in Cisco Product Documentation
at: http://www.cisco.com/c/en/us/td/docs/general/whatsnew/whatsnew.html.
Subscribe to What’s New in Cisco Product Documentation, which lists all new and revised Cisco
technical documentation as an RSS feed and delivers content directly to your desktop using a reader
application. The RSS feeds are a free service.
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
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Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
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CH A P T E R
1
Overview
This chapter introduces the underlying concepts for the Layer 3 unicast routing protocols in Cisco
NX-OS.
This chapter includes the following sections:
•
About Layer 3 Unicast Routing, page 1-1
•
Routing Algorithms, page 1-8
•
Layer 3 Virtualization, page 1-10
•
Cisco NX-OS Fowarding Architecture, page 1-10
•
Summary of Layer 3 Unicast Routing Features, page 1-12
•
Related Topics, page 1-15
About Layer 3 Unicast Routing
Layer 3 unicast routing involves two basic activities: determining optimal routing paths and packet
switching. You can use routing algorithms to calculate the optimal path from the router to a destination.
This calculation depends on the algorithm selected, route metrics, and other considerations such as load
balancing and alternate path discovery.
This section includes the following topics:
•
Routing Fundamentals, page 1-2
•
Packet Switching, page 1-2
•
Routing Metrics, page 1-3
•
Router IDs, page 1-5
•
Autonomous Systems, page 1-5
•
Convergence, page 1-6
•
Load Balancing and Equal Cost Multipath, page 1-6
•
Route Redistribution, page 1-6
•
Administrative Distance, page 1-7
•
Stub Routing, page 1-7
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Overview
About Layer 3 Unicast Routing
Routing Fundamentals
Routing protocols use a metric to evaluate the best path to the destination. A metric is a standard of
measurement, such as a path bandwidth, that routing algorithms use to determine the optimal path to a
destination. To aid path determination, routing algorithms initialize and maintain routing tables that
contain route information such as the IP destination address, the address of the next router, or the next
hop. Destination and next-hop associations tell a router that an IP destination can be reached optimally
by sending the packet to a particular router that represents the next hop on the way to the final
destination. When a router receives an incoming packet, it checks the destination address and attempts
to associate this address with the next hop. See the “Unicast RIB” section on page 1-10 for more
information about the route table.
Routing tables can contain other information, such as the data about the desirability of a path. Routers
compare metrics to determine optimal routes, and these metrics differ depending on the design of the
routing algorithm used. See the “Routing Metrics” section on page 1-3.
Routers communicate with one another and maintain their routing tables by transmitting a variety of
messages. The routing update message is one such message that consists of all or a portion of a routing
table. By analyzing routing updates from all other routers, a router can build a detailed picture of the
network topology. A link-state advertisement, which is another example of a message sent between
routers, informs other routers of the link state of the sending router. You can also use link information
to enable routers to determine optimal routes to network destinations. For more information, see the
“Routing Algorithms” section on page 1-8.
Packet Switching
In packet switching, a host determines that it must send a packet to another host. Having acquired a
router address by some means, the source host sends a packet that is addressed specifically to the router
physical (Media Access Control [MAC]-layer) address but with the IP (network layer) address of the
destination host.
The router examines the destination IP address and tries to find the IP address in the routing table. If the
router does not know how to forward the packet, it typically drops the packet. If the router knows how
to forward the packet, it changes the destination MAC address to the MAC address of the next-hop router
and transmits the packet.
The next hop might be the ultimate destination host or another router that executes the same switching
decision process. As the packet moves through the internetwork, its physical address changes, but its
protocol address remains constant (see Figure 1-1).
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About Layer 3 Unicast Routing
Figure 1-1
Packet Header Updates Through a Network
Source host
PC
Packet
To: Destination host
Router 1
(Protocol address)
(Physical address)
Packet
Router 1
To: Destination host
Router 2
(Protocol address)
(Physical address)
Router 2
To: Destination host (Protocol address)
Router 3
(Physical address)
Router 3
Packet
To: Destination host (Protocol address)
Destination host (Physical address)
Packet
182978
Destination host
PC
Routing Metrics
Routing algorithms use many different metrics to determine the best route. Sophisticated routing
algorithms can base route selection on multiple metrics.
This section includes the following metrics:
•
Path Length, page 1-4
•
Reliability, page 1-4
•
Routing Delay, page 1-4
•
Bandwidth, page 1-4
•
Load, page 1-4
•
Communication Cost, page 1-4
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Overview
About Layer 3 Unicast Routing
Path Length
The path length is the most common routing metric. Some routing protocols allow you to assign arbitrary
costs to each network link. In this case, the path length is the sum of the costs associated with each link
traversed. Other routing protocols define the hop count, which is a metric that specifies the number of
passes through internetworking products, such as routers, that a packet must take from a source to a
destination.
Reliability
The reliability, in the context of routing algorithms, is the dependability (in terms of the bit-error rate)
of each network link. Some network links might go down more often than others. After a network fails,
certain network links might be repaired more easily or more quickly than other links. The reliability
factors that you can take into account when assigning the reliability rating are arbitrary numeric values
that you usually assign to network links.
Routing Delay
The routing delay is the length of time required to move a packet from a source to a destination through
the internetwork. The delay depends on many factors, including the bandwidth of intermediate network
links, the port queues at each router along the way, the network congestion on all intermediate network
links, and the physical distance that the packet must travel. Because the routing delay is a combination
of several important variables, it is a common and useful metric.
Bandwidth
The bandwidth is the available traffic capacity of a link. For example, a 10-Gigabit Ethernet link is
preferable to a 1-Gigabit Ethernet link. Although the bandwidth is the maximum attainable throughput
on a link, routes through links with greater bandwidth do not necessarily provide better routes than
routes through slower links. For example, if a faster link is busier, the actual time required to send a
packet to the destination could be greater.
Load
The load is the degree to which a network resource, such as a router, is busy. You can calculate the load
in a variety of ways, including CPU usage and packets processed per second. Monitoring these
parameters on a continual basis can be resource intensive.
Communication Cost
The communication cost is a measure of the operating cost to route over a link. The communication cost
is another important metric, especially if you do not care about performance as much as operating
expenditures. For example, the line delay for a private line might be longer than a public line, but you
can send packets over your private line rather than through the public lines that cost money for usage
time.
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About Layer 3 Unicast Routing
Router IDs
Each routing process has an associated router ID. You can configure the router ID to any interface in the
system. If you do not configure the router ID, Cisco NX-OS selects the router ID based on the following
criteria:
•
Cisco NX-OS prefers loopback0 over any other interface. If loopback0 does not exist, then Cisco
NX-OS prefers the first loopback interface over any other interface type.
•
If you have not configured a loopback interface, Cisco NX-OS uses the first interface in the
configuration file as the router ID. If you configure any loopback interface after Cisco NX-OS
selects the router ID, the loopback interface becomes the router ID. If the loopback interface is not
loopback0 and you configure loopback0 with an IP address, the router ID changes to the IP address
of loopback0.
•
If the interface that the router ID is based on changes, that new IP address becomes the router ID. If
any other interface changes its IP address, there is no router ID change.
Autonomous Systems
An autonomous system (AS) is a network controlled by a single technical administration entity.
Autonomous systems divide global external networks into individual routing domains, where local
routing policies are applied. This organization simplifies routing domain administration and simplifies
consistent policy configuration.
Each autonomous system can support multiple interior routing protocols that dynamically exchange
routing information through route redistribution. The Regional Internet Registries (RIR) assign a unique
number to each public autonomous system that directly connects to the Internet. This autonomous
system number (AS number) identifies both the routing process and the autonomous system.
The Border Gateway Protocol (BGP) supports 4-byte AS numbers that can be represented in asplain and
asdot notations:
•
asplain—A decimal value notation where both 2-byte and 4-byte AS numbers are represented by
their decimal value. For example, 65526 is a 2-byte AS number, and 234567 is a 4-byte AS number.
•
asdot—An AS dot notation where 2-byte AS numbers are represented by their decimal value and
4-byte AS numbers are represented by a dot notation. For example, 2-byte AS number 65526 is
represented as 65526, and 4-byte AS number 65546 is represented as 1.10.
The BGP 4-byte AS number capability is used to propagate 4-byte-based AS path information across
BGP speakers that do not support 4-byte AS numbers.
Note
RFC 5396 is partially supported. The asplain and asdot notations are supported, but the asdot+ notation
is not.
Private autonomous system numbers are used for internal routing domains but must be translated by the
router for traffic that is routed out to the Internet. You should not configure routing protocols to advertise
private autonomous system numbers to external networks. By default, Cisco NX-OS does not remove
private autonomous system numbers from routing updates.
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About Layer 3 Unicast Routing
Note
The autonomous system number assignment for public and private networks is governed by the Internet
Assigned Number Authority (IANA). For information about autonomous system numbers, including the
reserved number assignment, or to apply to register an autonomous system number, see this URL:
http://www.iana.org/
Convergence
A key aspect to measure for any routing algorithm is how much time a router takes to react to network
topology changes. When a part of the network changes for any reason, such as a link failure, the routing
information in different routers might not match. Some routers will have updated information about the
changed topology, while other routers will still have the old information. The convergence is the amount
of time before all routers in the network have updated, matching routing information. The convergence
time varies depending on the routing algorithm. Fast convergence minimizes the chance of lost packets
caused by inaccurate routing information.
Load Balancing and Equal Cost Multipath
Routing protocols can use load balancing or equal cost multipath (ECMP) to share traffic across multiple
paths.When a router learns multiple routes to a specific network, it installs the route with the lowest
administrative distance in the routing table. If the router receives and installs multiple paths with the
same administrative distance and cost to a destination, load balancing can occur. Load balancing
distributes the traffic across all the paths, sharing the load. The number of paths used is limited by the
number of entries that the routing protocol puts in the routing table. Cisco NX-OS supports up to 16
paths to a destination.
The Enhanced Interior Gateway Routing Protocol (EIGRP) also supports unequal cost load balancing.
For more information, see Chapter 7, “Configuring EIGRP.”
Route Redistribution
If you have multiple routing protocols configured in your network, you can configure these protocols to
share routing information by configuring route redistribution in each protocol. For example, you can
configure the Open Shortest Path First (OSPF) protocol to advertise routes learned from the Border
Gateway Protocol (BGP). You can also redistribute static routes into any dynamic routing protocol. The
router that is redistributing routes from another protocol sets a fixed route metric for those redistributed
routes, which prevents incompatible route metrics between the different routing protocols. For example,
routes redistributed from EIGRP into OSPF are assigned a fixed link cost metric that OSPF understands.
Note
You are required to use route maps when you configure the redistribution of routing information.
Route redistribution also uses an administrative distance (see the “Administrative Distance” section on
page 1-7) to distinguish between routes learned from two different routing protocols. The preferred
routing protocol is given a lower administrative distance so that its routes are picked over routes from
another protocol with a higher administrative distance assigned.
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Administrative Distance
An administrative distance is a rating of the trustworthiness of a routing information source. A higher
value indicates a lower trust rating. Typically, a route can be learned through more than one protocol.
Administrative distance is used to discriminate between routes learned from more than one protocol. The
route with the lowest administrative distance is installed in the IP routing table.
Stub Routing
You can use stub routing in a hub-and-spoke network topology, where one or more end (stub) networks
are connected to a remote router (the spoke) that is connected to one or more distribution routers (the
hub). The remote router is adjacent only to one or more distribution routers. The only route for IP traffic
to follow into the remote router is through a distribution router. This type of configuration is commonly
used in WAN topologies in which the distribution router is directly connected to a WAN. The distribution
router can be connected to many more remote routers. Often, the distribution router is connected to 100
or more remote routers. In a hub-and-spoke topology, the remote router must forward all nonlocal traffic
to a distribution router, so it becomes unnecessary for the remote router to hold a complete routing table.
Generally, the distribution router sends only a default route to the remote router.
Only specified routes are propagated from the remote (stub) router. The stub router responds to all
queries for summaries, connected routes, redistributed static routes, external routes, and internal routes
with the message “inaccessible.” A router that is configured as a stub sends a special peer information
packet to all neighboring routers to report its status as a stub router.
Any neighbor that receives a packet that informs it of the stub status does not query the stub router for
any routes, and a router that has a stub peer does not query that peer. The stub router depends on the
distribution router to send the proper updates to all peers.
Figure 1-2 shows a simple hub-and-spoke configuration.
Figure 1-2
Simple Hub-and-Spoke Network
Distribution
router
(hub)
Remote
router
(spoke)
182979
Corporate
network
192.0.2.0/24
Internet
Stub routing does not prevent routes from being advertised to the remote router. Figure 1-2 shows that
the remote router can access the corporate network and the Internet through the distribution router only.
A full route table on the remote router, in this example, serves no functional purpose because the path to
the corporate network and the Internet is always through the distribution router. A larger route table
reduces only the amount of memory required by the remote router. The bandwidth and memory used can
be lessened by summarizing and filtering routes in the distribution router. In this network topology, the
remote router does not need to receive routes that have been learned from other networks because the
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Overview
Routing Algorithms
remote router must send all nonlocal traffic, regardless of its destination, to the distribution router. To
configure a true stub network, you should configure the distribution router to send only a default route
to the remote router.
OSPF supports stub areas, and the Enhanced Interior Gateway Routing Protocol (EIGRP) supports stub
routers.
Routing Algorithms
Routing algorithms determine how a router gathers and reports reachability information, how it deals
with topology changes, and how it determines the optimal route to a destination. Various types of routing
algorithms exist, and each algorithm has a different impact on network and router resources. Routing
algorithms use a variety of metrics that affect calculation of optimal routes. You can classify routing
algorithms by type, such as static or dynamic, and interior or exterior.
This section includes the following topics:
•
Static Routes and Dynamic Routing Protocols, page 1-8
•
Interior and Exterior Gateway Protocols, page 1-8
•
Distance Vector Protocols, page 1-9
•
Link-State Protocols, page 1-9
Static Routes and Dynamic Routing Protocols
Static routes are route table entries that you manually configure. These static routes do not change unless
you reconfigure them. Static routes are simple to design and work well in environments where network
traffic is relatively predictable and where network design is relatively simple.
Because static routing systems cannot react to network changes, you should not use them for large,
constantly changing networks. Most routing protocols today use dynamic routing algorithms that adjust
to changing network circumstances by analyzing incoming routing update messages. If the message
indicates that a network change has occurred, the routing software recalculates routes and sends out new
routing update messages. These messages permeate the network, triggering routers to rerun their
algorithms and change their routing tables accordingly.
You can supplement dynamic routing algorithms with static routes where appropriate. For example, you
should configure each subnetwork with a static route to the IP default gateway or router of last resort (a
router to which all unrouteable packets are sent).
Interior and Exterior Gateway Protocols
You can separate networks into unique routing domains or autonomous systems. An autonomous system
is a portion of an internetwork under common administrative authority that is regulated by a particular
set of administrative guidelines. Routing protocols that route between autonomous systems are called
exterior gateway protocols or interdomain protocols. The Border Gateway Protocol (BGP) is an example
of an exterior gateway protocol. Routing protocols used within an autonomous system are called interior
gateway protocols or intradomain protocols. EIGRP and OSPF are examples of interior gateway
protocols.
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Routing Algorithms
Distance Vector Protocols
Distance vector protocols use distance vector algorithms (also known as Bellman-Ford algorithms) that
call for each router to send all or some portion of its routing table to its neighbors. Distance vector
algorithms define routes by distance (for example, the number of hops to the destination) and direction
(for example, the next-hop router). These routes are then broadcast to the directly connected neighbor
routers. Each router uses these updates to verify and update the routing tables.
To prevent routing loops, most distance vector algorithms use split horizon with poison reverse which
means that the routes learned from an interface are set as unreachable and advertised back along the
interface that they were learned on during the next periodic update. This process prevents the router from
seeing its own route updates coming back.
Distance vector algorithms send updates at fixed intervals but can also send updates in response to
changes in route metric values. These triggered updates can speed up the route convergence time. The
Routing Information Protocol (RIP) is a distance vector protocol.
Link-State Protocols
The link-state protocols, also known as shortest path first (SPF), share information with neighboring
routers. Each router builds a link-state advertisement (LSA) that contains information about each link
and directly connected neighbor router.
Each LSA has a sequence number. When a router receives an LSA and updates its link-state database,
the LSA is flooded to all adjacent neighbors. If a router receives two LSAs with the same sequence
number (from the same router), the router does not flood the last LSA that it received to its neighbors
because it wants to prevent an LSA update loop. Because the router floods the LSAs immediately after
it receives them, the convergence time for link-state protocols is minimized.
Discovering neighbors and establishing adjacency is an important part of a link state protocol. Neighbors
are discovered using special Hello packets that also serve as keepalive notifications to each neighbor
router. Adjacency is the establishment of a common set of operating parameters for the link-state
protocol between neighbor routers.
The LSAs received by a router are added to the router’s link-state database. Each entry consists of the
following parameters:
•
Router ID (for the router that originated the LSA)
•
Neighbor ID
•
Link cost
•
Sequence number of the LSA
•
Age of the LSA entry
The router runs the SPF algorithm on the link-state database, building the shortest path tree for that
router. This SPF tree is used to populate the routing table.
In link-state algorithms, each router builds a picture of the entire network in its routing tables. The
link-state algorithms send small updates everywhere, while distance vector algorithms send larger
updates only to neighboring routers.
Because they converge more quickly, link-state algorithms are less likely to cause routing loops than
distance vector algorithms. However, link-state algorithms require more CPU power and memory than
distance vector algorithms and they can be more expensive to implement and support. Link-state
protocols are generally more scalable than distance vector protocols.
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Layer 3 Virtualization
OSPF is an example of a link-state protocol.
Layer 3 Virtualization
Cisco NX-OS supports multiple virtual routing and forwarding (VRF) instances and multiple Routing
Information Bases (RIBs) to support multiple address domains. Each VRF is associated with a RIB, and
this information is collected by the Forwarding Information Base (FIB). A VRF represents a Layer 3
addressing domain. Each Layer 3 interface (logical or physical) belongs to one VRF. For more
information, see Chapter 13, “Configuring Layer 3 Virtualization.”
Cisco NX-OS can segment operating system and hardware resources into virtual device contexts (VDCs)
that emulate virtual devices. The Cisco Nexus 9000 Series switch currently does not support multiple
VDCs. All switch resources are managed in the default VDC.
Cisco NX-OS Fowarding Architecture
The Cisco NX-OS forwarding architecture is responsible for processing all routing updates and
populating the forwarding information to all modules in the chassis.
This section includes the following topics:
•
Unicast RIB, page 1-10
•
Adjacency Manager, page 1-11
•
Unicast Forwarding Distribution Module, page 1-11
•
FIB, page 1-12
•
Hardware Forwarding, page 1-12
•
Software Forwarding, page 1-12
Unicast RIB
The Cisco NX-OS forwarding architecture consists of multiple components, as shown in Figure 1-3.
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Cisco NX-OS Fowarding Architecture
Figure 1-3
Cisco NX-OS Forwarding Architecture
ISIS
BGP
OSPF
ARP
Supervisor components
URIB
Adjacency Manager (AM)
Module components
Unicast Forwarding Information Base (UFIB)
182981
Unicast FIB Distribution Module (uFDM)
The unicast RIB exists on the active supervisor. It maintains the routing table with directly connected
routes, static routes, and routes learned from dynamic unicast routing protocols. The unicast RIB also
collects adjacency information from sources such as the Address Resolution Protocol (ARP). The
unicast RIB determines the best next hop for a given route and populates the unicast FIB on the modules
by using the services of the unicast FIB Distribution Module (FDM).
Each dynamic routing protocol must update the unicast RIB for any route that has timed out. The unicast
RIB then deletes that route and recalculates the best next hop for that route (if an alternate path is
available).
Adjacency Manager
The adjacency manager exists on the active supervisor and maintains adjacency information for different
protocols including ARP, Neighbor Discovery Protocol (NDP), and static configuration. The most basic
adjacency information is the Layer 3 to Layer 2 address mapping discovered by these protocols.
Outgoing Layer 2 packets use the adjacency information to complete the Layer 2 header.
The adjacency manager can trigger ARP requests to find a particular Layer 3 to Layer 2 mapping. The
new mapping becomes available when the corresponding ARP reply is received and processed. For IPv6,
the adjacency manager finds the Layer 3 to Layer 2 mapping information from NDP. For more
information, see Chapter 3, “Configuring IPv6.”
Unicast Forwarding Distribution Module
The unicast Forwarding Distribution Module (FDM) exists on the active supervisor and distributes the
forwarding path information from the unicast RIB and other sources. The unicast RIB generates
forwarding information that the unicast FIB programs into the hardware forwarding tables on the
standby supervisor and the modules. The unicast FDM also downloads the FIB information to newly
inserted modules.
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The unicast FDM gathers adjacency information, rewrite information, and other platform-dependent
information when updating routes in the unicast FIB. The adjacency and rewrite information consists of
interface, next hop, and Layer 3 to Layer 2 mapping information. The interface and next-hop information
is received in route updates from the unicast RIB. The Layer 3 to Layer 2 mapping is received from the
adjacency manager.
FIB
The unicast FIB exists on supervisors and switching modules and builds the information used for the
hardware forwarding engine. The unicast FIB receives route updates from the unicast FDM and sends
the information to be programmed in the hardware forwarding engine. The unicast FIB controls the
addition, deletion, and modification of routes, paths, and adjacencies.
The unicast FIBs are maintained on a per-VRF and per-address-family basis, that is, one for IPv4 and
one for IPv6 for each configured VRF. Based on route update messages, the unicast FIB maintains a
per-VRF prefix and next-hop adjacency information database. The next-hop adjacency data structure
contains the next-hop IP address and the Layer 2 rewrite information. Multiple prefixes could share a
next-hop adjacency information structure.
Hardware Forwarding
Cisco NX-OS supports distributed packet forwarding. The ingress port takes relevant information from
the packet header and passes the information to the local switching engine. The local switching engine
does the Layer 3 lookup and uses this information to rewrite the packet header. The ingress module
forwards the packet to the egress port. If the egress port is on a different module, the packet is forwarded
using the switch fabric to the egress module. The egress module does not participate in the Layer 3
forwarding decision.
You also use the show platform fib or show platform forwarding commands to display details on
hardware forwarding.
Software Forwarding
The software forwarding path in Cisco NX-OS is used mainly to handle features that are not supported
in the hardware or to handle errors encountered during the hardware processing. Typically, packets with
IP options or packets that need fragmentation are passed to the CPU on the active supervisor. All packets
that should be switched in the software or terminated go to the supervisor. The supervisor uses the
information provided by the unicast RIB and the adjacency manager to make the forwarding decisions.
The module is not involved in the software forwarding path.
Software forwarding is controlled by control plane policies. For more information, see the Cisco Nexus
9000 Series NX-OS Security Configuration Guide.
Summary of Layer 3 Unicast Routing Features
This section provides a brief introduction to the Layer 3 unicast features and protocols supported in
Cisco NX-OS.
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This section includes the following topics:
•
IPv4 and IPv6, page 1-13
•
IP Services, page 1-13
•
OSPF, page 1-13
•
EIGRP, page 1-13
•
IS-IS, page 1-14
•
BGP, page 1-14
•
RIP, page 1-14
•
Static Routing, page 1-14
•
Layer 3 Virtualization, page 1-14
•
Route Policy Manager, page 1-15
•
Policy-Based Routing, page 1-15
•
First Hop Redundancy Protocols, page 1-15
•
Object Tracking, page 1-15
IPv4 and IPv6
Layer 3 uses either the IPv4 or IPv6 protocol. IPv6 increases the number of network address bits from
32 bits (in IPv4) to 128 bits. For more information, see Chapter 2, “Configuring IPv4” or Chapter 3,
“Configuring IPv6.”
IP Services
IP Services includes Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS
Client) clients. For more information, see Chapter 4, “Configuring DNS.”
OSPF
The Open Shortest Path First (OSPF) protocol is a link-state routing protocol used to exchange network
reachability information within an autonomous system. Each OSPF router advertises information about
its active links to its neighbor routers. Link information consists of the link type, the link metric, and the
neighbor router that is connected to the link. The advertisements that contain this link information are
called link-state advertisements. For more information, see Chapter 5, “Configuring OSPFv2.”
EIGRP
The Enhanced Interior Gateway Routing Protocol (EIGRP) is a unicast routing protocol that has the
characteristics of both distance vector and link-state routing protocols. It is an improved version of IGRP,
which is a Cisco proprietary routing protocol. EIGRP relies on its neighbors to provide the routes. It
constructs the network topology from the routes advertised by its neighbors, similar to a link-state
protocol, and uses this information to select loop-free paths to destinations. For more information, see
Chapter 7, “Configuring EIGRP.”
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IS-IS
The Intermediate System-to-Intermediate System (IS-IS) protocol is an intradomain Open System
Interconnection (OSI) dynamic routing protocol specified in the International Organization for
Standardization (ISO) 10589. The IS-IS routing protocol is a link-state protocol. IS-IS features are as
follows:
•
Hierarchical routing
•
Classless behavior
•
Rapid flooding of new information
•
Fast Convergence
•
Very scalable
For more information, see Chapter 8, “Configuring IS-IS.”
BGP
The Border Gateway Protocol (BGP) is an inter-autonomous system routing protocol. A BGP router
advertises network reachability information to other BGP routers using Transmission Control Protocol
(TCP) as its reliable transport mechanism. The network reachability information includes the destination
network prefix, a list of autonomous systems that needs to be traversed to reach the destination, and the
next-hop router. Reachability information contains additional path attributes such as preference to a
route, origin of the route, community and others. For more information, see Chapter 9, “Configuring
Basic BGP” and Chapter 10, “Configuring Advanced BGP.”
RIP
The Routing Information Protocol (RIP) is a distance-vector protocol that uses a hop count as its metric.
RIP is widely used for routing traffic in the global Internet and is an Interior Gateway Protocol (IGP),
which means that it performs routing within a single autonomous system. For more information, see
Chapter 11, “Configuring RIP.”
Static Routing
Static routing allows you to enter a fixed route to a destination. This feature is useful for small networks
where the topology is simple. Static routing is also used with other routing protocols to control default
routes and route distribution. For more information, see Chapter 12, “Configuring Static Routing.”
Layer 3 Virtualization
Virtualization allows you to share physical resources across separate management domains. Cisco
NX-OS supports Layer 3 virtualization with virtual routing and forwarding (VRF). VRF provides a
separate address domain for configuring Layer 3 routing protocols. For more information, see
Chapter 13, “Configuring Layer 3 Virtualization.”
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Route Policy Manager
The Route Policy Manager provides a route filtering capability in Cisco NX-OS. It uses route maps to
filter routes distributed across various routing protocols and between different entities within a given
routing protocol. Filtering is based on specific match criteria, which is similar to packet filtering by
access control lists. For more information, see Chapter 15, “Configuring Route Policy Manager.”
Policy-Based Routing
Policy-based routing uses the Route Policy Manager to create policy route filters. These policy route
filters can forward a packet to a specified next hop based on the source of the packet or other fields in
the packet header. Policy routes can be linked to extended IP access lists so that routing might be based
on protocol types and port numbers. For more information, see Chapter 16, “Configuring Policy-Based
Routing.”
First Hop Redundancy Protocols
First hop redundancy protocols (FHRP), such as the Hot Standby Router Protocol (HSRP) and the
Virtual Router Redundancy Protocol (VRRP), allow you to provide redundant connections to your hosts.
If an active first-hop router fails, the FHRP automatically selects a standby router to take over. You do
not need to update the hosts with new IP addresses because the address is virtual and shared between
each router in the FHRP group. For more information on HSRP, see Chapter 17, “Configuring HSRP.”
For more information on VRRP, see Chapter 18, “Configuring VRRP.”
Object Tracking
Object tracking allows you to track specific objects on the network, such as the interface line protocol
state, IP routing, and route reachability, and take action when the tracked object’s state changes. This
feature allows you to increase the availability of the network and shorten the recovery time if an object
state goes down. For more information, see Chapter 19, “Configuring Object Tracking.”
Related Topics
The following Cisco documents are related to the Layer 3 features:
•
Cisco Nexus 9000 Series NX-OS Multicast Routing Configuration Guide
•
Cisco Nexus 9000 Series NX-OS High Availability and Redundancy Guide
•
Exploring Autonomous System Numbers:
http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_9-1/autonomous_system_numb
ers.html
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CH A P T E R
2
Configuring IPv4
This chapter describes how to configure Internet Protocol version 4 (IPv4), which includes addressing,
Address Resolution Protocol (ARP), and Internet Control Message Protocol (ICMP), on the Cisco
NX-OS device.
This chapter includes the following sections:
•
About IPv4, page 2-1
•
Licensing Requirements for IPv4, page 2-7
•
Prerequisites for IPv4, page 2-7
•
Guidelines and Limitations for IPv4, page 2-7
•
Default Settings, page 2-7
•
Configuring IPv4, page 2-7
•
Verifying the IPv4 Configuration, page 2-20
About IPv4
You can configure IP on the device to assign IP addresses to network interfaces. When you assign IP
addresses, you enable the interfaces and allow communication with the hosts on those interfaces.
You can configure an IP address as primary or secondary on a device. An interface can have one primary
IP address and multiple secondary addresses. All networking devices on an interface should share the
same primary IP address because the packets that are generated by the device always use the primary
IPv4 address. Each IPv4 packet is based on the information from a source or destination IP address. For
more information, see the “Multiple IPv4 Addresses” section on page 2-2.
You can use a subnet to mask the IP addresses. A mask is used to determine what subnet an IP address
belongs to. An IP address contains the network address and the host address. A mask identifies the bits
that denote the network number in an IP address. When you use the mask to subnet a network, the mask
is then referred to as a subnet mask. Subnet masks are 32-bit values that allow the recipient of IP packets
to distinguish the network ID portion of the IP address from the host ID portion of the IP address.
The IP feature is responsible for handling IPv4 packets that terminate in the supervisor module, as well
as forwarding of IPv4 packets, which includes IPv4 unicast/multicast route lookup and software access
control list (ACL) forwarding. The IP feature also manages the network interface IP address
configuration, duplicate address checks, static routes, and packet send/receive interface for IP clients.
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About IPv4
This section includes the following topics:
•
Multiple IPv4 Addresses, page 2-2
•
LPM Routing Modes, page 2-2
•
Address Resolution Protocol, page 2-3
•
ARP Caching, page 2-4
•
Static and Dynamic Entries in the ARP Cache, page 2-4
•
Devices That Do Not Use ARP, page 2-4
•
Reverse ARP, page 2-4
•
Proxy ARP, page 2-5
•
Local Proxy ARP, page 2-6
•
Gratuitous ARP, page 2-6
•
Glean Throttling, page 2-6
•
Path MTU Discovery, page 2-6
•
ICMP, page 2-6
•
Virtualization Support, page 2-7
Multiple IPv4 Addresses
Cisco NX-OS supports multiple IP addresses per interface. You can specify an unlimited number of
secondary addresses for a variety of situations. The most common are as follows:
Note
•
When there are not enough host IP addresses for a particular network interface. For example, if your
subnetting allows up to 254 hosts per logical subnet, but on one physical subnet you must have 300
host addresses, then you can use secondary IP addresses on the routers or access servers to allow
you to have two logical subnets that use one physical subnet.
•
Two subnets of a single network might otherwise be separated by another network. You can create
a single network from subnets that are physically separated by another network by using a secondary
address. In these instances, the first network is extended, or layered on top of the second network.
A subnet cannot appear on more than one active interface of the router at a time.
If any device on a network segment uses a secondary IPv4 address, all other devices on that same
network interface must also use a secondary address from the same network or subnet. The inconsistent
use of secondary addresses on a network segment can quickly cause routing loops.
LPM Routing Modes
By default, Cisco NX-OS programs routes in a hierarchical fashion to allow for the longest prefix match
(LPM) on the device. However, you can configure the device for different routing modes to support
significantly more LPM route entries.
The following tables list the LPM routing modes that are supported on the Cisco Nexus 9300 Series and
9500 Series switches.
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Table 2-1
LPM Routing Modes for Cisco Nexus 9300 Series Switches
LPM Routing Mode
Broadcom T2 Mode
Default system routing mode
3
Table 2-2
CLI Command
LPM Routing Modes for Cisco Nexus 9500 Series Switches
LPM Routing Mode
Broadcom T2 Mode
CLI Command
Default system routing mode
3 (for line cards);
4 (for fabric modules)
Max-host routing mode
2 (for line cards);
system routing max-mode host
3 (for fabric modules)
Nonhierarchical routing mode
3 (for line cards);
system routing non-hierarchical-routing
4 with max-l3-mode [max-l3-mode]
option (for line cards)
64-bit ALPM routing mode
Submode of mode 4
(for fabric modules)
system routing mode hierarchical
64b-alpm
For detailed configuration information, see the “Configuring IPv4” section on page 2-7.
Address Resolution Protocol
Networking devices and Layer 3 switches use Address Resolution Protocol (ARP) to map IP (network
layer) addresses to (Media Access Control [MAC]-layer) addresses to enable IP packets to be sent across
networks. Before a device sends a packet to another device, it looks in its own ARP cache to see if there
is a MAC address and corresponding IP address for the destination device. If there is no entry, the source
device sends a broadcast message to every device on the network.
Each device compares the IP address to its own. Only the device with the matching IP address replies to
the device that sends the data with a packet that contains the MAC address for the device. The source
device adds the destination device MAC address to its ARP table for future reference, creates a data-link
header and trailer that encapsulates the packet, and proceeds to transfer the data. Figure 2-1 shows the
ARP broadcast and response process.
Figure 2-1
ARP Process
Barney
135075
Fred
I need the address of 10.1.1.2.
I heard that broadcast. The message is for me.
Here is my MAC address: 00:1D:7E:1D:00:01.
When the destination device lies on a remote network that is beyond another device, the process is the
same except that the device that sends the data sends an ARP request for the MAC address of the default
gateway. After the address is resolved and the default gateway receives the packet, the default gateway
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broadcasts the destination IP address over the networks connected to it. The device on the destination
device network uses ARP to obtain the MAC address of the destination device and delivers the packet.
ARP is enabled by default.
The default system-defined CoPP policy rate limits ARP broadcast packets bound for the supervisor
module. The default system-defined CoPP policy prevents an ARP broadcast storm from affecting the
control plane traffic but does not affect bridged packets.
ARP Caching
ARP caching minimizes broadcasts and limits wasteful use of network resources. The mapping of IP
addresses to MAC addresses occurs at each hop (device) on the network for every packet sent over an
internetwork, which may affect network performance.
ARP caching stores network addresses and the associated data-link addresses in the memory for a period
of time, which minimizes the use of valuable network resources to broadcast for the same address each
time that a packet is sent. You must maintain the cache entries that are set to expire periodically because
the information might become outdated. Every device on a network updates its tables as addresses are
broadcast.
Static and Dynamic Entries in the ARP Cache
Static routing requires that you manually configure the IP addresses, subnet masks, gateways, and
corresponding MAC addresses for each interface of each device. Static routing requires more work to
maintain the route table. You must update the table each time you add or change routes.
Dynamic routing uses protocols that enable the devices in a network to exchange routing table
information with each other. Dynamic routing is more efficient than static routing because the route table
is automatically updated unless you add a time limit to the cache. The default time limit is 25 minutes
but you can modify the time limit if the network has many routes that are added and deleted from the
cache.
Devices That Do Not Use ARP
When a network is divided into two segments, a bridge joins the segments and filters traffic to each
segment based on MAC addresses. The bridge builds its own address table, which uses MAC addresses
only. A device has an ARP cache that contains both IP addresses and the corresponding MAC addresses.
Passive hubs are central-connection devices that physically connect other devices in a network. They
send messages out on all their ports to the devices and operate at Layer 1 but do not maintain an address
table.
Layer 2 switches determine which port of a device receives a message that is sent only to that port.
However, Layer 3 switches are devices that build an ARP cache (table).
Reverse ARP
Reverse ARP (RARP) as defined by RFC 903 works the same way as ARP, except that the RARP request
packet requests an IP address instead of a MAC address. RARP often is used by diskless workstations
because this type of device has no way to store IP addresses to use when they boot. The only address that
is known is the MAC address because it is burned into the hardware.
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Use of RARP requires an RARP server on the same network segment as the router interface. Figure 2-2
shows how RARP works.
Reverse ARP
RARP server
Device A
I am device A and sending
a broadcast that uses my
hardware address.
Can somone on the network
tell me what my IP address is?
Okay, your hardware address
is 00:1D:7E:1D:00:01 and
your IP address is 10.0.0.2
135218
Figure 2-2
RARP has several limitations. Because of these limitations, most businesses use DHCP to assign IP
addresses dynamically. DHCP is cost effective and requires less maintenance than RARP. The following
are the most important limitations:
•
Because RARP uses hardware addresses, if the internetwork is large with many physical networks,
a RARP server must be on every segment with an additional server for redundancy. Maintaining two
servers for every segment is costly.
•
Each server must be configured with a table of static mappings between the hardware addresses and
IP addresses. Maintenance of the IP addresses is difficult.
•
RARP only provides IP addresses of the hosts and not subnet masks or default gateways.
Proxy ARP
Proxy ARP enables a device that is physically located on one network appear to be logically part of a
different physical network connected to the same device or firewall. Proxy ARP allows you to hide a
device with a public IP address on a private network behind a router and still have the device appear to
be on the public network in front of the router. By hiding its identity, the router accepts responsibility
for routing packets to the real destination. Proxy ARP can help devices on a subnet reach remote subnets
without configuring routing or a default gateway.
When devices are not in the same data link layer network but in the same IP network, they try to transmit
data to each other as if they are on the local network. However, the router that separates the devices does
not send a broadcast message because routers do not pass hardware-layer broadcasts and the addresses
cannot be resolved.
When you enable Proxy ARP on the device and it receives an ARP request, it identifies the request as a
request for a system that is not on the local LAN. The device responds as if it is the remote destination
for which the broadcast is addressed, with an ARP response that associates the device’s MAC address
with the remote destination's IP address. The local device believes that it is directly connected to the
destination, while in reality its packets are being forwarded from the local subnetwork toward the
destination subnetwork by their local device. By default, Proxy ARP is disabled.
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Local Proxy ARP
You can use local Proxy ARP to enable a device to respond to ARP requests for IP addresses within a
subnet where normally no routing is required. When you enable local Proxy ARP, ARP responds to all
ARP requests for IP addresses within the subnet and forwards all traffic between hosts in the subnet. Use
this feature only on subnets where hosts are intentionally prevented from communicating directly by the
configuration on the device to which they are connected.
Gratuitous ARP
Gratuitous ARP sends a request with an identical source IP address and a destination IP address to detect
duplicate IP addresses. Cisco NX-OS supports enabling or disabling gratuitous ARP requests or ARP
cache updates.
Glean Throttling
If the Address Resolution Protocol (ARP) request for the next hop is not resolved when incoming IP
packets are forwarded in a line card, the line card forwards the packets to the supervisor (glean
throttling). The supervisor resolves the MAC address for the next hop and programs the hardware.
When an ARP request is sent, the software adds a /32 drop adjacency in the hardware to prevent the
packets to the same next-hop IP address to be forwarded to the supervisor. When the ARP is resolved,
the hardware entry is updated with the correct MAC address. If the ARP entry is not resolved before a
timeout period, the entry is removed from the hardware.
Path MTU Discovery
Path maximum transmission unit (MTU) discovery is a method for maximizing the use of available
bandwidth in the network between the endpoints of a TCP connection. It is described in RFC 1191.
Existing connections are not affected when this feature is turned on or off.
ICMP
You can use the Internet Control Message Protocol (ICMP) to provide message packets that report errors
and other information that is relevant to IP processing. ICMP generates error messages, such as ICMP
destination unreachable messages, ICMP Echo Requests (which send a packet on a round trip between
two hosts) and Echo Reply messages. ICMP also provides many diagnostic functions and can send and
redirect error packets to the host. By default, ICMP is enabled.
Some of the ICMP message types are as follows:
Note
•
Network error messages
•
Network congestion messages
•
Troubleshooting information
•
Timeout announcements
ICMP redirects are disabled on interfaces where the local proxy ARP feature is enabled.
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Configuring IPv4
Licensing Requirements for IPv4
Virtualization Support
IPv4 supports virtual routing and forwarding (VRF) instances.
Licensing Requirements for IPv4
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
IP requires no license. Any feature not included in a license package is bundled with the nx-os image and is
provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see
the Cisco NX-OS Licensing Guide.
Prerequisites for IPv4
IPv4 has the following prerequisites:
•
IPv4 can only be configured on Layer 3 interfaces.
Guidelines and Limitations for IPv4
IPv4 has the following configuration guidelines and limitations:
•
You can configure a secondary IP address only after you configure the primary IP address.
Default Settings
Table 2-3 lists the default settings for IP parameters.
Table 2-3
Default IP Parameters
Parameters
Default
ARP timeout
1500 seconds
Proxy ARP
Disabled
Configuring IPv4
This section includes the following topics:
•
Configuring IPv4 Addressing, page 2-8
•
Configuring Multiple IP Addresses, page 2-9
•
Configuring Max-Host Routing Mode (Cisco Nexus 9500 Series Switches Only), page 2-10
•
Configuring Nonhierarchical Routing Mode (Cisco Nexus 9500 Series Switches Only), page 2-11
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Note
•
Configuring 64-Bit ALPM Routing Mode (Cisco Nexus 9500 Series Switches Only), page 2-12
•
Configuring a Static ARP Entry, page 2-13
•
Configuring Proxy ARP, page 2-14
•
Configuring Local Proxy ARP, page 2-15
•
Configuring Gratuitous ARP, page 2-16
•
Configuring Path MTU Discovery, page 2-17
•
Configuring IP Directed Broadcasts, page 2-17
•
Configuring IP Glean Throttling, page 2-18
•
Configuring the Hardware IP Glean Throttle Maximum, page 2-18
•
Configuring a Hardware IP Glean Throttle Timeout, page 2-19
•
Configuring the Interface IP Address for the ICMP Source IP Field, page 2-20
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring IPv4 Addressing
You can assign a primary IP address for a network interface.
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ip address ip-address/length
4.
(Optional) show ip interface
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
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Configuring IPv4
Step 3
Command
Purpose
ip address ip-address/length
[secondary]
Specifies a primary or secondary IPv4 address for an
interface.
Example:
switch(config-if)# ip address
192.168.1.1 255.0.0.0
Step 4
•
The network mask can be a four-part dotted
decimal address. For example, 255.0.0.0 indicates
that each bit equal to 1 means the corresponding
address bit belongs to the network address.
•
The network mask can be indicated as a slash (/)
and a number, which is the prefix length. The
prefix length is a decimal value that indicates how
many of the high-order contiguous bits of the
address comprise the prefix (the network portion
of the address). A slash must precede the decimal
value and there is no space between the IP address
and the slash.
(Optional) Displays interfaces configured for IPv4.
show ip interface
Example:
switch(config-if)# show ip interface
Step 5
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring Multiple IP Addresses
You can only add secondary IP addresses after you configure primary IP addresses.
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ip address ip-address/length
4.
(Optional) show ip interface
5.
(Optional) copy running-config startup-config
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Configuring IPv4
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
Step 3
ip address ip-address/length
[secondary]
Specifies the configured address as a secondary IPv4
address.
Example:
switch(config-if)# ip address
192.168.1.1 255.0.0.0 secondary
Step 4
show ip interface
(Optional) Displays interfaces configured for IPv4.
Example:
switch(config-if)# show ip interface
Step 5
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring Max-Host Routing Mode (Cisco Nexus 9500 Series Switches Only)
By default, Cisco NX-OS programs routes in a hierarchical fashion (with fabric modules configured to
be in mode 4 and line card modules configured to be in mode 3), which allows for longest prefix match
(LPM) and host scale on the device.
You can modify the default LPM and host scale to program more hosts in the system, as might be
required when the node is positioned as a Layer-2 to Layer-3 boundary node.
Note
If you want to further scale the entries in the LPM table, see the “Configuring Nonhierarchical Routing
Mode (Cisco Nexus 9500 Series Switches Only)” section on page 2-11 to configure the device to
program all of the Layer 3 IPv4 and IPv6 routes on the line cards and none of the routes on the fabric
modules.
Note
This configuration impacts both the IPv4 and IPv6 address families.
Note
For the max-host routing mode scale numbers, see the Cisco Nexus 9000 Series NX-OS Verified
Scalability Guide.
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Configuring IPv4
SUMMARY STEPS
1.
configure terminal
2.
[no] system routing max-mode host
3.
(Optional) show forwarding route summary
4.
copy running-config startup-config
5.
reload
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] system routing max-mode host
Example:
switch(config)# system routing max-mode
host
Step 3
show forwarding route summary
Puts the line cards in Broadcom T2 mode 2 and the
fabric modules in Broadcom T2 mode 3 to increase the
number of supported hosts.
(Optional) Displays the LPM mode.
Example:
switch(config)# show forwarding route
summary
Step 4
copy running-config startup-config
Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Step 5
reload
Reboots the entire device.
Example:
switch(config)# reload
Configuring Nonhierarchical Routing Mode (Cisco Nexus 9500 Series Switches
Only)
If the host scale is small (as in a pure Layer 3 deployment), we recommend programming the longest
prefix match (LPM) routes in the line cards to improve convergence performance. Doing so programs
routes and hosts in the line cards and does not program any routes in the fabric modules.
Note
This configuration impacts both the IPv4 and IPv6 address families.
SUMMARY STEPS
1.
configure terminal
2.
[no] system routing non-hierarchical-routing [max-l3-mode]
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3.
(Optional) show forwarding route summary
4.
copy running-config startup-config
5.
reload
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Step 3
Example:
switch(config)# system routing
non-hierarchical-routing max-l3-mode
Puts the line cards in Broadcom T2 mode 3 (or
Broadcom T2 mode 4 if you use the max-l3-mode
option) to support a larger LPM scale. As a result, all
of the IPv4 and IPv6 routes will be programmed on the
line cards rather than on the fabric modules.
show forwarding route summary
(Optional) Displays the LPM mode.
[no] system routing
non-hierarchical-routing [max-l3-mode]
Example:
switch(config)# show forwarding route
summary
Mode 3:
120K IPv4 Host table
16k LPM table (> 65 < 127 1k entry
reserved)
Mode 4:
16k V4 host/4k V6 host
128k v4 LPM/20K V6 LPM
Step 4
copy running-config startup-config
Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Step 5
reload
Reboots the entire device.
Example:
switch(config)# reload
Configuring 64-Bit ALPM Routing Mode (Cisco Nexus 9500 Series Switches
Only)
You can use the 64-bit algorithmic longest prefix match (ALPM) feature to manage IPv4 and IPv6 route
table entries. In 64-bit ALPM routing mode, the device can store significantly more route entries. Using
this mode, you can program one of the following:
•
80,000 IPv6 entries and no IPv4 entries
•
No IPv6 entries and 128,000 IPv4 entries
•
x IPv6 entries and y IPv4 entries, where 2x + y <= 128,000
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Configuring IPv4
Note
This configuration impacts both the IPv4 and IPv6 address families.
Note
For the 64-bit ALPM routing mode scale numbers, see the Cisco Nexus 9000 Series NX-OS Verified
Scalability Guide.
SUMMARY STEPS
1.
configure terminal
2.
[no] system routing mode hierarchical 64b-alpm
3.
(Optional) show forwarding route summary
4.
copy running-config startup-config
5.
reload
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Step 3
Example:
switch(config)# system routing mode
hierarchical 64b-alpm
Causes all IPv4 and IPv6 LPM routes with a mask
length that is less than or equal to 64 to be
programmed in the fabric module. All host routes for
IPv4 and IPv6 and all LPM routes with a mask length
of 65 through 127 are programmed in the line card.
show forwarding route summary
(Optional) Displays the LPM mode.
[no] system routing mode hierarchical
64b-alpm
Example:
switch(config)# show forwarding route
summary
Step 4
copy running-config startup-config
Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Step 5
Reboots the entire device.
reload
Example:
switch(config)# reload
Configuring a Static ARP Entry
You can configure a static ARP entry on the device to map IP addresses to MAC hardware addresses,
including static multicast MAC addresses.
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Configuring IPv4
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ip arp ipaddr mac_addr
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
Step 3
ip arp ipaddr mac_addr
Example:
switch(config-if)# ip arp 192.168.1.1
0019.076c.1a78
Step 4
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
Associates an IP address with a MAC address as a
static entry.
(Optional) Copies the running configuration to the
startup configuration.
Configuring Proxy ARP
You can configure Proxy ARP on the device to determine the media addresses of hosts on other networks
or subnets.
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ip proxy-arp
4.
(Optional) copy running-config startup-config
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Configuring IPv4
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
Step 3
Enables Proxy ARP on the interface.
ip proxy-arp
Example:
switch(config-if)# ip proxy-arp
Step 4
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring Local Proxy ARP
You can configure Local Proxy ARP on the device.
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ip local-proxy-arp
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
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Step 3
Command
Purpose
ip local-proxy-arp
Enables Local Proxy ARP on the interface.
Example:
switch(config-if)# ip local-proxy-arp
Step 4
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring Gratuitous ARP
You can configure gratuitous ARP on an interface.
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ip arp gratuitous {request | update}
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
Step 3
ip arp gratuitous {request | update}
Example:
switch(config-if)# ip arp gratuitous
request
Step 4
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
Enables gratuitous ARP on the interface. The default
is enabled.
(Optional) Copies the running configuration to the
startup configuration.
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Configuring IPv4
Configuring Path MTU Discovery
You can configure path MTU discovery.
SUMMARY STEPS
1.
configure terminal
2.
ip tcp path-mtu-discovery
3.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
ip tcp path-mtu-discovery
Enables path MTU discovery.
Example:
switch(config)# ip tcp
path-mtu-discovery
Step 3
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring IP Directed Broadcasts
An IP directed broadcast is an IP packet whose destination address is a valid broadcast address for some
IP subnet but which originates from a node that is not itself part of that destination subnet.
A device that is not directly connected to its destination subnet forwards an IP directed broadcast in the
same way it forwards unicast IP packets destined to a host on that subnet. When a directed broadcast
packet reaches a device that is directly connected to its destination subnet, that packet is broadcast on
the destination subnet. The destination address in the IP header of the packet is rewritten to the
configured IP broadcast address for the subnet, and the packet is sent as a link-layer broadcast.
If directed broadcast is enabled for an interface, incoming IP packets whose addresses identify them as
directed broadcasts intended for the subnet to which that interface is attached are broadcasted on that
subnet. You can optionally filter those broadcasts through an IP access list such that only those packets
that pass through the access list are broadcasted on the subnet.
To enable IP directed broadcasts, use the following command in interface configuration mode:
Command
Purpose
ip directed-broadcast [acl]
Enables the translation of a directed broadcast to physical
broadcasts. You can optionally filter those broadcasts
through an IP access list.
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Configuring IPv4
Configuring IP Glean Throttling
We recommend that you configure IP glean throttling to filter the unnecessary glean packets that are sent
to the supervisor for ARP resolution for the next hops that are not reachable or do not exist. IP glean
throttling boosts software performance and helps to manage traffic more efficiently.
SUMMARY STEPS
1.
configure terminal
2.
[no] hardware ip glean throttle
3.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] hardware ip glean throttle
Enables IP glean throttling.
Example:
switch(config)# hardware ip glean
throttle
Step 3
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring the Hardware IP Glean Throttle Maximum
You can limit the maximum number of drop adjacencies that are installed in the Forwarding Information
Base (FIB).
SUMMARY STEPS
1.
configure terminal
2.
[no] hardware ip glean throttle maximum count
3.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] hardware ip glean throttle maximum
count
Configures the number of drop adjacencies that are
installed in the FIB.
Example:
switch(config)# hardware ip glean
throttle maximum 2134
Step 3
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Configuring a Hardware IP Glean Throttle Timeout
You can configure a timeout for the installed drop adjacencies to remain in the FIB.
SUMMARY STEPS
1.
configure terminal
2.
[no] hardware ip glean throttle maximum timeout timeout
3.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] hardware ip glean throttle maximum
timeout timeout
Configures the timeout for the installed drop
adjacencies to remain in the FIB.
Example:
switch(config)# hardware ip glean
throttle maximum timeout 300
The range is from 300 seconds (5 minutes) to 1800
seconds (30 minutes).
Note
Step 3
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
After the timeout period is exceeded, the drop
adjacencies are removed from the FIB.
(Optional) Copies the running configuration to the
startup configuration.
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Verifying the IPv4 Configuration
Configuring the Interface IP Address for the ICMP Source IP Field
You can configure an interface IP address for the ICMP source IP field to handle ICMP error messages.
SUMMARY STEPS
1.
configure terminal
2.
[no] ip source {ethernet slot/port | loopback number | port-channel number} icmp-errors
3.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] ip source {ethernet slot/port |
loopback number | port-channel number}
icmp-errors
Configures an interface IP address for the ICMP
source IP field to route ICMP error messages.
Example:
switch(config)# ip source loopback 0
icmp-errors
Step 3
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
Verifying the IPv4 Configuration
To display the IPv4 configuration information, perform one of the following tasks:
Command
Purpose
show ip adjacency
Displays the adjacency table.
show ip adjacency summary
Displays a summary of throttle adjacencies.
show ip arp
Displays the ARP table.
show ip arp summary
Displays a summary of the number of throttle
adjacencies.
show ip interface
Displays IP-related interface information.
show ip arp statistics [vrf vrf-name]
Displays the ARP statistics.
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3
Configuring IPv6
This chapter describes how to configure Internet Protocol version 6 (IPv6), which includes addressing,
on the Cisco NX-OS device.
This chapter includes the following sections:
•
About IPv6, page 3-1
•
Licensing Requirements for IPv6, page 3-13
•
Prerequisites for IPv6, page 3-13
•
Guidelines and Limitations for IPv6, page 3-13
•
Configuring IPv6, page 3-13
•
Verifying the IPv6 Configuration, page 3-19
•
Configuration Examples for IPv6, page 3-19
About IPv6
IPv6, which is designed to replace IPv4, increases the number of network address bits from 32 bits (in
IPv4) to 128 bits. IPv6 is based on IPv4 but it includes a much larger address space and other
improvements such as a simplified main header and extension headers.
The larger IPv6 address space allows networks to scale and provide global reachability. The simplified
IPv6 packet header format handles packets more efficiently. The flexibility of the IPv6 address space
reduces the need for private addresses and the use of Network Address Translation (NAT), which
translates private (not globally unique) addresses into a limited number of public addresses. IPv6 enables
new application protocols that do not require special processing by border routers at the edge of
networks.
IPv6 functionality, such as prefix aggregation, simplified network renumbering, and IPv6 site
multihoming capabilities, enable more efficient routing. IPv6 supports Routing Information Protocol
(RIP), Integrated Intermediate System-to-Intermediate System (IS-IS), Open Shortest Path First (OSPF)
for IPv6, and multiprotocol Border Gateway Protocol (BGP).
This section includes the following topics:
•
IPv6 Address Formats, page 3-2
•
IPv6 Unicast Addresses, page 3-3
•
IPv6 Anycast Addresses, page 3-6
•
IPv6 Multicast Addresses, page 3-7
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Configuring IPv6
About IPv6
•
IPv4 Packet Header, page 3-8
•
Simplified IPv6 Packet Header, page 3-8
•
DNS for IPv6, page 3-11
•
Path MTU Discovery for IPv6, page 3-11
•
CDP IPv6 Address Support, page 3-12
•
LPM Routing Modes, page 3-12
•
Virtualization Support, page 3-13
IPv6 Address Formats
An IPv6 address has 128 bits or 16 bytes. The address is divided into eight, 16-bit hexadecimal blocks
separated by colons (:) in the format: x:x:x:x:x:x:x:x. Two examples of IPv6 addresses are as follows:
2001:0DB8:7654:3210:FEDC:BA98:7654:3210
2001:0DB8:0:0:8:800:200C:417A
IPv6 addresses contain consecutive zeros within the address. You can use two colons (::) at the
beginning, middle, or end of an IPv6 address to replace the consecutive zeros. Table 3-1 shows a list of
compressed IPv6 address formats.
Note
You can use two colons (::) only once in an IPv6 address to replace the longest string of consecutive
zeros within the address.
You can use a double colon as part of the IPv6 address when consecutive 16-bit values are denoted as
zero. You can configure multiple IPv6 addresses per interface but only one link-local address.
The hexadecimal letters in IPv6 addresses are not case sensitive.
Table 3-1
Compressed IPv6 Address Formats
IPv6 Address Type
Preferred Format
Compressed Format
Unicast
2001:0:0:0:0DB8:800:200C:417A
2001::0DB8:800:200C:417A
Multicast
FF01:0:0:0:0:0:0:101
FF01::101
Loopback
0:0:0:0:0:0:0:0:1
::1
Unspecified
0:0:0:0:0:0:0:0:0
::
A node may use the loopback address listed in Table 3-1 to send an IPv6 packet to itself. The loopback
address in IPv6 is the same as the loopback address in IPv4. For more information, see Chapter 1,
“Overview.”
Note
You cannot assign the IPv6 loopback address to a physical interface. A packet that contains the IPv6
loopback address as its source or destination address must remain within the node that created the packet.
IPv6 routers do not forward packets that have the IPv6 loopback address as their source or destination
address.
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About IPv6
Note
You cannot assign an IPv6 unspecified address to an interface. You should not use the unspecified IPv6
addresses as destination addresses in IPv6 packets or the IPv6 routing header.
The IPv6-prefix is in the form documented in RFC 2373 where the IPv6 address is specified in
hexadecimal using 16-bit values between colons. The prefix length is a decimal value that indicates how
many of the high-order contiguous bits of the address comprise the prefix (the network portion of the
address). For example, 2001:0DB8:8086:6502::/32 is a valid IPv6 prefix.
IPv6 Unicast Addresses
An IPv6 unicast address is an identifier for a single interface on a single node. A packet that is sent to a
unicast address is delivered to the interface identified by that address. This section includes the following
topics:
•
Aggregatable Global Addresses, page 3-3
•
Link-Local Addresses, page 3-4
•
IPv4-Compatible IPv6 Addresses, page 3-5
•
Unique Local Addresses, page 3-5
•
Site-Local Address, page 3-6
Aggregatable Global Addresses
An aggregatable global address is an IPv6 address from the aggregatable global unicast prefix. The
structure of aggregatable global unicast addresses enables strict aggregation of routing prefixes that
limits the number of routing table entries in the global routing table. Aggregatable global addresses are
used on links that are aggregated upward through organizations and eventually to the Internet service
providers (ISPs).
Aggregatable global IPv6 addresses are defined by a global routing prefix, a subnet ID, and an interface
ID. Except for addresses that start with binary 000, all global unicast addresses have a 64-bit interface
ID. The IPv6 global unicast address allocation uses the range of addresses that start with binary value
001 (2000::/3). Figure 3-1 shows the structure of an aggregatable global address.
3
Aggregatable Global Address Format
Provider
Site
Host
45 bits
16 bits
64 bits
Global Routing Prefix
SLA
Interface ID
88119
Figure 3-1
001
Addresses with a prefix of 2000::/3 (001) through E000::/3 (111) are required to have 64-bit interface
identifiers in the extended universal identifier (EUI)-64 format. The Internet Assigned Numbers
Authority (IANA) allocates the IPv6 address space in the range of 2000::/16 to regional registries.
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About IPv6
The aggregatable global address consists of a 48-bit global routing prefix and a 16-bit subnet ID or
Site-Level Aggregator (SLA). In the IPv6 aggregatable global unicast address format document (RFC
2374), the global routing prefix included two other hierarchically structured fields called Top-Level
Aggregator (TLA) and Next-Level Aggregator (NLA). The IETF decided to remove the TLS and NLA
fields from the RFCs because these fields are policy based. Some existing IPv6 networks deployed
before the change might still use networks that are on the older architecture.
A subnet ID, which is a 16-bit subnet field, can be used by individual organizations to create a local
addressing hierarchy and to identify subnets. A subnet ID is similar to a subnet in IPv4, except that an
organization with an IPv6 subnet ID can support up to 65,535 individual subnets.
An interface ID identifies interfaces on a link. The interface ID is unique to the link. In many cases, an
interface ID is the same as or based on the link-layer address of an interface. Interface IDs used in
aggregatable global unicast and other IPv6 address types have 64 bits and are in the modified EUI-64
format.
Interface IDs are in the modified EUI-64 format in one of the following ways:
•
For all IEEE 802 interface types (for example, Ethernet and Fiber Distributed Data interfaces), the
first three octets (24 bits) are the Organizationally Unique Identifier (OUI) of the 48-bit link-layer
address (MAC address) of the interface, the fourth and fifth octets (16 bits) are a fixed hexadecimal
value of FFFE, and the last three octets (24 bits) are the last three octets of the MAC address. The
Universal/Local (U/L) bit, which is the seventh bit of the first octet, has a value of 0 or 1. Zero
indicates a locally administered identifier; 1 indicates a globally unique IPv6 interface identifier.
•
For all other interface types (for example, serial, loopback, ATM, and Frame Relay types), the
interface ID is similar to the interface ID for IEEE 802 interface types; however, the first MAC
address from the pool of MAC addresses in the router is used as the identifier (because the interface
does not have a MAC address).
For interfaces that use the Point-to-Point Protocol (PPP), where the interfaces at both ends of the
connection might have the same MAC address, the interface identifiers at both ends of the
connection are negotiated (picked randomly and, if necessary, reconstructed) until both
identifiers are unique. The first MAC address in the router is used as the identifier for interfaces
using PPP.
Note
If no IEEE 802 interface types are in the router, link-local IPv6 addresses are generated on the interfaces
in the router in the following sequence:
1.
The router is queried for MAC addresses (from the pool of MAC addresses in the router).
2.
If no MAC addresses are available in the router, the serial number of the router is used to form the
link-local addresses.
3.
If the serial number of the router cannot be used to form the link-local addresses, the router uses a
Message Digest 5 (MD5) hash to determine the MAC address of the router from the hostname of the
router.
Link-Local Addresses
A link-local address is an IPv6 unicast address that can be automatically configured on any interface
using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64
format. Link-local addresses are used in the Neighbor Discovery Protocol (NDP) and the stateless
autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes
do not need globally unique addresses to communicate. Figure 3-2 shows the structure of a link-local
address.
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About IPv6
IPv6 routers cannot forward packets that have link-local source or destination addresses to other links.
Figure 3-2
Link-Local Address Format
128 bits
0
Interface ID
1111 1110 10
52669
FE80::/10
10 bits
IPv4-Compatible IPv6 Addresses
An IPv4-compatible IPv6 address is an IPv6 unicast address that has zeros in the high-order 96 bits of
the address and an IPv4 address in the low-order 32 bits of the address. The format of an IPv4-compatible
IPv6 address is 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D. The entire 128-bit IPv4-compatible IPv6 address is
used as the IPv6 address of a node and the IPv4 address embedded in the low-order 32 bits is used as the
IPv4 address of the node. IPv4-compatible IPv6 addresses are assigned to nodes that support both the
IPv4 and IPv6 protocol stacks and are used in automatic tunnels. Figure 3-3 shows the structure of an
IPv4-compatible IPv6 address and a few acceptable formats for the address.
IPv4-Compatible IPv6 Address Format
96 bits
32 bits
0
IPv4 address
::192.168.30.1
= ::C0A8:1E01
52727
Figure 3-3
Unique Local Addresses
A unique local address is an IPv6 unicast address that is globally unique and is intended for local
communications. It is not expected to be routable on the global Internet and is routable inside of a limited
area, such as a site, and it may be routed between a limited set of sites. Applications may treat unique
local addresses like global scoped addresses.
A unique local address has the following characteristics:
•
It has a globally unique prefix (it has a high probability of uniqueness).
•
It has a well-known prefix to allow for easy filtering at site boundaries.
•
It allows sites to be combined or privately interconnected without creating any address conflicts or
requiring renumbering of interfaces that use these prefixes.
•
It is ISP-independent and can be used for communications inside of a site without having any
permanent or intermittent Internet connectivity.
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•
If it is accidentally leaked outside of a site through routing or the Domain Name Server (DNS), there
is no conflict with any other addresses.
Figure 3-4 shows the structure of a unique local address.
Figure 3-4
Unique Local Address Structure
/7
FC00
/48
/64
Interface ID
Global ID 41 bits
Local IPv6
Subnet prefix
Link prefix
• Prefix — FC00::/7 prefix to identify local IPv6 unicast addresses.
• Subnet ID — 16-bit subnet ID is an identifier of a subnet within the site.
• Interface ID — 64-bit ID
232389
• Global ID — 41-bit global identifier used to create a globally unique prefix.
Site-Local Address
Because RFC 3879 deprecates the use of site-local addresses, you should follow the recommendations
of unique local addressing (ULA) in RFC 4193 when you configure private IPv6 addresses.
IPv6 Anycast Addresses
An anycast address is an address that is assigned to a set of interfaces that belong to different nodes. A
packet sent to an anycast address is delivered to the closest interface—as defined by the routing protocols
in use—identified by the anycast address. Anycast addresses are syntactically indistinguishable from
unicast addresses because anycast addresses are allocated from the unicast address space. Assigning a
unicast address to more than one interface turns a unicast address into an anycast address. You must
configure the nodes to which the anycast address to recognize that the address is an anycast address.
Note
Anycast addresses can be used only by a router, not a host. Anycast addresses cannot be used as the
source address of an IPv6 packet.
Figure 3-5 shows the format of the subnet router anycast address; the address has a prefix concatenated
by a series of zeros (the interface ID). The subnet router anycast address can be used to reach a router
on the link that is identified by the prefix in the subnet router anycast address.
Figure 3-5
Subnet Router Anycast Address Format
Prefix
0000000000000...000
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About IPv6
IPv6 Multicast Addresses
An IPv6 multicast address is an IPv6 address that has a prefix of FF00::/8 (1111 1111). An IPv6
multicast address is an identifier for a set of interfaces that belong to different nodes. A packet sent to a
multicast address is delivered to all interfaces identified by the multicast address. The second octet
following the prefix defines the lifetime and scope of the multicast address. A permanent multicast
address has a lifetime parameter equal to 0; a temporary multicast address has a lifetime parameter equal
to 1. A multicast address that has the scope of a node, link, site, or organization, or a global scope, has
a scope parameter of 1, 2, 5, 8, or E, respectively. For example, a multicast address with the prefix
FF02::/16 is a permanent multicast address with a link scope. Figure 3-6 shows the format of the IPv6
multicast address.
Figure 3-6
IPv6 Multicast Address Format
128 bits
0
F
F
8 bits
4 bits
4 bits
Lifetime Scope
8 bits
Lifetime =
0 if permanent
1 if temporary
1 = node
2 = link
Scope = 5 = site
8 = organization
E = global
52671
1111 1111
Interface ID
IPv6 nodes (hosts and routers) are required to join (where received packets are destined for) the
following multicast groups:
•
All-nodes multicast group FF02:0:0:0:0:0:0:1 (the scope is link-local)
•
Solicited-node multicast group FF02:0:0:0:0:1:FF00:0000/104 for each of its assigned unicast and
anycast addresses
IPv6 routers must also join the all-routers multicast group FF02:0:0:0:0:0:0:2 (the scope is link-local).
The solicited-node multicast address is a multicast group that corresponds to an IPv6 unicast or anycast
address. IPv6 nodes must join the associated solicited-node multicast group for every unicast and
anycast address to which it is assigned. The IPv6 solicited-node multicast address has the prefix
FF02:0:0:0:0:1:FF00:0000/104 concatenated with the 24 low-order bits of a corresponding IPv6 unicast
or anycast address (see Figure 3-7). For example, the solicited-node multicast address that corresponds
to the IPv6 address 2037::01:800:200E:8C6C is FF02::1:FF0E:8C6C. Solicited-node addresses are used
in neighbor solicitation messages.
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Figure 3-7
IPv6 Solicited-Node Multicast Address Format
IPv6 unicast or anycast address
Prefix
Interface ID
24 bits
Solicited-node multicast address
FF02
0
1
FF
Lower 24
52672
128 bits
Note
IPv6 has no broadcast addresses. IPv6 multicast addresses are used instead of broadcast addresses.
IPv4 Packet Header
The base IPv4 packet header has 12 fields with a total size of 20 octets (160 bits) (see Figure 3-8). The
12 fields may be followed by an Options field, which is followed by a data portion that is usually the
transport-layer packet. The variable length of the Options field adds to the total size of the IPv4 packet
header. The shaded fields of the IPv4 packet header are not included in the IPv6 packet header.
Figure 3-8
Version
IPv4 Packet Header Format
Hd Len
Type of Service
Identification
Time to Live
Total Length
Flags
Protocol
Fragment Offset
Header Checksum
Source Address
20
octets
Destination Address
Padding
Data Portion
32 bits
Variable
length
51457
Options
Simplified IPv6 Packet Header
The base IPv6 packet header has 8 fields with a total size of 40 octets (320 bits) (see Figure 3-9).
Fragmentation is handled by the source of a packet and checksums at the data link layer and transport
layer are used. The User Datagram Protocol (UDP) checksum checks the integrity of the inner packet
and the base IPv6 packet header and Options field are aligned to 64 bits, which can facilitate the
processing of IPv6 packets.
Table 3-2 lists the fields in the base IPv6 packet header.
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Table 3-2
Base IPv6 Packet Header Fields
Field
Description
Version
Similar to the Version field in the IPv4 packet header, except that the
field lists number 6 for IPv6 instead of number 4 for IPv4.
Traffic Class
Similar to the Type of Service field in the IPv4 packet header. The
Traffic Class field tags packets with a traffic class that is used in
differentiated services.
Flow Label
New field in the IPv6 packet header. The Flow Label field tags
packets with a specific flow that differentiates the packets at the
network layer.
Payload Length
Similar to the Total Length field in the IPv4 packet header. The
Payload Length field indicates the total length of the data portion of
the packet.
Next Header
Similar to the Protocol field in the IPv4 packet header. The value of
the Next Header field determines the type of information that follows
the base IPv6 header. The type of information that follows the base
IPv6 header can be a transport-layer packet, for example, a TCP or
UDP packet, or an Extension Header, as shown in Figure 3-9.
Hop Limit
Similar to the Time to Live field in the IPv4 packet header. The value
of the Hop Limit field specifies the maximum number of routers that
an IPv6 packet can pass through before the packet is considered
invalid. Each router decrements the value by one. Because no
checksum is in the IPv6 header, the router can decrement the value
without needing to recalculate the checksum, which saves processing
resources.
Source Address
Similar to the Source Address field in the IPv4 packet header, except
that the field contains a 128-bit source address for IPv6 instead of a
32-bit source address for IPv4.
Destination Address
Similar to the Destination Address field in the IPv4 packet header,
except that the field contains a 128-bit destination address for IPv6
instead of a 32-bit destination address for IPv4.
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Figure 3-9
Version
IPv6 Packet Header Format
Traffic Class
Flow Label
Payload Length
Next Header
Hop Limit
Source Address
40
octets
Destination Address
Next Header
Extension Header information
Variable
length
51458
Data Portion
32 bits
Optional extension headers and the data portion of the packet are after the eight fields of the base IPv6
packet header. If present, each extension header is aligned to 64 bits. There is no fixed number of
extension headers in an IPv6 packet. Each extension header is identified by the Next Header field of the
previous header. Typically, the final extension header has a Next Header field of a transport-layer
protocol, such as TCP or UDP. Figure 3-10 shows the IPv6 extension header format.
Figure 3-10
IPv6 Extension Header Format
IPv6 base header
(40 octets)
IPv6
packet
Any number of
extension headers
Data (for example,
TCP or UDP)
Ext Header Length
Extension Header Data
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About IPv6
Table 3-3 lists the extension header types and their Next Header field values.
Table 3-3
IPv6 Extension Header Types
Header Type
Next Header
Value
Hop-by-hop options header
0
Header that is processed by all hops in the path of a
packet. When present, the hop-by-hop options header
always follows immediately after the base IPv6 packet
header.
Destination options header
60
Header that can follow any hop-by-hop options
header. The header is processed at the final destination
and at each visited address specified by a routing
header
Routing header
43
Header that is used for source routing.
Fragment header
44
Header that is used when a source fragments a packet
that is larger than the maximum transmission unit
(MTU) for the path between itself and a destination.
The Fragment header is used in each fragmented
packet.
Upper-layer headers
6 (TCP)
Headers that are used inside a packet to transport the
data. The two main transport protocols are TCP and
UDP.
17 (UDP)
Description
DNS for IPv6
IPv6 supports DNS record types that are supported in the DNS name-to-address and address-to-name
lookup processes. The DNS record types support IPv6 addresses (see Table 3-4).
Note
IPv6 also supports the reverse mapping of IPv6 addresses to DNS names.
Table 3-4
IPv6 DNS Record Types
Record Type
Description
Format
AAAA
Maps a hostname to an IPv6 address.
(Equivalent to an A record in IPv4.)
www.abc.test AAAA 3FFE:YYYY:C18:1::2
PTR
Maps an IPv6 address to a hostname.
(Equivalent to a PTR record in IPv4.)
2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.8.1.c.0
.y.y.y.y.e.f.f.3.ip6.int PTR www.abc.test
Path MTU Discovery for IPv6
As in IPv4, you can use path MTU discovery in IPv6 to allow a host to dynamically discover and adjust
to differences in the MTU size of every link along a data path. In IPv6, however, fragmentation is
handled by the source of a packet when the path MTU of one link along a given data path is not large
enough to accommodate the size of the packets. Having IPv6 hosts handle packet fragmentation saves
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About IPv6
IPv6 router processing resources and helps IPv6 networks run more efficiently. Once the path MTU is
reduced by the arrival of an ICMP Too Big message, Cisco NX-OS retains the lower value. The
connection does not increase the segment size to gauge the throughput.
Note
In IPv6, the minimum link MTU is 1280 octets. We recommend that you use an MTU value of 1500
octets for IPv6 links.
CDP IPv6 Address Support
You can use the Cisco Discovery Protocol (CDP) IPv6 address support for the neighbor information
feature to transfer IPv6 addressing information between two Cisco devices. Cisco Discovery Protocol
support for IPv6 addresses provides IPv6 information to network management products and
troubleshooting tools.
LPM Routing Modes
By default, Cisco NX-OS programs routes in a hierarchical fashion to allow for the longest prefix match
(LPM) on the device. However, you can configure the device for different routing modes to support
significantly more LPM route entries.
The following tables list the LPM routing modes that are supported on the Cisco Nexus 9300 Series and
9500 Series switches.
Table 3-5
LPM Routing Modes for Cisco Nexus 9300 Series Switches
LPM Routing Mode
Broadcom T2 Mode
Default system routing mode
3
Table 3-6
CLI Command
LPM Routing Modes for Cisco Nexus 9500 Series Switches
LPM Routing Mode
Broadcom T2 Mode
CLI Command
Default system routing mode
3 (for line cards);
4 (for fabric modules)
Max-host routing mode
2 (for line cards);
system routing max-mode host
3 (for fabric modules)
Nonhierarchical routing mode
3 (for line cards);
system routing non-hierarchical-routing
4 with max-l3-mode [max-l3-mode]
option (for line cards)
64-bit ALPM routing mode
Submode of mode 4
(for fabric modules)
system routing mode hierarchical
64b-alpm
For detailed configuration information, see the “Configuring IPv6” section on page 3-13.
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Licensing Requirements for IPv6
Virtualization Support
IPv6 supports virtual routing and forwarding (VRF) instances.
Licensing Requirements for IPv6
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
IPv6 requires no license. Any feature not included in a license package is bundled with the nx-os image and
is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see
the Cisco NX-OS Licensing Guide.
Prerequisites for IPv6
IPv6 has the following prerequisites:
•
You must be familiar with IPv6 basics such as IPv6 addressing and IPv6 header information.
•
Ensure that you follow the memory/processing guidelines when you make a device a dual-stack
device (IPv4/IPv6).
Guidelines and Limitations for IPv6
IPv6 has the following configuration guidelines and limitations:
•
IPv6 packets are transparent to Layer 2 LAN switches because the switches do not examine Layer
3 packet information before forwarding IPv6 frames. IPv6 hosts can be directly attached to Layer 2
LAN switches.
•
You can configure multiple IPv6 global addresses within the same prefix on an interface. However,
multiple IPv6 link-local addresses on an interface are not supported.
•
Because RFC 3879 deprecates the use of site-local addresses, you should configure private IPv6
addresses according to the recommendations of unique local addressing (ULA) in RFC 4193.
Configuring IPv6
This section includes the following topics:
•
Configuring IPv6 Addressing, page 3-14
•
Configuring Max-Host Routing Mode (Cisco Nexus 9500 Series Switches Only), page 3-16
•
Configuring Nonhierarchical Routing Mode (Cisco Nexus 9500 Series Switches Only), page 3-17
•
Configuring 64-Bit ALPM Routing Mode (Cisco Nexus 9500 Series Switches Only), page 3-18
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Configuring IPv6
Note
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring IPv6 Addressing
You must configure an IPv6 address on an interface so that the interface can forward IPv6 traffic. When
you configure a global IPv6 address on an interface, it automatically configures a link-local address and
activates IPv6 for that interface.
SUMMARY STEPS
1.
configure terminal
2.
interface ethernet number
3.
ipv6 address {addr [eui64] [route-preference preference] [secondary] tag tag-id]]
or
ipv6 address ipv6-address use-link-local-only
4.
(Optional) show ipv6 interface
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface ethernet number
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/3
switch(config-if)#
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Step 3
Command
Purpose
ipv6 address {addr [eui64]
[route-preference preference]
[secondary] tag tag-id]
or
ipv6 address ipv6-address
use-link-local-only
Specifies an IPv6 address assigned to the interface and
enables IPv6 processing on the interface.
Example:
switch(config-if)# ipv6 address
2001:0DB8::1/10
or
switch(config-if)# ipv6 address
use-link-local-only
Entering the ipv6 address command configures global
IPv6 addresses with an interface identifier (ID) in the
low-order 64 bits of the IPv6 address. Only the 64-bit
network prefix for the address needs to be specified;
the last 64 bits are automatically computed from the
interface ID.
Entering the ipv6 address use-link-local-only
command configures a link-local address on the
interface that is used instead of the link-local address
that is automatically configured when IPv6 is enabled
on the interface.
This command enables IPv6 processing on an
interface without configuring an IPv6 address.
Step 4
(Optional) Displays interfaces configured for IPv6.
show ipv6 interface
Example:
switch(config-if)# show ipv6 interface
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to configure an IPv6 address:
switch# configure terminal
switch(config)# interface ethernet 3/1
switch(config-if)# ipv6 address ?
A:B::C:D/LEN IPv6 prefix format: xxxx:xxxx/ml, xxxx:xxxx::/ml,
xxxx::xx/128
use-link-local-only Enable IPv6 on interface using only a single link-local
address
switch(config-if)# ipv6 address 2001:db8::/64 eui64
This example shows how to display an IPv6 interface:
switch(config-if)# show ipv6 interface ethernet 3/1
Ethernet3/1, Interface status: protocol-down/link-down/admin-down, iod: 36
IPv6 address: 2001:db8:0000:0000:0218:baff:fed8:239d
IPv6 subnet: 2001:db8::/64
IPv6 link-local address: fe80::0218:baff:fed8:239d (default)
IPv6 multicast routing: disabled
IPv6 multicast groups locally joined:
ff02::0001:ffd8:239d ff02::0002 ff02::0001 ff02::0001:ffd8:239d
IPv6 multicast (S,G) entries joined: none
IPv6 MTU: 1500 (using link MTU)
IPv6 RP inbound packet-filtering policy: none
IPv6 RP outbound packet-filtering policy: none
IPv6 inbound packet-filtering policy: none
IPv6 outbound packet-filtering policy: none
IPv6 interface statistics last reset: never
IPv6 interface RP-traffic statistics: (forwarded/originated/consumed)
Unicast packets: 0/0/0
Unicast bytes: 0/0/0
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Multicast packets: 0/0/0
Multicast bytes: 0/0/0
Configuring Max-Host Routing Mode (Cisco Nexus 9500 Series Switches Only)
By default, the device programs routes in a hierarchical fashion (with fabric modules configured to be
in mode 4 and line card modules configured to be in mode 3), which allows for longest prefix match
(LPM) and host scale on the device.
You can modify the default LPM and host scale to program more hosts in the system, as might be
required when the node is positioned as a Layer-2 to Layer-3 boundary node.
Note
If you want to further scale the entries in the LPM table, see the “Configuring Nonhierarchical Routing
Mode (Cisco Nexus 9500 Series Switches Only)” section on page 3-17 to configure the device to
program all of the Layer 3 IPv4 and IPv6 routes on the line cards and none of the routes on the fabric
modules.
Note
This configuration impacts both the IPv4 and IPv6 address families.
Note
For the max-host routing mode scale numbers, see the Cisco Nexus 9000 Series NX-OS Verified
Scalability Guide.
SUMMARY STEPS
1.
configure terminal
2.
[no] system routing max-mode host
3.
(Optional) show forwarding route summary
4.
copy running-config startup-config
5.
reload
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] system routing max-mode host
Example:
switch(config)# system routing max-mode
host
Puts the line cards in Broadcom T2 mode 2 and the
fabric modules in Broadcom T2 mode 3 to increase the
number of supported hosts.
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Configuring IPv6
Configuring IPv6
Step 3
Command
Purpose
show forwarding route summary
(Optional) Displays the LPM mode.
Example:
switch(config)# show forwarding route
summary
Step 4
copy running-config startup-config
Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Step 5
Reboots the entire device.
reload
Example:
switch(config)# reload
Configuring Nonhierarchical Routing Mode (Cisco Nexus 9500 Series Switches
Only)
If the host scale is small (as in a pure Layer 3 deployment), we recommend programming the longest
prefix match (LPM) routes in the line cards to improve convergence performance. Doing so programs
routes and hosts in the line cards and does not program any routes in the fabric modules.
Note
This configuration impacts both the IPv4 and IPv6 address families.
SUMMARY STEPS
1.
configure terminal
2.
[no] system routing non-hierarchical-routing [max-l3-mode]
3.
(Optional) show forwarding route summary
4.
copy running-config startup-config
5.
reload
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] system routing
non-hierarchical-routing [max-l3-mode]
Example:
switch(config)# system routing
non-hierarchical-routing max-l3-mode
Puts the line cards in Broadcom T2 mode 3 (or
Broadcom T2 mode 4 if you use the max-l3-mode
option) to support a larger LPM scale. As a result, all
of the IPv4 and IPv6 routes will be programmed on the
line cards rather than on the fabric modules.
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Configuring IPv6
Configuring IPv6
Step 3
Command
Purpose
show forwarding route summary
(Optional) Displays the LPM mode.
Example:
switch(config)# show forwarding route
summary
Mode 3:
120K IPv4 Host table
16k LPM table (> 65 < 127 1k entry
reserved)
Mode 4:
16k V4 host/4k V6 host
128k v4 LPM/20K V6 LPM
Step 4
copy running-config startup-config
Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Step 5
reload
Reboots the entire device.
Example:
switch(config)# reload
Configuring 64-Bit ALPM Routing Mode (Cisco Nexus 9500 Series Switches
Only)
You can use the 64-bit algorithmic longest prefix match (ALPM) feature to manage IPv4 and IPv6 route
table entries. In 64-bit ALPM routing mode, the device can store significantly more route entries. Using
this mode, you can program one of the following:
•
80,000 IPv6 entries and no IPv4 entries
•
No IPv6 entries and 128,000 IPv4 entries
•
x IPv6 entries and y IPv4 entries, where 2x + y <= 128,000
Note
This configuration impacts both the IPv4 and IPv6 address families.
Note
For the 64-bit ALPM routing mode scale numbers, see the Cisco Nexus 9000 Series NX-OS Verified
Scalability Guide.
SUMMARY STEPS
1.
configure terminal
2.
[no] system routing mode hierarchical 64b-alpm
3.
(Optional) show forwarding route summary
4.
copy running-config startup-config
5.
reload
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Configuring IPv6
Verifying the IPv6 Configuration
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Step 3
Example:
switch(config)# system routing mode
hierarchical 64b-alpm
Causes all IPv4 and IPv6 LPM routes with a mask
length that is less than or equal to 64 to be
programmed in the fabric module. All host routes for
IPv4 and IPv6 and all LPM routes with a mask length
of 65 through 127 are programmed in the line card.
show forwarding route summary
(Optional) Displays the LPM mode.
[no] system routing mode hierarchical
64b-alpm
Example:
switch(config)# show forwarding route
summary
Step 4
Saves this configuration change.
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
Step 5
Reboots the entire device.
reload
Example:
switch(config)# reload
Verifying the IPv6 Configuration
To display the IPv6 configuration, perform one of the following tasks:
Command
Purpose
show ipv6 interface
Displays IPv6-related interface information.
show ipv6 adjacency
Displays the adjacency table.
Configuration Examples for IPv6
This example shows how to configure IPv6:
configure terminal
interface ethernet 3/1
ipv6 address 2001:db8::/64 eui64
ipv6 nd reachable-time 10
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CH A P T E R
4
Configuring DNS
This chapter describes how to configure the Domain Name Server (DNS) client on the Cisco NX-OS
device.
This chapter includes the following sections:
•
About DNS Clients, page 4-1
•
Licensing Requirements for DNS Clients, page 4-3
•
Prerequisites for DNS Clients, page 4-3
•
Guidelines and Limitations for DNS, page 4-3
•
Default Settings, page 4-3
•
Configuring DNS Clients, page 4-3
•
Verifying the DNS Client Configuration, page 4-7
•
Configuration Examples for the DNS Client, page 4-7
About DNS Clients
This section includes the following topics:
•
DNS Client Overview, page 4-1
•
High Availability, page 4-2
•
Virtualization Support, page 4-2
DNS Client Overview
If your network devices require connectivity with devices in networks for which you do not control the
name assignment, you can assign device names that uniquely identify your devices within the entire
internetwork using the domain name server (DNS). DNS uses a hierarchical scheme for establishing host
names for network nodes, which allows local control of the segments of the network through a
client-server scheme. The DNS system can locate a network device by translating the hostname of the
device into its associated IP address.
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About DNS Clients
On the Internet, a domain is a portion of the naming hierarchy tree that refers to general groupings of
networks based on the organization type or geography. Domain names are pieced together with periods
(.) as the delimiting characters. For example, Cisco is a commercial organization that the Internet
identifies by a com domain, so its domain name is cisco.com. A specific hostname in this domain, the
File Transfer Protocol (FTP) system, for example, is identified as ftp.cisco.com.
Name Servers
Name servers keep track of domain names and know the parts of the domain tree for which they have
complete information. A name server may also store information about other parts of the domain tree.
To map domain names to IP addresses in Cisco NX-OS, you must identify the hostnames, specify a name
server, and enable the DNS service.
Cisco NX-OS allows you to statically map IP addresses to domain names. You can also configure Cisco
NX-OS to use one or more domain name servers to find an IP address for a host name.
DNS Operation
A name server handles client-issued queries to the DNS server for locally defined hosts within a
particular zone as follows:
•
An authoritative name server responds to DNS user queries for a domain name that is under its zone
of authority by using the permanent and cached entries in its own host table. If the query is for a
domain name that is under its zone of authority but for which it does not have any configuration
information, the authoritative name server replies that no such information exists.
•
A name server that is not configured as the authoritative name server responds to DNS user queries
by using information that it has cached from previously received query responses. If no router is
configured as the authoritative name server for a zone, queries to the DNS server for locally defined
hosts receive nonauthoritative responses.
Name servers answer DNS queries (forward incoming DNS queries or resolve internally generated DNS
queries) according to the forwarding and lookup parameters configured for the specific domain.
High Availability
Cisco NX-OS supports stateless restarts for the DNS client. After a reboot or supervisor switchover,
Cisco NX-OS applies the running configuration.
Virtualization Support
Cisco NX-OS supports multiple instances of the DNS clients that run on the same system. You can
configure a DNS client. You can optionally have a different DNS client configuration in each virtual
routing and forwarding (VRF) instance.
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Configuring DNS
Licensing Requirements for DNS Clients
Licensing Requirements for DNS Clients
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
DNS requires no license. Any feature not included in a license package is bundled with the nx-os image and
is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see
the Cisco NX-OS Licensing Guide.
Prerequisites for DNS Clients
The DNS client has the following prerequisites:
•
You must have a DNS name server on your network.
Guidelines and Limitations for DNS
The DNS client has the following configuration guidelines and limitations:
•
You configure the DNS client in a specific VRF. If you do not specify a VRF, Cisco NX-OS uses the
default VRF.
Default Settings
Table 4-1 lists the default settings for DNS client parameters.
Table 4-1
Default DNS Client Parameters
Parameters
Default
DNS client
Enabled
Configuring DNS Clients
This section includes the following topics:
Note
•
Configuring the DNS Client, page 4-4
•
Configuring Virtualization, page 4-5
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
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Configuring DNS Clients
Configuring the DNS Client
You can configure the DNS client to use a DNS server on your network.
BEFORE YOU BEGIN
Ensure that you have a domain name server on your network.
SUMMARY STEPS
1.
configure terminal
2.
ip host name address1 [address2... address6]
3.
(Optional) ip domain-name name [use-vrf vrf-name]
4.
(Optional) ip domain-list name [use-vrf vrf-name]
5.
(Optional) ip name-server address1 [address2... address6] [use-vrf vrf-name]
6.
(Optional) ip domain lookup
7.
(Optional) show hosts
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
ip host name address1 [address2...
address6]
Example:
switch(config)# ip host cisco-rtp
192.0.2.1
Step 3
ip domain-name name [use-vrf vrf-name]
Example:
switch(config)# ip domain-name
myserver.com
Defines up to six static hostname-to-address mappings
in the hostname cache. The address can be either an
IPv4 address or an IPv6 address.
(Optional) Defines the default domain name that Cisco
NX-OS uses to complete unqualified host names. You
can optionally define a VRF that Cisco NX-OS uses to
resolve this domain name if it cannot be resolved in the
VRF that you configured this domain name under.
Cisco NX-OS appends the default domain name to any
hostname that does not contain a complete domain
name before starting a domain-name lookup.
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Configuring DNS Clients
Step 4
Command
Purpose
ip domain-list name [use-vrf vrf-name]
(Optional) Defines additional domain names that
Cisco NX-OS can use to complete unqualified
hostnames. You can optionally define a VRF that Cisco
NX-OS uses to resolve these domain names if they
cannot be resolved in the VRF that you configured this
domain name under.
Example:
switch(config)# ip domain-list
mycompany.com
Cisco NX-OS uses each entry in the domain list to
append that domain name to any hostname that does
not contain a complete domain name before starting a
domain-name lookup. Cisco NX-OS continues this
process for each entry in the domain list until it finds a
match.
Step 5
Step 6
ip name-server address1 [address2...
address6] [use-vrf vrf-name]
(Optional) Defines up to six name servers. The address
can be either an IPv4 address or an IPv6 address.
Example:
switch(config)# ip name-server
192.0.2.22
You can optionally define a VRF that Cisco NX-OS
uses to reach this name server if it cannot be reached
in the VRF that you configured this name server under.
ip domain-lookup
(Optional) Enables DNS-based address translation.
This feature is enabled by default.
Example:
switch(config)# ip domain-lookup
Step 7
(Optional) Displays information about DNS.
show hosts
Example:
switch(config)# show hosts
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to configure a default domain name and enable DNS lookup:
switch# configure terminal
switch(config)# ip domain-name cisco.com
switch(config)# ip name-server 192.0.2.1 use-vrf management
switch(config)# ip domain-lookup
switch(config)# copy running-config startup-config
Configuring Virtualization
You can configure a DNS client within a VRF. If you do not enter VRF configuration mode, your DNS
client configuration applies to the default VRF.
You can optionally configure a DNS client to use a specified VRF other than the VRF under which you
configured the DNS client as a backup VRF. For example, you can configure a DNS client in the Red
VRF but use the Blue VRF to communicate with the DNS server if the server cannot be reached through
the Red VRF.
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Configuring DNS Clients
BEFORE YOU BEGIN
Ensure that you have a domain name server on your network.
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
(Optional) ip domain-name name [use-vrf vrf-name]
4.
(Optional) ip domain-list name [use-vrf vrf-name]
5.
(Optional) ip name-server server-address1 [server-address2... server-address6] [use-vrf vrf-name]
6.
(Optional) show hosts
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Creates a VRF and enters VRF configuration mode.
Example:
switch(config)# vrf context Red
switch(config-vrf)#
Step 3
ip domain-name name [use-vrf vrf-name]
Example:
switch(config-vrf)# ip domain-name
myserver.com
(Optional) Defines the default domain name server that
Cisco NX-OS uses to complete unqualified hostnames.
You can optionally define a VRF that Cisco NX-OS
uses to resolve this domain name server if it cannot be
resolved in the VRF under which you configured this
domain name.
Cisco NX-OS appends the default domain name to any
hostname that does not contain a complete domain
name before starting a domain-name lookup.
Step 4
ip domain-list name [use-vrf vrf-name]
Example:
switch(config-vrf)# ip domain-list
mycompany.com
(Optional) Defines additional domain name servers
that Cisco NX-OS can use to complete unqualified
hostnames. You can optionally define a VRF that Cisco
NX-OS uses to resolve this domain name server if it
cannot be resolved in the VRF under which you
configured this domain name.
Cisco NX-OS uses each entry in the domain list to
append that domain name to any hostname that does
not contain a complete domain name before starting a
domain-name lookup. Cisco NX-OS continues this
process for each entry in the domain list until it finds a
match.
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Verifying the DNS Client Configuration
Step 5
Step 6
Command
Purpose
ip name-server address1 [address2...
address6] [use-vrf vrf-name]
(Optional) Defines up to six name servers. The address
can be either an IPv4 address or an IPv6 address.
Example:
switch(config-vrf)# ip name-server
192.0.2.22
You can optionally define a VRF that Cisco NX-OS
uses to reach this name server if it cannot be reached
in the VRF that you configured this name server under.
show hosts
(Optional) Displays information about DNS.
Example:
switch(config-vrf)# show hosts
Step 7
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-vrf)# copy running-config
startup-config
This example shows how to configure a default domain name and enable DNS lookup within a VRF:
switch# configure terminal
switch(config)# vrf context Red
switch(config-vrf)# ip domain-name cisco.com
switch(config-vrf)# ip name-server 192.0.2.1 use-vrf management
switch(config-vrf)# copy running-config startup-config
Verifying the DNS Client Configuration
To display the DNS client configuration, perform one of the following tasks:
Command
Purpose
show hosts
Displays information about DNS.
Configuration Examples for the DNS Client
This example shows how to establish a domain list with several alternate domain names:
ip domain-list csi.com
ip domain-list telecomprog.edu
ip domain-list merit.edu
This example shows how to configure the hostname-to-address mapping process and specify IP
DNS-based translation. The example also configures the addresses of the name servers and the default
domain name.
ip domain-lookup
ip name-server 192.168.1.111 192.168.1.2
ip domain-name cisco.com
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Configuring DNS
CH A P T E R
5
Configuring OSPFv2
This chapter describes how to configure Open Shortest Path First version 2 (OSPFv2) for IPv4 networks
on the Cisco NX-OS device.
This chapter includes the following sections:
•
About OSPFv2, page 5-1
•
Licensing Requirements for OSPFv2, page 5-13
•
Prerequisites for OSPFv2, page 5-13
•
Guidelines and Limitations for OSPFv2, page 5-13
•
Default Settings, page 5-14
•
Configuring Basic OSPFv2, page 5-14
•
Configuring Advanced OSPFv2, page 5-23
•
Verifying the OSPFv2 Configuration, page 5-46
•
Monitoring OSPFv2, page 5-47
•
Configuration Examples for OSPFv2, page 5-47
•
Additional References, page 5-48
About OSPFv2
OSPFv2 is an IETF link-state protocol (see the “Link-State Protocols” section on page 1-9) for IPv4
networks. An OSPFv2 router sends a special message, called a hello packet, out each OSPF-enabled
interface to discover other OSPFv2 neighbor routers. Once a neighbor is discovered, the two routers
compare information in the Hello packet to determine if the routers have compatible configurations. The
neighbor routers try to establish adjacency, which means that the routers synchronize their link-state
databases to ensure that they have identical OSPFv2 routing information. Adjacent routers share
link-state advertisements (LSAs) that include information about the operational state of each link, the
cost of the link, and any other neighbor information. The routers then flood these received LSAs out
every OSPF-enabled interface so that all OSPFv2 routers eventually have identical link-state databases.
When all OSPFv2 routers have identical link-state databases, the network is converged (see the
“Convergence” section on page 1-6). Each router then uses Dijkstra’s Shortest Path First (SPF)
algorithm to build its route table.
You can divide OSPFv2 networks into areas. Routers send most LSAs only within one area, which
reduces the CPU and memory requirements for an OSPF-enabled router.
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About OSPFv2
OSPFv2 supports IPv4, while OSPFv3 supports IPv6. For more information, see Chapter 6,
“Configuring OSPFv3.”
Note
OSPFv2 on Cisco NX-OS supports RFC 2328. This RFC introduced a different method to calculate route
summary costs which is not compatible with the calculation used by RFC 1583. RFC 2328 also
introduced different selection criteria for AS-external paths. It is important to ensure that all routers
support the same RFC. Use the rfc1583compatibility command if your network includes routers that
are only compliant with RFC 1583. The default supported RFC standard for OSPFv2 might be different
for Cisco NX-OS and Cisco IOS. You must make adjustments to set the values identically. See the
“OSPF RFC Compatibility Mode Example” section on page 5-47 for more information.
This section includes the following topics:
•
Hello Packet, page 5-2
•
Neighbors, page 5-3
•
Adjacency, page 5-3
•
Designated Routers, page 5-3
•
Areas, page 5-4
•
Link-State Advertisements, page 5-5
•
OSPFv2 and the Unicast RIB, page 5-7
•
Authentication, page 5-7
•
Advanced Features, page 5-8
Hello Packet
OSPFv2 routers periodically send Hello packets on every OSPF-enabled interface. The hello interval
determines how frequently the router sends these Hello packets and is configured per interface. OSPFv2
uses Hello packets for the following tasks:
•
Neighbor discovery
•
Keepalives
•
Bidirectional communications
•
Designated router election (see the “Designated Routers” section on page 5-3)
The Hello packet contains information about the originating OSPFv2 interface and router, including the
assigned OSPFv2 cost of the link, the hello interval, and optional capabilities of the originating router.
An OSPFv2 interface that receives these Hello packets determines if the settings are compatible with the
receiving interface settings. Compatible interfaces are considered neighbors and are added to the
neighbor table (see the “Neighbors” section on page 5-3).
Hello packets also include a list of router IDs for the routers that the originating interface has
communicated with. If the receiving interface sees its own router ID in this list, bidirectional
communication has been established between the two interfaces.
OSPFv2 uses Hello packets as a keepalive message to determine if a neighbor is still communicating. If
a router does not receive a Hello packet by the configured dead interval (usually a multiple of the hello
interval), then the neighbor is removed from the local neighbor table.
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About OSPFv2
Neighbors
An OSPFv2 interface must have a compatible configuration with a remote interface before the two can
be considered neighbors. The two OSPFv2 interfaces must match the following criteria:
•
Hello interval
•
Dead interval
•
Area ID (see the “Areas” section on page 5-4)
•
Authentication
•
Optional capabilities
If there is a match, the following information is entered into the neighbor table:
•
Neighbor ID—The router ID of the neighbor.
•
Priority—Priority of the neighbor. The priority is used for designated router election (see the
“Designated Routers” section on page 5-3).
•
State—Indication of whether the neighbor has just been heard from, is in the process of setting up
bidirectional communications, is sharing the link-state information, or has achieved full adjacency.
•
Dead time—Indication of the time since the last Hello packet was received from this neighbor.
•
IP Address—The IP address of the neighbor.
•
Designated Router—Indication of whether the neighbor has been declared as the designated router
or as the backup designated router (see the “Designated Routers” section on page 5-3).
•
Local interface—The local interface that received the Hello packet for this neighbor.
Adjacency
Not all neighbors establish adjacency. Depending on the network type and designated router
establishment, some neighbors become fully adjacent and share LSAs with all their neighbors, while
other neighbors do not. For more information, see the “Designated Routers” section on page 5-3.
Adjacency is established using Database Description packets, Link State Request packets, and Link
State Update packets in OSPF. The Database Description packet includes just the LSA headers from the
link-state database of the neighbor (see the “Link-State Database” section on page 5-7). The local router
compares these headers with its own link-state database and determines which LSAs are new or updated.
The local router sends a Link State Request packet for each LSA that it needs new or updated information
on. The neighbor responds with a Link State Update packet. This exchange continues until both routers
have the same link-state information.
Designated Routers
Networks with multiple routers present a unique situation for OSPF. If every router floods the network
with LSAs, the same link-state information is sent from multiple sources. Depending on the type of
network, OSPFv2 might use a single router, the designated router (DR), to control the LSA floods and
represent the network to the rest of the OSPFv2 area (see the “Areas” section on page 5-4). If the DR
fails, OSPFv2 selects a backup designated router (BDR). If the DR fails, OSPFv2 uses the BDR.
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About OSPFv2
Network types are as follows:
•
Point-to-point—A network that exists only between two routers. All neighbors on a point-to-point
network establish adjacency and there is no DR.
•
Broadcast—A network with multiple routers that can communicate over a shared medium that
allows broadcast traffic, such as Ethernet. OSPFv2 routers establish a DR and BDR that controls
LSA flooding on the network. OSPFv2 uses the well-known IPv4 multicast addresses 224.0.0.5 and
a MAC address of 0100.5300.0005 to communicate with neighbors.
The DR and BDR are selected based on the information in the Hello packet. When an interface sends a
Hello packet, it sets the priority field and the DR and BDR field if it knows who the DR and BDR are.
The routers follow an election procedure based on which routers declare themselves in the DR and BDR
fields and the priority field in the Hello packet. As a final tie breaker, OSPFv2 chooses the highest router
IDs as the DR and BDR.
All other routers establish adjacency with the DR and the BDR and use the IPv4 multicast address
224.0.0.6 to send LSA updates to the DR and BDR. Figure 5-1 shows this adjacency relationship
between all routers and the DR.
DRs are based on a router interface. A router might be the DR for one network and not for another
network on a different interface.
DR in Multi-Access Network
Router A
Router B
Router D
or DR
Router C
Router E
= Multi-access network
= Logical connectivity to Designated Router for OSPF
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Figure 5-1
Areas
You can limit the CPU and memory requirements that OSPFv2 puts on the routers by dividing an
OSPFv2 network into areas. An area is a logical division of routers and links within an OSPFv2 domain
that creates separate subdomains. LSA flooding is contained within an area, and the link-state database
is limited to links within the area. You can assign an area ID to the interfaces within the defined area.
The Area ID is a 32-bit value that you can enter as a number or in dotted decimal notation, such as
10.2.3.1.
Cisco NX-OS always displays the area in dotted decimal notation.
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If you define more than one area in an OSPFv2 network, you must also define the backbone area, which
has the reserved area ID of 0. If you have more than one area, then one or more routers become area
border routers (ABRs). An ABR connects to both the backbone area and at least one other defined area
(see Figure 5-2).
Figure 5-2
OSPFv2 Areas
ABR1
Area 3
Area 0
ABR2
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Area 5
The ABR has a separate link-state database for each area to which it connects. The ABR sends Network
Summary (type 3) LSAs (see the “Route Summarization” section on page 5-10) from one connected area
to the backbone area. The backbone area sends summarized information about one area to another area.
In Figure 5-2, Area 0 sends summarized information about Area 5 to Area 3.
OSPFv2 defines one other router type: the autonomous system boundary router (ASBR). This router
connects an OSPFv2 area to another autonomous system. An autonomous system is a network controlled
by a single technical administration entity. OSPFv2 can redistribute its routing information into another
autonomous system or receive redistributed routes from another autonomous system. For more
information, see the “Advanced Features” section on page 5-8.
Link-State Advertisements
OSPFv2 uses link-state advertisements (LSAs) to build its routing table.
This section includes the following topics:
•
LSA Types, page 5-5
•
Link Cost, page 5-6
•
Flooding and LSA Group Pacing, page 5-6
•
Link-State Database, page 5-7
•
Opaque LSAs, page 5-7
LSA Types
Table 5-1 shows the LSA types supported by Cisco NX-OS.
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Table 5-1
LSA Types
Type
Name
Description
1
Router LSA
LSA sent by every router. This LSA includes the state and the cost of all
links and a list of all OSPFv2 neighbors on the link. Router LSAs trigger an
SPF recalculation. Router LSAs are flooded to local OSPFv2 area.
2
Network LSA
LSA sent by the DR. This LSA lists all routers in the multi-access network.
Network LSAs trigger an SPF recalculation. See the “Designated Routers”
section on page 5-3.
3
Network
Summary LSA
LSA sent by the area border router to an external area for each destination
in the local area. This LSA includes the link cost from the area border router
to the local destination. See the “Areas” section on page 5-4.
4
ASBR Summary LSA sent by the area border router to an external area. This LSA advertises
LSA
the link cost to the ASBR only. See the “Areas” section on page 5-4.
5
AS External
LSA
LSA generated by the ASBR. This LSA includes the link cost to an external
autonomous system destination. AS External LSAs are flooded throughout
the autonomous system. See the “Areas” section on page 5-4.
7
NSSA External
LSA
LSA generated by the ASBR within a not-so-stubby area (NSSA). This LSA
includes the link cost to an external autonomous system destination. NSSA
External LSAs are flooded only within the local NSSA. See the “Areas”
section on page 5-4.
9–11
Opaque LSAs
LSA used to extend OSPF. See the “Opaque LSAs” section on page 5-7.
Link Cost
Each OSPFv2 interface is assigned a link cost. The cost is an arbitrary number. By default, Cisco NX-OS
assigns a cost that is the configured reference bandwidth divided by the interface bandwidth. By default,
the reference bandwidth is 40 Gb/s. The link cost is carried in the LSA updates for each link.
Flooding and LSA Group Pacing
When an OSPFv2 router receives an LSA, it forwards that LSA out every OSPF-enabled interface,
flooding the OSPFv2 area with this information. This LSA flooding guarantees that all routers in the
network have identical routing information. LSA flooding depends on the OSPFv2 area configuration
(see the “Areas” section on page 5-4). The LSAs are flooded based on the link-state refresh time (every
30 minutes by default). Each LSA has its own link-state refresh time.
You can control the flooding rate of LSA updates in your network by using the LSA group pacing
feature. LSA group pacing can reduce high CPU or buffer usage. This feature groups LSAs with similar
link-state refresh times to allow OSPFv2 to pack multiple LSAs into an OSPFv2 Update message.
By default, LSAs with link-state refresh times within 10 seconds of each other are grouped together. You
should lower this value for large link-state databases or raise it for smaller databases to optimize the
OSPFv2 load on your network.
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Link-State Database
Each router maintains a link-state database for the OSPFv2 network. This database contains all the
collected LSAs, and includes information on all the routes through the network. OSPFv2 uses this
information to calculate the best path to each destination and populates the routing table with these best
paths.
LSAs are removed from the link-state database if no LSA update has been received within a set interval,
called the MaxAge. Routers flood a repeat of the LSA every 30 minutes to prevent accurate link-state
information from being aged out. Cisco NX-OS supports the LSA grouping feature to prevent all LSAs
from refreshing at the same time. For more information, see the “Flooding and LSA Group Pacing”
section on page 5-6.
Opaque LSAs
Opaque LSAs allow you to extend OSPF functionality. Opaque LSAs consist of a standard LSA header
followed by application-specific information. This information might be used by OSPFv2 or by other
applications. OSPFv2 uses Opaque LSAs to support OSPFv2 Graceful Restart capability (see the “High
Availability and Graceful Restart” section on page 5-11). Three Opaque LSA types are defined as
follows:
•
LSA type 9—Flooded to the local network.
•
LSA type 10—Flooded to the local area.
•
LSA type 11—Flooded to the local autonomous system.
OSPFv2 and the Unicast RIB
OSPFv2 runs the Dijkstra shortest path first algorithm on the link-state database. This algorithm selects
the best path to each destination based on the sum of all the link costs for each link in the path. The
resultant shortest path for each destination is then put in the OSPFv2 route table. When the OSPFv2
network is converged, this route table feeds into the unicast Routing Information Base (RIB). OSPFv2
communicates with the unicast RIB to do the following:
•
Add or remove routes
•
Handle route redistribution from other protocols
•
Provide convergence updates to remove stale OSPFv2 routes and for stub router advertisements (see
the “OSPFv2 Stub Router Advertisements” section on page 5-12)
OSPFv2 also runs a modified Dijkstra algorithm for fast recalculation for summary and external (type
3, 4, 5, and 7) LSA changes.
Authentication
You can configure authentication on OSPFv2 messages to prevent unauthorized or invalid routing
updates in your network. Cisco NX-OS supports two authentication methods:
•
Simple password authentication
•
MD5 authentication digest
You can configure the OSPFv2 authentication for an OSPFv2 area or per interface.
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Simple Password Authentication
Simple password authentication uses a simple cleartext password that is sent as part of the OSPFv2
message. The receiving OSPFv2 router must be configured with the same cleartext password to accept
the OSPFv2 message as a valid route update. Because the password is in cleartext, anyone who can watch
traffic on the network can learn the password.
MD5 Authentication
You should use MD5 authentication to authenticate OSPFv2 messages. You configure a password that is
shared at the local router and all remote OSPFv2 neighbors. For each OSPFv2 message, Cisco NX-OS
creates an MD5 one-way message digest based on the message itself and the encrypted password. The
interface sends this digest with the OSPFv2 message. The receiving OSPFv2 neighbor validates the
digest using the same encrypted password. If the message has not changed, the digest calculation is
identical and the OSPFv2 message is considered valid.
MD5 authentication includes a sequence number with each OSPFv2 message to ensure that no message
is replayed in the network.
Advanced Features
Cisco NX-OS supports advanced OSPFv2 features that enhance the usability and scalability of OSPFv2
in the network. This section includes the following topics:
•
Stub Area, page 5-8
•
Not-So-Stubby Area, page 5-9
•
Virtual Links, page 5-9
•
Route Redistribution, page 5-10
•
Route Summarization, page 5-10
•
High Availability and Graceful Restart, page 5-11
•
OSPFv2 Stub Router Advertisements, page 5-12
•
Multiple OSPFv2 Instances, page 5-12
•
SPF Optimization, page 5-12
•
BFD, page 5-12
•
Virtualization Support, page 5-12
Stub Area
You can limit the amount of external routing information that floods an area by making it a stub area. A
stub area is an area that does not allow AS External (type 5) LSAs (see the “Link-State Advertisements”
section on page 5-5). These LSAs are usually flooded throughout the local autonomous system to
propagate external route information. Stub areas have the following requirements:
•
All routers in the stub area are stub routers. See the “Stub Routing” section on page 1-7.
•
No ASBR routers exist in the stub area.
•
You cannot configure virtual links in the stub area.
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Figure 5-3 shows an example of an OSPFv2 autonomous system where all routers in area 0.0.0.10 have
to go through the ABR to reach external autonomous systems. Area 0.0.0.10 can be configured as a stub
area.
Figure 5-3
Stub Area
ABR
Backbone
Area 10
ASBR
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Stub area
Stub areas use a default route for all traffic that must go through the backbone area to the external
autonomous system. The default route is 0.0.0.0 for IPv4.
Not-So-Stubby Area
A Not-so-Stubby Area (NSSA) is similar to a stub area, except that an NSSA allows you to import
autonomous system external routes within an NSSA using redistribution. The NSSA ASBR redistributes
these routes and generates NSSA External (type 7) LSAs that it floods throughout the NSSA. You can
optionally configure the ABR that connects the NSSA to other areas to translate this NSSA External LSA
to AS External (type 5) LSAs. The ABR then floods these AS External LSAs throughout the OSPFv2
autonomous system. Summarization and filtering are supported during the translation. See the
“Link-State Advertisements” section on page 5-5 for information about NSSA External LSAs.
You can, for example, use NSSA to simplify administration if you are connecting a central site using
OSPFv2 to a remote site that is using a different routing protocol. Before NSSA, the connection between
the corporate site border router and a remote router could not be run as an OSPFv2 stub area because
routes for the remote site could not be redistributed into a stub area. With NSSA, you can extend OSPFv2
to cover the remote connection by defining the area between the corporate router and remote router as
an NSSA (see the “Configuring NSSA” section on page 5-27).
The backbone Area 0 cannot be an NSSA.
Virtual Links
Virtual links allow you to connect an OSPFv2 area ABR to a backbone area ABR when a direct physical
connection is not available. Figure 5-4 shows a virtual link that connects Area 3 to the backbone area
through Area 5.
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Figure 5-4
Virtual Links
Area 0
ABR2
ABR1
Area 3
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Area 5
You can also use virtual links to temporarily recover from a partitioned area, which occurs when a link
within the area fails, isolating part of the area from reaching the designated ABR to the backbone area.
Route Redistribution
OSPFv2 can learn routes from other routing protocols by using route redistribution. See the “Route
Redistribution” section on page 1-6. You configure OSPFv2 to assign a link cost for these redistributed
routes or a default link cost for all redistributed routes.
Route redistribution uses route maps to control which external routes are redistributed. You must
configure a route map with the redistribution to control which routes are passed into OSPFv2. A route
map allows you to filter routes based on attributes such as the destination, origination protocol, route
type, route tag, and so on. You can use route maps to modify parameters in the AS External (type 5) and
NSSA External (type 7) LSAs before these external routes are advertised in the local OSPFv2
autonomous system. See Chapter 15, “Configuring Route Policy Manager,” for information about
configuring route maps.
Route Summarization
Because OSPFv2 shares all learned routes with every OSPF-enabled router, you might want to use route
summarization to reduce the number of unique routes that are flooded to every OSPF-enabled router.
Route summarization simplifies route tables by replacing more-specific addresses with an address that
represents all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and
10.1.3.0/24 with one summary address, 10.1.0.0/16.
Typically, you would summarize at the boundaries of area border routers (ABRs). Although you could
configure summarization between any two areas, it is better to summarize in the direction of the
backbone so that the backbone receives all the aggregate addresses and injects them, already
summarized, into other areas. The two types of summarization are as follows:
•
Inter-area route summarization
•
External route summarization
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You configure inter-area route summarization on ABRs, summarizing routes between areas in the
autonomous system. To take advantage of summarization, you should assign network numbers in areas
in a contiguous way to be able to lump these addresses into one range.
External route summarization is specific to external routes that are injected into OSPFv2 using route
redistribution. You should make sure that external ranges that are being summarized are contiguous.
Summarizing overlapping ranges from two different routers could cause packets to be sent to the wrong
destination. Configure external route summarization on ASBRs that are redistributing routes into OSPF.
When you configure a summary address, Cisco NX-OS automatically configures a discard route for the
summary address to prevent routing black holes and route loops.
High Availability and Graceful Restart
Cisco NX-OS provides a multilevel high-availability architecture. OSPFv2 supports stateful restart,
which is also referred to as non-stop routing (NSR). If OSPFv2 experiences problems, it attempts to
restart from its previous run-time state. The neighbors do not register any neighbor event in this case. If
the first restart is not successful and another problem occurs, OSPFv2 attempts a graceful restart.
A graceful restart, or nonstop forwarding (NSF), allows OSPFv2 to remain in the data forwarding path
through a process restart. When OSPFv2 needs to perform a graceful restart, it sends a link-local opaque
(type 9) LSA, called a grace LSA (see the “Opaque LSAs” section on page 5-7). This restarting OSPFv2
platform is called NSF capable.
The grace LSA includes a grace period, which is a specified time that the neighbor OSPFv2 interfaces
hold onto the LSAs from the restarting OSPFv2 interface. (Typically, OSPFv2 tears down the adjacency
and discards all LSAs from a down or restarting OSPFv2 interface.) The participating neighbors, which
are called NSF helpers, keep all LSAs that originate from the restarting OSPFv2 interface as if the
interface was still adjacent.
When the restarting OSPFv2 interface is operational again, it rediscovers its neighbors, establishes
adjacency, and starts sending its LSA updates again. At this point, the NSF helpers recognize that the
graceful restart has finished.
Stateful restart is used in the following scenarios:
•
First recovery attempt after the process experiences problems
•
User-initiated switchover using the system switchover command
Graceful restart is used in the following scenarios:
•
Second recovery attempt after the process experiences problems within a 4-minute interval
•
Manual restart of the process using the restart ospf command
•
Active supervisor removal
•
Active supervisor reload using the reload module active-sup command
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OSPFv2 Stub Router Advertisements
You can configure an OSPFv2 interface to act as a stub router using the OSPFv2 Stub Router
Advertisements feature. Use this feature when you want to limit the OSPFv2 traffic through this router,
such as when you want to introduce a new router to the network in a controlled manner or limit the load
on a router that is already overloaded. You might also want to use this feature for various administrative
or traffic engineering reasons.
OSPFv2 stub router advertisements do not remove the OSPFv2 router from the network topology, but
they do prevent other OSPFv2 routers from using this router to route traffic to other parts of the network.
Only the traffic that is destined for this router or directly connected to this router is sent.
OSPFv2 stub router advertisements mark all stub links (directly connected to the local router) to the cost
of the local OSPFv2 interface. All remote links are marked with the maximum cost (0xFFFF).
Multiple OSPFv2 Instances
Cisco NX-OS supports multiple instances of the OSPFv2 protocol that run on the same node. You cannot
configure multiple instances over the same interface. By default, every instance uses the same system
router ID. You must manually configure the router ID for each instance if the instances are in the same
OSPFv2 autonomous system. For the number of supported OSPFv2 instances, see the Cisco Nexus 9000
Series NX-OS Verified Scalability Guide.
SPF Optimization
Cisco NX-OS optimizes the SPF algorithm in the following ways:
•
Partial SPF for Network (type 2) LSAs, Network Summary (type 3) LSAs, and AS External (type
5) LSAs—When there is a change on any of these LSAs, Cisco NX-OS performs a faster partial
calculation rather than running the whole SPF calculation.
•
SPF timers—You can configure different timers for controlling SPF calculations. These timers
include exponential backoff for subsequent SPF calculations. The exponential backoff limits the
CPU load of multiple SPF calculations.
BFD
This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol that
provides fast forwarding-path failure detection times. BFD provides subsecond failure detection
between two adjacent devices and can be less CPU-intensive than protocol hello messages because some
of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 9000
Series NX-OS Interfaces Configuration Guide for more information.
Virtualization Support
Cisco NX-OS supports multiple process instances for OSPFv2. Each OSPFv2 instance can support
multiple virtual routing and forwarding (VRF) instances, up to the system limit. For the number of
supported OSPFv2 instances, see the Cisco Nexus 9000 Series NX-OS Verified Scalability Guide.
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Licensing Requirements for OSPFv2
Licensing Requirements for OSPFv2
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
OSPFv2 requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Prerequisites for OSPFv2
OSPFv2 has the following prerequisites:
•
You must be familiar with routing fundamentals to configure OSPF.
•
You are logged on to the switch.
•
You have configured at least one interface for IPv4 that can communicate with a remote OSPFv2
neighbor.
•
You have installed the Enterprise Services license.
•
You have completed the OSPFv2 network strategy and planning for your network. For example, you
must decide whether multiple areas are required.
•
You have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Guidelines and Limitations for OSPFv2
OSPFv2 has the following configuration guidelines and limitations:
•
Cisco NX-OS displays areas in dotted decimal notation regardless of whether you enter the area in
decimal or dotted decimal notation.
•
All OSPFv2 routers must operate in the same RFC compatibility mode. OSPFv2 for Cisco NX-OS
complies with RFC 2328. Use the rfc1583compatibility command in router configuration mode if
your network includes routers that support only RFC 1583.
•
In scaled scenarios, when the number of interfaces and link-state advertisements in an OSPF process
is large, the snmp-walk on OSPF MIB objects is expected to time out with a small-values timeout
at the SNMP agent. If your observe a timeout on the querying SNMP agent while polling OSPF MIB
objects, increase the timeout value on the polling SNMP agent.
•
The following guidelines and limitations apply to the administrative distance feature:
– When an OSPF route has two or more equal cost paths, configuring the administrative distance
is nondeterministic for the match ip route-source command.
– Configuring the administrative distance is supported only for the match route-type, match ip
address prefix-list, and match ip route-source prefix-list commands. The other match
statements are ignored.
– There is no preference among the match route-type, match ip address, and match ip
route-source commands for setting the administrative distance of OSPF routes. In this way, the
behavior of the table map for setting the administrative distance in Cisco NX-OS OSPF is
different from that in Cisco IOS OSPF.
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Default Settings
– The discard route is always assigned an administrative distance of 220. No configuration in the
table map applies to OSPF discard routes.
•
Note
If you configure the delay restore seconds command in vPC configuration mode and if the VLANs
on the multichassis EtherChannel trunk (MCT) are announced by OSPFv2 or OSPFv3 using switch
virtual interfaces (SVIs), those SVIs are announced with MAX_LINK_COST on the vPC secondary
node for the duration of the configured time. As a result, all route or host programming completes
after the vPC synchronization operation (on a peer reload of the secondary vPC node) before
attracting traffic. This behavior allows for minimal packet loss for any north-to-south traffic.
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Default Settings
Table 5-2 lists the default settings for OSPFv2 parameters.
Table 5-2
Default OSPFv2 Parameters
Parameters
Default
Administrative distance
110
Hello interval
10 seconds
Dead interval
40 seconds
Discard routes
Enabled
Graceful restart grace period
60 seconds
OSPFv2 feature
Disabled
Stub router advertisement announce time
600 seconds
Reference bandwidth for link cost calculation
40 Gb/s
LSA minimal arrival time
1000 milliseconds
LSA group pacing
10 seconds
SPF calculation initial delay time
200 milliseconds
SPF minimum hold time
5000 milliseconds
SPF calculation initial delay time
1000 milliseconds
Configuring Basic OSPFv2
Configure OSPFv2 after you have designed your OSPFv2 network.
This section includes the following topics:
•
Enabling OSPFv2, page 5-15
•
Creating an OSPFv2 Instance, page 5-16
•
Configuring Optional Parameters on an OSPFv2 Instance, page 5-17
•
Configuring Networks in OSPFv2, page 5-18
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Configuring Basic OSPFv2
•
Configuring Authentication for an Area, page 5-20
•
Configuring Authentication for an Interface, page 5-21
Enabling OSPFv2
You must enable the OSPFv2 feature before you can configure OSPFv2.
SUMMARY STEPS
1.
configure terminal
2.
feature ospf
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enables the OSPFv2 feature.
feature ospf
Example:
switch(config)# feature ospf
Step 3
(Optional) Displays enabled and disabled features.
show feature
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To disable the OSPFv2 feature and remove all associated configuration, use the no feature ospf
command in global configuration mode:
Command
Purpose
no feature ospf
Disables the OSPFv2 feature and removes all
associated configuration.
Example:
switch(config)# no feature ospf
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Configuring Basic OSPFv2
Creating an OSPFv2 Instance
The first step in configuring OSPFv2 is to create an OSPFv2 instance. You assign a unique instance tag
for this OSPFv2 instance. The instance tag can be any string.
For more information about OSPFv2 instance parameters, see the “Configuring Advanced OSPFv2”
section on page 5-23.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Use the show ip ospf instance-tag command to verify that the instance tag is not in use.
OSPFv2 must be able to obtain a router identifier (for example, a configured loopback address) or you
must configure the router ID option.
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
router-id ip-address
4.
(Optional) show ip ospf instance-tag
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
router-id ip-address
Example:
switch(config-router)# router-id
192.0.2.1
Step 4
show ip ospf instance-tag
Creates a new OSPFv2 instance with the configured
instance tag.
(Optional) Configures the OSPFv2 router ID. This IP
address identifies this OSPFv2 instance and must exist
on a configured interface in the system.
(Optional) Displays OSPF information.
Example:
switch(config-router)# show ip ospf 201
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
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To remove the OSPFv2 instance and all associated configuration, use the no router ospf command in
global configuration mode.
Command
Purpose
no router ospf instance-tag
Deletes the OSPF instance and the associated
configuration.
Example:
switch(config)# no router ospf 201
Note
This command does not remove the OSPF configuration in interface mode. You must manually remove
any OSPFv2 commands configured in interface mode.
Configuring Optional Parameters on an OSPFv2 Instance
You can configure optional parameters for OSPF.
For more information about OSPFv2 instance parameters, see the “Configuring Advanced OSPFv2”
section on page 5-23.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
OSPFv2 must be able to obtain a router identifier (for example, a configured loopback address) or you
must configure the router ID option.
DETAILED STEPS
You can configure the following optional parameters for OSPFv2 in router configuration mode:
Command
Purpose
distance number
Configures the administrative distance for this
OSPFv2 instance. The range is from 1 to 255. The
default is 110.
Example:
switch(config-router)# distance 25
log-adjacency-changes [detail]
Example:
switch(config-router)#
log-adjacency-changes
maximum-paths path-number
Example:
switch(config-router)# maximum-paths 4
passive-interface default
Example:
switch(config-router)# passive-interface
default
Generates a system message whenever a neighbor
changes state.
Configures the maximum number of equal OSPFv2
paths to a destination in the route table. This
command is used for load balancing. The range is
from 1 to 64. The default is 8.
Suppresses routing updates on all interfaces. This
command is overridden by the VRF or interface
command mode configuration.
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Configuring Basic OSPFv2
This example shows how to create an OSPFv2 instance:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# copy running-config startup-config
Configuring Networks in OSPFv2
You can configure a network to OSPFv2 by associating it through the interface that the router uses to
connect to that network (see the “Neighbors” section on page 5-3). You can add all networks to the
default backbone area (Area 0), or you can create new areas using any decimal number or an IP address.
Note
All areas must connect to the backbone area either directly or through a virtual link.
Note
OSPF is not enabled on an interface until you configure a valid IP address for that interface.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
ip address ip-prefix/length
4.
ip router ospf instance-tag area area-id [secondaries none]
5.
(Optional) show ip ospf instance-tag interface interface-type slot/port
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
Assigns an IP address and subnet mask to this
interface.
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Step 4
Command
Purpose
ip router ospf instance-tag area area-id
[secondaries none]
Adds the interface to the OSPFv2 instance and area.
Example:
switch(config-if)# ip router ospf 201
area 0.0.0.15
Step 5
show ip ospf instance-tag interface
interface-type slot/port
(Optional) Displays OSPF information.
Example:
switch(config-if)# show ip ospf 201
interface ethernet 1/2
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
You can configure the following optional parameters for OSPFv2 in interface configuration mode:
Command
Purpose
ip ospf cost number
Configures the OSPFv2 cost metric for this
interface. The default is to calculate cost metric,
based on the reference bandwidth and interface
bandwidth. The range is from 1 to 65535.
Example:
switch(config-if)# ip ospf cost 25
ip ospf dead-interval seconds
Example:
switch(config-if)# ip ospf dead-interval
50
ip ospf hello-interval seconds
Example:
switch(config-if)# ip ospf hello-interval
25
ip ospf mtu-ignore
Example:
switch(config-if)# ip ospf mtu-ignore
[default | no] ip ospf passive-interface
Example:
switch(config-if)# ip ospf
passive-interface
ip ospf priority number
Example:
switch(config-if)# ip ospf priority 25
Configures the OSPFv2 dead interval, in seconds.
The range is from 1 to 65535. The default is four
times the hello interval, in seconds.
Configures the OSPFv2 hello interval, in seconds.
The range is from 1 to 65535. The default is 10
seconds.
Configures OSPFv2 to ignore any IP MTU
mismatch with a neighbor. The default is to not
establish adjacency if the neighbor MTU does not
match the local interface MTU.
Suppresses routing updates on the interface. This
command overrides the router or VRF command
mode configuration. The default option removes
this interface mode command and reverts to the
router or VRF configuration, if present.
Configures the OSPFv2 priority, used to determine
the DR for an area. The range is from 0 to 255. The
default is 1. See the “Designated Routers” section
on page 5-3.
Shuts down the OSPFv2 instance on this interface.
ip ospf shutdown
Example:
switch(config-if)# ip ospf shutdown
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Configuring Basic OSPFv2
This example shows how to add a network area 0.0.0.10 in OSPFv2 instance 201:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# ip address 192.0.2.1/16
switch(config-if)# ip router ospf 201 area 0.0.0.10
switch(config-if)# copy running-config startup-config
Use the show ip ospf interface command to verify the interface configuration. Use the show ip ospf
neighbor command to see the neighbors for this interface.
Configuring Authentication for an Area
You can configure authentication for all networks in an area or for individual interfaces in the area.
Interface authentication configuration overrides area authentication.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Ensure that all neighbors on an interface share the same authentication configuration, including the
shared authentication key.
Create the keychain for this authentication configuration. See the Cisco Nexus 9000 Series NX-OS
Security Configuration Guide.
For OSPFv2, the key identifier in the key key-id command supports values from 0 to 255 only.
Note
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
area area-id authentication [message-digest]
4.
interface interface-type slot/port
5.
(Optional) ip ospf authentication-key [0 | 3] key
or
ip ospf message-digest-key key-id md5 [0 | 3] key
6.
(Optional) show ip ospf instance-tag interface interface-type slot/port
7.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
area area-id authentication
[message-digest]
Creates a new OSPFv2 instance with the configured
instance tag.
Configures the authentication mode for an area.
Example:
switch(config-router)# area 0.0.0.10
authentication
Step 4
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config-router)# interface
ethernet 1/2
switch(config-if)#
Step 5
ip ospf authentication-key [0 | 3] key
Example:
switch(config-if)# ip ospf
authentication-key 0 mypass
ip ospf message-digest-key key-id md5 [0
| 3] key
Example:
switch(config-if)# ip ospf
message-digest-key 21 md5 0 mypass
Step 6
show ip ospf instance-tag interface
interface-type slot/port
(Optional) Configures simple password authentication
for this interface. Use this command if the
authentication is not set to keychain or message-digest.
0 configures the password in cleartext. 3 configures the
password as 3DES encrypted.
(Optional) Configures message digest authentication
for this interface. Use this command if the
authentication is set to message-digest. The key-id
range is from 1 to 255. The MD5 option 0 configures
the password in cleartext and 3 configures the pass key
as 3DES encrypted.
(Optional) Displays OSPF information.
Example:
switch(config-if)# show ip ospf 201
interface ethernet 1/2
Step 7
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Configuring Authentication for an Interface
You can configure authentication for individual interfaces in the area. Interface authentication
configuration overrides area authentication.
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BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Ensure that all neighbors on an interface share the same authentication configuration, including the
shared authentication key.
Create the keychain for this authentication configuration. See the Cisco Nexus 9000 Series NX-OS
Security Configuration Guide.
Note
For OSPFv2, the key identifier in the key key-id command supports values from 0 to 255 only.
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
ip ospf authentication [message-digest]
4.
(Optional) ip ospf authentication key-chain key-id
5.
(Optional) ip ospf authentication-key [0 | 3 | 7] key
6.
(Optional) ip ospf message-digest-key key-id md5 [0 | 3 | 7] key
7.
(Optional) show ip ospf instance-tag interface interface-type slot/port
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ip ospf authentication [message-digest]
Example:
switch(config-if)# ip ospf
authentication
Step 4
ip ospf authentication key-chain key-id
Example:
switch(config-if)# ip ospf
authentication key-chain Test1
Enables interface authentication mode for OSPFv2 for
either cleartext or message-digest type. Use this
command to override area-based authentication for
this interface. All neighbors must share this
authentication type.
(Optional) Configures interface authentication to use
keychains for OSPFv2. See the Cisco Nexus 9000
Series NX-OS Security Configuration Guide for details
on keychains.
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Step 5
Command
Purpose
ip ospf authentication-key [0 | 3 | 7]
key
(Optional) Configures simple password authentication
for this interface. Use this command if the
authentication is not set to keychain or message-digest.
Example:
switch(config-if)# ip ospf
authentication-key 0 mypass
Step 6
ip ospf message-digest-key key-id md5 [0
| 3 | 7] key
Example:
switch(config-if)# ip ospf
message-digest-key 21 md5 0 mypass
Step 7
show ip ospf instance-tag interface
interface-type slot/port
The options are as follows:
•
0—Configures the password in cleartext.
•
3—Configures the pass key as 3DES encrypted.
•
7—Configures the key as Cisco type 7 encrypted.
(Optional) Configures message digest authentication
for this interface. Use this command if the
authentication is set to message-digest.The key-id
range is from 1 to 255. The MD5 options are as
follows:
•
0—Configures the password in cleartext.
•
3—Configures the pass key as 3DES encrypted.
•
7—Configures the key as Cisco type 7 encrypted.
(Optional) Displays OSPF information.
Example:
switch(config-if)# show ip ospf 201
interface ethernet 1/2
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to set an interface for simple, unencrypted passwords and set the password for
Ethernet interface 1/2:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# ip router ospf 201 area 0.0.0.10
switch(config-if)# ip ospf authentication
switch(config-if)# ip ospf authentication-key 0 mypass
switch(config-if)# copy running-config startup-config
Configuring Advanced OSPFv2
Configure OSPFv2 after you have designed your OSPFv2 network.
This section includes the following topics:
•
Configuring Filter Lists for Border Routers, page 5-24
•
Configuring Stub Areas, page 5-25
•
Configuring a Totally Stubby Area, page 5-27
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•
Configuring NSSA, page 5-27
•
Configuring Virtual Links, page 5-29
•
Configuring Redistribution, page 5-31
•
Limiting the Number of Redistributed Routes, page 5-33
•
Configuring Route Summarization, page 5-35
•
Configuring Stub Route Advertisements, page 5-36
•
Configuring the Administrative Distance of Routes, page 5-37
•
Modifying the Default Timers, page 5-40
•
Configuring Graceful Restart, page 5-42
•
Restarting an OSPFv2 Instance, page 5-44
Configuring Filter Lists for Border Routers
You can separate your OSPFv2 domain into a series of areas that contain related networks. All areas must
connect to the backbone area through an area border router (ABR). OSPFv2 domains can connect to
external domains through an autonomous system border router (ASBR). See the “Areas” section on
page 5-4.
ABRs have the following optional configuration parameters:
•
Area range—Configures route summarization between areas. See the “Configuring Route
Summarization” section on page 5-35.
•
Filter list—Filters the Network Summary (type 3) LSAs that are allowed in from an external area.
ASBRs also support filter lists.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Create the route map that the filter list uses to filter IP prefixes in incoming or outgoing Network
Summary (type 3) LSAs. See Chapter 15, “Configuring Route Policy Manager.”
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
area area-id filter-list route-map map-name {in | out}
4.
(Optional) show ip ospf policy statistics area id filter-list {in | out}
5.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
area area-id filter-list route-map
map-name {in | out}
Creates a new OSPFv2 instance with the configured
instance tag.
Filters incoming or outgoing Network Summary (type
3) LSAs on an ABR.
Example:
switch(config-router)# area 0.0.0.10
filter-list route-map FilterLSAs in
Step 4
show ip ospf policy statistics area id
filter-list {in | out}
(Optional) Displays OSPF policy information.
Example:
switch(config-if)# show ip ospf policy
statistics area 0.0.0.10 filter-list in
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to configure a filter list in area 0.0.0.10:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 filter-list route-map FilterLSAs in
switch(config-router)# copy running-config startup-config
Configuring Stub Areas
You can configure a stub area for part of an OSPFv2 domain where external traffic is not necessary. Stub
areas block AS External (type 5) LSAs and limit unnecessary routing to and from selected networks. See
the “Stub Area” section on page 5-8. You can optionally block all summary routes from going into the
stub area.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Ensure that there are no virtual links or ASBRs in the proposed stub area.
SUMMARY STEPS
1.
configure terminal
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2.
router ospf instance-tag
3.
area area-id stub
4.
(Optional) area area-id default-cost cost
5.
(Optional) show ip ospf instance-tag
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
area area-id stub
Creates a new OSPFv2 instance with the configured
instance tag.
Creates this area as a stub area.
Example:
switch(config-router)# area 0.0.0.10
stub
Step 4
area area-id default-cost cost
Example:
switch(config-router)# area 0.0.0.10
default-cost 25
Step 5
show ip ospf instance-tag
(Optional) Sets the cost metric for the default summary
route sent into this stub area. The range is from 0 to
16777215. The default is 1.
(Optional) Displays OSPF information.
Example:
switch(config-if)# show ip ospf 201
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to create a stub area:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 stub
switch(config-router)# copy running-config startup-config
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Configuring a Totally Stubby Area
You can create a totally stubby area and prevent all summary route updates from going into the stub area.
To create a totally stubby area, use the following command in router configuration mode:
Command
Purpose
area area-id stub no-summary
Creates this area as a totally stubby area.
Example:
switch(config-router)# area 20 stub
no-summary
Configuring NSSA
You can configure an NSSA for part of an OSPFv2 domain where limited external traffic is required. For
information about NSSAs, see the “Not-So-Stubby Area” section on page 5-9. You can optionally
translate this external traffic to an AS External (type 5) LSA and flood the OSPFv2 domain with this
routing information. An NSSA can be configured with the following optional parameters:
•
No redistribution—Redistributed routes bypass the NSSA and are redistributed to other areas in the
OSPFv2 autonomous system. Use this option when the NSSA ASBR is also an ABR.
•
Default information originate—Generates an NSSA External (type 7) LSA for a default route to the
external autonomous system. Use this option on an NSSA ASBR if the ASBR contains the default
route in the routing table. This option can be used on an NSSA ABR whether or not the ABR
contains the default route in the routing table.
•
Route map—Filters the external routes so that only those routes that you want are flooded
throughout the NSSA and other areas.
•
Translate—Translates NSSA External LSAs to AS External LSAs for areas outside the NSSA. Use
this command on an NSSA ABR to flood the redistributed routes throughout the OSPFv2
autonomous system. You can optionally suppress the forwarding address in these AS External LSAs.
If you choose this option, the forwarding address is set to 0.0.0.0.
•
No summary—Blocks all summary routes from flooding the NSSA. Use this option on the NSSA
ABR.
BEFORE YOU BEGIN
Ensure that you have enabled the OSPF feature (see the “Enabling OSPFv2” section on page 5-15).
Ensure that there are no virtual links in the proposed NSSA and that it is not the backbone area.
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
area area-id nssa [no-redistribution] [default-information-originate [route-map map-name]]
[no-summary] [translate type7 {always | never} [suppress-fa]]
4.
(Optional) area area-id default-cost cost
5.
(Optional) show ip ospf instance-tag
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6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
area area-id nssa [no-redistribution]
[default-information-originate
[route-map map-name]] [no-summary]
[translate type7 {always | never}
[suppress-fa]]
Creates a new OSPFv2 instance with the configured
instance tag.
Creates this area as an NSSA.
Example:
switch(config-router)# area 0.0.0.10
nssa
Step 4
area area-id default-cost cost
Example:
switch(config-router)# area 0.0.0.10
default-cost 25
Step 5
show ip ospf instance-tag
(Optional) Sets the cost metric for the default summary
route sent into this NSSA.
(Optional) Displays OSPF information.
Example:
switch(config-if)# show ip ospf 201
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to create an NSSA that blocks all summary route updates:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 nssa no-summary
switch(config-router)# copy running-config startup-config
This example shows how to create an NSSA that generates a default route:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 nssa default-info-originate
switch(config-router)# copy running-config startup-config
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This example shows how to create an NSSA that filters external routes and blocks all summary route
updates:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 nssa route-map ExternalFilter no-summary
switch(config-router)# copy running-config startup-config
This example shows how to create an NSSA that always translates NSSA External (type 5) LSAs to AS
External (type 7) LSAs:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 nssa translate type 7 always
switch(config-router)# copy running-config startup-config
Configuring Virtual Links
A virtual link connects an isolated area to the backbone area through an intermediate area. See the
“Virtual Links” section on page 5-9. You can configure the following optional parameters for a virtual
link:
Note
•
Authentication—Sets a simple password or MD5 message digest authentication and associated keys.
•
Dead interval—Sets the time that a neighbor waits for a Hello packet before declaring the local
router as dead and tearing down adjacencies.
•
Hello interval—Sets the time between successive Hello packets.
•
Retransmit interval—Sets the estimated time between successive LSAs.
•
Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.
You must configure the virtual link on both routers involved before the link becomes active.
You cannot add a virtual link to a stub area.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
area area-id virtual-link router-id
4.
(Optional) show ip ospf virtual-link [brief]
5.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Creates a new OSPFv2 instance with the configured
instance tag.
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
Creates one end of a virtual link to a remote router.
You must create the virtual link on that remote router
to complete the link.
area area-id virtual-link router-id
Example:
switch(config-router)# area 0.0.0.10
virtual-link 10.1.2.3
switch(config-router-vlink)#
Step 4
(Optional) Displays OSPF virtual link information.
show ip ospf virtual-link [brief]
Example:
switch(config-router-vlink)# show ip ospf
virtual-link
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-vlink)# copy
running-config startup-config
You can configure the following optional commands in virtual link configuration mode:
Command
Purpose
authentication [key-chain key-id |
message-digest | null]
(Optional) Overrides area-based authentication for this
virtual link.
Example:
switch(config-router-vlink)#
authentication message-digest
authentication-key [0 | 3] key
Example:
switch(config-router-vlink)#
authentication-key 0 mypass
dead-interval seconds
Example:
switch(config-router-vlink)#
dead-interval 50
hello-interval seconds
Example:
switch(config-router-vlink)#
hello-interval 25
(Optional) Configures a simple password for this virtual
link. Use this command if the authentication is not set to
keychain or message-digest. 0 configures the password in
cleartext. 3 configures the password as 3DES encrypted.
(Optional) Configures the OSPFv2 dead interval, in
seconds. The range is from 1 to 65535. The default is four
times the hello interval, in seconds.
(Optional) Configures the OSPFv2 hello interval, in
seconds. The range is from 1 to 65535. The default is 10
seconds.
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Configuring Advanced OSPFv2
Command
Purpose
message-digest-key key-id md5 [0 | 3]
key
(Optional) Configures message digest authentication for
this virtual link. Use this command if the authentication
is set to message-digest. 0 configures the password in
cleartext. 3 configures the pass key as 3DES encrypted.
Example:
switch(config-router-vlink)#
message-digest-key 21 md5 0 mypass
retransmit-interval seconds
Example:
switch(config-router-vlink)#
retransmit-interval 50
transmit-delay seconds
Example:
switch(config-router-vlink)#
transmit-delay 2
(Optional) Configures the OSPFv2 retransmit interval, in
seconds. The range is from 1 to 65535. The default is 5.
(Optional) Configures the OSPFv2 transmit-delay, in
seconds. The range is from 1 to 450. The default is 1.
This example shows how to create a simple virtual link between two ABRs.
The configuration for ABR 1 (router ID 27.0.0.55) is as follows:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 virtual-link 10.1.2.3
switch(config-router)# copy running-config startup-config
The configuration for ABR 2 (Router ID 10.1.2.3) is as follows:
switch# configure terminal
switch(config)# router ospf 101
switch(config-router)# area 0.0.0.10 virtual-link 27.0.0.55
switch(config-router)# copy running-config startup-config
Configuring Redistribution
You can redistribute routes learned from other routing protocols into an OSPFv2 autonomous system
through the ASBR.
You can configure the following optional parameters for route redistribution in OSPF:
•
Note
•
Note
Default information originate—Generates an AS External (type 5) LSA for a default route to the
external autonomous system.
Default information originate ignores match statements in the optional route map.
Default metric—Sets all redistributed routes to the same cost metric.
If you redistribute static routes, Cisco NX-OS also redistributes the default static route.
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Configuring Advanced OSPFv2
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
Create the necessary route maps used for redistribution.
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name
4.
default-information originate [always] [route-map map-name]
5.
default-metric cost
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
redistribute {bgp id | direct | eigrp id
| isis id | ospf id | rip id | static}
route-map map-name
Creates a new OSPFv2 instance with the configured
instance tag.
Redistributes the selected protocol into OSPF through
the configured route map.
If you redistribute static routes, Cisco NX-OS
also redistributes the default static route.
Note
Example:
switch(config-router)# redistribute bgp
route-map FilterExternalBGP
Step 4
default-information originate [always]
[route-map map-name]
Example:
switch(config-router)#
default-information-originate route-map
DefaultRouteFilter
Creates a default route into this OSPF domain if the
default route exists in the RIB. Use the following
optional keywords:
•
always —Always generates the default route of
0.0.0. even if the route does not exist in the RIB.
•
route-map—Generates the default route if the
route map returns true.
Note
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This command ignores match statements in
the route map.
Chapter 5
Configuring OSPFv2
Configuring Advanced OSPFv2
Command
Purpose
Step 5
default-metric cost
Step 6
copy running-config startup-config
Sets the cost metric for the redistributed routes. This
command does not apply to directly connected routes.
Example:
Use a route map to set the default metric for directly
switch(config-router)# default-metric 25
connected routes.
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to redistribute the Border Gateway Protocol (BGP) into OSPF:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# redistribute bgp route-map FilterExternalBGP
switch(config-router)# copy running-config startup-config
Limiting the Number of Redistributed Routes
Route redistribution can add many routes to the OSPFv2 route table. You can configure a maximum limit
to the number of routes accepted from external protocols. OSPFv2 provides the following options to
configure redistributed route limits:
•
Fixed limit—Logs a message when OSPFv2 reaches the configured maximum. OSPFv2 does not
accept any more redistributed routes. You can optionally configure a threshold percentage of the
maximum where OSPFv2 logs a warning when that threshold is passed.
•
Warning only—Logs a warning only when OSPFv2 reaches the maximum. OSPFv2 continues to
accept redistributed routes.
•
Withdraw—Starts the timeout period when OSPFv2 reaches the maximum. After the timeout period,
OSPFv2 requests all redistributed routes if the current number of redistributed routes is less than the
maximum limit. If the current number of redistributed routes is at the maximum limit, OSPFv2
withdraws all redistributed routes. You must clear this condition before OSPFv2 accepts more
redistributed routes.
•
You can optionally configure the timeout period.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name
4.
redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]
5.
(Optional) show running-config ospf
6.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
redistribute {bgp id | direct | eigrp id
| isis id | ospf id | rip id | static}
route-map map-name
Creates a new OSPFv2 instance with the configured
instance tag.
Redistributes the selected protocol into OSPF through
the configured route map.
Example:
switch(config-router)# redistribute bgp
route-map FilterExternalBGP
Step 4
redistribute maximum-prefix max
[threshold] [warning-only | withdraw
[num-retries timeout]]
Example:
switch(config-router)# redistribute
maximum-prefix 1000 75 warning-only
Step 5
show running-config ospf
Specifies a maximum number of prefixes that OSPFv2
distributes. The range is from 1 to 65535. Optionally
specifies the following:
•
threshold—Percentage of maximum prefixes that
trigger a warning message.
•
warning-only—Logs a warning message when
the maximum number of prefixes is exceeded.
•
withdraw—Withdraws all redistributed routes.
Optionally tries to retrieve the redistributed
routes. The num-retries range is from 1 to 12. The
timeout is 60 to 600 seconds. The default is 300
seconds. Use the clear ip ospf redistribution
command if all routes are withdrawn.
(Optional) Displays the OSPFv2 configuration.
Example:
switch(config-router)# show
running-config ospf
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to limit the number of redistributed routes into OSPF:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# redistribute bgp route-map FilterExternalBGP
switch(config-router)# redistribute maximum-prefix 1000 75
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Configuring Route Summarization
You can configure route summarization for inter-area routes by configuring an address range that is
summarized. You can also configure route summarization for external, redistributed routes by
configuring a summary address for those routes on an ASBR. For more information, see the “Route
Summarization” section on page 5-10.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
area area-id range ip-prefix/length [no-advertise] [cost cost]
or
4.
summary-address ip-prefix/length [no-advertise | tag tag-id]
5.
(Optional) show ip ospf summary-address
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
area area-id range ip-prefix/length
[no-advertise] [cost cost]
Example:
switch(config-router)# area 0.0.0.10
range 10.3.0.0/16
Step 4
summary-address ip-prefix/length
[no-advertise | tag tag]
Example:
switch(config-router)# summary-address
10.5.0.0/16 tag 2
Creates a new OSPFv2 instance with the configured
instance tag.
Creates a summary address on an ABR for a range of
addresses and optionally does not advertise this
summary address in a Network Summary (type 3)
LSA. The cost range is from 0 to 16777215.
Creates a summary address on an ASBR for a range of
addresses and optionally assigns a tag for this
summary address that can be used for redistribution
with route maps.
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Step 5
Command
Purpose
show ip ospf summary-address
(Optional) Displays information about OSPF summary
addresses.
Example:
switch(config-router)# show ip ospf
summary-address
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to create summary addresses between areas on an ABR:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# area 0.0.0.10 range 10.3.0.0/16
switch(config-router)# copy running-config startup-config
This example shows how to create summary addresses on an ASBR:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# summary-address 10.5.0.0/16
switch(config-router)# no discard-route internal
switch(config-router)# copy running-config startup-config
Configuring Stub Route Advertisements
Use stub route advertisements when you want to limit the OSPFv2 traffic through this router for a short
time. For more information, see the “OSPFv2 Stub Router Advertisements” section on page 5-12.
Stub route advertisements can be configured with the following optional parameters:
Note
•
On startup—Sends stub route advertisements for the specified announce time.
•
Wait for BGP—Sends stub router advertisements until BGP converges.
You should not save the running configuration of a router when it is configured for a graceful shutdown
because the router continues to advertise a maximum metric after it is reloaded.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
max-metric router-lsa [external-lsa [max-metric-value]] [include-stub] [on-startup {seconds |
wait-for bgp tag}] [summary-lsa [max-metric-value]]
4.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Creates a new OSPFv2 instance with the configured
instance tag.
Step 3
max-metric router-lsa [external-lsa
[max-metric-value]] [include-stub]
[on-startup {seconds | wait-for bgp
tag}] [summary-lsa [max-metric-value]]
Example:
switch(config-router)# max-metric
router-lsa
Configures OSPFv2 stub route advertisements.
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to enable the stub router advertisements on startup for the default 600 seconds:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# max-metric router-lsa on-startup
switch(config-router)# copy running-config startup-config
Configuring the Administrative Distance of Routes
You can set the administrative distance of routes added by OSPFv2 into the RIB.
The administrative distance is a rating of the trustworthiness of a routing information source. A higher
value indicates a lower trust rating. Typically, a route can be learned through more than one routing
protocol. The administrative distance is used to discriminate between routes learned from more than one
routing protocol. The route with the lowest administrative distance is installed in the IP routing table.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
See the guidelines and limitations for this feature in the “Guidelines and Limitations for OSPFv2”
section on page 5-13.
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
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3.
[no] table-map map-name
4.
exit
5.
route-map map-name [permit | deny] [seq]
6.
match route-type route-type
7.
match ip route-source prefix-list name
8.
match ip address prefix-list name
9.
set distance value
10. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
[no] table-map map-name
Example:
switch(config-router)# table-map foo
Step 4
exit
Creates a new OSPFv2 instance with the configured
instance tag.
Configures the policy for filtering or modifying
OSPFv2 routes before sending them to the RIB. You
can enter up to 63 alphanumeric characters for the map
name.
Exits router configuration mode.
Example:
switch(config-router)# exit
switch(config)#
Step 5
route-map map-name [permit | deny] [seq]
Example:
switch(config)# route-map foo permit 10
switch(config-route-map)#
Creates a route map or enters route-map configuration
mode for an existing route map. Use seq to order the
entries in a route map.
Note
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The permit option enables you to set the
distance. If you use the deny option, the
default distance is applied.
Chapter 5
Configuring OSPFv2
Configuring Advanced OSPFv2
Step 6
Command
Purpose
match route-type route-type
Matches against one of the following route types:
Example:
switch(config-route-map)# match
route-type external
Step 7
match ip route-source prefix-list name
Example:
switch(config-route-map)# match ip
route-source prefix-list p1
Step 8
match ip address prefix-list name
Example:
switch(config-route-map)# match ip
address prefix-list p1
Step 9
set distance value
Example:
switch(config-route-map)# set distance
150
Step 10
copy running-config startup-config
•
external—The external route (BGP, EIGRP, and
OSPF type 1 or 2)
•
inter-area—OSPF inter-area route
•
internal—The internal route (including the OSPF
intra- or inter-area)
•
intra-area—OSPF intra-area route
•
nssa-external—The NSSA external route (OSPF
type 1 or 2).
•
type-1—The OSPF external type 1 route
•
type-2—The OSPF external type 2 route
Matches the IPv4 route source address or router ID of
a route to one or more IP prefix lists. Use the ip
prefix-list command to create the prefix list.
Matches against one or more IPv4 prefix lists. Use the
ip prefix-list command to create the prefix list.
Sets the administrative distance of routes for OSPFv2.
The range is from 1 to 255.
(Optional) Saves this configuration change.
Example:
switch(config-route-map)# copy
running-config startup-config
This example shows how to configure the OSPFv2 administrative distance for inter-area routes to 150,
for external routes to 200, and for all prefixes in prefix list p1 to 190:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# table-map foo
switch(config-router)# exit
switch(config)# route-map foo permit 10
switch(config-route-map)# match route-type inter-area
switch(config-route-map)# set distance 150
switch(config)# route-map foo permit 20
switch(config-route-map)# match route-type external
switch(config-route-map)# set distance 200
switch(config)# route-map foo permit 30
switch(config-route-map)# match ip route-source prefix-list p1
switch(config-route-map)# match ip address prefix-list p1
switch(config-route-map)# set distance 190
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Modifying the Default Timers
OSPFv2 includes a number of timers that control the behavior of protocol messages and shortest path
first (SPF) calculations. OSPFv2 includes the following optional timer parameters:
•
LSA arrival time—Sets the minimum interval allowed between LSAs that arrive from a neighbor.
LSAs that arrive faster than this time are dropped.
•
Pacing LSAs—Sets the interval at which LSAs are collected into a group and refreshed,
checksummed, or aged. This timer controls how frequently LSA updates occur and optimizes how
many are sent in an LSA update message (see the “Flooding and LSA Group Pacing” section on
page 5-6).
•
Throttle LSAs—Sets the rate limits for generating LSAs. This timer controls how frequently LSAs
are generated after a topology change occurs.
•
Throttle SPF calculation—Controls how frequently the SPF calculation is run.
At the interface level, you can also control the following timers:
•
Retransmit interval—Sets the estimated time between successive LSAs.
•
Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.
See the “Configuring Networks in OSPFv2” section on page 5-18 for information about the hello
interval and dead timer.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
timers lsa-arrival msec
4.
timers lsa-group-pacing seconds
5.
timers throttle lsa start-time hold-interval max-time
6.
timers throttle spf delay-time hold-time
7.
interface type slot/port
8.
ip ospf hello-interval seconds
9.
ip ospf dead-interval seconds
10. ip ospf retransmit-interval seconds
11. ip ospf transmit-delay seconds
12. (Optional) show ip ospf
13. (Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
timers lsa-arrival msec
Example:
switch(config-router)# timers
lsa-arrival 2000
Step 4
timers lsa-group-pacing seconds
Example:
switch(config-router)# timers
lsa-group-pacing 200
Step 5
Creates a new OSPFv2 instance with the configured
instance tag.
Sets the LSA arrival time in milliseconds. The range is
from 10 to 600000. The default is 1000 milliseconds.
Sets the interval in seconds for grouping LSAs. The
range is from 1 to 1800. The default is 10 seconds.
timers throttle lsa start-time
hold-interval max-time
Sets the rate limit in milliseconds for generating LSAs
with the following timers:
Example:
switch(config-router)# timers throttle
lsa 3000
start-time—The range is from 0 to 5000 milliseconds.
The default value is 0 milliseconds.
hold-interval—The range is from 50 to 30,000
milliseconds. The default value is 5000 milliseconds.
max-time—The range is from 50 to 30,000
milliseconds. The default value is 5000 milliseconds.
Step 6
Step 7
Example:
switch(config-router)# timers throttle
spf 3000 2000 4000
Sets the SPF best-path schedule initial delay time and
the minimum hold time in seconds between SPF
best-path calculations. The range is from 1 to 600000.
The default is no delay time and a 5000-millisecond
hold time.
interface type slot/port
Enters interface configuration mode.
timers throttle spf delay-time hold-time
max-wait
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 8
ip ospf hello-interval seconds
Example:
switch(config-if)# ip ospf
hello-interval 30
Step 9
ip ospf dead-interval seconds
Example:
switch(config-if)# ip ospf dead-interval
30
Sets the hello interval for this interface. The range is
from 1 to 65535. The default is 10.
Sets the dead interval for this interface. The range is
from 1 to 65535.
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Step 10
Command
Purpose
ip ospf retransmit-interval seconds
Sets the estimated time in seconds between LSAs
transmitted from this interface. The range is from 1 to
65535. The default is 5.
Example:
switch(config-if)# ip ospf
retransmit-interval 30
Step 11
ip ospf transmit-delay seconds
Example:
switch(config-if)# ip ospf
transmit-delay 600
switch(config-if)#
Step 12
show ip ospf
Sets the estimated time in seconds to transmit an LSA
to a neighbor. The range is from 1 to 450. The default
is 1.
(Optional) Displays information about OSPF.
Example:
switch(config-if)# show ip ospf
Step 13
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to control LSA flooding with the lsa-group-pacing option:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# timers lsa-group-pacing 300
switch(config-router)# copy running-config startup-config
Configuring Graceful Restart
Graceful restart is enabled by default. You can configure the following optional parameters for graceful
restart in an OSPFv2 instance:
•
Grace period—Configures how long neighbors should wait after a graceful restart has started before
tearing down adjacencies.
•
Helper mode disabled—Disables helper mode on the local OSPFv2 instance. OSPFv2 does not
participate in the graceful restart of a neighbor.
•
Planned graceful restart only—Configures OSPFv2 to support graceful restart only in the event of a
planned restart.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
Ensure that all neighbors are configured for graceful restart with matching optional parameters set.
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
graceful-restart
4.
(Optional) graceful-restart grace-period seconds
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5.
(Optional) graceful-restart helper-disable
6.
(Optional) graceful-restart planned-only
7.
(Optional) show ip ospf instance-tag
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
graceful-restart
Example:
switch(config-router)# graceful-restart
Step 4
graceful-restart grace-period seconds
Example:
switch(config-router)# graceful-restart
grace-period 120
Step 5
graceful-restart helper-disable
Example:
switch(config-router)# graceful-restart
helper-disable
Step 6
graceful-restart planned-only
Example:
switch(config-router)# graceful-restart
planned-only
Step 7
show ip ospf instance-tag
Creates a new OSPFv2 instance with the configured
instance tag.
Enables a graceful restart. A graceful restart is enabled
by default.
(Optional) Sets the grace period, in seconds. The range
is from 5 to 1800. The default is 60 seconds.
(Optional) Disables helper mode. This feature is
enabled by default.
(Optional) Configures a graceful restart for planned
restarts only.
(Optional) Displays OSPF information.
Example:
switch(config-if)# show ip ospf 201
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to enable a graceful restart if it has been disabled and set the grace period to
120 seconds:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# graceful-restart
switch(config-router)# graceful-restart grace-period 120
switch(config-router)# copy running-config startup-config
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Configuring Advanced OSPFv2
Restarting an OSPFv2 Instance
You can restart an OSPv2 instance. This action clears all neighbors for the instance.
To restart an OSPFv2 instance and remove all associated neighbors, use the following command:
Command
Purpose
restart ospf instance-tag
Restarts the OSPFv2 instance and removes all
neighbors.
Example:
switch(config)# restart ospf 201
Configuring OSPFv2 with Virtualization
You can configure multiple OSPFv2 instances. You can also create multiple VRFs and use the same or
multiple OSPFv2 instances in each VRF. You assign an OSPFv2 interface to a VRF.
Note
Configure all other parameters for an interface after you configure the VRF for an interface. Configuring
a VRF for an interface deletes all the configuration for that interface.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv2” section on page 5-15).
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf_name
3.
router ospf instance-tag
4.
vrf vrf-name
5.
(Optional) maximum-paths paths
6.
interface interface-type slot/port
7.
vrf member vrf-name
8.
ip-address ip-prefix/length
9.
router ospf instance-tag area area-id
10. (Optional) copy running-config startup-config
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Configuring Advanced OSPFv2
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context
RemoteOfficeVRF
switch(config-vrf)#
Step 3
router ospf instance-tag
Example:
switch(config-vrf)# router ospf 201
switch(config-router)#
Step 4
Creates a new VRF and enters VRF configuration
mode.
Creates a new OSPFv2 instance with the configured
instance tag.
Enters VRF configuration mode.
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
Step 5
maximum-paths paths
Example:
switch(config-router-vrf)# maximum-paths
4
Step 6
interface interface-type slot/port
(Optional) Configures the maximum number of equal
OSPFv2 paths to a destination in the route table for this
VRF. This feature is used for load balancing.
Enters interface configuration mode.
Example:
switch(config-router-vrf)# interface
ethernet 1/2
switch(config-if)#
Step 7
Adds this interface to a VRF.
vrf member vrf-name
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Step 8
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
Step 9
ip router ospf instance-tag area area-id
Example:
switch(config-if)# ip router ospf 201
area 0
Step 10
copy running-config startup-config
Configures an IP address for this interface. You must
do this step after you assign this interface to a VRF.
Assigns this interface to the OSPFv2 instance and area
configured.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
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Verifying the OSPFv2 Configuration
This example shows how to create a VRF and add an interface to the VRF:
switch# configure terminal
switch(config)# vrf context NewVRF
switch(config)# router ospf 201
switch(config)# interface ethernet 1/2
switch(config-if)# vrf member NewVRF
switch(config-if)# ip address 192.0.2.1/16
switch(config-if)# ip router ospf 201 area 0
switch(config)# copy running-config startup-config
Verifying the OSPFv2 Configuration
To display the OSPFv2 configuration, perform one of the following tasks:
Command
Purpose
show ip ospf
Displays the OSPFv2 configuration.
show ip ospf border-routers [vrf
{vrf-name | all | default | management}]
Displays the OSPFv2 border router configuration.
show ip ospf database [vrf {vrf-name | all Displays the OSPFv2 link-state database summary.
| default | management}]
show ip ospf interface number [vrf
{vrf-name | all | default | management}]
Displays the OSPFv2 interface configuration.
show ip ospf lsa-content-changed-list
neighbor-id interface-type number [vrf
{vrf-name | all | default | management}]
Displays the OSPFv2 LSAs that have changed.
show ip ospf neighbors [neighbor-id]
[detail] [interface-type number] [vrf
{vrf-name | all | default | management}]
[summary]
Displays the list of OSPFv2 neighbors.
show ip ospf request-list neighbor-id
Displays the list of OSPFv2 link-state requests.
interface-type number [vrf {vrf-name | all
| default | management}]
show ip ospf retransmission-list
neighbor-id interface-type number [vrf
{vrf-name | all | default | management}]
Displays the list of OSPFv2 link-state retransmissions.
Displays the internal OSPFv2 routes.
show ip ospf route [ospf-route]
[summary] [vrf {vrf-name | all | default |
management}]
show ip ospf summary-address [vrf
{vrf-name | all | default | management}]
Displays information about the OSPFv2 summary
addresses.
show ip ospf virtual-links [brief] [vrf
{vrf-name | all | default | management}]
Displays information about OSPFv2 virtual links.
show ip ospf vrf {vrf-name | all | default | Displays information about the VRF-based OSPFv2
management}
configuration.
show running-configuration ospf
Displays the current running OSPFv2 configuration.
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Monitoring OSPFv2
Monitoring OSPFv2
To display OSPFv2 statistics, use the following commands:
Command
Purpose
show ip ospf policy statistics area area-id
filter-list {in | out} [vrf {vrf-name | all |
default | management}]
Displays the OSPFv2 route policy statistics for an area.
show ip ospf policy statistics redistribute Displays the OSPFv2 route policy statistics.
{bgp id | direct | eigrp id | isis id | ospf id |
rip id | static} [vrf {vrf-name | all | default
| management}]
show ip ospf statistics [vrf {vrf-name | all Displays the OSPFv2 event counters.
| default | management}]
show ip ospf traffic [interface-type
number] [vrf {vrf-name | all | default |
management}]
Displays the OSPFv2 packet counters.
Configuration Examples for OSPFv2
The following example shows how to configure OSPFv2:
feature ospf
router ospf 201
router-id 290.0.2.1
interface ethernet 1/2
ip router ospf 201 area 0.0.0.10
ip ospf authentication
ip ospf authentication-key 0 mypass
OSPF RFC Compatibility Mode Example
The following example shows how to configure OSPF to be compatible with routers that comply with
RFC 1583:
Note
You must configure RFC 1583 compatibility on any VRF that connects to routers running only RFC1583
compatible OSPF.
switch# configure terminal
switch(config)# feature ospf
switch(config)# router ospf Test1
switch(config-router)# rfc1583compatibility
switch(config-router)# vrf A
switch(config-router-vrf)# rfc1583compatibility
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Additional References
Additional References
For additional information related to implementing OSPF, see the following sections:
•
Related Documents, page 5-48
•
MIBs, page 5-48
Related Documents
Related Topic
Document Title
OSPFv3 for IPv6 networks
Chapter 6, “Configuring OSPFv3”
Route maps
Chapter 15, “Configuring Route Policy Manager”
MIBs
MIBs
MIBs Link
MIBs related to OSPFv2
To locate and download supported MIBs, go to the following URL:
ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MI
BSupportList.html
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6
Configuring OSPFv3
This chapter describes how to configure Open Shortest Path First version 3 (OSPFv3) for IPv6 networks
on the Cisco NX-OS device.
This chapter includes the following sections:
•
About OSPFv3, page 6-1
•
Licensing Requirements for OSPFv3, page 6-13
•
Prerequisites for OSPFv3, page 6-13
•
Guidelines and Limitations for OSPFv3, page 6-14
•
Default Settings, page 6-14
•
Configuring Basic OSPFv3, page 6-15
•
Configuring Advanced OSPFv3, page 6-21
•
Verifying the OSPFv3 Configuration, page 6-44
•
Monitoring OSPFv3, page 6-45
•
Configuration Examples for OSPFv3, page 6-45
•
Related Topics, page 6-45
•
Additional References, page 6-45
About OSPFv3
OSPFv3 is an IETF link-state protocol (see “Overview” section on page 1-1). An OSPFv3 router sends
a special message, called a hello packet, out each OSPF-enabled interface to discover other OSPFv3
neighbor routers. Once a neighbor is discovered, the two routers compare information in the Hello packet
to determine if the routers have compatible configurations. The neighbor routers attempt to establish
adjacency, which means that the routers synchronize their link-state databases to ensure that they have
identical OSPFv3 routing information. Adjacent routers share link-state advertisements (LSAs) that
include information about the operational state of each link, the cost of the link, and any other neighbor
information. The routers then flood these received LSAs out every OSPF-enabled interface so that all
OSPFv3 routers eventually have identical link-state databases. When all OSPFv3 routers have identical
link-state databases, the network is converged (see the “Convergence” section on page 1-6). Each router
then uses Dijkstra’s Shortest Path First (SPF) algorithm to build its route table.
You can divide OSPFv3 networks into areas. Routers send most LSAs only within one area, which
reduces the CPU and memory requirements for an OSPF-enabled router.
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About OSPFv3
OSPFv3 supports IPv6. For information about OSPF for IPv4, see Chapter 5, “Configuring OSPFv2.”
This section includes the following topics:
•
Comparison of OSPFv3 and OSPFv2, page 6-2
•
Hello Packet, page 6-2
•
Neighbors, page 6-3
•
Adjacency, page 6-3
•
Designated Routers, page 6-4
•
Areas, page 6-5
•
Link-State Advertisement, page 6-5
•
Multi-Area Adjacency, page 6-7
•
OSPFv3 and the IPv6 Unicast RIB, page 6-8
•
Address Family Support, page 6-8
•
Advanced Features, page 6-8
Comparison of OSPFv3 and OSPFv2
Much of the OSPFv3 protocol is the same as in OSPFv2. OSPFv3 is described in RFC 2740.
The key differences between the OSPFv3 and OSPFv2 protocols are as follows:
•
OSPFv3 expands on OSPFv2 to provide support for IPv6 routing prefixes and the larger size of IPv6
addresses.
•
LSAs in OSPFv3 are expressed as prefix and prefix length instead of address and mask.
•
The router ID and area ID are 32-bit numbers with no relationship to IPv6 addresses.
•
OSPFv3 uses link-local IPv6 addresses for neighbor discovery and other features.
•
OSPFv3 can use the IPv6 authentication trailer (RFC 6506) or IPSec (RFC 4552) for authentication.
However, neither of these options is supported on Cisco NX-OS.
•
OSPFv3 redefines LSA types.
Hello Packet
OSPFv3 routers periodically send Hello packets on every OSPF-enabled interface. The hello interval
determines how frequently the router sends these Hello packets and is configured per interface. OSPFv3
uses Hello packets for the following tasks:
•
Neighbor discovery
•
Keepalives
•
Bidirectional communications
•
Designated router election (see the “Designated Routers” section on page 6-4)
The Hello packet contains information about the originating OSPFv3 interface and router, including the
assigned OSPFv3 cost of the link, the hello interval, and optional capabilities of the originating router.
An OSPFv3 interface that receives these Hello packets determines if the settings are compatible with the
receiving interface settings. Compatible interfaces are considered neighbors and are added to the
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neighbor table (see the “Neighbors” section on page 6-3).
Hello packets also include a list of router IDs for the routers that the originating interface has
communicated with. If the receiving interface sees its own router ID in this list, bidirectional
communication has been established between the two interfaces.
OSPFv3 uses Hello packets as a keepalive message to determine if a neighbor is still communicating. If
a router does not receive a Hello packet by the configured dead interval (usually a multiple of the hello
interval), then the neighbor is removed from the local neighbor table.
Neighbors
An OSPFv3 interface must have a compatible configuration with a remote interface before the two can
be considered neighbors. The two OSPFv3 interfaces must match the following criteria:
•
Hello interval
•
Dead interval
•
Area ID (see the “Areas” section on page 6-5)
•
Optional capabilities
If there is a match, the information is entered into the neighbor table:
•
Neighbor ID—The router ID of the neighbor router.
•
Priority—Priority of the neighbor router. The priority is used for designated router election (see the
“Designated Routers” section on page 6-4).
•
State—Indication of whether the neighbor has just been heard from, is in the process of setting up
bidirectional communications, is sharing the link-state information, or has achieved full adjacency.
•
Dead time—Indication of how long since the last Hello packet was received from this neighbor.
•
Link-local IPv6 Address—The link-local IPv6 address of the neighbor.
•
Designated Router—Indication of whether the neighbor has been declared the designated router or
backup designated router (see the “Designated Routers” section on page 6-4).
•
Local interface—The local interface that received the Hello packet for this neighbor.
When the first Hello packet is received from a new neighbor, the neighbor is entered into the neighbor
table in the initialization state. Once bidirectional communication is established, the neighbor state
becomes two-way. ExStart and exchange states come next, as the two interfaces exchange their link-state
database. Once this is all complete, the neighbor moves into the full state, which signifies full adjacency.
If the neighbor fails to send any Hello packets in the dead interval, the neighbor is moved to the down
state and is no longer considered adjacent.
Adjacency
Not all neighbors establish adjacency. Depending on the network type and designated router
establishment, some neighbors become fully adjacent and share LSAs with all their neighbors, while
other neighbors do not. For more information, see the “Designated Routers” section on page 6-4.
Adjacency is established using Database Description packets, Link State Request packets, and Link
State Update packets in OSPFv3. The Database Description packet includes the LSA headers from the
link-state database of the neighbor (see the “Link-State Database” section on page 6-7). The local router
compares these headers with its own link-state database and determines which LSAs are new or updated.
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The local router sends a Link State Request packet for each LSA that it needs new or updated information
on. The neighbor responds with a Link State Update packet. This exchange continues until both routers
have the same link-state information.
Designated Routers
Networks with multiple routers present a unique situation for OSPFv3. If every router floods the network
with LSAs, the same link-state information is sent from multiple sources. Depending on the type of
network, OSPFv3 might use a single router, the designated router (DR), to control the LSA floods and
represent the network to the rest of the OSPFv3 area (see the “Areas” section on page 6-5). If the DR
fails, OSPFv3 selects a backup designated router (BDR). If the DR fails, OSPFv3 uses the BDR.
Network types are as follows:
•
Point-to-point—A network that exists only between two routers. All neighbors on a point-to-point
network establish adjacency and there is no DR.
•
Broadcast—A network with multiple routers that can communicate over a shared medium that
allows broadcast traffic, such as Ethernet. OSPFv3 routers establish a DR and BDR that controls
LSA flooding on the network. OSPFv3 uses the well-known IPv6 multicast addresses, FF02::5, and
a MAC address of 0100.5300.0005 to communicate with neighbors.
The DR and BDR are selected based on the information in the Hello packet. When an interface sends a
Hello packet, it sets the priority field and the DR and BDR field if it knows who the DR and BDR are.
The routers follow an election procedure based on which routers declare themselves in the DR and BDR
fields and the priority field in the Hello packet. As a final determinant, OSPFv3 chooses the highest
router IDs as the DR and BDR.
All other routers establish adjacency with the DR and the BDR and use the IPv6 multicast address
FF02::6 to send LSA updates to the DR and BDR. Figure 6-1 shows this adjacency relationship between
all routers and the DR.
DRs are based on a router interface. A router might be the DR for one network and not for another
network on a different interface.
DR in Multi-Access Network
Router A
Router B
Router D
or DR
Router C
Router E
= Multi-access network
= Logical connectivity to Designated Router for OSPF
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About OSPFv3
Areas
You can limit the CPU and memory requirements that OSPFv3 puts on the routers by dividing an
OSPFv3 network into areas. An area is a logical division of routers and links within an OSPFv3 domain
that creates separate subdomains. LSA flooding is contained within an area, and the link-state database
is limited to links within the area. You can assign an area ID to the interfaces within the defined area.
The Area ID is a 32-bit value that can be expressed as a number or in dotted decimal notation, such as
10.2.3.1.
Cisco NX-OS always displays the area in dotted decimal notation.
If you define more than one area in an OSPFv3 network, you must also define the backbone area, which
has the reserved area ID of 0. If you have more than one area, then one or more routers become area
border routers (ABRs). An ABR connects to both the backbone area and at least one other defined area
(see Figure 6-2).
Figure 6-2
OSPFv3 Areas
ABR1
Area 3
Area 0
ABR2
182983
Area 5
The ABR has a separate link-state database for each area which it connects to. The ABR sends Inter-Area
Prefix (type 3) LSAs (see the “Route Summarization” section on page 6-11) from one connected area to
the backbone area. The backbone area sends summarized information about one area to another area. In
Figure 6-2, Area 0 sends summarized information about Area 5 to Area 3.
OSPFv3 defines one other router type: the autonomous system boundary router (ASBR). This router
connects an OSPFv3 area to another autonomous system. An autonomous system is a network controlled
by a single technical administration entity. OSPFv3 can redistribute its routing information into another
autonomous system or receive redistributed routes from another autonomous system. For more
information, see the “Advanced Features” section on page 6-8.
Link-State Advertisement
OSPFv3 uses link-state advertisements (LSAs) to build its routing table.
This section includes the following topics:
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•
LSA Types, page 6-6
•
Link Cost, page 6-6
•
Flooding and LSA Group Pacing, page 6-7
•
Link-State Database, page 6-7
LSA Types
Table 6-1 shows the LSA types supported by Cisco NX-OS.
Table 6-1
LSA Types
Type
Name
Description
1
Router LSA
LSA sent by every router. This LSA includes the state and cost of all links
but does not include prefix information. Router LSAs trigger an SPF
recalculation. Router LSAs are flooded to the local OSPFv3 area.
2
Network LSA
LSA sent by the DR. This LSA lists all routers in the multi-access network
but does not include prefix information. Network LSAs trigger an SPF
recalculation. See the “Designated Routers” section on page 6-4.
3
Inter-Area
Prefix LSA
LSA sent by the area border router to an external area for each destination
in local area. This LSA includes the link cost from the border router to the
local destination. See the “Areas” section on page 6-5.
4
Inter-Area
Router LSA
LSA sent by the area border router to an external area. This LSA advertises
the link cost to the ASBR only. See the “Areas” section on page 6-5.
5
AS External
LSA
LSA generated by the ASBR. This LSA includes the link cost to an external
autonomous system destination. AS External LSAs are flooded throughout
the autonomous system. See the “Areas” section on page 6-5.
7
Type-7 LSA
LSA generated by the ASBR within an NSSA. This LSA includes the link
cost to an external autonomous system destination. Type-7 LSAs are
flooded only within the local NSSA. See the “Areas” section on page 6-5.
8
Link LSA
LSA sent by every router, using a link-local flooding scope (see the
“Flooding and LSA Group Pacing” section on page 6-7. This LSA includes
the link-local address and IPv6 prefixes for this link.
9
Intra-Area
Prefix LSA
LSA sent by every router. This LSA includes any prefix or link state
changes. Intra-Area Prefix LSAs are flooded to the local OSPFv3 area. This
LSA does not trigger an SPF recalculation.
11
Grace LSAs
LSA sent by a restarting router, using a link-local flooding scope. This LSA
is used for a graceful restart of OSPFv3. See the “High Availability and
Graceful Restart” section on page 6-12.
Link Cost
Each OSPFv3 interface is assigned a link cost. The cost is an arbitrary number. By default, Cisco NX-OS
assigns a cost that is the configured reference bandwidth divided by the interface bandwidth. By default,
the reference bandwidth is 40 Gb/s. The link cost is carried in the LSA updates for each link.
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Flooding and LSA Group Pacing
OSPFv3 floods LSA updates to different sections of the network, depending on the LSA type. OSPFv3
uses the following flooding scopes:
•
Link-local—LSA is flooded only on the local link. Used for Link LSAs and Grace LSAs.
•
Area-local—LSA is flooded throughout a single OSPF area only. Used for Router LSAs, Network
LSAs, Inter-Area-Prefix LSAs, Inter-Area-Router LSAs, and Intra-Area-Prefix LSAs.
•
AS scope—LSA is flooded throughout the routing domain. An AS scope is used for AS External
LSAs.
LSA flooding guarantees that all routers in the network have identical routing information. LSA flooding
depends on the OSPFv3 area configuration (see the “Areas” section on page 6-5). The LSAs are flooded
based on the link-state refresh time (every 30 minutes by default). Each LSA has its own link-state
refresh time.
You can control the flooding rate of LSA updates in your network by using the LSA group pacing
feature. LSA group pacing can reduce high CPU or buffer utilization. This feature groups LSAs with
similar link-state refresh times to allow OSPFv3 to pack multiple LSAs into an OSPFv3 Update
message.
By default, LSAs with link-state refresh times within 10 seconds of each other are grouped together. You
should lower this value for large link-state databases or raise it for smaller databases to optimize the
OSPFv3 load on your network.
Link-State Database
Each router maintains a link-state database for the OSPFv3 network. This database contains all the
collected LSAs and includes information on all the routes through the network. OSPFv3 uses this
information to calculate the bast path to each destination and populates the routing table with these best
paths.
LSAs are removed from the link-state database if no LSA update has been received within a set interval,
called the MaxAge. Routers flood a repeat of the LSA every 30 minutes to prevent accurate link-state
information from being aged out. Cisco NX-OS supports the LSA grouping feature to prevent all LSAs
from refreshing at the same time. For more information, see the “Flooding and LSA Group Pacing”
section on page 6-7.
Multi-Area Adjacency
OSPFv3 multi-area adjacency allows you to configure a link on the primary interface that is in more than
one area. This link becomes the preferred intra-area link in those areas. Multi-area adjacency establishes
a point-to-point unnumbered link in an OSPFv3 area that provides a topological path for that area. The
primary adjacency uses the link to advertise an unnumbered point-to-point link in the Router LSA for
the corresponding area when the neighbor state is full.
The multi-area interface exists as a logical construct over an existing primary interface for OSPF;
however, the neighbor state on the primary interface is independent of the multi-area interface. The
multi-area interface establishes a neighbor relationship with the corresponding multi-area interface on
the neighboring router. See the “Configuring Multi-Area Adjacency” section on page 6-27 for more
information.
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OSPFv3 and the IPv6 Unicast RIB
OSPFv3 runs the Dijkstra shortest path first algorithm on the link-state database. This algorithm selects
the best path to each destination based on the sum of all the link costs for each link in the path. The
shortest path for each destination is then put in the OSPFv3 route table. When the OSPFv3 network is
converged, this route table feeds into the IPv6 unicast Routing Information Base (RIB). OSPFv3
communicates with the IPv6 unicast RIB to do the following:
•
Add or remove routes
•
Handle route redistribution from other protocols
•
Provide convergence updates to remove stale OSPFv3 routes and for stub router advertisements (see
the “Multiple OSPFv3 Instances” section on page 6-12)
OSPFv3 also runs a modified Dijkstra algorithm for fast recalculation for Inter-Area Prefix, Inter-Area
Router, AS-External, type-7, and Intra-Area Prefix (type 3, 4, 5, 7, 8) LSA changes.
Address Family Support
Cisco NX-OS supports multiple address families, such as unicast IPv6 and multicast IPv6. OSPFv3
features that are specific to an address family are as follows:
•
Default routes
•
Route summarization
•
Route redistribution
•
Filter lists for border routers
•
SPF optimization
Use the address-family ipv6 unicast command to enter the IPv6 unicast address family configuration
mode when configuring these features.
Advanced Features
Cisco NX-OS supports advanced OSPFv3 features that enhance the usability and scalability of OSPFv3
in the network.
This section includes the following topics:
•
Stub Area, page 6-9
•
Not-So-Stubby Area, page 6-10
•
Virtual Links, page 6-10
•
Route Redistribution, page 6-11
•
Route Summarization, page 6-11
•
High Availability and Graceful Restart, page 6-12
•
Multiple OSPFv3 Instances, page 6-12
•
SPF Optimization, page 6-13
•
Virtualization Support, page 6-13
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About OSPFv3
Stub Area
You can limit the amount of external routing information that floods an area by making it a stub area. A
stub area is an area that does not allow AS External (type 5) LSAs (see the “Link-State Advertisement”
section on page 6-5). These LSAs are usually flooded throughout the local autonomous system to
propagate external route information. Stub areas have the following requirements:
•
All routers in the stub area are stub routers. See the “Stub Routing” section on page 1-7.
•
No ASBR routers exist in the stub area.
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You cannot configure virtual links in the stub area.
•
Figure 6-3 shows an example an OSPFv3 autonomous system where all routers in area 0.0.0.10 have to
go through the ABR to reach external autonomous systems. Area 0.0.0.10 can be configured as a stub
area.
Figure 6-3
Stub Area
ABR
Backbone
Area 10
ASBR
182984
Stub area
Stub areas use a default route for all traffic that needs to go through the backbone area to the external
autonomous system. The default route is an Inter-Area-Prefix LSA with the prefix length set to 0 for
IPv6.
Not-So-Stubby Area
A Not-So-Stubby Area (NSSA) is similar to the stub area, except that an NSSA allows you to import
autonomous system external routes within an NSSA using redistribution. The NSSA ASBR redistributes
these routes and generates type-7 LSAs that it floods throughout the NSSA. You can optionally configure
the ABR that connects the NSSA to other areas to translate this type-7 LSA to AS External (type 5)
LSAs. The ABR then floods these AS External LSAs throughout the OSPFv3 autonomous system.
Summarization and filtering are supported during the translation. See the “Link-State Advertisement”
section on page 6-5 for details on type-7 LSAs.
You can, for example, use NSSA to simplify administration if you are connecting a central site using
OSPFv3 to a remote site that is using a different routing protocol. Before NSSA, the connection between
the corporate site border router and a remote router could not be run as an OSPFv3 stub area because
routes for the remote site could not be redistributed into a stub area. With NSSA, you can extend OSPFv3
to cover the remote connection by defining the area between the corporate router and remote router as
an NSSA (see the “Configuring NSSA” section on page 6-25).
The backbone Area 0 cannot be an NSSA.
Virtual Links
Virtual links allow you to connect an OSPFv3 area ABR to a backbone area ABR when a direct physical
connection is not available. Figure 6-4 shows a virtual link that connects Area 3 to the backbone area
through Area 5.
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Figure 6-4
Virtual Links
Area 0
ABR2
ABR1
Area 3
182985
Area 5
You can also use virtual links to temporarily recover from a partitioned area, which occurs when a link
within the area fails, isolating part of the area from reaching the designated ABR to the backbone area.
Route Redistribution
OSPFv3 can learn routes from other routing protocols by using route redistribution. See the “Route
Redistribution” section on page 1-6. You configure OSPFv3 to assign a link cost for these redistributed
routes or a default link cost for all redistributed routes.
Route redistribution uses route maps to control which external routes are redistributed. You must
configure a route map with the redistribution to control which routes are passed into OSPFv2. A route
map allows you to filter routes based on attributes such as the destination, origination protocol, route
type, route tag, and so on. You can use route maps to modify parameters in the AS External (type 5) and
NSSA External (type 7) LSAs before these external routes are advertised in the local OSPFv3
autonomous system. For more information, see Chapter 15, “Configuring Route Policy Manager.”
Route Summarization
Because OSPFv3 shares all learned routes with every OSPF-enabled router, you might want to use route
summarization to reduce the number of unique routes that are flooded to every OSPF-enabled router.
Route summarization simplifies route tables by replacing more-specific addresses with an address that
represents all the specific addresses. For example, you can replace 2010:11:22:0:1000::1 and
2010:11:22:0:2000:679:1 with one summary address, 2010:11:22::/32.
Typically, you would summarize at the boundaries of area border routers (ABRs). Although you could
configure summarization between any two areas, it is better to summarize in the direction of the
backbone so that the backbone receives all the aggregate addresses and injects them, already
summarized, into other areas. The two types of summarization are as follows:
•
Inter-area route summarization
•
External route summarization
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You configure inter-area route summarization on ABRs, summarizing routes between areas in the
autonomous system. To take advantage of summarization, assign network numbers in areas in a
contiguous way to be able to lump these addresses into one range.
External route summarization is specific to external routes that are injected into OSPFv3 using route
redistribution. You should make sure that external ranges that are being summarized are contiguous.
Summarizing overlapping ranges from two different routers could cause packets to be sent to the wrong
destination. Configure external route summarization on ASBRs that are redistributing routes into OSPF.
When you configure a summary address, Cisco NX-OS automatically configures a discard route for the
summary address to prevent routing black holes and route loops.
High Availability and Graceful Restart
Cisco NX-OS provides a multilevel high-availability architecture. OSPFv3 supports stateful restart,
which is also referred to as non-stop routing (NSR). If OSPFv3 experiences problems, it attempts to
restart from its previous run-time state. The neighbors do not register any neighbor event in this case. If
the first restart is not successful and another problem occurs, OSPFv3 attempts a graceful restart.
A graceful restart, or non-stop forwarding (NSF), allows OSPFv3 to remain in the data forwarding path
through a process restart. When OSPFv3 needs to perform a graceful restart, it sends a link-local Grace
(type 11) LSA. This restarting OSPFv3 platform is called NSF capable.
The Grace LSA includes a grace period, which is a specified time that the neighbor OSPFv3 interfaces
hold onto the LSAs from the restarting OSPFv3 interface. (Typically, OSPFv3 tears down the adjacency
and discards all LSAs from a down or restarting OSPFv3 interface.) The participating neighbors, which
are called NSF helpers, keep all LSAs that originate from the restarting OSPFv3 interface as if the
interface was still adjacent.
When the restarting OSPFv3 interface is operational again, it rediscovers its neighbors, establishes
adjacency, and starts sending its LSA updates again. At this point, the NSF helpers recognize that the
graceful restart has finished.
Stateful restart is used in the following scenarios:
•
First recovery attempt after the process experiences problems
•
User-initiated switchover using the system switchover command
Graceful restart is used in the following scenarios:
•
Second recovery attempt after the process experiences problems within a 4-minute interval
•
Manual restart of the process using the restart ospfv3 command
•
Active supervisor removal
•
Active supervisor reload using the reload module active-sup command
Multiple OSPFv3 Instances
Cisco NX-OS supports multiple instances of the OSPFv3 protocol. By default, every instance uses the
same system router ID. You must manually configure the router ID for each instance if the instances are
in the same OSPFv3 autonomous system. For the number of supported OSPFv3 instances, see the Cisco
Nexus 9000 Series NX-OS Verified Scalability Guide.
The OSPFv3 header includes an instance ID field to identify that OSPFv3 packet for a particular OSPFv3
instance. You can assign the OSPFv3 instance. The interface drops all OSPFv3 packets that do not have
a matching OSPFv3 instance ID in the packet header.
Cisco NX-OS allows only one OSPFv3 instance on an interface.
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Licensing Requirements for OSPFv3
SPF Optimization
Cisco NX-OS optimizes the SPF algorithm in the following ways:
•
Partial SPF for Network (type 2) LSAs, Inter-Area Prefix (type 3) LSAs, and AS External (type 5)
LSAs—When there is a change on any of these LSAs, Cisco NX-OS performs a faster partial
calculation rather than running the whole SPF calculation.
•
SPF timers—You can configure different timers for controlling SPF calculations. These timers
include exponential backoff for subsequent SPF calculations. The exponential backoff limits the
CPU load of multiple SPF calculations.
Virtualization Support
Cisco NX-OS supports multiple process instances for OSPFv3. Each OSPFv3 instance can support
multiple virtual routing and forwarding (VRF) instances, up to the system limit. For the number of
supported OSPFv3 instances, see the Cisco Nexus 9000 Series NX-OS Verified Scalability Guide.
Licensing Requirements for OSPFv3
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
OSPFv3 requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Prerequisites for OSPFv3
OSPFv3 has the following prerequisites:
•
You must be familiar with routing fundamentals to configure OSPFv3.
•
You must be logged on to the switch.
•
You have configured at least one interface for IPv6 that is capable of communicating with a remote
OSPFv3 neighbor.
•
You have installed the Enterprise Services license.
•
You have completed the OSPFv3 network strategy and planning for your network. For example, you
must decide whether multiple areas are required.
•
You have enabled OSPF (see the “Enabling OSPFv3” section on page 6-15).
•
You are familiar with IPv6 addressing and basic configuration. See Chapter 3, “Configuring IPv6”
for information on IPv6 routing and addressing.
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Guidelines and Limitations for OSPFv3
Guidelines and Limitations for OSPFv3
OSPFv3 has the following configuration guidelines and limitations:
•
Bidirectional Forwarding Detection (BFD) is not supported for OSPFv3.
•
Cisco NX-OS displays areas in dotted decimal notation regardless of whether you enter the area in
decimal or dotted decimal notation.
•
If you configure OSPFv3 in a virtual port channel (vPC) environment, use the following timer
commands in router configuration mode on the core switch to ensure fast OSPF convergence when
a vPC peer link is shut down:
switch (config-router)# timers throttle spf 1 50 50
switch (config-router)# timers lsa-arrival 10
•
In scaled scenarios, when the number of interfaces and link-state advertisements in an OSPF process
is large, the snmp-walk on OSPF MIB objects is expected to time out with a small-values timeout
at the SNMP agent. If your observe a timeout on the querying SNMP agent while polling OSPF MIB
objects, increase the timeout value on the polling SNMP agent.
•
The following guidelines and limitations apply to the administrative distance feature:
– When an OSPF route has two or more equal cost paths, configuring the administrative distance
is non-deterministic for the match ip route-source command.
– For matching route sources in OSPFv3 routes, you must configure match ip route-source
instead of match ipv6 route-source because the route sources and router IDs for OSPFv3 are
IPv4 addresses.
– Configuring the administrative distance is supported only for the match route-type, match
ipv6 address prefix-list, and match ip route-source prefix-list commands. The other match
statements are ignored.
– The discard route is always assigned an administrative distance of 220. No configuration in the
table map applies to OSPF discard routes.
– There is no preference among the match route-type, match ipv6 address, and match ip
route-source commands for setting the administrative distance of OSPF routes. In this way, the
behavior of the table map for setting the administrative distance in Cisco NX-OS OSPF is
different from that in Cisco IOS OSPF.
•
Note
If you configure the delay restore seconds command in vPC configuration mode and if the VLANs
on the multichassis EtherChannel trunk (MCT) are announced by OSPFv2 or OSPFv3 using switch
virtual interfaces (SVIs), those SVIs are announced with MAX_LINK_COST on the vPC secondary
node for the duration of the configured time. As a result, all route or host programming completes
after the vPC synchronization operation (on a peer reload of the secondary vPC node) before
attracting traffic. This behavior allows for minimal packet loss for any north-to-south traffic.
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Default Settings
Table 6-2 lists the default settings for OSPFv3 parameters.
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Table 6-2
Default OSPFv3 Parameters
Parameters
Default
Administrative distance
110
Hello interval
10 seconds
Dead interval
40 seconds
Discard routes
Enabled
Graceful restart grace period
60 seconds
Graceful restart notify period
15 seconds
OSPFv3 feature
Disabled
Stub router advertisement announce time
600 seconds
Reference bandwidth for link cost calculation
40 Gb/s
LSA minimal arrival time
1000 milliseconds
LSA group pacing
10 seconds
SPF calculation initial delay time
0 milliseconds
SPF calculation hold time
5000 milliseconds
SPF calculation initial delay time
0 milliseconds
Configuring Basic OSPFv3
Configure OSPFv3 after you have designed your OSPFv3 network.
This section includes the following topics:
•
Enabling OSPFv3, page 6-15
•
Creating an OSPFv3 Instance, page 6-16
•
Configuring Networks in OSPFv3, page 6-19
Enabling OSPFv3
You must enable OSPFv3 before you can configure OSPFv3.
SUMMARY STEPS
1.
configure terminal
2.
feature ospfv3
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
feature ospfv3
Enables OSPFv3.
Example:
switch(config)# feature ospfv3
Step 3
show feature
(Optional) Displays enabled and disabled features.
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To disable the OSPFv3 feature and remove all associated configuration, use the following command in
global configuration mode:
Command
Purpose
no feature ospfv3
Disables the OSPFv3 feature and removes all
associated configuration.
Example:
switch(config)# no feature ospfv3
Creating an OSPFv3 Instance
The first step in configuring OSPFv3 is to create an instance or OSPFv3 instance. You assign a unique
instance tag for this OSPFv3 instance. The instance tag can be any string. For each OSPFv3 instance,
you can also configure the following optional parameters:
•
Router ID—Configures the router ID for this OSPFv3 instance. If you do not use this parameter, the
router ID selection algorithm is used. For more information, see the “Router IDs” section on
page 1-5.
•
Administrative distance—Rates the trustworthiness of a routing information source. For more
information, see the “Administrative Distance” section on page 1-7.
•
Log adjacency changes—Creates a system message whenever an OSPFv3 neighbor changes its
state.
•
Name lookup—Translates OSPF router IDs to hostnames, either by looking up the local hosts
database or querying DNS names in IPv6.
•
Maximum paths—Sets the maximum number of equal paths that OSPFv3 installs in the route table
for a particular destination. Use this parameter for load balancing between multiple paths.
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•
Reference bandwidth—Controls the calculated OSPFv3 cost metric for a network. The calculated
cost is the reference bandwidth divided by the interface bandwidth. You can override the calculated
cost by assigning a link cost when a network is added to the OSPFv3 instance. For more information,
see the “Configuring Networks in OSPFv3” section on page 6-19.
For more information about OSPFv3 instance parameters, see the “Configuring Advanced OSPFv3”
section on page 6-21.
BEFORE YOU BEGIN
You must enable OSPFv3 (see the “Enabling OSPFv3” section on page 6-15).
Ensure that the OSPFv3 instance tag that you plan on using is not already in use on this router.
Use the show ospfv3 instance-tag command to verify that the instance tag is not in use.
OSPFv3 must be able to obtain a router identifier (for example, a configured loopback address) or you
must configure the router ID option.
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
(Optional) router-id ip-address
4.
(Optional) show ipv6 ospfv3 instance-tag
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
router-id ip-address
Example:
switch(config-router)# router-id
192.0.2.1
Creates a new OSPFv3 instance with the configured
instance tag.
(Optional) Configures the OSPFv3 router ID. This ID
uses the dotted decimal notation and identifies this
OSPFv3 instance and must exist on a configured
interface in the system.
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Step 4
Command
Purpose
show ipv6 ospfv3 instance-tag
(Optional) Displays OSPFv3 information.
Example:
switch(config-router)# show ipv6 ospfv3
201
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To remove the OSPFv3 instance and all associated configuration, use the following command in
configuration mode:
Command
Purpose
no router ospfv3 instance-tag
Deletes the OSPFv3 instance and all associated
configuration.
Example:
switch(config)# no router ospfv3 201
Note
This command does not remove OSPF configuration in interface mode. You must manually remove any
OSPFv3 commands configured in interface mode.
You can configure the following optional parameters for OSPFv3 in router configuration mode:
Command
Purpose
log-adjacency-changes [detail]
Generates a system message whenever a neighbor
changes state.
Example:
switch(config-router)#
log-adjacency-changes
passive-interface default
Example:
switch(config-router)# passive-interface
default
Suppresses routing updates on all interfaces. This
command is overridden by the VRF or interface
command mode configuration.
You can configure the following optional parameters for OSPFv3 in address family configuration mode:
Command
Purpose
distance number
Configures the administrative distance for this
OSPFv3 instance. The range is from 1 to 255. The
default is 110.
Example:
switch(config-router-af)# distance 25
maximum-paths paths
Example:
switch(config-router-af)# maximum-paths 4
Configures the maximum number of equal OSPFv3
paths to a destination in the route table. This
command is used for load balancing. The range is
from 1 to 64. The default is 8.
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This example shows how to create an OSPFv3 instance:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# copy running-config startup-config
Configuring Networks in OSPFv3
You can configure a network to OSPFv3 by associating it through the interface that the router uses to
connect to that network (see the “Neighbors” section on page 6-3). You can add all networks to the
default backbone area (Area 0), or you can create new areas using any decimal number or an IP address.
Note
All areas must connect to the backbone area either directly or through a virtual link.
Note
OSPFv3 is not enabled on an interface until you configure a valid IPv6 address for that interface.
BEFORE YOU BEGIN
You must enable OSPFv3 (see the “Enabling OSPFv3” section on page 6-15).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
ipv6 address ipv6-prefix/length
4.
ipv6 router ospfv3 instance-tag area area-id [secondaries none]
5.
(Optional) show ipv6 ospfv3 instance-tag interface interface-type slot/port
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ipv6 address ipv6-prefix/length
Assigns an IPv6 address to this interface.
Example:
switch(config-if)# ipv6 address
2001:0DB8::1/48
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Step 4
Command
Purpose
ipv6 router ospfv3 instance-tag area
area-id [secondaries none]
Adds the interface to the OSPFv3 instance and area.
Example:
switch(config-if)# ipv6 router ospfv3
201 area 0
Step 5
show ipv6 ospfv3 instance-tag interface
interface-type slot/port
(Optional) Displays OSPFv3 information.
Example:
switch(config-if)# show ipv6 ospfv3 201
interface ethernet 1/2
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
You can configure the following optional parameters for OSPFv3 in interface configuration mode:
Command
Purpose
ospfv3 cost number
Configures the OSPFv3 cost metric for this
interface. The default is to calculate a cost metric,
based on the reference bandwidth and interface
bandwidth. The range is from 1 to 65535.
Example:
switch(config-if)# ospfv3 cost 25
ospfv3 dead-interval seconds
Example:
switch(config-if)# ospfv3 dead-interval 50
ospfv3 hello-interval seconds
Example:
switch(config-if)# ospfv3 hello-interval
25
ospfv3 instance instance
Example:
switch(config-if)# ospfv3 instance 25
Configures the OSPFv3 dead interval, in seconds.
The range is from 1 to 65535. The default is four
times the hello interval, in seconds.
Configures the OSPFv3 hello interval, in seconds.
The range is from 1 to 65535. The default is 10
seconds.
Configures the OSPFv3 instance ID. The range is
from 0 to 255. The default is 0. The instance ID is
link-local in scope.
Example:
switch(config-if)# ospfv3 mtu-ignore
Configures OSPFv3 to ignore any IP maximum
transmission unit (MTU) mismatch with a
neighbor. The default is to not establish adjacency
if the neighbor MTU does not match the local
interface MTU.
ospfv3 network {broadcast | point-point}
Sets the OSPFv3 network type.
ospfv3 mtu-ignore
Example:
switch(config-if)# ospfv3 network
broadcast
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Command
Purpose
[default | no] ospfv3 passive-interface
Suppresses routing updates on the interface. This
command overrides the router or VRF command
mode configuration. The default option removes
this interface mode command and reverts to the
router or VRF configuration, if present.
Example:
switch(config-if)# ospfv3
passive-interface
ospfv3 priority number
Example:
switch(config-if)# ospfv3 priority 25
Configures the OSPFv3 priority, used to determine
the DR for an area. The range is from 0 to 255. The
default is 1. See the “Designated Routers” section
on page 6-4.
Shuts down the OSPFv3 instance on this interface.
ospfv3 shutdown
Example:
switch(config-if)# ospfv3 shutdown
This example shows how to add a network area 0.0.0.10 in OSPFv3 instance 201:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# ipv6 address 2001:0DB8::1/48
switch(config-if)# ipv6 ospfv3 201 area 0.0.0.10
switch(config-if)# copy running-config startup-config
Configuring Advanced OSPFv3
Configure OSPFv3 after you have designed your OSPFv3 network.
This section includes the following topics:
•
Configuring Filter Lists for Border Routers, page 6-22
•
Configuring Stub Areas, page 6-23
•
Configuring a Totally Stubby Area, page 6-24
•
Configuring NSSA, page 6-25
•
Configuring Multi-Area Adjacency, page 6-27
•
Configuring Virtual Links, page 6-28
•
Configuring Redistribution, page 6-30
•
Limiting the Number of Redistributed Routes, page 6-32
•
Configuring Route Summarization, page 6-34
•
Configuring the Administrative Distance of Routes, page 6-35
•
Modifying the Default Timers, page 6-38
•
Configuring Graceful Restart, page 6-40
•
Restarting an OSPFv3 Instance, page 6-42
•
Configuring OSPFv3 with Virtualization, page 6-42
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Configuring Advanced OSPFv3
Configuring Filter Lists for Border Routers
You can separate your OSPFv3 domain into a series of areas that contain related networks. All areas must
connect to the backbone area through an area border router (ABR). OSPFv3 domains can connect to
external domains as well through an autonomous system border router (ASBR). See the “Areas” section
on page 6-5.
ABRs have the following optional configuration parameters:
•
Area range—Configures route summarization between areas. For more information, see the
“Configuring Route Summarization” section on page 6-34.
•
Filter list—Filters the Inter-Area Prefix (type 3) LSAs on an ABR that are allowed in from an
external area.
ASBRs also support filter lists.
BEFORE YOU BEGIN
Create the route map that the filter list uses to filter IP prefixes in incoming or outgoing Inter-Area Prefix
(type 3) LSAs. See Chapter 15, “Configuring Route Policy Manager.”
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
address-family ipv6 unicast
4.
area area-id filter-list route-map map-name {in | out}
5.
(Optional) show ipv6 ospfv3 policy statistics area id filter-list {in | out}
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
address-family ipv6 unicast
Creates a new OSPFv3 instance with the configured
instance tag.
Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
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Step 4
Command
Purpose
area area-id filter-list route-map
map-name {in | out}
Filters incoming or outgoing Inter-Area Prefix (type 3)
LSAs on an ABR.
Example:
switch(config-router-af)# area 0.0.0.10
filter-list route-map FilterLSAs in
Step 5
show ipv6 ospfv3 policy statistics area
id filter-list {in | out}
(Optional) Displays OSPFv3 policy information.
Example:
switch(config-if)# show ipv6 ospfv3
policy statistics area 0.0.0.10
filter-list in
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to enable graceful restart if it has been disabled:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# area 0.0.0.10 filter-list route-map FilterLSAs in
switch(config-router-af)# copy running-config startup-config
Configuring Stub Areas
You can configure a stub area for part of an OSPFv3 domain where external traffic is not necessary. Stub
areas block AS External (type 5) LSAs, limiting unnecessary routing to and from selected networks. See
the “Stub Area” section on page 6-9. You can optionally block all summary routes from going into the
stub area.
BEFORE YOU BEGIN
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
Ensure that there are no virtual links or ASBRs in the proposed stub area.
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
area area-id stub
4.
(Optional) address-family ipv6 unicast
5.
(Optional) area area-id default-cost cost
6.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
area area-id stub
Creates a new OSPFv3 instance with the configured
instance tag.
Creates this area as a stub area.
Example:
switch(config-router)# area 0.0.0.10
stub
Step 4
address-family ipv6 unicast
(Optional) Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 5
area area-id default-cost cost
Example:
switch(config-router-af)# area 0.0.0.10
default-cost 25
Step 6
copy running-config startup-config
(Optional) Sets the cost metric for the default summary
route sent into this stub area. The range is from 0 to
16777215.
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to create a stub area that blocks all summary route updates:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 stub no-summary
switch(config-router)# copy running-config startup-config
Configuring a Totally Stubby Area
You can create a totally stubby area and prevent all summary route updates from going into the stub area.
To create a totally stubby area, use the following command in router configuration mode:
Command
Purpose
area area-id stub no-summary
Creates this area as a totally stubby area.
Example:
switch(config-router)# area 20 stub
no-summary
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Configuring NSSA
You can configure an NSSA for part of an OSPFv3 domain where limited external traffic is required. See
the “Not-So-Stubby Area” section on page 6-10. You can optionally translate this external traffic to an
AS External (type 5) LSA and flood the OSPFv3 domain with this routing information. An NSSA can
be configured with the following optional parameters:
•
No redistribution—Redistributes routes that bypass the NSSA to other areas in the OSPFv3
autonomous system. Use this option when the NSSA ASBR is also an ABR.
•
Default information originate—Generates a Type-7 LSA for a default route to the external
autonomous system. Use this option on an NSSA ASBR if the ASBR contains the default route in
the routing table. This option can be used on an NSSA ABR whether or not the ABR contains the
default route in the routing table.
•
Route map—Filters the external routes so that only those routes you want are flooded throughout
the NSSA and other areas.
•
Translate—Translates Type-7 LSAs to AS External (type 5) LSAs for areas outside the NSSA. Use
this command on an NSSA ABR to flood the redistributed routes throughout the OSPFv3
autonomous system. You can optionally suppress the forwarding address in these AS External LSAs.
•
No summary—Blocks all summary routes from flooding the NSSA. Use this option on the NSSA
ABR.
BEFORE YOU BEGIN
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
Ensure that there are no virtual links in the proposed NSSA and that it is not the backbone area.
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
area area-id nssa [no-redistribution] [default-information-originate] [route-map map-name]
[no-summary] [translate type7 {always | never} [suppress-fa]]
4.
(Optional) address-family ipv6 unicast
5.
(Optional) area area-id default-cost cost
6.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
area area-id nssa [no-redistribution]
[default-information-originate]
[route-map map-name] [no-summary]
[translate type7 {always | never}
[suppress-fa]]
Creates a new OSPFv3 instance with the configured
instance tag.
Creates this area as an NSSA.
Example:
switch(config-router)# area 0.0.0.10
nssa
Step 4
address-family ipv6 unicast
(Optional) Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 5
area area-id default-cost cost
Example:
switch(config-router-af)# area 0.0.0.10
default-cost 25
Step 6
copy running-config startup-config
(Optional) Sets the cost metric for the default summary
route sent into this NSSA. The range is from 0 to
16777215.
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to create an NSSA that blocks all summary route updates:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 nssa no-summary
switch(config-router)# copy running-config startup-config
This example shows how to create an NSSA that generates a default route:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 nssa default-info-originate
switch(config-router)# copy running-config startup-config
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This example shows how to create an NSSA that filters external routes and blocks all summary route
updates:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 nssa route-map ExternalFilter no-summary
switch(config-router)# copy running-config startup-config
This example shows how to create an NSSA that always translates Type-7 LSAs to AS External (type 5)
LSAs:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 nssa translate type 7 always
switch(config-router)# copy running-config startup-config
This example shows how to create an NSSA that blocks all summary route updates:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 nssa no-summary
switch(config-router)# copy running-config startup-config
Configuring Multi-Area Adjacency
You can add more than one area to an existing OSPFv3 interface. The additional logical interfaces
support multi-area adjacency.
BEFORE YOU BEGIN
You must enable OSPFv3 (see the “Enabling OSPFv3” section on page 6-15).
Ensure that you have configured a primary area for the interface (see the “Configuring Networks in
OSPFv3” section on page 6-19).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
ipv6 router ospfv3 instance-tag multi-area area-id
4.
(Optional) show ipv6 ospfv3 instance-tag interface interface-type slot/port
5.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ipv6 router ospfv3 instance-tag
multi-area area-id
Adds the interface to another area.
Example:
switch(config-if)# ipv6 router ospfv3
201 multi-area 3
Step 4
show ipv6 ospfv3 instance-tag interface
interface-type slot/port
(Optional) Displays OSPFv3 information.
Example:
switch(config-if)# show ipv6 ospfv3 201
interface ethernet 1/2
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to add a second area to an OSPFv3 interface:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# ipv6 address 2001:0DB8::1/48
switch(config-if)# ipv6 ospfv3 201 area 0.0.0.10
switch(config-if)# ipv6 ospfv3 201 multi-area 20
switch(config-if)# copy running-config startup-config
Configuring Virtual Links
A virtual link connects an isolated area to the backbone area through an intermediate area. See the
“Virtual Links” section on page 6-10. You can configure the following optional parameters for a virtual
link:
•
Dead interval—Sets the time that a neighbor waits for a Hello packet before declaring the local
router as dead and tearing down adjacencies.
•
Hello interval—Sets the time between successive Hello packets.
•
Retransmit interval—Sets the estimated time between successive LSAs.
•
Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.
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Note
You must configure the virtual link on both routers involved before the link becomes active.
BEFORE YOU BEGIN
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
area area-id virtual-link router-id
4.
(Optional) show ipv6 ospfv3 virtual-link [brief]
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
area area-id virtual-link router-id
Example:
switch(config-router)# area 0.0.0.10
virtual-link 2001:0DB8::1
switch(config-router-vlink)#
Step 4
show ipv6 ospfv3 virtual-link [brief]
Example:
switch(config-if)# show ipv6 ospfv3
virtual-link
Step 5
copy running-config startup-config
Creates a new OSPFv3 instance with the configured
instance tag.
Creates one end of a virtual link to a remote router.
You must create the virtual link on that remote router
to complete the link.
(Optional) Displays OSPFv3 virtual link
information.
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy running-config
startup-config
You can configure the following optional commands in virtual link configuration mode:
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Command
Purpose
dead-interval seconds
(Optional) Configures the OSPFv3 dead interval, in
seconds. The range is from 1 to 65535. The default is four
times the hello interval, in seconds.
Example:
switch(config-router-vlink)#
dead-interval 50
hello-interval seconds
Example:
switch(config-router-vlink)#
hello-interval 25
retransmit-interval seconds
Example:
switch(config-router-vlink)#
retransmit-interval 50
transmit-delay seconds
Example:
switch(config-router-vlink)#
transmit-delay 2
(Optional) Configures the OSPFv3 hello interval, in
seconds. The range is from 1 to 65535. The default is 10
seconds.
(Optional) Configures the OSPFv3 retransmit interval, in
seconds. The range is from 1 to 65535. The default is 5.
(Optional) Configures the OSPFv3 transmit-delay, in
seconds. The range is from 1 to 450. The default is 1.
These examples show how to create a simple virtual link between two ABRs:
Configuration for ABR 1 (router ID 2001:0DB8::1) is as follows:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# area 0.0.0.10 virtual-link 2001:0DB8::10
switch(config-router)# copy running-config startup-config
Configuration for ABR 2 (router ID 2001:0DB8::10) is as follows:
switch# configure terminal
switch(config)# router ospf 101
switch(config-router)# area 0.0.0.10 virtual-link 2001:0DB8::1
switch(config-router)# copy running-config startup-config
Configuring Redistribution
You can redistribute routes learned from other routing protocols into an OSPFv3 autonomous system
through the ASBR.
You can configure the following optional parameters for route redistribution in OSPF:
•
Note
•
Note
Default information originate—Generates an AS External (type 5) LSA for a default route to the
external autonomous system.
Default information originate ignores match statements in the optional route map.
Default metric—Sets all redistributed routes to the same cost metric.
If you redistribute static routes, Cisco NX-OS also redistributes the default static route.
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BEFORE YOU BEGIN
Create the necessary route maps used for redistribution.
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
address-family ipv6 unicast
4.
redistribute {bgp id | direct | isis id | rip id | static} route-map map-name
5.
default-information originate [always] [route-map map-name]
6.
default-metric cost
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
address-family ipv6 unicast
Creates a new OSPFv3 instance with the configured
instance tag.
Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 4
Step 5
redistribute {bgp id | direct | isis id
| rip id | static} route-map map-name
Redistributes the selected protocol into OSPFv3
through the configured route map.
Example:
switch(config-router-af)# redistribute
bgp route-map FilterExternalBGP
Note
default-information originate [always]
[route-map map-name]
Creates a default route into this OSPFv3 domain if the
default route exists in the RIB. Use the following
optional keywords:
Example:
switch(config-router-af)#
default-information-originate route-map
DefaultRouteFilter
If you redistribute static routes, Cisco NX-OS
also redistributes the default static route.
•
always —Always generates the default route of
0.0.0. even if the route does not exist in the RIB.
•
route-map—Generates the default route if the
route map returns true.
Note
This command ignores match statements in
the route map.
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Step 6
Step 7
Command
Purpose
default-metric cost
Example:
switch(config-router-af)# default-metric
25
Sets the cost metric for the redistributed routes. The
range is from 1 to 16777214. This command does not
apply to directly connected routes. Use a route map to
set the default metric for directly connected routes.
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to redistribute the Border Gateway Protocol (BGP) into OSPFv3:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# redistribute bgp route-map FilterExternalBGP
switch(config-router-af)# copy running-config startup-config
Limiting the Number of Redistributed Routes
Route redistribution can add many routes to the OSPFv3 route table. You can configure a maximum limit
to the number of routes accepted from external protocols. OSPFv3 provides the following options to
configure redistributed route limits:
•
Fixed limit—Logs a message when OSPFv3 reaches the configured maximum. OSPFv3 does not
accept any more redistributed routes. You can optionally configure a threshold percentage of the
maximum where OSPFv3 logs a warning when that threshold is passed.
•
Warning only—Logs a warning only when OSPFv3 reaches the maximum. OSPFv3 continues to
accept redistributed routes.
•
Withdraw—Starts the configured timeout period when OSPFv3 reaches the maximum. After the
timeout period, OSPFv3 requests all redistributed routes if the current number of redistributed
routes is less than the maximum limit. If the current number of redistributed routes is at the
maximum limit, OSPFv3 withdraws all redistributed routes. You must clear this condition before
OSPFv3 accepts more redistributed routes. You can optionally configure the timeout period.
BEFORE YOU BEGIN
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
address-family ipv6 unicast
4.
redistribute {bgp id | direct | isis id | rip id | static} route-map map-name
5.
redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]
6.
(Optional) show running-config ospfv3
7.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
address-family ipv6 unicast
Creates a new OSPFv3 instance with the configured
instance tag.
Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 4
redistribute {bgp id | direct | isis id
| rip id | static} route-map map-name
Redistributes the selected protocol into OSPFv3
through the configured route map.
Example:
switch(config-router-af)# redistribute
bgp route-map FilterExternalBGP
Step 5
redistribute maximum-prefix max
[threshold] [warning-only | withdraw
[num-retries timemout]]
Example:
switch(config-router)# redistribute
maximum-prefix 1000 75 warning-only
Step 6
show running-config ospfv3
Specifies a maximum number of prefixes that OSPFv2
distributes. The range is from 1 to 65535. Optionally,
specifies the following:
•
threshold—Percentage of maximum prefixes that
triggers a warning message.
•
warning-only—Logs an warning message when
the maximum number of prefixes is exceeded.
•
withdraw—Withdraws all redistributed routes
and optionally tries to retrieve the redistributed
routes. The num-retries range is from 1 to 12. The
timeout range is from 60 to 600 seconds. The
default is 300 seconds.
(Optional) Displays the OSPFv3 configuration.
Example:
switch(config-router)# show
running-config ospf
Step 7
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
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This example shows how to limit the number of redistributed routes into OSPF:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# redistribute bgp route-map FilterExternalBGP
switch(config-router-af)# redistribute maximum-prefix 1000 75
Configuring Route Summarization
You can configure route summarization for inter-area routes by configuring an address range that is
summarized. You can also configure route summarization for external, redistributed routes by
configuring a summary address for those routes on an ASBR. For more information, see the “Route
Summarization” section on page 6-11.
BEFORE YOU BEGIN
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
address-family ipv6 unicast
4.
area area-id range ipv6-prefix/length [no-advertise] [cost cost]
or
5.
summary-address ipv6-prefix/length [no-advertise] [tag tag]
6.
(Optional) show ipv6 ospfv3 summary-address
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
address-family ipv6 unicast
Creates a new OSPFv3 instance with the configured
instance tag.
Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
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Step 4
Command
Purpose
area area-id range ipv6-prefix/length
[no-advertise] [cost cost]
Creates a summary address on an ABR for a range of
addresses and optionally advertises this summary
address in a Inter-Area Prefix (type 3) LSA. The cost
range is from 0 to 16777215.
Example:
switch(config-router-af)# area 0.0.0.10
range 2001:0DB8::/48 advertise
Step 5
summary-address ipv6-prefix/length
[no-advertise][tag tag]
Example:
switch(config-router-af)#
summary-address 2001:0DB8::/48 tag 2
Creates a summary address on an ASBR for a range of
addresses and optionally assigns a tag for this
summary address that can be used for redistribution
with route maps.
Step 6
show ipv6 ospfv3 summary-address
(Optional) Displays information about OSPFv3
summary addresses.
Example:
switch(config-router)# show ipv6 ospfv3
summary-address
Step 7
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to create summary addresses between areas on an ABR:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# address-family ipv6 unicast
switch(config-router)# area 0.0.0.10 range 2001:0DB8::/48
switch(config-router)# copy running-config startup-config
This example shows how to create summary addresses on an ASBR:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# address-family ipv6 unicast
switch(config-router)# summary-address 2001:0DB8::/48
switch(config-router)# no discard route internal
switch(config-router)# copy running-config startup-config
Configuring the Administrative Distance of Routes
You can set the administrative distance of routes added by OSPFv3 into the RIB.
The administrative distance is a rating of the trustworthiness of a routing information source. A higher
value indicates a lower trust rating. Typically, a route can be learned through more than one routing
protocol. The administrative distance is used to discriminate between routes learned from more than one
routing protocol. The route with the lowest administrative distance is installed in the IP routing table.
BEFORE YOU BEGIN
Ensure that you have enabled OSPF (see the “Enabling OSPFv3” section on page 6-15).
See the guidelines and limitations for this feature in the “Guidelines and Limitations for OSPFv3”
section on page 6-14.
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SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
address-family ipv6 unicast
4.
[no] table-map map-name
5.
exit
6.
exit
7.
route-map map-name [permit | deny] [seq]
8.
match route-type route-type
9.
match ip route-source prefix-list name
10. match ipv6 address prefix-list name
11. set distance value
12. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config)# router ospf 201
switch(config-router)#
Step 3
address-family ipv6 unicast
Creates a new OSPFv3 instance with the configured
instance tag.
Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 4
[no] table-map map-name
Example:
switch(config-router-af)# table-map foo
Step 5
exit
Configures the policy for filtering or modifying
OSPFv3 routes before sending them to the RIB. You
can enter up to 63 alphanumeric characters for the map
name.
Exits router address-family configuration mode.
Example:
switch(config-router-af)# exit
switch(config-router)#
Step 6
exit
Exits router configuration mode.
Example:
switch(config-router)# exit
switch(config)#
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Step 7
Command
Purpose
route-map map-name [permit | deny] [seq]
Creates a route map or enters route-map configuration
mode for an existing route map. Use seq to order the
entries in a route map.
Example:
switch(config)# route-map foo permit 10
switch(config-route-map)#
Step 8
match route-type route-type
Example:
switch(config-route-map)# match
route-type external
Step 9
match ip route-source prefix-list name
Example:
switch(config-route-map)# match ip
route-source prefix-list p1
Step 10
match ipv6 address prefix-list name
Example:
switch(config-route-map)# match ipv6
address prefix-list p1
Step 11
set distance value
Example:
switch(config-route-map)# set distance
150
Step 12
copy running-config startup-config
Note
The permit option enables you to set the
distance. If you use the deny option, the
default distance is applied.
Matches against one of the following route types:
•
external—The external route (BGP, EIGRP, and
OSPF type 1 or 2)
•
inter-area—OSPF inter-area route
•
internal—The internal route (including the OSPF
intra- or inter-area)
•
intra-area—OSPF intra-area route
•
nssa-external—The NSSA external route (OSPF
type 1 or 2)
•
type-1—The OSPF external type 1 route
•
type-2—The OSPF external type 2 route
Matches the IPv6 route source address or router ID of
a route to one or more IP prefix lists. Use the ip
prefix-list command to create the prefix list.
Note
For OSPFv3, the router ID is 4 bytes.
Matches against one or more IPv6 prefix lists. Use the
ip prefix-list command to create the prefix list.
Sets the administrative distance of routes for OSPFv3.
The range is from 1 to 255.
(Optional) Saves this configuration change.
Example:
switch(config-route-map)# copy
running-config startup-config
This example shows how to configure the OSPFv3 administrative distance for inter-area routes to 150,
for external routes to 200, and for all prefixes in prefix list p1 to 190:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# table-map foo
switch(config-router)# exit
switch(config)# exit
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switch(config)# route-map
switch(config-route-map)#
switch(config-route-map)#
switch(config)# route-map
switch(config-route-map)#
switch(config-route-map)#
switch(config)# route-map
switch(config-route-map)#
switch(config-route-map)#
switch(config-route-map)#
foo permit 10
match route-type inter-area
set distance 150
foo permit 20
match route-type external
set distance 200
foo permit 30
match ip route-source prefix-list p1
match ipv6 address prefix-list p1
set distance 190
Modifying the Default Timers
OSPFv3 includes a number of timers that control the behavior of protocol messages and shortest path
first (SPF) calculations. OSPFv3 includes the following optional timer parameters:
•
LSA arrival time—Sets the minimum interval allowed between LSAs arriving from a neighbor.
LSAs that arrive faster than this time are dropped.
•
Pacing LSAs—Sets the interval at which LSAs are collected into a group and refreshed,
checksummed, or aged. This timer controls how frequently LSA updates occur and optimizes how
many are sent in an LSA update message (see the “Flooding and LSA Group Pacing” section on
page 6-7).
•
Throttle LSAs—Sets rate limits for generating LSAs. This timer controls how frequently LSAs are
generated after a topology change occurs.
•
Throttle SPF calculation—Controls how frequently the SPF calculation is run.
At the interface level, you can also control the following timers:
•
Retransmit interval—Sets the estimated time between successive LSAs.
•
Transmit delay—Sets the estimated time to transmit an LSA to a neighbor.
See the “Configuring Networks in OSPFv3” section on page 6-19 for information on the hello interval
and dead timer.
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
timers lsa-arrival msec
4.
timers lsa-group-pacing seconds
5.
timers throttle lsa start-time hold-interval max-time
6.
address-family ipv6 unicast
7.
timers throttle spf delay-time hold-time
8.
interface type slot/port
9.
ospfv3 retransmit-interval seconds
10. ospfv3 transmit-delay seconds
11. (Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
timers lsa-arrival msec
Example:
switch(config-router)# timers
lsa-arrival 2000
Step 4
timers lsa-group-pacing seconds
Example:
switch(config-router)# timers
lsa-group-pacing 200
Step 5
Creates a new OSPFv3 instance with the configured
instance tag.
Sets the LSA arrival time in milliseconds. The range is
from 10 to 600000. The default is 1000 milliseconds.
Sets the interval in seconds for grouping LSAs. The
range is from 1 to 1800. The default is 10 seconds.
timers throttle lsa start-time
hold-interval max-time
Sets the rate limit in milliseconds for generating LSAs.
You can configure the following timers:
Example:
switch(config-router)# timers throttle
lsa network 350 5000 6000
start-time—The range is from 50 to 5000 milliseconds.
The default value is 50 milliseconds.
hold-interval—The range is from 50 to 30,000
milliseconds. The default value is 5000 milliseconds.
max-time—The range is from 50 to 30,000
milliseconds. The default value is 5000 milliseconds.
Step 6
address-family ipv6 unicast
Enters IPv6 unicast address family mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 7
timers throttle spf delay-time hold-time
Example:
switch(config-router)# timers throttle
spf 3000 2000
Step 8
interface type slot/port
Sets the SPF best-path schedule initial delay time and
the minimum hold time in seconds between SPF
best-path calculations. The range is from 1 to 600000.
The default is no delay time and 5000 millisecond hold
time.
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 9
ospfv3 retransmit-interval seconds
Example:
switch(config-if)# ospfv3
retransmit-interval 30
Sets the estimated time in seconds between LSAs
transmitted from this interface. The range is from 1 to
65535. The default is 5.
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Step 10
Command
Purpose
ospfv3 transmit-delay seconds
Sets the estimated time in seconds to transmit an LSA
to a neighbor. The range is from 1 to 450. The default
is 1.
Example:
switch(config-if)# ospfv3 transmit-delay
600
switch(config-if)#
Step 11
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to control LSA flooding with the lsa-group-pacing option:
switch# configure terminal
switch(config)# router ospf 201
switch(config-router)# timers lsa-group-pacing 300
switch(config-router)# copy running-config startup-config
Configuring Graceful Restart
Graceful restart is enabled by default. You can configure the following optional parameters for graceful
restart in an OSPFv3 instance:
•
Grace period—Configures how long neighbors should wait after a graceful restart has started before
tearing down adjacencies.
•
Helper mode disabled—Disables helper mode on the local OSPFv3 instance. OSPFv3 does not
participate in the graceful restart of a neighbor.
•
Planned graceful restart only—Configures OSPFv3 to support graceful restart only in the event of a
planned restart.
BEFORE YOU BEGIN
You must enable OSPFv3 (see the “Enabling OSPFv3” section on page 6-15).
Ensure that all neighbors are configured for graceful restart with matching optional parameters set.
SUMMARY STEPS
1.
configure terminal
2.
router ospfv3 instance-tag
3.
graceful-restart
4.
graceful-restart grace-period seconds
5.
graceful-restart helper-disable
6.
graceful-restart planned-only
7.
(Optional) show ipv6 ospfv3 instance-tag
8.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 3
graceful-restart
Example:
switch(config-router)# graceful-restart
Step 4
graceful-restart grace-period seconds
Example:
switch(config-router)# graceful-restart
grace-period 120
Step 5
graceful-restart helper-disable
Creates a new OSPFv3 instance with the configured
instance tag.
Enables graceful restart. A graceful restart is enabled
by default.
Sets the grace period, in seconds. The range is from 5
to 1800. The default is 60 seconds.
Disables helper mode. Enabled by default.
Example:
switch(config-router)# graceful-restart
helper-disable
Step 6
graceful-restart planned-only
Configures graceful restart for planned restarts only.
Example:
switch(config-router)# graceful-restart
planned-only
Step 7
show ipv6 ospfv3 instance-tag
(Optional) Displays OSPFv3 information.
Example:
switch(config-if)# show ipv6 ospfv3 201
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to enable graceful restart if it has been disabled and set the grace period to 120
seconds:
switch# configure terminal
switch(config)# router ospfv3 201
switch(config-router)# graceful-restart
switch(config-router)# graceful-restart grace-period 120
switch(config-router)# copy running-config startup-config
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Restarting an OSPFv3 Instance
You can restart an OSPv3 instance. This action clears all neighbors for the instance.
To restart an OSPFv3 instance and remove all associated neighbors, use the following command:
Command
Purpose
restart ospfv3 instance-tag
Restarts the OSPFv3 instance and removes all
neighbors.
Example:
switch(config)# restart ospfv3 201
Configuring OSPFv3 with Virtualization
You can configure multiple OSPFv3 instances. You can also create multiple VRFs and use the same or
multiple OSPFv3 instances in each VRF. You assign an OSPFv3 interface to a VRF.
Note
Configure all other parameters for an interface after you configure the VRF for an interface. Configuring
a VRF for an interface deletes all the configuration for that interface.
BEFORE YOU BEGIN
You must enable OSPF (see the “Enabling OSPFv3” section on page 6-15).
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf_name
3.
router ospfv3 instance-tag
4.
vrf vrf-name
5.
(Optional) maximum-paths paths
6.
interface type slot/port
7.
vrf member vrf-name
8.
ipv6 address ipv6-prefix/length
9.
ipv6 ospfv3 instance-tag area area-id
10. (Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context
RemoteOfficeVRF
switch(config-vrf)#
Step 3
router ospfv3 instance-tag
Example:
switch(config)# router ospfv3 201
switch(config-router)#
Step 4
Creates a new VRF and enters VRF configuration
mode.
Creates a new OSPFv3 instance with the configured
instance tag.
Enters VRF configuration mode.
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
Step 5
maximum-paths paths
Example:
switch(config-router-vrf)# maximum-paths
4
Step 6
interface type slot/port
(Optional) Configures the maximum number of equal
OSPFv3 paths to a destination in the route table for this
VRF. Use this command for load balancing.
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 7
Adds this interface to a VRF.
vrf member vrf-name
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Step 8
ipv6 address ipv6-prefix/length
Example:
switch(config-if)# ipv6 address
2001:0DB8::1/48
Step 9
ipv6 ospfv3 instance-tag area area-id
Example:
switch(config-if)# ipv6 ospfv3 201 area
0
Step 10
copy running-config startup-config
Configures an IP address for this interface. You must
do this step after you assign this interface to a VRF.
Assigns this interface to the OSPFv3 instance and area
configured.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
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Verifying the OSPFv3 Configuration
This example shows how to create a VRF and add an interface to the VRF:
switch# configure terminal
switch(config)# vrf context NewVRF
switch(config-vrf)# exit
switch(config)# router ospfv3 201
switch(config-router)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# vrf member NewVRF
switch(config-if)# ipv6 address 2001:0DB8::1/48
switch(config-if)# ipv6 ospfv3 201 area 0
switch(config-if)# copy running-config startup-config
Verifying the OSPFv3 Configuration
To display the OSPFv3 configuration, perform one of the following tasks:
Command
Purpose
show ipv6 ospfv3
Displays the OSPFv3 configuration.
show ipv6 ospfv3 border-routers
Displays the internal OSPF routing table entries
to an ABR and ASBR.
show ipv6 ospfv3 database
Displays lists of information related to the
OSPFv3 database for a specific router.
show ipv6 ospfv3 interface type number [vrf
{vrf-name | all | default | management}]
Displays the OSPFv3 interface configuration.
show ipv6 ospfv3 neighbors
Displays the neighbor information. Use the clear
ospfv3 neighbors command to remove adjacency
with all neighbors.
show ipv6 ospfv3 request-list
Displays a list of LSAs requested by a router.
show ipv6 ospfv3 retransmission-list
Displays a list of LSAs waiting to be
retransmitted.
show ipv6 ospfv3 summary-address
Displays a list of all summary address
redistribution information configured under an
OSPFv3 instance.
show running-configuration ospfv3
Displays the current running OSPFv3
configuration.
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Monitoring OSPFv3
Monitoring OSPFv3
To display OSPFv3 statistics, use the following commands:
Command
Purpose
show ipv6 ospfv3 memory
Displays the OSPFv3 memory usage statistics.
show ipv6 ospfv3 policy statistics area
Displays the OSPFv3 route policy statistics for an area.
area-id filter-list {in | out} [vrf {vrf-name
| all | default | management}]
Displays the OSPFv3 route policy statistics.
show ipv6 ospfv3 policy statistics
redistribute {bgp id| direct | isis id | rip id
| static} vrf {vrf-name | all | default |
management}]
show ipv6 ospfv3 statistics [vrf {vrf-name Displays the OSPFv3 event counters.
| all | default | management}]
show ipv6 ospfv3 traffic [interface-type
number] [vrf {vrf-name | all | default |
management}]
Displays the OSPFv3 packet counters.
Configuration Examples for OSPFv3
This example shows how to configure OSPFv3:
feature ospfv3
router ospfv3 201
router-id 290.0.2.1
interface ethernet 1/2
ipv6 address 2001:0DB8::1/48
ipv6 ospfv3 201 area 0.0.0.10
Related Topics
The following topics can give more information on OSPF:
•
Chapter 5, “Configuring OSPFv2”
•
Chapter 15, “Configuring Route Policy Manager”
Additional References
For additional information related to implementing OSPF, see the following sections:
•
MIBs, page 6-46
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Additional References
MIBs
MIBs
MIBs Link
MIBs related to OSPFv3
To locate and download supported MIBs, go to the following URL:
ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MI
BSupportList.html
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7
Configuring EIGRP
This chapter describes how to configure the Enhanced Interior Gateway Routing Protocol (EIGRP) on
the Cisco NX-OS device.
This chapter includes the following sections:
•
About EIGRP, page 7-1
•
Licensing Requirements for EIGRP, page 7-9
•
Prerequisites for EIGRP, page 7-9
•
Guidelines and Limitations for EIGRP, page 7-9
•
Default Settings, page 7-10
•
Configuring Basic EIGRP, page 7-10
•
Configuring Advanced EIGRP, page 7-15
•
Configuring Virtualization for EIGRP, page 7-29
•
Verifying the EIGRP Configuration, page 7-31
•
Monitoring EIGRP, page 7-31
•
Configuration Examples for EIGRP, page 7-31
•
Related Topics, page 7-32
•
Additional References, page 7-32
About EIGRP
EIGRP combines the benefits of distance vector protocols with the features of link-state protocols.
EIGRP sends out periodic Hello messages for neighbor discovery. Once EIGRP learns a new neighbor,
it sends a one-time update of all the local EIGRP routes and route metrics. The receiving EIGRP router
calculates the route distance based on the received metrics and the locally assigned cost of the link to
that neighbor. After this initial full route table update, EIGRP sends incremental updates to only those
neighbors affected by the route change. This process speeds convergence and minimizes the bandwidth
used by EIGRP.
This section includes the following topics:
•
EIGRP Components, page 7-2
•
EIGRP Route Updates, page 7-3
•
Advanced EIGRP, page 7-5
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About EIGRP
EIGRP Components
EIGRP has the following basic components:
•
Reliable Transport Protocol, page 7-2
•
Neighbor Discovery and Recovery, page 7-2
•
Diffusing Update Algorithm, page 7-2
Reliable Transport Protocol
The Reliable Transport Protocol guarantees ordered delivery of EIGRP packets to all neighbors. (See the
“Neighbor Discovery and Recovery” section on page 7-2.) The Reliable Transport Protocol supports an
intermixed transmission of multicast and unicast packets. The reliable transport can send multicast
packets quickly when unacknowledged packets are pending. This provision helps to ensure that the
convergence time remains low for various speed links. See the “Configuring Advanced EIGRP” section
on page 7-15 for details about modifying the default timers that control the multicast and unicast packet
transmissions.
The Reliable Transport Protocol includes the following message types:
•
Hello—Used for neighbor discovery and recovery. By default, EIGRP sends a periodic multicast
Hello message on the local network at the configured hello interval. By default, the hello interval is
5 seconds.
•
Acknowledgement—Verify reliable reception of Updates, Queries, and Replies.
•
Updates—Send to affected neighbors when routing information changes. Updates include the route
destination, address mask, and route metrics such as delay and bandwidth. The update information
is stored in the EIGRP topology table.
•
Queries and Replies—Sent as part of the Diffusing Update Algorithm used by EIGRP.
Neighbor Discovery and Recovery
EIGRP uses the Hello messages from the Reliable Transport Protocol to discover neighboring EIGRP
routers on directly attached networks. EIGRP adds neighbors to the neighbor table. The information in
the neighbor table includes the neighbor address, the interface it was learned on, and the hold time,
which indicates how long EIGRP should wait before declaring a neighbor unreachable. By default, the
hold time is three times the hello interval or 15 seconds.
EIGRP sends a series of Update messages to new neighbors to share the local EIGRP routing
information. This route information is stored in the EIGRP topology table. After this initial transmission
of the full EIGRP route information, EIGRP sends Update messages only when a routing change occurs.
These Update messages contain only the new or changed information and are sent only to the neighbors
affected by the change. See the “EIGRP Route Updates” section on page 7-3.
EIGRP also uses the Hello messages as a keepalive to its neighbors. As long as Hello messages are
received, Cisco NX-OS can determine that a neighbor is alive and functioning.
Diffusing Update Algorithm
The Diffusing Update Algorithm (DUAL) calculates the routing information based on the destination
networks in the topology table. The topology table includes the following information:
•
IPv4 or IPv6 address/mask—The network address and network mask for this destination.
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About EIGRP
•
Successors—The IP address and local interface connection for all feasible successors or neighbors
that advertise a shorter distance to the destination than the current feasible distance.
•
Feasibility distance (FD)—The lowest calculated distance to the destination. The feasibility distance
is the sum of the advertised distance from a neighbor plus the cost of the link to that neighbor.
DUAL uses the distance metric to select efficient, loop-free paths. DUAL selects routes to insert into the
unicast Routing Information Base (RIB) based on feasible successors. When a topology change occurs,
DUAL looks for feasible successors in the topology table. If there are feasible successors, DUAL selects
the feasible successor with the lowest feasible distance and inserts that into the unicast RIB, avoiding
unnecessary recomputation.
When there are no feasible successors but there are neighbors advertising the destination, DUAL
transitions from the passive state to the active state and triggers a recomputation to determine a new
successor or next-hop router to the destination. The amount of time required to recompute the route
affects the convergence time. EIGRP sends Query messages to all neighbors, searching for feasible
successors. Neighbors that have a feasible successor send a Reply message with that information.
Neighbors that do not have feasible successors trigger a DUAL recomputation.
EIGRP Route Updates
When a topology change occurs, EIGRP sends an Update message with only the changed routing
information to affected neighbors. This Update message includes the distance information to the new or
updated network destination.
The distance information in EIGRP is represented as a composite of available route metrics, including
bandwidth, delay, load utilization, and link reliability. Each metric has an associated weight that
determines if the metric is included in the distance calculation. You can configure these metric weights.
You can fine-tune link characteristics to achieve optimal paths, but we recommend that you use the
default settings for most configurable metrics.
This section includes the following topics:
•
Internal Route Metrics, page 7-3
•
Wide Metrics, page 7-4
•
External Route Metrics, page 7-4
•
EIGRP and the Unicast RIB, page 7-5
Internal Route Metrics
Internal routes are routes that occur between neighbors within the same EIGRP autonomous system.
These routes have the following metrics:
•
Next hop—The IP address of the next-hop router.
•
Delay—The sum of the delays configured on the interfaces that make up the route to the destination
network. The delay is configured in tens of microseconds.
•
Bandwidth—The calculation from the lowest configured bandwidth on an interface that is part of
the route to the destination.
Note
We recommend that you use the default bandwidth value. This bandwidth parameter is also used
by EIGRP.
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•
MTU—The smallest maximum transmission unit value along the route to the destination.
•
Hop count—The number of hops or routers that the route passes through to the destination. This
metric is not directly used in the DUAL computation.
•
Reliability—An indication of the reliability of the links to the destination.
•
Load—An indication of how much traffic is on the links to the destination.
By default, EIGRP uses the bandwidth and delay metrics to calculate the distance to the destination. You
can modify the metric weights to include the other metrics in the calculation.
Wide Metrics
EIGRP supports wide (64-bit) metrics to improve route selection on higher-speed interfaces or bundled
interfaces. Routers supporting wide metrics can interoperate with routers that do not support wide
metrics as follows:
•
A router that supports wide metrics—Adds local wide metrics values to the received values and
sends the information on.
•
A router that does not support wide metrics— Sends any received metrics on without changing the
values.
EIGRP uses the following equation to calculate path cost with wide metrics:
metric = [k1 x bandwidth + (k2 x bandwidth)/(256 – load) + k3 x delay + k6 x extended attributes]
x [k5/(reliability + k4)]
Since the unicast RIB cannot support 64-bit metric values, EIGRP wide metrics use the following
equation with a RIB scaling factor to convert the 64-bit metric value to a 32-bit value:
RIB Metric = (Wide Metric / RIB scale value).
where the RIB scale value is a configurable parameter.
EIGRP wide metrics introduce the following two new metric values represented as k6 in the EIGRP
metrics configuration:
•
Jitter—(Measured in microseconds) accumulated across all links in the route path. Routes lower
jitter values are preferred for EIGRP path selection.
•
Energy—(Measured in watts per kilobit) accumulated across all links in the route path. Routes lower
energy values are preferred for EIGRP path selection.
EIGRP prefers a path with no jitter or energy metric values or lower jitter or metric values over a path
with higher values.
Note
EIGRP wide metrics are sent with a TLV version of 2. For more information, see the “Enabling Wide
Metrics” section on page 7-27.
External Route Metrics
External routes are routes that occur between neighbors in different EIGRP autonomous systems. These
routes have the following metrics:
•
Next hop—The IP address of the next-hop router.
•
Router ID—The router ID of the router that redistributed this route into EIGRP.
•
AS number—The autonomous system number of the destination.
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About EIGRP
•
Protocol ID—A code that represents the routing protocol that learned the destination route.
•
Tag—An arbitrary tag that can be used for route maps.
•
Metric—The route metric for this route from the external routing protocol.
EIGRP and the Unicast RIB
EIGRP adds all learned routes to the EIGRP topology table and the unicast RIB. When a topology
change occurs, EIGRP uses these routes to search for a feasible successor. EIGRP also listens for
notifications from the unicast RIB for changes in any routes redistributed to EIGRP from another routing
protocol.
Advanced EIGRP
You can use the advanced features of EIGRP to optimize your EIGRP configuration.
This section includes the following topics:
•
Address Families, page 7-5
•
Authentication, page 7-6
•
Stub Routers, page 7-6
•
Route Summarization, page 7-6
•
Route Redistribution, page 7-7
•
Load Balancing, page 7-7
•
Split Horizon, page 7-7
•
BFD, page 7-8
•
Virtualization Support, page 7-8
•
Graceful Restart and High Availability, page 7-8
•
Multiple EIGRP Instances, page 7-9
Address Families
EIGRP supports both IPv4 and IPv6 address families. For backward compatibility, you can configure
EIGRPv4 in route configuration mode or in IPV4 address family mode. You must configure EIGRP for
IPv6 in address family mode.
Address family configuration mode includes the following EIGRP features:
•
Authentication
•
AS number
•
Default route
•
Metrics
•
Distance
•
Graceful restart
•
Logging
•
Load balancing
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About EIGRP
•
Redistribution
•
Router ID
•
Stub router
•
Timers
You cannot configure the same feature in more than one configuration mode. For example, if you
configure the default metric in router configuration mode, you cannot configure the default metric in
address family mode.
Authentication
You can configure authentication on EIGRP messages to prevent unauthorized or invalid routing updates
in your network. EIGRP authentication supports MD5 authentication digest.
You can configure the EIGRP authentication per virtual routing and forwarding (VRF) instance or
interface using keychain management for the authentication keys. Keychain management allows you to
control changes to the authentication keys used by MD5 authentication digest. See the Cisco Nexus 9000
Series NX-OS Security Configuration Guide for more details about creating keychains.
For MD5 authentication, you configure a password that is shared at the local router and all remote
EIGRP neighbors. When an EIGRP message is created, Cisco NX-OS creates an MD5 one-way message
digest based on the message itself and the encrypted password and sends this digest along with the
EIGRP message. The receiving EIGRP neighbor validates the digest using the same encrypted password.
If the message has not changed, the calculation is identical and the EIGRP message is considered valid.
MD5 authentication also includes a sequence number with each EIGRP message that is used to ensure
that no message is replayed in the network.
Stub Routers
You can use the EIGRP stub routing feature to improve network stability, reduce resource usage, and
simplify stub router configuration. Stub routers connect to the EIGRP network through a remote router.
See the “Stub Routing” section on page 1-7.
When using EIGRP stub routing, you need to configure the distribution and remote routers to use EIGRP
and configure only the remote router as a stub. EIGRP stub routing does not automatically enable
summarization on the distribution router. In most cases, you need to configure summarization on the
distribution routers.
Without EIGRP stub routing, even after the routes that are sent from the distribution router to the remote
router have been filtered or summarized, a problem might occur. For example, if a route is lost
somewhere in the corporate network, EIGRP could send a query to the distribution router. The
distribution router could then send a query to the remote router even if routes are summarized. If a
problem communicating over the WAN link between the distribution router and the remote router occurs,
EIGRP could get stuck in an active condition and cause instability elsewhere in the network. EIGRP stub
routing allows you to prevent queries to the remote router.
Route Summarization
You can configure a summary aggregate address for a specified interface. Route summarization
simplifies route tables by replacing a number of more-specific addresses with an address that represents
all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with
one summary address, 10.1.0.0/16.
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About EIGRP
If more specific routes are in the routing table, EIGRP advertises the summary address from the interface
with a metric equal to the minimum metric of the more specific routes.
Note
EIGRP does not support automatic route summarization.
Route Redistribution
You can use EIGRP to redistribute static routes, routes learned by other EIGRP autonomous systems, or
routes from other protocols. You must configure a route map with the redistribution to control which
routes are passed into EIGRP. A route map allows you to filter routes based on attributes such as the
destination, origination protocol, route type, route tag, and so on. See Chapter 15, “Configuring Route
Policy Manager.”
You also configure the default metric that is used for all imported routes into EIGRP.
You use distribute lists to filter routes from routing updates. These filtered routes are applied to each
interface with the ip distribute-list eigrp command.
Load Balancing
You can use load balancing to allow a router to distribute traffic over all the router network ports that are
the same distance from the destination address. Load balancing increases the usage of network segments,
which increases effective network bandwidth.
Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in
the EIGRP route table and the unicast RIB. You can configure EIGRP to load balance traffic across some
or all of those paths.
Note
EIGRP in Cisco NX-OS does not support unequal cost load balancing.
Split Horizon
You can use split horizon to ensure that EIGRP never advertises a route out of the interface where it was
learned.
Split horizon is a method that controls the sending of EIGRP update and query packets. When you enable
split horizon on an interface, Cisco NX-OS does not send update and query packets for destinations that
were learned from this interface. Controlling update and query packets in this manner reduces the
possibility of routing loops.
Split horizon with poison reverse configures EIGRP to advertise a learned route as unreachable back
through that the interface that EIGRP learned the route from.
EIGRP uses split horizon or split horizon with poison reverse in the following scenarios:
•
Exchanging topology tables for the first time between two routers in startup mode.
•
Advertising a topology table change.
•
Sending a Query message.
By default, the split horizon feature is enabled on all interfaces.
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About EIGRP
BFD
This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol designed to
provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between
two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the
BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 9000 Series
NX-OS Interfaces Configuration Guide for more information.
Virtualization Support
EIGRP supports Virtual Routing and Forwarding instances (VRFs).
Graceful Restart and High Availability
Cisco NX-OS supports nonstop forwarding and graceful restart for EIGRP.
You can use nonstop forwarding for EIGRP to forward data packets along known routes in the FIB while
the EIGRP routing protocol information is being restored following a failover. With nonstop forwarding
(NSF), peer networking devices do not experience routing flaps. During failover, data traffic is
forwarded through intelligent modules while the standby supervisor becomes active.
If a Cisco NX-OS system experiences a cold reboot, the device does not forward traffic to the system
and removes the system from the network topology. In this scenario, EIGRP experiences a stateless
restart, and all neighbors are removed. Cisco NX-OS applies the startup configuration, and EIGRP
rediscovers the neighbors and shares the full EIGRP routing information again.
A dual supervisor platform that runs Cisco NX-OS can experience a stateful supervisor switchover.
Before the switchover occurs, EIGRP uses a graceful restart to announce that EIGRP will be unavailable
for some time. During a switchover, EIGRP uses nonstop forwarding to continue forwarding traffic
based on the information in the FIB, and the system is not taken out of the network topology.
The graceful restart-capable router uses Hello messages to notify its neighbors that a graceful restart
operation has started. When a graceful restart-aware router receives a notification from a graceful
restart-capable neighbor that a graceful restart operation is in progress, both routers immediately
exchange their topology tables. The graceful restart-aware router performs the following actions to assist
the restarting router as follows:
•
The router expires the EIGRP Hello hold timer to reduce the time interval set for Hello messages.
This process allows the graceful restart-aware router to reply to the restarting router more quickly
and reduces the amount of time required for the restarting router to rediscover neighbors and rebuild
the topology table.
•
The router starts the route-hold timer. This timer sets the period of time that the graceful
restart-aware router will hold known routes for the restarting neighbor. The default time period is
240 seconds.
•
The router notes in the peer list that the neighbor is restarting, maintains adjacency, and holds known
routes for the restarting neighbor until the neighbor signals that it is ready for the graceful
restart-aware router to send its topology table or the route-hold timer expires. If the route-hold timer
expires on the graceful restart-aware router, the graceful restart-aware router discards held routes
and treats the restarting router as a new router that joins the network and reestablishes adjacency.
After the switchover, Cisco NX-OS applies the running configuration, and EIGRP informs the neighbors
that it is operational again.
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Licensing Requirements for EIGRP
Multiple EIGRP Instances
Cisco NX-OS supports multiple instances of the EIGRP protocol that run on the same system. Every
instance uses the same system router ID. You can optionally configure a unique router ID for each
instance. For the number of supported EIGRP instances, see the Cisco Nexus 9000 Series NX-OS Verified
Scalability Guide.
Licensing Requirements for EIGRP
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
EIGRP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Prerequisites for EIGRP
EIGRP has the following prerequisites:
•
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
Guidelines and Limitations for EIGRP
EIGRP has the following configuration guidelines and limitations:
•
A metric configuration (either through the default-metric configuration option or through a route
map) is required for redistribution from any other protocol, connected routes, or static routes (see
Chapter 15, “Configuring Route Policy Manager”).
•
For graceful restart, an NSF-aware router must be up and completely converged with the network
before it can assist an NSF-capable router in a graceful restart operation.
•
For graceful restart, neighboring devices participating in the graceful restart must be NSF-aware or
NSF-capable.
•
Cisco NX-OS EIGRP is compatible with EIGRP in the Cisco IOS software.
•
Do not change the metric weights without a good reason. If you change the metric weights, you must
apply the change to all EIGRP routers in the same autonomous system.
•
A mix of standard metrics and wide metrics in an EIGRP network with interface speeds of 1 Gigabit
or greater may result in suboptimal routing.
•
Consider using stubs for larger networks.
•
Avoid redistribution between different EIGRP autonomous systems because the EIGRP vector
metric will not be preserved.
•
The no {ip | ipv6} next-hop-self command does not guarantee reachability of the next hop.
•
The {ip | ipv6} passive-interface eigrp command suppresses neighbors from forming.
•
Cisco NX-OS does not support IGRP or connecting IGRP and EIGRP clouds.
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Default Settings
Note
•
Autosummarization is disabled by default and cannot be enabled.
•
Cisco NX-OS supports only IP.
•
High availability is not supported with EIGRP aggressive timers.
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Default Settings
Table 7-1 lists the default settings for EIGRP parameters.
Table 7-1
Default EIGRP Parameters
Parameters
Administrative distance
Bandwidth percent
Default metric for redistributed routes
Default
•
Internal routes—90
•
External routes—170
50 percent
•
Bandwidth—100000 Kb/s
•
Delay—100 (10 microsecond units)
•
Reliability—255
•
Loading—1
•
MTU—1500
EIGRP feature
Disabled
Hello interval
5 seconds
Hold time
15 seconds
Equal-cost paths
8
Metric weights
101000
Next-hop address advertised
IP address of local interface
NSF convergence time
120
NSF route-hold time
240
NSF signal time
20
Redistribution
Disabled
Split horizon
Enabled
Configuring Basic EIGRP
This section includes the following topics:
•
Enabling the EIGRP Feature, page 7-11
•
Creating an EIGRP Instance, page 7-12
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•
Restarting an EIGRP Instance, page 7-14
•
Shutting Down an EIGRP Instance, page 7-14
•
Configuring a Passive Interface for EIGRP, page 7-15
•
Shutting Down EIGRP on an Interface, page 7-15
Enabling the EIGRP Feature
You must enable EIGRP before you can configure EIGRP.
SUMMARY STEPS
1.
configure terminal
2.
feature eigrp
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enables the EIGRP feature.
feature eigrp
Example:
switch(config)# feature eigrp
Step 3
show feature
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Displays information about enabled
features.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To disable the EIGRP feature and remove all associated configuration, use the following command in
configuration mode:
Command
Purpose
no feature eigrp
Disables the EIGRP feature and removes all
associated configuration.
Example:
switch(config)# no feature eigrp
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Creating an EIGRP Instance
You can create an EIGRP instance and associate an interface with that instance. You assign a unique
autonomous system number for this EIGRP process (see the “Autonomous Systems” section on
page 1-5). Routes are not advertised or accepted from other autonomous systems unless you enable route
redistribution.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
EIGRP must be able to obtain a router ID (for example, a configured loopback address) or you must
configure the router ID option.
If you configure an instance tag that does not qualify as an AS number, you must configure the AS
number explicitly or this EIGRP instance remains in the shutdown state. For IPv6, this number must be
configured under address family.
SUMMARY STEPS
1.
configure terminal
2.
router eigrp instance-tag
3.
(Optional) autonomous-system as-number
4.
(Optional) log-adjacency-changes
5.
(Optional) log-neighbor-warnings [seconds]
6.
interface interface-type slot/port
7.
{ip | ipv6} router eigrp instance-tag
8.
(Optional) show {ip | ipv6} eigrp interfaces
9.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Creates a new EIGRP process with the configured
instance tag. The instance tag can be any
case-sensitive, alphanumeric string up to 20
characters.
If you configure an instance-tag that does not qualify
as an AS number, you must use the
autonomous-system command to configure the AS
number explicitly or this EIGRP instance will remain
in the shutdown state.
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Step 3
Command
Purpose
autonomous-system as-number
(Optional) Configures a unique AS number for this
EIGRP instance. The range is from 1 to 65535.
Example:
switch(config-router)# autonomous-system
33
Step 4
(Optional) Generates a system message whenever an
adjacency changes state. This command is enabled by
default.
log-adjacency-changes
Example:
switch(config-router)#
log-adjacency-changes
Step 5
log-neighbor-warnings [seconds]
Example:
switch(config-router)#
log-neighbor-warnings
Step 6
interface interface-type slot/port
Example:
switch(config-router)# interface
ethernet 1/2
switch(config-if)#
(Optional) Generates a system message whenever a
neighbor warning occurs. You can configure the time
between warning messages, from 1 to 65535, in
seconds. The default is 10 seconds. This command is
enabled by default.
Enters interface configuration mode. Use ? to
determine the slot and port ranges.
Step 7
Associates this interface with the configured EIGRP
process. The instance tag can be any case-sensitive,
Example:
alphanumeric string up to 20 characters.
switch(config-if)# ip router eigrp Test1
Step 8
show {ip | ipv6} eigrp interfaces
{ip | ipv6} router eigrp instance-tag
Example:
switch(config-if)# show ip eigrp
interfaces
Step 9
copy running-config startup-config
(Optional) Displays information about EIGRP
interfaces.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To remove the EIGRP process and the associated configuration, use the following command in the
configuration mode:
Command
Purpose
no router eigrp instance-tag
Deletes the EIGRP process and all associated
configuration.
Example:
switch(config)# no router eigrp Test1
Note
You should also remove any EIGRP commands configured in interface mode if you remove the EIGRP
process.
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Configuring Basic EIGRP
This example shows how to create an EIGRP process and configure an interface for EIGRP:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config)# interface ethernet 1/2
switch(config-if)# ip router eigrp Test1
switch(config-if)# no shutdown
switch(config-if)# copy running-config startup-config
For more information about other EIGRP parameters, see the “Configuring Advanced EIGRP” section
on page 7-15.
Restarting an EIGRP Instance
You can restart an EIGRP instance. This action clears all neighbors for the instance.
To restart an EIGRP instance and remove all associated neighbors, use the following commands:
Command
Purpose
flush-routes
(Optional) Flushes all EIGRP routes in the unicast
RIB when this EIGRP instance restarts.
Example:
switch(config)# flush-routes
restart eigrp instance-tag
Example:
switch(config)# restart eigrp Test1
Restarts the EIGRP instance and removes all
neighbors. The instance tag can be any
case-sensitive, alphanumeric string up to 20
characters.
Shutting Down an EIGRP Instance
You can gracefully shut down an EIGRP instance. This action removes all routes and adjacencies but
preserves the EIGRP configuration.
To disable an EIGRP instance, use the following command in router configuration mode:
Command
Purpose
switch(config-router)# shutdown
Disables this instance of EIGRP. The EIGRP router
configuration remains.
Example:
switch(config-router)# shutdown
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Configuring Advanced EIGRP
Configuring a Passive Interface for EIGRP
You can configure a passive interface for EIGRP. A passive interface does not participate in EIGRP
adjacency, but the network address for the interface remains in the EIGRP topology table.
To configure a passive interface for EIGRP, use the following command in interface configuration mode:
Command
Purpose
{ip | ipv6} passive-interface eigrp
instance-tag
Suppresses EIGRP hellos, which prevents neighbors
from forming and sending routing updates on an
EIGRP interface. The instance-tag argument can be
any case-sensitive, alphanumeric string up to 20
characters.
Example:
switch(config-if)# ip passive-interface
eigrp tag10
Shutting Down EIGRP on an Interface
You can gracefully shut down EIGRP on an interface. This action removes all adjacencies and stops
EIGRP traffic on this interface but preserves the EIGRP configuration.
To disable EIGRP on an interface, use the following command in interface configuration mode:
Command
Purpose
switch(config-if)# {ip | ipv6} eigrp
instance-tag shutdown
Disables EIGRP on this interface. The EIGRP
interface configuration remains. The instance tag can
be any case-sensitive, alphanumeric string up to 20
characters.
Example:
switch(config-router)# ip eigrp Test1
shutdown
Configuring Advanced EIGRP
This section includes the following topics:
•
Configuring Authentication in EIGRP, page 7-16
•
Configuring EIGRP Stub Routing, page 7-18
•
Configuring a Summary Address for EIGRP, page 7-18
•
Redistributing Routes into EIGRP, page 7-19
•
Limiting the Number of Redistributed Routes, page 7-21
•
Configuring Load Balancing in EIGRP, page 7-23
•
Configuring Graceful Restart for EIGRP, page 7-24
•
Adjusting the Interval Between Hello Packets and the Hold Time, page 7-26
•
Disabling Split Horizon, page 7-26
•
Enabling Wide Metrics, page 7-27
•
Tuning EIGRP, page 7-27
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Configuring Authentication in EIGRP
You can configure authentication between neighbors for EIGRP. See the “Authentication” section on
page 7-6.
You can configure EIGRP authentication for the EIGRP process or for individual interfaces. The
interface EIGRP authentication configuration overrides the EIGRP process-level authentication
configuration.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
Ensure that all neighbors for an EIGRP process share the same authentication configuration, including
the shared authentication key.
Create the keychain for this authentication configuration. For more information, see the Cisco Nexus
9000 Series NX-OS Security Configuration Guide.
SUMMARY STEPS
1.
configure terminal
2.
router eigrp instance-tag
3.
address-family {ipv4 | ipv6} unicast
4.
authentication key-chain key-chain
5.
authentication mode md5
6.
interface interface-type slot/port
7.
{ip | ipv6} router eigrp instance-tag
8.
{ip | ipv6} authentication key-chain eigrp instance-tag key-chain
9.
{ip | ipv6} authentication mode eigrp instance-tag md5
10. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Creates a new EIGRP process with the configured
instance tag. The instance tag can be any
case-sensitive, alphanumeric string up to 20
characters.
If you configure an instance-tag that does not qualify
as an AS number, you must use the
autonomous-system command to configure the AS
number explicitly or this EIGRP instance will remain
in the shutdown state.
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Step 3
Command
Purpose
address-family {ipv4 | ipv6} unicast
Enters the address-family configuration mode. This
command is optional for IPv4.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
authentication key-chain key-chain
Example:
switch(config-router-af)# authentication
key-chain routeKeys
Step 5
authentication mode md5
Example:
switch(config-router-af)# authentication
mode md5
Step 6
interface interface-type slot/port
Example:
switch(config-router-af) interface
ethernet 1/2
switch(config-if)#
Associates a keychain with this EIGRP process for this
VRF. The keychain can be any case-sensitive,
alphanumeric string up to 20 characters.
Configures MD5 message digest authentication mode
for this VRF.
Enters interface configuration mode. Use ? to find the
supported interfaces.
Step 7
Associates this interface with the configured EIGRP
process. The instance tag can be any case-sensitive,
Example:
alphanumeric string up to 20 characters.
switch(config-if)# ip router eigrp Test1
Step 8
{ip | ipv6} authentication key-chain
eigrp instance-tag key-chain
{ip | ipv6} router eigrp instance-tag
Example:
switch(config-if)# ip authentication
key-chain eigrp Test1 routeKeys
Step 9
{ip | ipv6} authentication mode eigrp
instance-tag md5
Example:
switch(config-if)# ip authentication
mode eigrp Test1 md5
Step 10
copy running-config startup-config
Associates a keychain with this EIGRP process for this
interface. This configuration overrides the
authentication configuration set in the router VRF
mode.
The instance tag can be any case-sensitive,
alphanumeric string up to 20 characters.
Configures the MD5 message digest authentication
mode for this interface. This configuration overrides
the authentication configuration set in the router VRF
mode.
The instance tag can be any case-sensitive,
alphanumeric string up to 20 characters.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
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This example shows how to configure MD5 message digest authentication for EIGRP over Ethernet
interface 1/2:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# ip router eigrp Test1
switch(config-if)# ip authentication key-chain eigrp Test1 routeKeys
switch(config-if)# ip authentication mode eigrp Test1 md5
switch(config-if)# copy running-config startup-config
Configuring EIGRP Stub Routing
To configure a router for EIGRP stub routing, use the following command in address-family
configuration mode:
Command
Purpose
switch(config-router-af)# stub [direct |
receive-only | redistributed [direct]
leak-map map-name]
Configures a remote router as an EIGRP stub router.
The map name can be any case-sensitive,
alphanumeric string up to 20 characters.
Example:
switch(config-router-af)# eigrp stub
redistributed
This example shows how to configure a stub router to advertise directly connected and redistributed
routes:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# stub direct redistributed
switch(config-router-af)# copy running-config startup-config
Use the show ip eigrp neighbor detail command to verify that a router has been configured as a stub
router. The last line of the output shows the stub status of the remote or spoke router.
This example shows output from the show ip eigrp neighbor detail command:
Router# show ip eigrp neighbor detail
IP-EIGRP neighbors for process 201
H
Address
Interface
0
Hold Uptime
SRTT
(sec)
(ms)
10.1.1.2
Se3/1
11 00:00:59
1
Version 12.1/1.2, Retrans: 2, Retries: 0
Stub Peer Advertising ( CONNECTED SUMMARY ) Routes
RTO
Q Seq Type
Cnt Num
4500 0 7
Configuring a Summary Address for EIGRP
You can configure a summary aggregate address for a specified interface. If any more specific routes are
in the routing table, EIGRP advertises the summary address out the interface with a metric equal to the
minimum of all more specific routes. See the “Route Summarization” section on page 7-6.
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To configure a summary aggregate address, use the following command in interface configuration mode:
Command
Purpose
switch(config-if)# {ip | ipv6}
summary-address eigrp instance-tag
ip-prefix/length [distance | leak-map
map-name]
Configures a summary aggregate address as either
an IP address and network mask or an IP
prefix/length. The instance tag and map name can
be any case-sensitive, alphanumeric string up to 20
characters.
Example:
switch(config-if)# ip summary-address
eigrp Test1 192.0.2.0/8
You can optionally configure the administrative
distance for this aggregate address. The default
administrative distance is 5 for aggregate
addresses.
This example shows how to cause EIGRP to summarize network 192.0.2.0 out Ethernet 1/2 only:
switch(config)# interface ethernet 1/2
switch(config-if)# ip summary-address eigrp Test1 192.0.2.0 255.255.255.0
Redistributing Routes into EIGRP
You can redistribute routes in EIGRP from other routing protocols.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
You must configure the metric (either through the default-metric configuration option or through a route
map) for routes redistributed from any other protocol.
You must create a route map to control the types of routes that are redistributed into EIGRP. See
Chapter 15, “Configuring Route Policy Manager.”
SUMMARY STEPS
1.
configure terminal
2.
router eigrp instance-tag
3.
address-family {ipv4 | ipv6} unicast
4.
redistribute {bgp as | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | direct | static} route-map
name
5.
default-metric bandwidth delay reliability loading mtu
6.
(Optional) show {ip | ipv6} eigrp route-map statistics redistribute
7.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Creates a new EIGRP process with the
configured instance tag. The instance tag can
be any case-sensitive, alphanumeric string up
to 20 characters.
If you configure an instance-tag that does not
qualify as an AS number, you must use the
autonomous-system command to configure
the AS number explicitly or this EIGRP
instance will remain in the shutdown state.
Step 3
address-family {ipv4 | ipv6} unicast
Example:
switch(config-router)# address-family ipv4
unicast
switch(config-router-af)#
Step 4
redistribute {bgp as| {eigrp | isis | ospf |
ospfv3 | rip} instance-tag | direct | static}
route-map name
Example:
switch(config-router-af)# redistribute bgp 100
route-map BGPFilter
Step 5
default-metric bandwidth delay reliability
loading mtu
Example:
switch(config-router-af)# default-metric
500000 30 200 1 1500
Step 6
show {ip | ipv6} eigrp route-map statistics
redistribute
Enters the address-family configuration mode.
This command is optional for IPv4.
Injects routes from one routing domain into
EIGRP. The instance tag and map name can be
any case-sensitive, alphanumeric string up to
20 characters.
Sets the metrics assigned to routes learned
through route redistribution. The default
values are as follows:
•
bandwidth—100000 Kb/s
•
delay—100 (10 microsecond units)
•
reliability—255
•
loading—1
•
MTU—1492
(Optional) Displays information about EIGRP
route map statistics.
Example:
switch(config-router-af)# show ip eigrp
route-map statistics redistribute bgp
Step 7
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
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Configuring Advanced EIGRP
The following example shows how to redistribute BGP into EIGRP for IPv4:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# redistribute bgp 100 route-map BGPFilter
switch(config-router)# default-metric 500000 30 200 1 1500
switch(config-router)# copy running-config startup-config
Limiting the Number of Redistributed Routes
Route redistribution can add many routes to the EIGRP route table. You can configure a maximum limit
to the number of routes accepted from external protocols. EIGRP provides the following options to
configure redistributed route limits:
•
Fixed limit—Logs a message when EIGRP reaches the configured maximum. EIGRP does not
accept any more redistributed routes. You can optionally configure a threshold percentage of the
maximum where EIGRP logs a warning when that threshold is passed.
•
Warning only—Logs a warning only when EIGRP reaches the maximum. EIGRP continues to
accept redistributed routes.
•
Withdraw—Starts the timeout period when EIGRP reaches the maximum. After the timeout period,
EIGRP requests all redistributed routes if the current number of redistributed routes is less than the
maximum limit. If the current number of redistributed routes is at the maximum limit, EIGRP
withdraws all redistributed routes. You must clear this condition before EIGRP accepts more
redistributed routes. You can optionally configure the timeout period.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
SUMMARY STEPS
1.
configure terminal
2.
router eigrp instance-tag
3.
redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name
4.
redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]
5.
(Optional) show running-config eigrp
6.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Step 3
redistribute {bgp id | direct | eigrp id
| isis id | ospf id | rip id | static}
route-map map-name
Creates a new EIGRP instance with the configured
instance tag.
Redistributes the selected protocol into EIGRP
through the configured route map.
Example:
switch(config-router)# redistribute bgp
route-map FilterExternalBGP
Step 4
redistribute maximum-prefix max
[threshold] [warning-only | withdraw
[num-retries timeout]]
Example:
switch(config-router)# redistribute
maximum-prefix 1000 75 warning-only
Step 5
show running-config eigrp
Specifies a maximum number of prefixes that EIGRP
distributes. The range is from 1 to 65535. Optionally
specifies the following:
•
threshold—Percentage of maximum prefixes that
triggers a warning message.
•
warning-only—Logs an warning message when
the maximum number of prefixes is exceeded.
•
withdraw—Withdraws all redistributed routes.
Optionally tries to retrieve the redistributed
routes. The num-retries range is from 1 to 12. The
timeout is from 60 to 600 seconds. The default is
300 seconds. Use the clear ip eigrp
redistribution command if all routes are
withdrawn.
(Optional) Displays the EIGRP configuration.
Example:
switch(config-router)# show
running-config eigrp
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to limit the number of redistributed routes into EIGRP:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# redistribute bgp route-map FilterExternalBGP
switch(config-router)# redistribute maximum-prefix 1000 75
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Configuring Load Balancing in EIGRP
You can configure load balancing in EIGRP. You can configure the number of Equal Cost Multiple Path
(ECMP) routes using the maximum paths option. See the “Configuring Load Balancing in EIGRP”
section on page 7-23.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
SUMMARY STEPS
1.
configure terminal
2.
router eigrp instance-tag
3.
address-family {ipv4 | ipv6} unicast
4.
maximum-paths num-paths
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Creates a new EIGRP process with the
configured instance tag. The instance tag can
be any case-sensitive, alphanumeric string up
to 20 characters.
If you configure an instance-tag that does not
qualify as an AS number, you must use the
autonomous-system command to configure
the AS number explicitly or this EIGRP
instance remains in the shutdown state.
Step 3
address-family {ipv4 | ipv6} unicast
Example:
switch(config-router)# address-family ipv4
unicast
switch(config-router-af)#
Step 4
Step 5
Enters the address-family configuration mode.
This command is optional for IPv4.
Example:
switch(config-router-af)# maximum-paths 5
Sets the number of equal cost paths that
EIGRP accepts in the route table. The range is
from 1 to 32. The default is 8.
copy running-config startup-config
(Optional) Saves this configuration change.
maximum-paths num-paths
Example:
switch(config-router-af)# copy running-config
startup-config
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This example shows how to configure equal cost load balancing for EIGRP over IPv4 with a maximum
of six equal cost paths:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# maximum-paths 6
switch(config-router)# copy running-config startup-config
Configuring Graceful Restart for EIGRP
You can configure graceful restart or nonstop forwarding for EIGRP. See the “Graceful Restart and High
Availability” section on page 7-8.
Note
Graceful restart is enabled by default.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
An NSF-aware router must be up and completely converged with the network before it can assist an
NSF-capable router in a graceful restart operation.
Neighboring devices participating in the graceful restart must be NSF-aware or NSF-capable.
SUMMARY STEPS
1.
configure terminal
2.
router eigrp instance-tag
3.
address-family {ipv4 | ipv6} unicast
4.
graceful-restart
5.
timers nsf converge seconds
6.
timers nsf route-hold seconds
7.
timers nsf signal seconds
8.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Creates a new EIGRP process with the
configured instance tag. The instance tag can
be any case-sensitive, alphanumeric string up
to 20 characters.
If you configure an instance-tag that does not
qualify as an AS number, you must use the
autonomous-system command to configure
the AS number explicitly or this EIGRP
instance remains in the shutdown state.
Step 3
address-family {ipv4 | ipv6} unicast
Example:
switch(config-router)# address-family ipv4
unicast
switch(config-router-af)#
Step 4
graceful-restart
Example:
switch(config-router-af)# graceful-restart
Step 5
timers nsf converge seconds
Example:
switch(config-router-af)# timers nsf converge
100
Step 6
timers nsf route-hold seconds
Example:
switch(config-router-af)# timers nsf
route-hold 200
Step 7
Step 8
Enters the address-family configuration mode.
This command is optional for IPv4.
Enables graceful restart. This feature is
enabled by default.
Sets the time limit for the convergence after a
switchover. The range is from 60 to 180
seconds. The default is 120.
Sets the hold time for routes learned from the
graceful restart-aware peer. The range is from
20 to 300 seconds. The default is 240.
Example:
switch(config-router-af)# timers nsf signal 15
Sets the time limit for signaling a graceful
restart. The range is from 10 to 30 seconds.
The default is 20.
copy running-config startup-config
(Optional) Saves this configuration change.
timers nsf signal seconds
Example:
switch(config-router-af)# copy running-config
startup-config
This example shows how to configure graceful restart for EIGRP over IPv6 using the default timer
values:
switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# graceful-restart
switch(config-router-af)# copy running-config startup-config
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Adjusting the Interval Between Hello Packets and the Hold Time
You can adjust the interval between Hello messages and the hold time.
By default, Hello messages are sent every 5 seconds. The hold time is advertised in Hello messages and
indicates to neighbors the length of time that they should consider the sender valid. The default hold time
is three times the hello interval, or 15 seconds.
To change the interval between hello packets, use the following command in interface configuration
mode:
Command
Purpose
switch(config-if)# {ip | ipv6}
hello-interval eigrp instance-tag
seconds
Configures the hello interval for an EIGRP routing
process. The instance tag can be any case-sensitive,
alphanumeric string up to 20 characters. The range is
from 1 to 65535 seconds. The default is 5.
Example:
switch(config-if)# ip hello-interval
eigrp Test1 30
On very congested and large networks, the default hold time might not be sufficient time for all routers
to receive hello packets from their neighbors. In this case, you might want to increase the hold time.
To change the hold time, use the following command in interface configuration mode:
Command
Purpose
switch(config-if)# {ip | ipv6}
hold-time eigrp instance-tag seconds
Configures the hold time for an EIGRP routing process.
The instance tag can be any case-sensitive,
alphanumeric string up to 20 characters. The range is
from 1 to 65535.
Example:
switch(config-if)# ipv6 hold-time eigrp
Test1 30
Use the show ip eigrp interface detail command to verify the timer configuration.
Disabling Split Horizon
You can use split horizon to block route information from being advertised by a router out of any
interface from which that information originated. Split horizon usually optimizes communications
among multiple routing devices, particularly when links are broken.
By default, split horizon is enabled on all interfaces.
To disable split horizon, use the following command in interface configuration mode:
Command
Purpose
switch(config-if)# no {ip | ipv6}
split-horizon eigrp instance-tag
Disables split horizon.
Example:
switch(config-if)# no ip split-horizon eigrp
Test1
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Enabling Wide Metrics
To enable wide metrics, use the following command in router or address family configuration mode:
Command
Purpose
switch(config-router)# metrics version 64bit
Enables 64-bit metric values.
Example:
switch(config-router)# metrics version 64bit
To optionally configure a scaling factor for the RIB, use the following commands in router or address
family configuration mode:
Command
Purpose
switch(config-router)# metrics rib-scale
value
(Optional) Configures the scaling factor used to
convert the 64-bit metric values to 32 bit in the
RIB. The range is from 1 to 255. The default is
128.
Example:
switch(config-router)# metrics rib-scale 128
Tuning EIGRP
You can configure optional parameters to tune EIGRP for your network.
You can configure the following optional parameters in address-family configuration mode:
Command
Purpose
default-information originate [always |
route-map map-name]
Originates or accepts the default route with prefix
0.0.0.0/0. When a route-map is supplied, the
default route is originated only when the route map
yields a true condition. The map name can be any
case-sensitive, alphanumeric string up to 20
characters.
Example:
switch(config-router-af)#
default-information originate always
distance internal external
Example:
switch(config-router-af)# distance 25 100
metric max-hops hop-count
Example:
switch(config-router-af)# metric max-hops
70
Configures the administrative distance for this
EIGRP process. The range is from 1 to 255. The
internal value sets the distance for routes learned
from within the same autonomous system (the
default value is 90). The external value sets the
distance for routes learned from an external
autonomous system (the default value is 170).
Sets the maximum allowed hops for an advertised
route. Routes over this maximum are advertised as
unreachable. The range is from 1 to 255. The
default is 100.
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Command
Purpose
metric weights tos k1 k2 k3 k4 k5 k6
Adjusts the EIGRP metric or K value. EIGRP uses
the following formula to determine the total metric
to the network:
Example:
switch(config-router-af)# metric weights 0
1 3 2 1 0
metric = [k1 x bandwidth + (k2 x bandwidth)/(256
– load) + k3 x delay + k6 x extended attributes] *
[k5/(reliability + k4)]
Default values and ranges are as follows:
timers active-time {time-limit | disabled}
Example:
switch(config-router-af)# timers
active-time 200
•
TOS—0. The range is from 0 to 8.
•
k1—1. The range is from 0 to 255.
•
k2—0. The range is from 0 to 255.
•
k3—1. The range is from 0 to 255.
•
k4—0. The range is from 0 to 255.
•
k5—0. The range is from 0 to 255.
•
k6—0. The range is from 0 to 255.
Sets the time the router waits in minutes (after
sending a query) before declaring the route to be
stuck in the active (SIA) state. The range is from 1
to 65535. The default is 3.
You can configure the following optional parameters in interface configuration mode:
Command
Purpose
{ip | ipv6} bandwidth eigrp instance-tag
bandwidth
Configures the bandwidth metric for EIGRP on an
interface. The instance tag can be any
case-sensitive, alphanumeric string up to 20
characters. The bandwidth range is from 1 to
2,560,000,000 Kb/s.
Example:
switch(config-if)# ip bandwidth eigrp
Test1 30000
{ip | ipv6} bandwidth-percent eigrp
instance-tag percent
Example:
switch(config-if)# ip bandwidth-percent
eigrp Test1 30
no {ip | ipv6} delay eigrp instance-tag
delay
Example:
switch(config-if)# ip delay eigrp Test1
100
Configures the percentage of bandwidth that
EIGRP might use on an interface. The instance tag
can be any case-sensitive, alphanumeric string up
to 20 characters.
The percent range is from 0 to 100. The default is
50.
Configures the delay metric for EIGRP on an
interface. The instance tag can be any
case-sensitive, alphanumeric string up to 20
characters. The delay range is from 1 to 16777215
(in tens of microseconds).
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Configuring Virtualization for EIGRP
Command
Purpose
{ip | ipv6} distribute-list eigrp
instance-tag
{prefix-list name| route-map name} {in |
out}
Configures the route filtering policy for EIGRP on
this interface. The instance tag, prefix list name,
and route map name can be any case-sensitive,
alphanumeric string up to 20 characters.
Example:
switch(config-if)# ip distribute-list
eigrp Test1 route-map EigrpTest in
no {ip | ipv6} next-hop-self eigrp
instance-tag
Example:
switch(config-if)# ipv6 next-hop-self
eigrp Test1
{ip | ipv6} offset-list eigrp instance-tag
{prefix-list name| route-map name} {in |
out} offset
Example:
switch(config-if)# ip offset-list eigrp
Test1 prefix-list EigrpList in
{ip | ipv6} passive-interface eigrp
instance-tag
Example:
switch(config-if)# ip passive-interface
eigrp Test1
Configures EIGRP to use the received next-hop
address rather than the address for this interface.
The default is to use the IP address of this interface
for the next-hop address. The instance tag can be
any case-sensitive, alphanumeric string up to 20
characters.
Adds an offset to incoming and outgoing metrics to
routes learned by EIGRP. The instance tag, prefix
list name, and route map name can be any
case-sensitive, alphanumeric string up to 20
characters.
Suppresses EIGRP hellos, which prevents
neighbors from forming and sending routing
updates on an EIGRP interface. The instance tag
can be any case-sensitive, alphanumeric string up
to 20 characters.
Configuring Virtualization for EIGRP
You can configure multiple EIGRP processes, create multiple VRFs, and use the same or multiple
EIGRP processes in each VRF. You assign an interface to a VRF.
Note
Configure all other parameters for an interface after you configure the VRF for an interface. Configuring
a VRF for an interface deletes all other configuration for that interface.
BEFORE YOU BEGIN
You must enable EIGRP (see the “Enabling the EIGRP Feature” section on page 7-11).
Create the VRFs.
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
router eigrp instance-tag
4.
interface ethernet slot/port
5.
vrf member vrf-name
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Configuring Virtualization for EIGRP
6.
{ip | ipv6} router eigrp instance-tag
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context
RemoteOfficeVRF
switch(config-vrf)#
Step 3
router eigrp instance-tag
Example:
switch(config)# router eigrp Test1
switch(config-router)#
Creates a new VRF and enters VRF configuration
mode. The VRF name can be any case-sensitive,
alphanumeric string up to 20 characters.
Creates a new EIGRP process with the configured
instance tag. The instance tag can be any
case-sensitive, alphanumeric string up to 20
characters.
If you configure an instance-tag that does not qualify
as an AS number, you must use the
autonomous-system command to configure the AS
number explicitly or this EIGRP instance remains in
the shutdown state.
Step 4
interface ethernet slot/port
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 5
vrf member vrf-name
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Enters interface configuration mode. Use ? to find the
slot and port ranges.
Adds this interface to a VRF. The VRF name can be
any case-sensitive, alphanumeric string up to 20
characters.
Step 6
Adds this interface to the EIGRP process. The instance
tag can be any case-sensitive, alphanumeric string up
Example:
to 20 characters.
switch(config-if)# ip router eigrp Test1
Step 7
copy running-config startup-config
{ip | ipv6} router eigrp instance-tag
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to create a VRF and add an interface to the VRF:
switch# configure terminal
switch(config)# vrf context NewVRF
switch(config-vrf)# router eigrp Test1
switch(config-router)# interface ethernet 1/2
switch(config-if)# ip router eigrp Test1
switch(config-if)# vrf member NewVRF
switch(config-if)# copy running-config startup-config
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Verifying the EIGRP Configuration
Verifying the EIGRP Configuration
To display the EIGRP configuration, perform one of the following tasks:
Command
Purpose
show {ip | ipv6} eigrp [instance-tag]
Displays a summary of the configured EIGRP processes.
show {ip | ipv6} eigrp [instance-tag]
interfaces [type number] [brief] [detail]
Displays information about all configured EIGRP
interfaces.
show {ip | ipv6} eigrp instance-tag
neighbors [type number] [detail]
Displays information about all the EIGRP neighbors. Use
this command to verify the EIGRP neighbor
configuration.
show {ip | ipv6} eigrp [instance-tag] route Displays information about all the EIGRP routes.
[ip-prefix/length] [active] [all-links]
[detail-links] [pending] [summary]
[zero-successors] [vrf vrf-name]
show {ip | ipv6} eigrp [instance-tag]
topology [ip-prefix/length] [active]
[all-links] [detail-links] [pending]
[summary] [zero-successors] [vrf
vrf-name]
Displays information about the EIGRP topology table.
show running-configuration eigrp
Displays the current running EIGRP configuration.
Monitoring EIGRP
To display EIGRP statistics, use the following commands:
Command
Purpose
show {ip | ipv6} eigrp [instance-tag]
accounting [vrf vrf-name]
Displays accounting statistics for EIGRP.
show {ip | ipv6} eigrp [instance-tag]
route-map statistics redistribute
Displays redistribution statistics for EIGRP.
show {ip | ipv6} eigrp [instance-tag]
traffic [vrf vrf-name]
Displays traffic statistics for EIGRP.
Configuration Examples for EIGRP
This example shows how to configure EIGRP:
feature eigrp
interface ethernet 1/2
ip address 192.0.2.55/24
ip router eigrp Test1
no shutdown
router eigrp Test1
router-id 192.0.2.1
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Related Topics
The following example shows how to use a route map with the distribute-list command to filter routes
that are dynamically received from (or advertised to) EIGRP peers. The example configures a route map
to match an EIGRP external protocol metric route with an allowable deviation of 100, a source protocol
of BGP, and an autonomous system number of 45000. When the two match clauses are true, the tag value
of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for
an EIGRP process.
switch(config)# route-map metric-range
switch(config-route-map)# match metric external 500 +- 100
switch(config-route-map)# match source-protocol bgp 45000
switch(config-route-map)# set tag 5
switch(config-route-map)# exit
switch(config)# router eigrp 1
switch(config-router)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# ip address 172.16.0.0
switch(config-if)# ip router eigrp 1
switch(config-if)# ip distribute-list eigrp 1 route-map metric-range in
The following example shows how to use a route map with the redistribute command to allow routes
that are redistributed from the routing table to be filtered with a route map before being admitted into an
EIGRP topology table. The example shows how to configure a route map to match EIGRP routes with a
metric of 110, 200, or an inclusive range of 700 to 800. When the match clause is true, the tag value of
the destination routing protocol is set to 10. The route map is used to redistribute EIGRP packets.
switch(config)# route-map metric-eigrp
switch(config-route-map)# match metric 110 200 750 +- 50
switch(config-route-map)# set tag 10
switch(config-route-map)# exit
switch(config)# router eigrp 1
switch(config-router)# redistribute eigrp route-map metric-eigrp
switch(config-router)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# ip address 172.16.0.0
switch(config-if)# ip router eigrp 1
Related Topics
See Chapter 15, “Configuring Route Policy Manager,” for more information on route maps.
Additional References
For additional information related to implementing EIGRP, see the following sections:
•
Related Documents, page 7-33
•
MIBs, page 7-33
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Additional References
Related Documents
Related Topic
Document Title
http://www.cisco.com/warp/public/103/1.html
Introduction to EIGRP Tech Note
http://www.cisco.com/en/US/tech/tk365/technologies
_q_and_a_item09186a008012dac4.shtml
EIGRP Frequently Asked Questions
MIBs
MIBs
MIBs Link
MIBs related to EIGRP
To locate and download supported MIBs, go to the following URL:
ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MI
BSupportList.html
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CH A P T E R
8
Configuring IS-IS
This chapter describes how to configure Integrated Intermediate System-to-Intermediate System (IS-IS)
on the Cisco NX-OS device.
This chapter includes the following sections:
•
About IS-IS, page 8-1
•
Licensing Requirements for IS-IS, page 8-6
•
Prerequisites for IS-IS, page 8-6
•
Guidelines and Limitations for IS-IS, page 8-6
•
Default Settings, page 8-7
•
Configuring IS-IS, page 8-7
•
Verifying the IS-IS Configuration, page 8-30
•
Monitoring IS-IS, page 8-31
•
Configuration Examples for IS-IS, page 8-32
•
Related Topics, page 8-32
About IS-IS
IS-IS is an Interior Gateway Protocol (IGP) based on Standardization (ISO)/International Engineering
Consortium (IEC) 10589. Cisco NX-OS supports Internet Protocol version 4 (IPv4) and IPv6. IS-IS is a
dynamic link-state routing protocol that can detect changes in the network topology and calculate
loop-free routes to other nodes in the network. Each router maintains a link-state database that describes
the state of the network and sends packets on every configured link to discover neighbors. IS-IS floods
the link-state information across the network to each neighbor. The router also sends advertisements and
updates on the link-state database through all the existing neighbors.
This section includes the following topics:
•
IS-IS Overview, page 8-2
•
IS-IS Authentication, page 8-3
•
Mesh Groups, page 8-4
•
Overload Bit, page 8-4
•
Route Summarization, page 8-4
•
Route Redistribution, page 8-5
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•
Load Balancing, page 8-5
•
BFD, page 8-5
•
Virtualization Support, page 8-5
•
High Availability and Graceful Restart, page 8-5
•
Multiple IS-IS Instances, page 8-6
IS-IS Overview
IS-IS sends a hello packet out every configured interface to discover IS-IS neighbor routers. The hello
packet contains information, such as the authentication, area, and supported protocols, which the
receiving interface uses to determine compatibility with the originating interface. The hello packets are
also padded to ensure that IS-IS establishes adjacencies only with interfaces that have matching
maximum transmission unit (MTU) settings. Compatible interfaces form adjacencies, which update
routing information in the link-state database through link-state update messages (LSPs). By default, the
router sends a periodic LSP refresh every 10 minutes and the LSPs remain in the link-state database for
20 minutes (the LSP lifetime). If the router does not receive an LSP refresh before the end of the LSP
lifetime, the router deletes the LSP from the database.
The LSP interval must be less than the LSP lifetime or the LSPs time out before they are refreshed.
IS-IS sends periodic hello packets to adjacent routers. If you configure transient mode for hello packets,
these hello packets do not include the excess padding used before IS-IS establishes adjacencies. If the
MTU value on adjacent routers changes, IS-IS can detect this change and send padded hello packets for
a period of time. IS-IS uses this feature to detect mismatched MTU values on adjacent routers. For more
information, see the “Configuring the Transient Mode for Hello Padding” section on page 8-18.
IS-IS Areas
You can design IS-IS networks as a single area that includes all routers in the network or as multiple
areas that connect into a backbone or Level 2 area. Routers in a nonbackbone area are Level 1 routers
that establish adjacencies within a local area (intra-area routing). Level 2 area routers establish
adjacencies to other Level 2 routers and perform routing between Level 1 areas (inter-area routing). A
router can have both Level 1 and Level 2 areas configured. These Level 1/Level 2 routers act as area
border routers that route information from the local area to the Level 2 backbone area (see Figure 8-1).
Within a Level 1 area, routers know how to reach all other routers in that area. The Level 2 routers know
how to reach other area border routers and other Level 2 routers. Level 1/Level 2 routers straddle the
boundary between two areas, routing traffic to and from the Level 2 backbone area. Level1/Level2
routers use the attached (ATT) bit signal Level 1 routers to set a default route to this Level1/Level2 router
to connect to the Level 2 area.
In some instances, such as when you have two or more Level1/Level 2 routers in an area, you may want
to control which Level1/Level2 router that the Level 1 routers use as the default route to the Level 2 area.
You can configure which Level1/Level2 router sets the attached bit. For more information, see the
“Verifying the IS-IS Configuration” section on page 8-30.
Each IS-IS instance in Cisco NX-OS supports either a single Level 1 or Level 2 area, or one of each. By
default, all IS-IS instances automatically support Level 1 and Level 2 routing.
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About IS-IS
Figure 8-1
IS-IS Network Divided into Areas
L1-2 IS
L1 IS
L1 IS
L2 IS
L1 IS
L1 IS
L1-2 IS
L2 IS
L1 IS
L1-2 IS
185054
L1 link
L2 link
L1-2 link
An autonomous system boundary router (ASBR) advertises external destinations throughout the IS-IS
autonomous system. External routes are the routes redistributed into IS-IS from any other protocol.
NET and System ID
Each IS-IS instance has an associated network entity title (NET). The NET is comprised of the IS-IS
system ID, which uniquely identifies this IS-IS instance in the area and the area ID. For example, if the
NET is 47.0004.004d.0001.0001.0c11.1111.00, the system ID is 0000.0c11.1111.00 and the area is ID
47.0004.004d.0001.
Designated Intermediate System
IS-IS uses a designated intermediate system (DIS) in broadcast networks to prevent each router from
forming unnecessary links with every other router on the broadcast network. IS-IS routers send LSPs to
the DIS, which manages all the link-state information for the broadcast network. You can configure the
IS-IS priority that IS-IS uses to select the DIS in an area.
Note
No DIS is required on a point-to-point network.
IS-IS Authentication
You can configure authentication to control adjacencies and the exchange of LSPs. Routers that want to
become neighbors must exchange the same password for their configured level of authentication. IS-IS
blocks a router that does not have the correct password. You can configure IS-IS authentication globally
or for an individual interface for Level 1, Level 2, or both Level 1/Level 2 routing.
IS-IS supports the following authentication methods:
•
Clear text—All packets exchanged carry a cleartext 128-bit password.
•
MD5 digest—All packets exchanged carry a message digest that is based on a 128-bit key.
To provide protection against passive attacks, IS-IS never sends the MD5 secret key as cleartext through
the network. In addition, IS-IS includes a sequence number in each packet to protect against replay
attacks.
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About IS-IS
You can use also keychains for hello and LSP authentication. See the Cisco Nexus 9000 Series NX-OS
Security Configuration Guide for information on keychain management.
Mesh Groups
A mesh group is a set of interfaces in which all routers reachable over the interfaces have at least one
link to every other router. Many links can fail without isolating one or more routers from the network.
In normal flooding, an interface receives a new LSP and floods the LSP out over all other interfaces on
the router. With mesh groups, when an interface that is part of a mesh group receives a new LSP, the
interface does not flood the new LSP over the other interfaces that are part of that mesh group.
Note
You may want to limit LSPs in certain mesh network topologies to improve network scalability. Limiting
LSP floods might also reduce the reliability of the network (in case of failures). For this reason, we
recommend that you use mesh groups only if specifically required, and then only after you make a
careful network design.
You can also configure mesh groups in block mode for parallel links between routers. In this mode, all
LSPs are blocked on that interface in a mesh group after the routers initially exchange their link-state
information.
Overload Bit
IS-IS uses the overload bit to tell other routers not to use the local router to forward traffic but to continue
routing traffic destined for that local router.
You may want to use the overload bit in these situations:
•
The router is in a critical condition.
•
Graceful introduction and removal of the router to/from the network.
•
Other (administrative or traffic engineering) reasons such as waiting for BGP convergence.
Route Summarization
You can configure a summary aggregate address. Route summarization simplifies route tables by
replacing a number of more-specific addresses with an address that represents all the specific addresses.
For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one summary address,
10.1.0.0/16.
If more specific routes are in the routing table, IS-IS advertises the summary address with a metric equal
to the minimum metric of the more specific routes.
Note
Cisco NX-OS does not support automatic route summarization.
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About IS-IS
Route Redistribution
You can use IS-IS to redistribute static routes, routes learned by other IS-IS autonomous systems, or
routes from other protocols. You must configure a route map with the redistribution to control which
routes are passed into IS-IS. A route map allows you to filter routes based on attributes such as the
destination, origination protocol, route type, route tag, and so on. For more information, see Chapter 15,
“Configuring Route Policy Manager.”
Whenever you redistribute routes into an IS-IS routing domain, Cisco NX-OS does not, by default,
redistribute the default route into the IS-IS routing domain. You can generate a default route into IS-IS,
which can be controlled by a route policy.
You also configure the default metric that is used for all imported routes into IS-IS.
Load Balancing
You can use load balancing to allow a router to distribute traffic over all the router network ports that are
the same distance from the destination address. Load balancing increases the utilization of network
segments and increases the effective network bandwidth.
Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in
the IS-IS route table and the unicast RIB. You can configure IS-IS to load balance traffic across some or
all of those paths.
BFD
This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol designed to
provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between
two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the
BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 9000 Series
NX-OS Interfaces Configuration Guide for more information.
Virtualization Support
Cisco NX-OS supports multiple process instances for IS-IS. Each IS-IS instance can support multiple
virtual routing and forwarding (VRF) instances, up to the system limit. For the number of supported
IS-IS instances, see the Cisco Nexus 9000 Series NX-OS Verified Scalability Guide.
High Availability and Graceful Restart
Cisco NX-OS provides a multilevel high-availability architecture. IS-IS supports stateful restart, which
is also referred to as non-stop routing (NSR). If IS-IS experiences problems, it attempts to restart from
its previous run-time state. The neighbors would not register any neighbor event in this case. If the first
restart is not successful and another problem occurs, IS-IS attempts a graceful restart as per RFC 3847.
A graceful restart, or non-stop forwarding (NSF), allows IS-IS to remain in the data forwarding path
through a process restart. When the restarting IS-IS interface is operational again, it rediscovers its
neighbors, establishes adjacency, and starts sending its updates again. At this point, the NSF helpers
recognize that the graceful restart has finished.
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Licensing Requirements for IS-IS
A stateful restart is used in the following scenarios:
•
First recovery attempt after process experiences problems
•
User-initiated switchover using the system switchover command
A graceful restart is used in the following scenarios:
Note
•
Second recovery attempt after the process experiences problems within a 4-minute interval
•
Manual restart of the process using the restart isis command
•
Active supervisor removal
•
Active supervisor reload using the reload module active-sup command
Graceful restart is on by default, and we strongly recommend that you do not disable it.
Multiple IS-IS Instances
Cisco NX-OS supports multiple instances of the IS-IS protocol that run on the same node. You cannot
configure multiple instances over the same interface. Every instance uses the same system router ID. For
the number of supported IS-IS instances, see the Cisco Nexus 9000 Series NX-OS Verified Scalability
Guide.
Licensing Requirements for IS-IS
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
IS-IS requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Prerequisites for IS-IS
IS-IS has the following prerequisites:
•
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
Guidelines and Limitations for IS-IS
IS-IS has the following configuration guidelines and limitations:
•
Because the default reference bandwidth is different for Cisco NX-OS and Cisco IOS, the advertised
tunnel IS-IS metric is different for these two operating systems.
•
Bidirectional Forwarding Detection (BFD) is not supported for IS-ISv6.
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Default Settings
Default Settings
Table 8-1 lists the default settings for IS-IS parameters.
Table 8-1
Default IS-IS Parameters
Parameters
Default
Administrative distance
115
Area level
Level-1-2
DIS priority
64
Graceful restart
Enabled
Hello multiplier
3
Hello padding
Enabled
Hello time
10 seconds
IS-IS feature
Disabled
LSP interval
33
LSP MTU
1492
Maximum LSP lifetime
1200 seconds
Maximum paths
8
Metric
40
Reference bandwidth
40 Gbps
Configuring IS-IS
To configure IS-IS, follow these steps:
Step 1
Enable the IS-IS feature (see the “Enabling the IS-IS Feature” section on page 8-9).
Step 2
Create an IS-IS instance (see the “Creating an IS-IS Instance” section on page 8-9).
Step 3
Add an interface to the IS-IS instance (see the “Configuring IS-IS on an Interface” section on page 8-12).
Step 4
Configure optional features, such as authentication, mesh groups, and dynamic host exchange.
This section contains the following topics:
•
IS-IS Configuration Modes, page 8-8
•
Enabling the IS-IS Feature, page 8-9
•
Creating an IS-IS Instance, page 8-9
•
Restarting an IS-IS Instance, page 8-12
•
Shutting Down IS-IS, page 8-12
•
Configuring IS-IS on an Interface, page 8-12
•
Shutting Down IS-IS on an Interface, page 8-14
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Note
•
Configuring IS-IS Authentication in an Area, page 8-14
•
Configuring IS-IS Authentication on an Interface, page 8-15
•
Configuring a Mesh Group, page 8-17
•
Configuring a Designated Intermediate System, page 8-17
•
Configuring Dynamic Host Exchange, page 8-17
•
Setting the Overload Bit, page 8-17
•
Configuring the Attached Bit, page 8-18
•
Configuring the Transient Mode for Hello Padding, page 8-18
•
Configuring a Summary Address, page 8-18
•
Configuring Redistribution, page 8-20
•
Limiting the Number of Redistributed Routes, page 8-21
•
Disabling Strict Adjacency Mode, page 8-23
•
Configuring a Graceful Restart, page 8-24
•
Configuring Virtualization, page 8-26
•
Tuning IS-IS, page 8-28
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
IS-IS Configuration Modes
The following sections show how to enter each of the configuration modes. From a mode, you can enter
the ? command to display the commands available in that mode.
This section includes the following topics:
•
Router Configuration Mode, page 8-8
•
Router Address Family Configuration Mode, page 8-8
Router Configuration Mode
This example shows how to enter router configuration mode:
switch#: configure terminal
switch(config)# router isis isp
switch(config-router)#
Router Address Family Configuration Mode
This example shows how to enter router address family configuration mode:
switch(config)# router isis isp
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)#
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Configuring IS-IS
Enabling the IS-IS Feature
You must enable the IS-IS feature before you can configure IS-IS.
SUMMARY STEPS
1.
configure terminal
2.
feature isis
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enables the IS-IS feature.
feature isis
Example:
switch(config)# feature isis
Step 3
(Optional) Displays enabled and disabled features.
show feature
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To disable the IS-IS feature and remove all associated configuration, use the following command in
configuration mode:
Command
Purpose
no feature isis
Disables the IS-IS feature and removes all
associated configurations.
Example:
switch(config)# no feature isis
Creating an IS-IS Instance
You can create an IS-IS instance and configure the area level for that instance.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
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Configuring IS-IS
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
net network-entity-title
4.
(Optional) is-type {level-1 | level-2 | level-1-2}
5.
(Optional) show isis [vrf vrf-name] process
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
net network-entity-title
Creates a new IS-IS instance with the configured
instance tag.
Configures the NET for this IS-IS instance.
Example:
switch(config-router)# net
47.0004.004d.0001.0001.0c11.1111.00
Step 4
is-type {level-1 | level-2 | level-1-2}
Example:
switch(config-router)# is-type level-2
Step 5
show isis [vrf vrf-name] process
Example:
switch(config)# show isis process
Step 6
copy running-config startup-config
(Optional) Configures the area level for this IS-IS
instance. The default is level-1-2.
(Optional) Displays a summary of IS-IS information
for all IS-IS instances.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To remove the IS-IS instance and the associated configuration, use the following command in
configuration mode:
Command
Purpose
no router isis instance-tag
Deletes the IS-IS instance and all associated
configurations.
Example:
switch(config)# no router isis Enterprise
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Note
You must also remove any IS-IS commands that are configured in interface mode to completely remove
all configurations for the IS-IS instance.
You can configure the following optional parameters for IS-IS:
Command
Purpose
distance value
Sets the administrative distance for IS-IS. The
range is from 1 to 255. The default is 115.
Example:
switch(config-router)# distance 30
Sends a system message whenever an IS-IS
neighbor changes the state.
log-adjacency-changes
Example:
switch(config-router)#
log-adjacency-changes
lsp-mtu size
Example:
switch(config-router)# lsp-mtu 600
maximum-paths number
Example:
switch(config-router)# maximum-paths 6
reference-bandwidth bandwidth-value {Mbps
| Gbps}
Example:
switch(config-router)# reference-bandwidth
100 Gbps
Sets the MTU for LSPs in this IS-IS instance. The
range is from 128 to 4352 bytes. The default is
1492.
Configures the maximum number of equal-cost
paths that IS-IS maintains in the route table. The
range is from 1 to 64. The default is 8.
Sets the default reference bandwidth used for
calculating the IS-IS cost metric. The range is from
1 to 4000 Gbps. The default is 40 Gbps.
This example shows how to create an IS-IS instance in a level 2 area:
switch# configure terminal
switch(config)# router isis Enterprise
switch(config-router)# net 47.0004.004d.0001.0001.0c11.1111.00
switch(config-router)# is-type level 2
switch(config-router)# copy running-config startup-config
To clear neighbor statistics and remove adjacencies, use the following command in router configuration
mode:
Command
Purpose
clear isis [instance-tag] adjacency [* |
system-id | interface]
Example:
switch(config-if)# clear isis adjacency *
Clears neighbor statistics and removed adjacencies
for this IS-IS instance.
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Configuring IS-IS
Restarting an IS-IS Instance
You can restart an IS-IS instance. This action clears all neighbors for the instance.
To restart an IS-IS instance and remove all associated neighbors, use the following command:
Command
Purpose
restart isis instance-tag
Restarts the IS-IS instance and removes all
neighbors.
Example:
switch(config)# restart isis Enterprise
Shutting Down IS-IS
You can shut down the IS-IS instance. This action disables this IS-IS instance and retains the
configuration.
To shut down the IS-IS instance, use the following command in router configuration mode:
Command
Purpose
shutdown
Disables the IS-IS instance.
Example:
switch(config-router)# shutdown
Configuring IS-IS on an Interface
You can add an interface to an IS-IS instance.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
(Optional) medium {broadcast | p2p}
4.
{ip | ipv6} router isis instance-tag
5.
(Optional) show isis [vrf vrf-name] [instance-tag] interface [interface-type slot/port]
6.
(Optional) copy running-config startup-config
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Configuring IS-IS
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
medium {broadcast | p2p}
Example:
switch(config-if)# medium p2p
Step 4
{ip | ipv6} router isis instance-tag
Example:
switch(config-if)# ip router isis
Enterprise
Step 5
show isis [vrf vrf-name] [instance-tag]
interface [interface-type slot/port]
(Optional) Configures the broadcast or point-to-point
mode for the interface. IS-IS inherits this mode.
Associates this IPv4 or IPv6 interface with an IS-IS
instance.
(Optional) Displays IS-IS information for an interface.
Example:
switch(config)# show isis Enterprise
ethernet 1/2
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
You can configure the following optional parameters for IS-IS in interface mode:
Command
Purpose
isis circuit-type {level-1 | level-2 |
level-1-2}
Sets the type of adjacency that this interface
participates in. Use this command only for routers
that participate in both Level 1 and Level 2 areas.
Example:
switch(config-if)# isis circuit-type
level-2
isis metric value {level-1 | level-2}
Example:
switch(config-if)# isis metric 30
isis passive {level-1 | level-2 |
level-1-2}
Example:
switch(config-if)# isis passive level-2
Sets the IS-IS metric for this interface. The range is
from 1 to 16777214. The default is 10.
Prevents the interface from forming adjacencies but
still advertises the prefix associated with the
interface.
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Configuring IS-IS
This example shows how to add Ethernet 1/2 interface to an IS-IS instance:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# ip router isis Enterprise
switch(config-if)# copy running-config startup-config
Shutting Down IS-IS on an Interface
You can gracefully shut down IS-IS on an interface. This action removes all adjacencies and stops IS-IS
traffic on this interface but preserves the IS-IS configuration.
To disable IS-IS on an interface, use the following command in interface configuration mode:
Command
Purpose
switch(config-if)# isis shutdown
Disables IS-IS on this interface. The IS-IS interface
configuration remains.
Example:
switch(config-router)# isis shutdown
Configuring IS-IS Authentication in an Area
You can configure IS-IS to authenticate LSPs in an area.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
authentication-type {cleartext | md5} {level-1 | level-2}
4.
authentication key-chain key {level-1 | level-2}
5.
(Optional) authentication-check {level-1 | level-2}
6.
(Optional) copy running-config startup-config
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Configuring IS-IS
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
authentication-type {cleartext | md5}
{level-1 | level-2}
Example:
switch(config-router)#
authentication-type cleartext level-2
Step 4
authentication key-chain key {level-1 |
level-2}
Creates a new IS-IS instance with the configured
instance tag.
Sets the authentication method used for a Level 1 or
Level 2 area as cleartext or as an MD5 authentication
digest.
Configures the authentication key used for an IS-IS
area-level authentication.
Example:
switch(config-router)# authentication
key-chain ISISKey level-2
Step 5
authentication-check {level-1 | level-2}
Example:
switch(config-router)#
authentication-check level-2
Step 6
copy running-config startup-config
(Optional) Enables checking the authentication
parameters in a received packet.
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to configure cleartext authentication on an IS-IS instance:
switch# configure terminal
switch(config)# router isis Enterprise
switch(config-router)# authentication-type cleartext level-2
switch(config-router)# authentication key-chain ISISKey level-2
switch(config-router)# copy running-config startup-config
Configuring IS-IS Authentication on an Interface
You can configure IS-IS to authenticate Hello packets on an interface.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
SUMMARY STEPS
1.
configure terminal
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Configuring IS-IS
2.
interface interface-type slot/port
3.
isis authentication-type {cleartext | md5} {level-1 | level-2}
4.
isis authentication key-chain key {level-1 | level-2}
5.
(Optional) isis authentication-check {level-1 | level-2}
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
isis authentication-type {cleartext |
md5} {level-1 | level-2}
Sets the authentication type for IS-IS on this interface
as cleartext or as an MD5 authentication digest.
Example:
switch(config-if)# isis
authentication-type cleartext level-2
Step 4
isis authentication key-chain key
{level-1 | level-2}
Configures the authentication key used for IS-IS on
this interface.
Example:
switch(config-if)# isis
authentication-key ISISKey level-2
Step 5
isis authentication-check {level-1 |
level-2}
(Optional) Enables checking the authentication
parameters in a received packet.
Example:
switch(config-if)# isis
authentication-check
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to configure cleartext authentication on an IS-IS instance:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# isis authentication-type cleartext level-2
switch(config-if)# isis authentication key-chain ISISKey
switch(config-if)# copy running-config startup-config
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Configuring IS-IS
Configuring a Mesh Group
You can add an interface to a mesh group to limit the amount of LSP flooding for interfaces in that mesh
group. You can optionally block all LSP flooding on an interface in a mesh group.
To add an interface to a mesh group, use the following command in interface configuration mode:
Command
Purpose
isis mesh-group {blocked | mesh-id}
Adds this interface to a mesh group. The range is
from 1 to 4294967295.
Example:
switch(config-if)# isis mesh-group 1
Configuring a Designated Intermediate System
You can configure a router to become the designated intermediate system (DIS) for a multiaccess
network by setting the interface priority.
To configure the DIS, use the following command in interface configuration mode:
Command
Purpose
isis priority number {level-1 | level-2}
Sets the priority for DIS selection. The range is
from 0 to 127. The default is 64.
Example:
switch(config-if)# isis priority 100
level-1
Configuring Dynamic Host Exchange
You can configure IS-IS to map between the system ID and the hostname for a router using dynamic host
exchange.
To configure dynamic host exchange, use the following command in router configuration mode:
Command
Purpose
hostname dynamic
Enables dynamic host exchange.
Example:
switch(config-router)# hostname dynamic
Setting the Overload Bit
You can configure the router to signal other routers not to use this router as an intermediate hop in their
shortest path first (SPF) calculations. You can optionally configure the overload bit temporarily on
startup, until BGP converges.
In addition to setting the overload bit, you might also want to suppress certain types of IP prefix
advertisements from LSPs for Level 1 or Level 2 traffic.
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Configuring IS-IS
To set the overload bit, use the following command in router configuration mode:
Command
Purpose
set-overload-bit {always | on-startup
{seconds | wait-for bgp as-number}}
[suppress [interlevel | external]]
Sets the overload bit for IS-IS. The seconds range
is from 5 to 86400.
Example:
switch(config-router)# set-overload-bit
on-startup 30
Configuring the Attached Bit
You can configure the attached bit to control which Level 1/Level 2 router that the Level 1 routers use
as the default route to the Level 2 area. If you disable setting the attached bit, the Level 1 routers do not
use this Level 1/Level 2 router to reach the Level 2 area.
To configure the attached bit for a Level 1/Level 2 router, use the following command in router
configuration mode:
Command
Purpose
[no] attached-bit
Example:
switch(config-router)# no attached-bit
Configures the Level 1/Level 2 router to set the
attached bit. This feature is enabled by default.
Configuring the Transient Mode for Hello Padding
You can configure the transient mode for hello padding to pad hello packets when IS-IS establishes
adjacency and remove that padding after IS-IS establishes adjacency.
To configure the mode for hello padding, use the following command in router configuration mode:
Command
Purpose
[no] isis hello-padding
Pads the hello packet to the full maximum
transmission unit (MTU). The default is enabled.
Use the no form of this command to configure the
transient mode of hello padding.
Example:
switch(config-if)# no isis hello-padding
Configuring a Summary Address
You can create aggregate addresses that are represented in the routing table by a summary address. One
summary address can include multiple groups of addresses for a given level. Cisco NX-OS advertises
the smallest metric of all the more-specific routes.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
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Configuring IS-IS
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
address-family {ipv4 | ipv6} unicast
4.
summary-address ip-prefix/mask-len {level-1 | level-2 | level-1-2}
5.
(Optional) show isis [vrf vrf-name] {ip | ipv6} summary-address ip-prefix [longer-prefixes]
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
address-family {ipv4 | ipv6} unicast
Creates a new IS-IS instance with the configured
instance tag.
Enters address family configuration mode.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
summary-address ip-prefix/mask-len
{level-1 | level-2 | level-1-2}
Configures a summary address for an IS-IS area for
IPv4 or IPv6 addresses.
Example:
switch(config-router-af)#
summary-address 192.0.2.0/24 level-2
Step 5
show isis [vrf vrf-name] {ip | ipv6}
summary-address ip-prefix
[longer-prefixes]
(Optional) Displays IS-IS IPv4 or IPv6 summary
address information.
Example:
switch(config-if)# show isis ip
summary-address
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to configure an IPv4 unicast summary address for IS-IS:
switch# configure terminal
switch(config)# router isis Enterprise
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# summary-address 192.0.2.0/24 level-2
switch(config-router-af)# copy running-config startup-config
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Configuring IS-IS
Configuring Redistribution
You can configure IS-IS to accept routing information from another routing protocol and redistribute that
information through the IS-IS network. You can optionally assign a default route for redistributed routes.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
address-family {ipv4 | ipv6} unicast
4.
redistribute {bgp as | direct |{eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map
map-name
5.
(Optional) default-information originate [always] [route-map map-name]
6.
(Optional) distribute {level-1 | level-2} into {level-1 | level-2} {route-map route-map | all}
7.
(Optional) show isis [vrf vrf-name] {ip | ipv6} route ip-prefix [detail | longer-prefixes [summary
| detail]]
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
address-family {ipv4 | ipv6} unicast
Creates a new IS-IS instance with the configured
instance tag.
Enters address family configuration mode.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
redistribute {bgp as | {eigrp | isis |
ospf | ospfv3 | rip} instance-tag |
static | direct} route-map map-name
Redistributes routes from other protocols into IS-IS.
See the “Configuring Route Maps” section on
page 15-11 for more information about route maps.
Example:
switch(config-router-af)# redistribute
eigrp 201 route-map ISISmap
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Step 5
Command
Purpose
default-information originate [always]
[route-map map-name]
(Optional) Generates a default route into IS-IS.
Example:
switch(config-router-af)#
default-information originate always
Step 6
distribute {level-1 | level-2} into
{level-1 | level-2} {route-map route-map
| all}
(Optional) Redistributes routes from one IS-IS level to
the other IS-IS level.
Example:
switch(config-router-af)# distribute
level-1 into level-2 all
Step 7
show isis [vrf vrf-name] {ip | ipv6}
route ip-prefix [detail |
longer-prefixes [summary | detail]]
(Optional) Shows the IS-IS routes.
Example:
switch(config-router-af)# show isis ip
route
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
This example shows how to redistribute EIGRP into IS-IS:
switch# configure terminal
switch(config)# router isis Enterprise
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# redistribute eigrp 201 route-map ISISmap
switch(config-router-af)# copy running-config startup-config
Limiting the Number of Redistributed Routes
Route redistribution can add many routes to the IS-IS route table. You can configure a maximum limit
to the number of routes accepted from external protocols. IS-IS provides the following options to
configure redistributed route limits:
•
Fixed limit—Logs a message when IS-IS reaches the configured maximum. IS-IS does not accept
any more redistributed routes. You can optionally configure a threshold percentage of the maximum
where IS-IS logs a warning when that threshold is passed.
•
Warning only—Logs a warning only when IS-IS reaches the maximum. IS-IS continues to accept
redistributed routes.
•
Withdraw—Starts the timeout period when IS-IS reaches the maximum. After the timeout period,
IS-IS requests all redistributed routes if the current number of redistributed routes is less than the
maximum limit. If the current number of redistributed routes is at the maximum limit, IS-IS
withdraws all redistributed routes. You must clear this condition before IS-IS accepts more
redistributed routes. You can optionally configure the timeout period.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
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Configuring IS-IS
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
redistribute {bgp id | direct | eigrp id | isis id | ospf id | rip id | static} route-map map-name
4.
redistribute maximum-prefix max [threshold] [warning-only | withdraw [num-retries timeout]]
5.
(Optional) show running-config isis
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
redistribute {bgp id | direct | eigrp id
| isis id | ospf id | rip id | static}
route-map map-name
Creates a new IS-IS instance with the configured
instance tag.
Redistributes the selected protocol into IS-IS through
the configured route map.
Example:
switch(config-router)# redistribute bgp
route-map FilterExternalBGP
Step 4
redistribute maximum-prefix max
[threshold] [warning-only | withdraw
[num-retries timeout]]
Example:
switch(config-router)# redistribute
maximum-prefix 1000 75 warning-only
Specifies a maximum number of prefixes that IS-IS
distributes. The range is from 1 to 65535. You can
optionally specify the following:
•
threshold—Percentage of maximum prefixes that
triggers a warning message.
•
warning-only—Logs a warning message when
the maximum number of prefixes is exceeded.
•
withdraw—Withdraws all redistributed routes.
You can optionally try to retrieve the redistributed
routes. The num-retries range is from 1 to 12. The
timeout is 60 to 600 seconds. The default is 300
seconds. Use the clear isis redistribution
command if all routes are withdrawn.
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Step 5
Command
Purpose
show running-config isis
(Optional) Displays the IS-IS configuration.
Example:
switch(config-router)# show
running-config isis
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to limit the number of redistributed routes into IS-IS:
switch# configure terminal
switch(config)# router eigrp isis Enterprise
switch(config-router)# redistribute bgp route-map FilterExternalBGP
switch(config-router)# redistribute maximum-prefix 1000 75
Disabling Strict Adjacency Mode
When both IPv4 and IPv6 address families are enabled, strict adjacency mode is enabled by default. In
this mode, the device does not form an adjacency with any router that does not have both address families
enabled. You can disable strict adjacency mode using the no adjacency-check command.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
address-family ipv4 unicast
4.
no adjacency-check
5.
exit
6.
address-family ipv6 unicast
7.
no adjacency-check
8.
(Optional) show running-config isis
9.
(Optional) copy running-config startup-config
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Configuring IS-IS
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
address-family ipv4 unicast
Creates a new IS-IS instance with the configured
instance tag.
Enters address family configuration mode.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
no adjacency-check
Example:
switch(config-router-af)# no
adjacency-check
Step 5
exit
Disables strict adjacency mode for the IPv4 address
family.
Exits address family configuration mode.
Example:
switch(config-router-af)# exit
switch(config-router)#
Step 6
address-family ipv6 unicast
Enters address family configuration mode.
Example:
switch(config-router)# address-family
ipv6 unicast
switch(config-router-af)#
Step 7
no adjacency-check
Example:
switch(config-router-af)# no
adjacency-check
Step 8
show running-config isis
Disables strict adjacency mode for the IPv6 address
family.
(Optional) Displays the IS-IS configuration.
Example:
switch(config-router-af)# show
running-config isis
Step 9
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
Configuring a Graceful Restart
You can configure a graceful restart for IS-IS.
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Configuring IS-IS
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
Create the VRFs.
SUMMARY STEPS
1.
configure terminal
2.
router isis instance-tag
3.
graceful-restart
4.
graceful-restart t3 manual time
5.
(Optional) show running-config isis
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router isis instance-tag
Creates a new IS-IS process with the configured name.
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 3
graceful-restart
Example:
switch(config-router)# graceful-restart
Step 4
graceful-restart t3 manual time
Example:
switch(config-router)# graceful-restart
t3 manual 300
Step 5
show running-config isis
Enables a graceful restart and the graceful restart
helper functionality. Enabled by default.
Configures the graceful restart T3 timer. The range is
from 30 to 65535 seconds. The default is 60.
(Optional) Displays the IS-IS configuration.
Example:
switch(config-router)# show
running-config isis
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to enable a graceful restart:
switch# configure terminal
switch(config)# router isis Enterprise
switch(config-router)# graceful-restart
switch(config-router)# copy running-config startup-config
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Chapter 8
Configuring IS-IS
Configuring IS-IS
Configuring Virtualization
You can configure multiple IS-IS instances and multiple VRFs and use the same or multiple IS-IS
instances in each VRF. You assign an IS-IS interface to a VRF.
You must configure a NET for the configured VRF.
Note
Configure all other parameters for an interface after you configure the VRF for an interface. Configuring
a VRF for an interface deletes all the configuration for that interface.
BEFORE YOU BEGIN
You must enable IS-IS (see the “Enabling the IS-IS Feature” section on page 8-9).
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf_name
3.
exit
4.
router isis instance-tag
5.
(Optional) vrf vrf_name
6.
net network-entity-title
7.
exit
8.
interface type slot/port
9.
vrf member vrf-name
10. {ip | ipv6} address ip-prefix/length
11. {ip | ipv6} router isis instance-tag
12. (Optional) show isis [vrf vrf-name] [instance-tag] interface [interface-type slot/port]
13. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context
RemoteOfficeVRF
switch(config-vrf)#
Creates a new VRF and enters VRF configuration
mode.
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Configuring IS-IS
Step 3
Command
Purpose
exit
Exits VRF configuration mode.
Example:
switch(config-vrf)# exit
switch(config)#
Step 4
router isis instance-tag
Example:
switch(config)# router isis Enterprise
switch(config-router)#
Step 5
Creates a new IS-IS instance with the configured
instance tag.
(Optional) Enters VRF configuration mode.
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
Step 6
net network-entity-title
Configures the NET for this IS-IS instance.
Example:
switch(config-router-vrf)# net
47.0004.004d.0001.0001.0c11.1111.00
Step 7
Exits router VRF configuration mode.
exit
Example:
switch(config-router-vrf)# exit
switch(config-router)#
Step 8
interface ethernet slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 9
Adds this interface to a VRF.
vrf member vrf-name
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Step 10
{ip | ipv6} address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
Step 11
{ip | ipv6} router isis instance-tag
Example:
switch(config-if)# ip router isis
Enterprise
Step 12
show isis [vrf vrf-name] [instance-tag]
interface [interface-type slot/port]
Configures an IP address for this interface. You must
do this step after you assign this interface to a VRF.
Associates this IPv4 or IPv6 interface with an IS-IS
instance.
(Optional) Displays IS-IS information for an interface.
in a VRF.
Example:
switch(config-if)# show isis Enterprise
ethernet 1/2
Step 13
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
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Configuring IS-IS
Configuring IS-IS
This example shows how to create a VRF and add an interface to the VRF:
switch# configure terminal
switch(config)# vrf context NewVRF
switch(config-vrf)# exit
switch(config)# router isis Enterprise
switch(config-router)# vrf NewVRF
switch(config-router-vrf)# net 47.0004.004d.0001.0001.0c11.1111.00
switch(config-router-vrf)# interface ethernet 1/2
switch(config-if)# vrf member NewVRF
switch(config-if)# ip address 192.0.2.1/16
switch(config-if)# ip router isis Enterprise
switch(config-if)# copy running-config startup-config
Tuning IS-IS
You can tune IS-IS to match your network requirements.
You can use the following optional commands in router configuration mode to tune IS-IS:
Command
Purpose
lsp-gen-interval [level-1 | level-2]
lsp-max-wait [lsp-initial-wait
lsp-second-wait]
Configures the IS-IS throttle for LSP generation.
The optional parameters are as follows:
•
lsp-max-wait—The maximum wait between
the trigger and LSP generation. The range is
from 500 to 65535 milliseconds.
•
lsp-initial-wait—The initial wait between the
trigger and LSP generation. The range is from
50 to 65535 milliseconds.
•
lsp-second-wait—The second wait used for
LSP throttle during backoff. The range is from
50 to 65535 milliseconds.
Example:
switch(config-router)# lsp-gen-interval
level-1 500 500 500
max-lsp-lifetime lifetime
Example:
switch(config-router)# max-lsp-lifetime
500
metric-style transition
Example:
switch(config-router)# metric-style
transition
Sets the maximum LSP lifetime in seconds. The
range is from 1 to 65535. The default is 1200.
Enables IS-IS to generate and accept both narrow
metric-style Type Length Value (TLV) objects and
wide metric-style TLV objects. The default is
disabled.
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Configuring IS-IS
Command
Purpose
spf-interval [level-1 | level-2]
spf-max-wait [spf-initial-wait
spf-second-wait]
Configures the interval between LSA arrivals. The
optional parameters are as follows:
•
lsp-max-wait—The maximum wait between
the trigger and SPF computation. The range is
from 500 to 65535 milliseconds.
•
lsp-initial-wait—The initial wait between the
trigger and SPF computation. The range is
from 50 to 65535 milliseconds.
•
lsp-second-wait—The second wait used for
SPF computation during backoff. The range is
from 50 to 65535 milliseconds.
Example:
switch(config-router)# spf-interval
level-2 500 500 500
You can use the following optional command in router address configuration mode:
Command
Purpose
adjacency-check
Performs an adjacency check to verify that an IS-IS
instance forms an adjacency only with a remote
IS-IS entity that supports the same address family.
This command is enabled by default.
Example:
switch(config-router-af)# adjacency-check
You can use the following optional commands in interface configuration mode to tune IS-IS:
Command
Purpose
isis csnp-interval seconds [level-1 |
level-2]
Sets the complete sequence number PDU (CNSP)
interval in seconds for IS-IS. The range is from 1 to
65535. The default is 10.
Example:
switch(config-if)# isis csnp-interval 20
isis hello-interval seconds [level-1 |
level-2]
Sets the hello interval in seconds for IS-IS. The
range is from 1 to 65535. The default is 10.
Example:
switch(config-if)# isis hello-interval 20
isis hello-multiplier num [level-1 |
level-2]
Example:
switch(config-if)# isis hello-multiplier
20
isis lsp-interval milliseconds
Example:
switch(config-if)# isis lsp-interval 20
Specifies the number of IS-IS hello packets that a
neighbor must miss before the router tears down an
adjacency. The range is from 3 to 1000. The default
is 3.
Sets the interval in milliseconds between LSPs sent
on this interface during flooding. The range is from
10 to 65535. The default is 33.
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Configuring IS-IS
Verifying the IS-IS Configuration
Verifying the IS-IS Configuration
To display the IS-IS configuration, perform one of the following tasks:
Command
Purpose
show isis [instance-tag] adjacency [interface]
[detail | summary] [vrf vrf-name]
Displays the IS-IS adjacencies. Use the clear isis
adjacency command to clear these statistics.
Displays the IS-IS LSP database.
show isis [instance-tag] database [level-1 |
level-2] [detail | summary] [LSP ID] [{ip | ipv6}
prefix ip-prefix] | | [router-id router-id] |
[adjacency node-id] | [zero-sequence]} [vrf
vrf-name]
show isis [instance-tag] hostname [vrf vrf-name] Displays the dynamic host exchange information.
show isis [instance-tag] interface [brief |
interface] [level-1 | level-2] [vrf vrf-name]
Displays the IS-IS interface information.
show isis [instance-tag] mesh-group [mesh-id]
[vrf vrf-name]
Displays the mesh group information.
show isis [instance-tag] protocol [vrf vrf-name]
Displays information about the IS-IS protocol.
show isis [instance-tag] {ip | ipv6} redistribute
route [ip-address | summary] [[ip-prefix]
[longer-prefixes [summary]] [vrf vrf-name]
Displays the IS-IS route redistribution
information.
show isis [instance-tag] {ip | ipv6} route
[ip-address | summary] [ip-prefix
[longer-prefixes [summary]] [detail] [vrf
vrf-name]
Displays the IS-IS route table.
show isis [instance-tag] rrm [interface] [vrf
vrf-name]
Displays the IS-IS interface retransmission
information.
show isis [instance-tag] srm [interface] [vrf
vrf-name]
Displays the IS-IS interface flooding information.
show isis [instance-tag] ssn [interface] [vrf
vrf-name]
Displays the IS-IS interface PSNP information.
show isis [instance-tag] {ip | ipv6}
summary-address [ip-address] | [ip-prefix] [vrf
vrf-name]
Displays the IS-IS summary address information.
show running-configuration isis
Displays the current running IS-IS configuration.
show tech-support isis [detail]
Displays the technical support details for IS-IS.
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Configuring IS-IS
Monitoring IS-IS
Monitoring IS-IS
To display IS-IS statistics, use the following commands:
Command
Purpose
show isis [instance-tag] adjacency [interface]
[system-ID] [detail] [summary] [vrf vrf-name]
Displays the IS-IS adjacency statistics.
show isis [instance-tag] database [level-1 |
level-2] [detail | summary] [lsip] {[adjacency
id] {ip | ipv6} prefix prefix] [router-id id]
[zero-sequence]} [vrf vrf-name]
Displays the IS-IS database statistics.
show isis [instance-tag] statistics [interface] [vrf Displays the IS-IS interface statistics.
vrf-name]
show isis {ip | ipv6} route-map statistics
redistribute {bgp id | eigrp id | isis id | ospf id |
rip id | static} [vrf vrf-name]
Displays the IS-IS redistribution statistics.
show isis route-map statistics distribute
{level-1 | level-2} into {level-1 | level-2}} [vrf
vrf-name]
Displays IS-IS distribution statistics for routes
distributed between levels.
show isis [instance-tag] spf-log [detail] [vrf
vrf-name]
Displays the IS-IS SPF calculation statistics.
show isis [instance-tag] traffic [interface] [vrf
vrf-name]
Displays the IS-IS traffic statistics.
To clear IS-IS configuration statistics, perform one of the following tasks:
Command
Purpose
clear isis [instance-tag] adjacency [* | [interface] Clears the IS-IS adjacency statistics.
[system-id id]] [vrf vrf-name]
clear isis {ip | ipv6} route-map statistics
redistribute {bgp id | direct | eigrp id | isis id |
ospf id | rip id | static} [vrf vrf-name]
Clears the IS-IS redistribution statistics.
clear isis route-map statistics distribute
{level-1 | level-2} into {level-1 | level-2} [vrf
vrf-name]
Clears IS-IS distribution statistics for routes
distributed between levels.
clear isis [instance-tag] statistics [* | interface]
[vrf vrf-name]
Clears the IS-IS interface statistics.
clear isis [instance-tag] traffic [* | interface] [vrf Clears the IS-IS traffic statistics.
vrf-name]
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Configuring IS-IS
Configuration Examples for IS-IS
Configuration Examples for IS-IS
This example shows how to configure IS-IS:
router isis Enterprise
is-type level-1
net 49.0001.0000.0000.0003.00
graceful-restart
address-family ipv4 unicast
default-information originate
interface ethernet 2/1
ip address 192.0.2.1/24
isis circuit-type level-1
ip router isis Enterprise
Related Topics
See the Chapter 15, “Configuring Route Policy Manager,” for more information on route maps.
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9
Configuring Basic BGP
This chapter describes how to configure Border Gateway Protocol (BGP) on the Cisco NX-OS device.
This chapter includes the following sections:
•
About Basic BGP, page 9-1
•
Licensing Requirements for Basic BGP, page 9-7
•
Prerequisites for BGP, page 9-7
•
Guidelines and Limitations for BGP, page 9-8
•
Default Settings, page 9-8
•
CLI Configuration Modes, page 9-9
•
Configuring Basic BGP, page 9-10
•
Verifying the Basic BGP Configuration, page 9-21
•
Monitoring BGP Statistics, page 9-23
•
Configuration Examples for Basic BGP, page 9-23
•
Related Topics, page 9-23
•
Where to Go Next, page 9-24
•
Additional References, page 9-24
About Basic BGP
Cisco NX-OS supports BGP version 4, which includes multiprotocol extensions that allow BGP to carry
routing information for IP multicast routes and multiple Layer 3 protocol address families. BGP uses
TCP as a reliable transport protocol to create TCP sessions with other BGP-enabled devices.
BGP uses a path-vector routing algorithm to exchange routing information between BGP-enabled
networking devices or BGP speakers. Based on this information, each BGP speaker determines a path to
reach a particular destination while detecting and avoiding paths with routing loops. The routing
information includes the actual route prefix for a destination, the path of autonomous systems to the
destination, and additional path attributes.
BGP selects a single path, by default, as the best path to a destination host or network. Each path carries
well-known mandatory, well-known discretionary, and optional transitive attributes that are used in BGP
best-path analysis. You can influence BGP path selection by altering some of these attributes by
configuring BGP policies. See the “Route Policies and Resetting BGP Sessions” section on page 10-3
for more information.
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BGP also supports load balancing or equal-cost multipath (ECMP). See the “Load Sharing and
Multipath” section on page 10-6 for more information.
This section includes the following topics:
•
BGP Autonomous Systems, page 9-2
•
Administrative Distance, page 9-2
•
BGP Peers, page 9-3
•
BGP Router Identifier, page 9-3
•
BGP Path Selection, page 9-4
•
BGP and the Unicast RIB, page 9-7
•
BGP Prefix Independent Convergence Core, page 9-7
•
BGP Virtualization, page 9-7
BGP Autonomous Systems
An autonomous system (AS) is a network controlled by a single administration entity. An autonomous
system forms a routing domain with one or more interior gateway protocols (IGPs) and a consistent set
of routing policies. BGP supports 16-bit and 32-bit autonomous system numbers. For more information,
see the “Autonomous Systems” section on page 1-5.
Separate BGP autonomous systems dynamically exchange routing information through external BGP
(eBGP) peering sessions. BGP speakers within the same autonomous system can exchange routing
information through internal BGP (iBGP) peering sessions.
4-Byte AS Number Support
BGP supports 2-byte autonomous system (AS) numbers in plain-text notation or as.dot notation and
4-byte AS numbers in plain-text notation.
Administrative Distance
An administrative distance is a rating of the trustworthiness of a routing information source. By default,
BGP uses the administrative distances shown in Table 9-1.
Table 9-1
Note
BGP Default Administrative Distances
Distance
Default Value
Function
External
20
Applied to routes learned from eBGP.
Internal
200
Applied to routes learned from iBGP.
Local
220
Applied to routes originated by the router.
The administrative distance does not influence the BGP path selection algorithm, but it does influence
whether BGP-learned routes are installed in the IP routing table.
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About Basic BGP
For more information, see the “Administrative Distance” section on page 1-7.
BGP Peers
A BGP speaker does not discover another BGP speaker automatically. You must configure the
relationships between BGP speakers. A BGP peer is a BGP speaker that has an active TCP connection
to another BGP speaker.
BGP Sessions
BGP uses TCP port 179 to create a TCP session with a peer. When a TCP connection is established
between peers, each BGP peer initially exchanges all of its routes—the complete BGP routing
table—with the other peer. After this initial exchange, the BGP peers send only incremental updates
when a topology change occurs in the network or when a routing policy change occurs. In the periods of
inactivity between these updates, peers exchange special messages called keepalives. The hold time is
the maximum time limit that can elapse between receiving consecutive BGP update or keepalive
messages.
Cisco NX-OS supports the following peer configuration options:
•
Individual IPv4 or IPv4 address—BGP establishes a session with the BGP speaker that matches the
remote address and AS number.
•
IPv4 or IPv6 prefix peers for a single AS number—BGP establishes sessions with BGP speakers that
match the prefix and the AS number.
•
Dynamic AS number prefix peers—BGP establishes sessions with BGP speakers that match the
prefix and an AS number from a list of configured AS numbers.
Dynamic AS Numbers for Prefix Peers
Cisco NX-OS accepts a range or list of AS numbers to establish BGP sessions. For example, if you
configure BGP to use IPv4 prefix 192.0.2.0/8 and AS numbers 33, 66, and 99, BGP establishes a session
with 192.0.2.1 with AS number 66 but rejects a session from 192.0.2.2 with AS number 50.
Cisco NX-OS does not associate prefix peers with dynamic AS numbers as either interior BGP (iBGP)
or external BGP (eBGP) sessions until after the session is established. See Chapter 10, “Configuring
Advanced BGP” for more information on iBGP and eBGP.
Note
The dynamic AS number prefix peer configuration overrides the individual AS number configuration
that is inherited from a BGP template. For more information, see Chapter 10, “Configuring Advanced
BGP.”
BGP Router Identifier
To establish BGP sessions between peers, BGP must have a router ID, which is sent to BGP peers in the
OPEN message when a BGP session is established. The BGP router ID is a 32-bit value that is often
represented by an IPv4 address. You can configure the router ID. By default, Cisco NX-OS sets the
router ID to the IPv4 address of a loopback interface on the router. If no loopback interface is configured
on the router, the software chooses the highest IPv4 address configured to a physical interface on the
router to represent the BGP router ID. The BGP router ID must be unique to the BGP peers in a network.
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About Basic BGP
If BGP does not have a router ID, it cannot establish any peering sessions with BGP peers.
BGP Path Selection
BGP supports sending and receiving multiple paths per prefix and advertising such paths. For
information on configuring additional BGP paths, see Chapter 10, “Configuring Advanced BGP.”
The best-path algorithm runs each time that a path is added or withdrawn for a given network. The
best-path algorithm also runs if you change the BGP configuration. BGP selects the best path from the
set of valid paths available for a given network.
Cisco NX-OS implements the BGP best-path algorithm in the following steps:
Step 1
Compares two paths to determine which is better (see the “Step 1—Comparing Pairs of Paths” section
on page 9-4).
Step 2
Explores all paths and determines in which order to compare the paths to select the overall best path (see
the “Step 2—Determining the Order of Comparisons” section on page 9-6).
Step 3
Determines whether the old and new best paths differ enough so that the new best path should be used
(see the “Step 3—Determining the Best-Path Change Suppression” section on page 9-6).
Note
The order of comparison determined in Step 2 is important. Consider the case where you have three
paths, A, B, and C. When Cisco NX-OS compares A and B, it chooses A. When Cisco NX-OS compares
B and C, it chooses B. But when Cisco NX-OS compares A and C, it might not choose A because some
BGP metrics apply only among paths from the same neighboring autonomous system and not among all
paths.
The path selection uses the BGP AS-path attribute. The AS-path attribute includes the list of autonomous
system numbers (AS numbers) traversed in the advertised path. If you subdivide your BGP autonomous
system into a collection or confederation of autonomous systems, the AS-path contains confederation
segments that list these locally defined autonomous systems.
Step 1—Comparing Pairs of Paths
This first step in the BGP best-path algorithm compares two paths to determine which path is better. The
following sequence describes the basic steps that Cisco NX-OS uses to compare two paths to determine
the better path:
1.
Cisco NX-OS chooses a valid path for comparison. (For example, a path that has an unreachable
next hop is not valid.)
2.
Cisco NX-OS chooses the path with the highest weight.
3.
Cisco NX-OS chooses the path with the highest local preference.
4.
If one of the paths is locally originated, Cisco NX-OS chooses that path.
5.
Cisco NX-OS chooses the path with the shorter AS-path.
Note
When calculating the length of the AS-path, Cisco NX-OS ignores confederation segments and
counts AS sets as 1. See the “AS Confederations” section on page 10-4 for more information.
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6.
Cisco NX-OS chooses the path with the lower origin. The Interior Gateway Protocol (IGP) is
considered lower than EGP.
7.
Cisco NX-OS chooses the path with the lower multiexit discriminator (MED).
You can configure a number of options that affect whether or not this step is performed. In general,
Cisco NX-OS compares the MED of both paths if the paths were received from peers in the same
autonomous system; otherwise, Cisco NX-OS skips the MED comparison.
You can configure Cisco NX-OS to always perform the best-path algorithm MED comparison,
regardless of the peer autonomous system in the paths. See the “Tuning the Best-Path Algorithm”
section on page 10-10 for more information. Otherwise, Cisco NX-OS performs a MED comparison
that depends on the AS-path attributes of the two paths being compared:
a. If a path has no AS-path or the AS-path starts with an AS_SET, the path is internal and Cisco
NX-OS compares the MED to other internal paths.
b. If the AS-path starts with an AS_SEQUENCE, the peer autonomous system is the first AS
number in the sequence and Cisco NX-OS compares the MED to other paths that have the same
peer autonomous system.
c. If the AS-path contains only confederation segments or starts with confederation segments
followed by an AS_SET, the path is internal and Cisco NX-OS compares the MED to other
internal paths.
d. If the AS-path starts with confederation segments that are followed by an AS_SEQUENCE, the
peer autonomous system is the first AS number in the AS_SEQUENCE and Cisco NX-OS
compares the MED to other paths that have the same peer autonomous system.
Note
If Cisco NX-OS receives no MED attribute with the path, Cisco NX-OS considers the MED
to be 0 unless you configure the best-path algorithm to set a missing MED to the highest
possible value. See the “Tuning the Best-Path Algorithm” section on page 10-10 for more
information.
e. If the nondeterministic MED comparison feature is enabled, the best-path algorithm uses the
Cisco IOS style of MED comparison. See the “Tuning the Best-Path Algorithm” section on
page 10-10 for more information.
8.
If one path is from an internal peer and the other path is from an external peer, Cisco NX-OS chooses
the path from the external peer.
9.
If the paths have different IGP metrics to their next-hop addresses, Cisco NX-OS chooses the path
with the lower IGP metric.
10. Cisco NX-OS uses the path that was selected by the best-path algorithm the last time that it was run.
If all path parameters in Step 1 through Step 9 are the same, you can configure the best-path algorithm
to compare the router IDs. See the “Tuning the Best-Path Algorithm” section on page 10-10 for more
information. If the path includes an originator attribute, Cisco NX-OS uses that attribute as the router ID
to compare to; otherwise, Cisco NX-OS uses the router ID of the peer that sent the path. If the paths have
different router IDs, Cisco NX-OS chooses the path with the lower router ID.
Note
When using the attribute originator as the router ID, it is possible that two paths have the same
router ID. It is also possible to have two BGP sessions with the same peer router, so you could
receive two paths with the same router ID.
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About Basic BGP
11. Cisco NX-OS selects the path with the shorter cluster length. If a path was not received with a cluster
list attribute, the cluster length is 0.
12. Cisco NX-OS chooses the path received from the peer with the lower IP address. Locally generated
paths (for example, redistributed paths) have a peer IP address of 0.
Note
Paths that are equal after Step 9 can be used for multipath if you configure multipath. See the “Load
Sharing and Multipath” section on page 10-6 for more information.
Step 2—Determining the Order of Comparisons
The second step of the BGP best-path algorithm implementation is to determine the order in which Cisco
NX-OS compares the paths:
1.
Cisco NX-OS partitions the paths into groups. Within each group, Cisco NX-OS compares the MED
among all paths. Cisco NX-OS uses the same rules as in the “Step 1—Comparing Pairs of Paths”
section on page 9-4 to determine whether MED can be compared between any two paths. Typically,
this comparison results in one group being chosen for each neighbor autonomous system. If you
configure the bgp bestpath med always command, Cisco NX-OS chooses just one group that
contains all the paths.
2.
Cisco NX-OS determines the best path in each group by iterating through all paths in the group and
keeping track of the best one so far. Cisco NX-OS compares each path with the temporary best path
found so far and if the new path is better, it becomes the new temporary best path and Cisco NX-OS
compares it with the next path in the group.
3.
Cisco NX-OS forms a set of paths that contain the best path selected from each group in Step 2.
Cisco NX-OS selects the overall best path from this set of paths by going through them as in Step 2.
Step 3—Determining the Best-Path Change Suppression
The next part of the implementation is to determine whether Cisco NX-OS uses the new best path or
suppresses the new best path. The router can continue to use the existing best path if the new one is
identical to the old path (if the router ID is the same). Cisco NX-OS continues to use the existing best
path to avoid route changes in the network.
You can turn off the suppression feature by configuring the best-path algorithm to compare the router
IDs. See the “Tuning the Best-Path Algorithm” section on page 10-10 for more information. If you
configure this feature, the new best path is always preferred to the existing one.
You cannot suppress the best-path change if any of the following conditions occur:
•
The existing best path is no longer valid.
•
Either the existing or new best paths were received from internal (or confederation) peers or were
locally generated (for example, by redistribution).
•
The paths were received from the same peer (the paths have the same router ID).
•
The paths have different weights, local preferences, origins, or IGP metrics to their next-hop
addresses.
•
The paths have different MEDs.
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Licensing Requirements for Basic BGP
BGP and the Unicast RIB
BGP communicates with the unicast Routing Information Base (unicast RIB) to store IPv4 routes in the
unicast routing table. After selecting the best path, if BGP determines that the best path change needs to
be reflected in the routing table, it sends a route update to the unicast RIB.
BGP receives route notifications regarding changes to its routes in the unicast RIB. It also receives route
notifications about other protocol routes to support redistribution.
BGP also receives notifications from the unicast RIB regarding next-hop changes. BGP uses these
notifications to keep track of the reachability and IGP metric to the next-hop addresses.
Whenever the next-hop reachability or IGP metrics in the unicast RIB change, BGP triggers a best-path
recalculation for affected routes.
BGP communicates with the IPv6 unicast RIB to perform these operations for IPv6 routes.
BGP Prefix Independent Convergence Core
The BGP prefix independent convergence (PIC) core feature allows for faster convergence for traffic
destined to BGP prefixes that share the same remote next hop in case of a failure in the core of the
network. Pure IP traffic can benefit from this feature. It is enabled by default and cannot be disabled.
BGP Virtualization
BGP supports virtual routing and forwarding (VRF) instances.
Licensing Requirements for Basic BGP
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
BGP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Prerequisites for BGP
BGP has the following prerequisites:
•
You must enable BGP (see the “Enabling BGP” section on page 9-11).
•
You should have a valid router ID configured on the system.
•
You must have an AS number, either assigned by a Regional Internet Registry (RIR) or locally
administered.
•
You must configure at least one IGP that is capable of recursive next-hop resolution.
•
You must configure an address family under a neighbor for the BGP session establishment.
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Guidelines and Limitations for BGP
Guidelines and Limitations for BGP
BGP has the following configuration guidelines and limitations:
•
The dynamic AS number prefix peer configuration overrides the individual AS number
configuration inherited from a BGP template.
•
If you configure a dynamic AS number for prefix peers in an AS confederation, BGP establishes
sessions with only the AS numbers in the local confederation.
•
BGP sessions created through a dynamic AS number prefix peer ignore any configured eBGP
multihop time-to-live (TTL) value or a disabled check for directly connected peers.
•
Configure a router ID for BGP to avoid automatic router ID changes and session flaps.
•
Use the maximum-prefix configuration option per peer to restrict the number of routes received and
system resources used.
•
Configure the update source to establish a session with BGP/eBGP multihop sessions.
•
Specify a BGP policy if you configure redistribution.
•
Define the BGP router ID within a VRF.
•
For IPv6 neighbors, Cisco recommends that you configure a router ID per VRF. If a VRF does not
have any IPv4 interfaces, the IPv6 BGP neighbor will not come up because its router ID must be an
IPv4 address. The numerically lowest loopback IPv4 address is elected to be the router ID. If a
loopback address does not exist, the lowest IP address from the VRF interfaces is elected. If that
does not exist, the BGP neighbor relationship is not established.
•
If you decrease the keepalive and hold timer values, you might experience BGP session flaps.
•
The BGP minimum route advertisement interval (MRAI) value for all iBGP and eBGP sessions is
zero and is not configurable.
•
If you configure VRFs, install the Advanced Services license and enter the desired VRF (see
Chapter 13, “Configuring Layer 3 Virtualization”).
•
Although the show ip bgp commands are available for verifying the BGP configuration, Cisco
recommends using the show bgp commands instead.
Default Settings
Table 9-2 lists the default settings for BGP parameters.
Table 9-2
Default BGP Parameters
Parameters
Default
BGP feature
Disabled
Keep alive interval
60 seconds
Hold timer
180 seconds
BGP PIC core
Enabled
Auto-summary
Always disabled
Synchronization
Always disabled
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CLI Configuration Modes
CLI Configuration Modes
The following sections describe how to enter each of the CLI configuration modes for BGP. From a
mode, you can enter the ? command to display the commands available in that mode.
Global Configuration Mode
Use global configuration mode to create a BGP process and configure advanced features such as AS
confederation and route dampening. For more information, see Chapter 10, “Configuring Advanced
BGP.”
This example shows how to enter router configuration mode:
switch# configuration
switch(config)# router bgp 64496
switch(config-router)#
BGP supports VRF. You can configure BGP within the appropriate VRF if you are using VRFs in your
network. See the “Configuring Virtualization” section on page 10-50 for more information.
This example shows how to enter VRF configuration mode:
switch(config)# router bgp 64497
switch(config-router)# vrf vrf_A
switch(config-router-vrf)#
Address Family Configuration Mode
You can optionally configure the address families that BGP supports. Use the address-family command
in router configuration mode to configure features for an address family. Use the address-family
command in neighbor configuration mode to configure the specific address family for the neighbor.
You must configure the address families if you are using route redistribution, address aggregation, load
balancing, and other advanced features.
This example shows how to enter address family configuration mode from the router configuration
mode:
switch(config)# router bgp 64496
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)#
This example shows how to enter VRF address family configuration mode if you are using VRFs:
switch(config)# router bgp 64497
switch(config-router)# vrf vrf_A
switch(config-router-vrf)# address-family ipv6 unicast
switch(config-router-vrf-af)#
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Neighbor Configuration Mode
Cisco NX-OS provides the neighbor configuration mode to configure BGP peers. You can use neighbor
configuration mode to configure all parameters for a peer.
This example shows how to enter neighbor configuration mode:
switch(config)# router bgp 64496
switch(config-router)# neighbor 192.0.2.1
switch(config-router-neighbor)#
This example shows how to enter VRF neighbor configuration mode:
switch(config)# router bgp 64497
switch(config-router)# vrf vrf_A
switch(config-router-vrf)# neighbor 192.0.2.1
switch(config-router-vrf-neighbor)#
Neighbor Address Family Configuration Mode
An address family configuration submode inside the neighbor configuration submode is available for
entering address family-specific neighbor configuration and enabling the address family for the
neighbor. Use this mode for advanced features such as limiting the number of prefixes allowed for this
neighbor and removing private AS numbers for eBGP.
This example shows how to enter neighbor address family configuration mode:
switch(config)# router bgp 64496
switch(config-router# neighbor 192.0.2.1
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)#
This example shows how to enter VRF neighbor address family configuration mode:
switch(config)# router bgp 64497
switch(config-router)# vrf vrf_A
switch(config-router-vrf)# neighbor 209.165.201.1
switch(config-router-vrf-neighbor)# address-family ipv4 unicast
switch(config-router-vrf-neighbor-af)#
Configuring Basic BGP
To configure a basic BGP, you must enable BGP and configure a BGP peer. Configuring a basic BGP
network consists of a few required tasks and many optional tasks. You must configure a BGP routing
process and BGP peers.
This section includes the following topics:
•
Enabling BGP, page 9-11
•
Creating a BGP Instance, page 9-12
•
Restarting a BGP Instance, page 9-14
•
Shutting Down BGP, page 9-14
•
Configuring BGP Peers, page 9-14
•
Configuring Dynamic AS Numbers for Prefix Peers, page 9-16
•
Clearing BGP Information, page 9-18
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Note
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Enabling BGP
You must enable BGP before you can configure BGP.
SUMMARY STEPS
1.
configure terminal
2.
feature bgp
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enables BGP.
feature bgp
Example:
switch(config)# feature bgp
Step 3
(Optional) Displays enabled and disabled features.
show feature
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Use the no feature bgp command to disable BGP and remove all associated configuration.
Command
Purpose
no feature bgp
Disables BGP and removes all associated
configuration.
Example:
switch(config)# no feature bgp
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Creating a BGP Instance
You can create a BGP instance and assign a router ID to the BGP instance. For more information, see
the “BGP Router Identifier” section on page 9-3.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
BGP must be able to obtain a router ID (for example, a configured loopback address).
SUMMARY STEPS
1.
configure terminal
2.
router bgp autonomous-system-number
3.
(Optional) router-id ip-address
4.
(Optional) address-family {ipv4 | ipv6} {unicast | multicast}
5.
(Optional) network {ip-address/length | ip-address mask mask} [route-map map-name]
6.
(Optional) show bgp all
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp autonomous-system-number
Example:
switch(config)# router bgp 64496
switch(config-router)#
Step 3
router-id ip-address
Example:
switch(config-router)# router-id
192.0.2.255
Step 4
address-family {ipv4 | ipv6} {unicast |
multicast}
Enables BGP and assigns the AS number to the local
BGP speaker. The AS number can be a 16-bit integer
or a 32-bit integer in the form of a higher 16-bit
decimal number and a lower 16-bit decimal number in
xx.xx format.
(Optional) Configures the BGP router ID. This IP
address identifies this BGP speaker.
(Optional) Enters global address family configuration
mode for the IPv4 or IPv6 address family.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
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Step 5
Command
Purpose
network {ip-address/length | ip-address
mask mask} [route-map map-name]
(Optional) Specifies a network as local to this
autonomous system and adds it to the BGP routing
table.
Example:
switch(config-router-af)# network
10.10.10.0/24
Example:
switch(config-router-af)# network
10.10.10.0 mask 255.255.255.0
Step 6
show bgp all
Example:
switch(config-router-af)# show bgp all
Step 7
copy running-config startup-config
For exterior protocols, the network command controls
which networks are advertised. Interior protocols use
the network command to determine where to send
updates.
(Optional) Displays information about all BGP address
families.
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
Use the no router bgp command to remove the BGP process and the associated configuration.
Command
Purpose
no router bgp autonomous-system-number
Deletes the BGP process and the associated
configuration.
Example:
switch(config)# no router bgp 201
This example shows how to enable BGP with the IPv4 unicast address family and manually add one
network to advertise:
switch# configure terminal
switch(config)# router bgp 64496
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# network 192.0.2.0
switch(config-router-af)# copy running-config startup-config
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Restarting a BGP Instance
You can restart a BGP instance and clear all peer sessions for the instance.
To restart a BGP instance and remove all associated peers, use the following command:
Command
Purpose
restart bgp instance-tag
Restarts the BGP instance and resets or
reestablishes all peering sessions.
Example:
switch(config)# restart bgp 201
Shutting Down BGP
You can shut down the BGP and gracefully disable BGP while retaining the configuration.
To shut down BGP, use the following command in router configuration mode:
Command
Purpose
shutdown
Gracefully shuts down BGP.
Example:
switch(config-router)# shutdown
Configuring BGP Peers
You can configure a BGP peer within a BGP process. Each BGP peer has an associated keepalive timer
and hold timers. You can set these timers either globally or for each BGP peer. A peer configuration
overrides a global configuration.
Note
You must configure the address family under neighbor configuration mode for each peer.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
SUMMARY STEPS
1.
configure terminal
2.
router bgp autonomous-system-number
3.
neighbor {ip-address | ipv6-address} remote-as as-number
4.
(Optional) description text
5.
(Optional) timers keepalive-time hold-time
6.
(Optional) shutdown
7.
address-family {ipv4 | ipv6} {unicast | multicast}
8.
(Optional) weight value
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9.
(Optional) show bgp {ipv4 | ipv6} {unicast | multicast} neighbors
10. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp autonomous-system-number
Example:
switch(config)# router bgp 64496
switch(config-router)#
Step 3
neighbor {ip-address | ipv6-address}
remote-as as-number
Example:
switch(config-router)# neighbor
209.165.201.1 remote-as 64497
switch(config-router-neighbor)#
Step 4
description text
Example:
switch(config-router-neighbor)#
description Peer Router B
switch(config-router-neighbor)#
Step 5
timers keepalive-time hold-time
Example:
switch(config-router-neighbor)# timers
30 90
Step 6
shutdown
Step 7
address-family {ipv4 | ipv6} {unicast |
multicast}
Enables BGP and assigns the AS number to the local
BGP speaker. The AS number can be a 16-bit integer
or a 32-bit integer in the form of a higher 16-bit
decimal number and a lower 16-bit decimal number in
xx.xx format.
Configures the IPv4 or IPv6 address and AS number
for a remote BGP peer. The ip-address format is
x.x.x.x. The ipv6-address format is A:B::C:D.
(Optional) Adds a description for the neighbor. The
description is an alphanumeric string up to 80
characters.
(Optional) Adds the keepalive and hold time BGP
timer values for the neighbor. The range is from 0 to
3600 seconds. The default is 60 seconds for the
keepalive time and 180 seconds for the hold time.
(Optional). Administratively shuts down this BGP
neighbor. This command triggers an automatic
Example:
notification and session reset for the BGP neighbor
switch(config-router-neighbor)# shutdown
sessions.
Enters neighbor address family configuration mode for
the IPv4 or IPv6 address family.
Example:
switch(config-router-neighbor)#
address-family ipv4 unicast
switch(config-router-neighbor-af)#
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Step 8
Command
Purpose
weight value
(Optional) Sets the default weight for routes from this
neighbor. The range is from 0 to 65535.
Example:
switch(config-router-neighbor-af)#
weight 100
All routes learned from this neighbor have the assigned
weight initially. The route with the highest weight is
chosen as the preferred route when multiple routes are
available to a particular network. The weights assigned
with the set weight route-map command override the
weights assigned with this command.
If you specify a BGP peer policy template, all the
members of the template inherit the characteristics
configured with this command.
Step 9
show bgp {ipv4 | ipv6} {unicast |
multicast} neighbors
(Optional) Displays information about BGP peers.
Example:
switch(config-router-neighbor-af)# show
bgp ipv4 unicast neighbors
Step 10
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af) copy
running-config startup-config
This example shows how to configure a BGP peer:
switch# configure terminal
switch(config)# router bgp 64496
switch(config-router)# neighbor 192.0.2.1 remote-as 64497
switch(config-router-neighbor)# description Peer Router B
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# weight 100
switch(config-router-neighbor-af)# copy running-config startup-config
Configuring Dynamic AS Numbers for Prefix Peers
You can configure multiple BGP peers within a BGP process. You can limit BGP session establishment
to a single AS number or multiple AS numbers in a route map.
BGP sessions configured through dynamic AS numbers for prefix peers ignore the ebgp-multihop
command and the disable-connected-check command.
You can change the list of AS numbers in the route map, but you must use the no neighbor command to
change the route-map name. Changes to the AS numbers in the configured route map affect only new
sessions.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
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SUMMARY STEPS
1.
configure terminal
2.
router bgp autonomous-system-number
3.
neighbor prefix remote-as route-map map-name
4.
(Optional) show bgp {ipv4 | ipv6} {unicast | multicast} neighbors
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp autonomous-system-number
Example:
switch(config)# router bgp 64496
switch(config-router)#
Step 3
neighbor prefix remote-as route-map
map-name
Example:
switch(config-router)# neighbor
192.0.2.0/8 remote-as routemap BGPPeers
switch(config-router-neighbor)#
Step 4
show bgp {ipv4 | ipv6} {unicast |
multicast} neighbors
Enables BGP and assigns the AS number to the local
BGP speaker. The AS number can be a 16-bit integer
or a 32-bit integer in the form of a higher 16-bit
decimal number and a lower 16-bit decimal number in
xx.xx format.
Configures the IPv4 or IPv6 prefix and a route map for
the list of accepted AS numbers for the remote BGP
peers. The prefix format for IPv4 is x.x.x.x/length. The
length range is from 1 to 32. The prefix format for IPv6
is A:B::C:D/length. The length range is from 1 to 128.
The map-name can be any case-sensitive,
alphanumeric string up to 63 characters.
(Optional) Displays information about BGP peers.
Example:
switch(config-router-neighbor-af)# show
bgp ipv4 unicast neighbors
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)# copy
running-config startup-config
This example shows how to configure dynamic AS numbers for a prefix peer:
switch# configure terminal
switch(config)# route-map BGPPeers
switch(config-route-map)# match as-number 64496, 64501-64510
switch(config-route-map)# match as-number as-path-list List1, List2
switch(config-route-map)# exit
switch(config)# router bgp 64496
switch(config-router)# neighbor 192.0.2.0/8 remote-as route-map BGPPeers
switch(config-router-neighbor)# description Peer Router B
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# copy running-config startup-config
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See Chapter 15, “Configuring Route Policy Manager.” for information on route maps.
Clearing BGP Information
To clear BGP information, use the following commands:
Command
Purpose
clear bgp all {neighbor | * | as-number |
peer-template name | prefix} [vrf vrf-name]
Clears one or more neighbors from all address
families. * clears all neighbors in all address
families. The arguments are as follows:
•
neighbor—IPv4 or IPv6 address of a
neighbor.
•
as-number—Autonomous system number.
The AS number can be a 16-bit integer or a
32-bit integer in the form of higher 16-bit
decimal number and a lower 16-bit decimal
number in xx.xx format.
•
name—Peer template name. The name can be
any case-sensitive, alphanumeric string up to
64 characters.
•
prefix—IPv4 or IPv6 prefix. All neighbors
within that prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
clear bgp all dampening [vrf vrf-name]
Clears route flap dampening networks in all
address families. The vrf-name can be any
case-sensitive, alphanumeric string up to 64
characters.
clear bgp all flap-statistics [vrf vrf-name]
Clears route flap statistics in all address families.
The vrf-name can be any case-sensitive,
alphanumeric string up to 64 characters.
clear bgp {ipv4 | ipv6} {unicast | multicast}
dampening [vrf vrf-name]
Clears route flap dampening networks in the
selected address family. The vrf-name can be any
case-sensitive, alphanumeric string up to 64
characters.
clear bgp {ipv4 | ipv6} {unicast | multicast}
flap-statistics [vrf vrf-name]
Clears route flap statistics in the selected address
family. The vrf-name can be any case-sensitive,
alphanumeric string up to 64 characters.
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Command
Purpose
clear bgp {ipv4 | ipv6} {unicast | multicast}
Clears one or more neighbors from the selected
{neighbor | * | as-number | peer-template name | address family. * clears all neighbors in the
prefix} [vrf vrf-name]
address family. The arguments are as follows:
•
neighbor—The IPv4 or IPv6 address of a
neighbor.
•
as-number— Autonomous system number.
The AS number can be a 16-bit integer or a
32-bit integer in the form of higher 16-bit
decimal number and a lower 16-bit decimal
number in xx.xx format.
•
name—Peer template name. The name can be
any case-sensitive, alphanumeric string up to
64 characters.
•
prefix—IPv4 or IPv6 prefix. All neighbors
within that prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
clear ip bgp {ip {unicast | multicast}}
Clears one or more neighbors. * clears all
{neighbor | * | as-number | peer-template name | neighbors in the address family. The arguments
prefix} [vrf vrf-name]
are as follows:
•
neighbor—IPv4 or IPv6 address of a
neighbor.
•
as-number— Autonomous system number.
The AS number can be a 16-bit integer or a
32-bit integer in the form of higher 16-bit
decimal number and a lower 16-bit decimal
number in xx.xx format.
•
name—Peer template name. The name can be
any case-sensitive, alphanumeric string up to
64 characters.
•
prefix—IPv4 or IPv6 prefix. All neighbors
within that prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
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Command
Purpose
clear ip bgp dampening [ip-neighbor | ip-prefix] Clears route flap dampening in one or more
[vrf vrf-name]
networks. The arguments are as follows:
clear ip bgp flap-statistics [ip-neighbor |
ip-prefix] [vrf vrf-name]
•
ip-neighbor—IPv4 address of a neighbor.
•
ip-prefix—IPv4. All neighbors within that
prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
Clears route flap statistics in one or more
networks. The arguments are as follows:
•
ip-neighbor—IPv4 address of a neighbor.
•
ip-prefix—IPv4. All neighbors within that
prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
clear ip mbgp {ip {unicast | multicast}}
Clears one or more neighbors. * clears all
{neighbor | * | as-number | peer-template name | neighbors in the address family. The arguments
prefix} [vrf vrf-name]
are as follows:
•
neighbor—IPv4 or IPv6 address of a
neighbor.
•
as-number— Autonomous system number.
The AS number can be a 16-bit integer or a
32-bit integer in the form of higher 16-bit
decimal number and a lower 16-bit decimal
number in xx.xx format.
•
name—Peer template name. The name can be
any case-sensitive, alphanumeric string up to
64 characters.
•
prefix—IPv4 or IPv6 prefix. All neighbors
within that prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
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Verifying the Basic BGP Configuration
Command
Purpose
clear ip mbgp dampening [ip-neighbor |
ip-prefix] [vrf vrf-name]
Clears route flap dampening in one or more
networks. The arguments are as follows:
clear ip mbgp flap-statistics [ip-neighbor |
ip-prefix] [vrf vrf-name]
•
ip-neighbor—IPv4 address of a neighbor.
•
ip-prefix—IPv4. All neighbors within that
prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
Clears route flap statistics one or more networks.
The arguments are as follows:
•
ip-neighbor—IPv4 address of a neighbor.
•
ip-prefix—IPv4. All neighbors within that
prefix are cleared.
•
vrf-name—VRF name. All neighbors in that
VRF are cleared. The name can be any
case-sensitive, alphanumeric string up to 64
characters.
Verifying the Basic BGP Configuration
To display the BGP configuration, perform one of the following tasks:
Command
Purpose
show bgp all [summary] [vrf vrf-name]
Displays the BGP information for all address
families.
show bgp convergence [vrf vrf-name]
Displays the BGP information for all address
families.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] community {regexp
expression | [community] [no-advertise]
[no-export] [no-export-subconfed]} [vrf
vrf-name]
Displays the BGP routes that match a BGP
community.
show bgp [vrf vrf-name] {ipv4 | ipv6} {unicast | Displays the BGP routes that match a BGP
multicast} [ip-address | ipv6-prefix]
community list.
community-list list-name [vrf vrf-name]
show bgp {ipv4 | ipv6} {unicast | multicast}
Displays the BGP routes that match a BGP
[ip-address | ipv6-prefix] extcommunity {regexp extended community.
expression | generic [non-transitive | transitive]
aa4:nn [exact-match]} [vrf vrf-name]
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] extcommunity-list
list-name [exact-match]} [vrf vrf-name]
Displays the BGP routes that match a BGP
extended community list.
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Verifying the Basic BGP Configuration
Command
Purpose
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] {dampening
dampened-paths [regexp expression]} [vrf
vrf-name]
Displays the information for BGP route
dampening. Use the clear bgp dampening
command to clear the route flap dampening
information.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] history-paths [regexp
expression] [vrf vrf-name]
Displays the BGP route history paths.
show bgp {ipv4 | ipv6} {unicast | multicast}
Displays the information for the BGP filter list.
[ip-address | ipv6-prefix] filter-list list-name [vrf
vrf-name]
show bgp {ipv4 | ipv6} {unicast | multicast}
Displays the information for BGP peers. Use the
[ip-address | ipv6-prefix] neighbors [ip-address | clear bgp neighbors command to clear these
ipv6-prefix] [vrf vrf-name]
neighbors.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] {nexthop |
nexthop-database} [vrf vrf-name]
Displays the information for the BGP route next
hop.
show bgp paths
Displays the BGP path information.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] policy name [vrf
vrf-name]
Displays the BGP policy information. Use the
clear bgp policy command to clear the policy
information.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] prefix-list list-name
[vrf vrf-name]
Displays the BGP routes that match the prefix list.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] received-paths [vrf
vrf-name]
Displays the BGP paths stored for soft
reconfiguration.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] regexp expression [vrf
vrf-name]
Displays the BGP routes that match the AS_path
regular expression.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] route-map map-name
[vrf vrf-name]
Displays the BGP routes that match the route
map.
show bgp peer-policy name [vrf vrf-name]
Displays the information about BGP peer
policies.
show bgp peer-session name [vrf vrf-name]
Displays the information about BGP peer
sessions.
show bgp peer-template name [vrf vrf-name]
Displays the information about BGP peer
templates. Use the clear bgp peer-template
command to clear all neighbors in a peer template.
show bgp process
Displays the BGP process information.
show {ip | ipv6} bgp options
Displays the BGP status and configuration
information.
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Monitoring BGP Statistics
Command
Purpose
show {ip | ipv6} mbgp options
Displays the BGP status and configuration
information.
show running-configuration bgp
Displays the current running BGP configuration.
Monitoring BGP Statistics
To display BGP statistics, use the following commands:
Command
Purpose
show bgp {ipv4 | ipv6} {unicast |
multicast} [ip-address | ipv6-prefix]
flap-statistics [vrf vrf-name]
Displays the BGP route flap statistics. Use the clear bgp
flap-statistics command to clear these statistics.
show bgp sessions [vrf vrf-name]
Displays the BGP sessions for all peers. Use the clear
bgp sessions command to clear these statistics.
show bgp statistics
Displays the BGP statistics.
Configuration Examples for Basic BGP
This example shows a basic BGP configuration:
switch(config)# feature bgp
switch(config)# router bgp 64496
switch(config-router)# neighbor 2001:DB8:0:1::55 remote-as 64496
switch(config-router-neighbor)# address-family ipv6 unicast
switch(config-router-af)# next-hop-self
Related Topics
The following topics relate to BGP:
•
Chapter 10, “Configuring Advanced BGP”
•
Chapter 15, “Configuring Route Policy Manager”
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Where to Go Next
Where to Go Next
See Chapter 10, “Configuring Advanced BGP,” for details on the following features:
•
Peer templates
•
Route redistribution
•
Route maps
Additional References
For additional information related to implementing BGP, see the following sections:
•
MIBs, page 9-24
MIBs
MIBs
MIBs Link
MIBs related to BGP
To locate and download supported MIBs, go to the following URL:
ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MI
BSupportList.html
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CH A P T E R
10
Configuring Advanced BGP
This chapter describes how to configure advanced features of the Border Gateway Protocol (BGP) on the
Cisco NX-OS device.
This chapter includes the following sections:
•
About Advanced BGP, page 10-1
•
Licensing Requirements for Advanced BGP, page 10-12
•
Prerequisites for Advanced BGP, page 10-12
•
Guidelines and Limitations for Advanced BGP, page 10-12
•
Default Settings for Advanced BGP, page 10-13
•
Configuring Advanced BGP, page 10-13
•
Verifying the Advanced BGP Configuration, page 10-52
•
Monitoring BGP Statistics, page 10-53
•
Configuration Examples, page 10-54
•
Related Topics, page 10-54
•
Additional References, page 10-54
About Advanced BGP
BGP is an interdomain routing protocol that provides loop-free routing between organizations or
autonomous systems. Cisco NX-OS supports BGP version 4. BGP version 4 includes multiprotocol
extensions that allow BGP to carry routing information for IP multicast routes and multiple Layer 3
protocol address families. BGP uses TCP as a reliable transport protocol to create TCP sessions with
other BGP-enabled devices called BGP peers. When connecting to an external organization, the router
creates external BGP (eBGP) peering sessions. BGP peers within the same organization exchange
routing information through internal BGP (iBGP) peering sessions.
This section includes the following topics:
•
Peer Templates, page 10-2
•
Authentication, page 10-2
•
Route Policies and Resetting BGP Sessions, page 10-3
•
eBGP, page 10-3
•
iBGP, page 10-3
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•
Capabilities Negotiation, page 10-6
•
Route Dampening, page 10-6
•
Load Sharing and Multipath, page 10-6
•
BGP Additional Paths, page 10-7
•
Route Aggregation, page 10-8
•
BGP Conditional Advertisement, page 10-8
•
BGP Next-Hop Address Tracking, page 10-8
•
Route Redistribution, page 10-9
•
BFD, page 10-9
•
Tuning BGP, page 10-10
•
Multiprotocol BGP, page 10-10
•
Graceful Restart and High Availability, page 10-11
•
Low Memory Handling, page 10-11
•
Virtualization Support, page 10-12
Peer Templates
BGP peer templates allow you to create blocks of common configuration that you can reuse across
similar BGP peers. Each block allows you to define a set of attributes that a peer then inherits. You can
choose to override some of the inherited attributes as well, making it a very flexible scheme for
simplifying the repetitive nature of BGP configurations.
Cisco NX-OS implements three types of peer templates:
•
The peer-session template defines BGP peer session attributes, such as the transport details, remote
autonomous system number of the peer, and session timers. A peer-session template can also inherit
attributes from another peer-session template (with locally defined attributes that override the
attributes from an inherited peer-session).
•
A peer-policy template defines the address-family dependent policy aspects for a peer including the
inbound and outbound policy, filter lists, and prefix lists. A peer-policy template can inherit from a
set of peer-policy templates. Cisco NX-OS evaluates these peer-policy templates in the order
specified by the preference value in the inherit configuration. The lowest number is preferred over
higher numbers.
•
The peer template can inherit the peer-session and peer-policy templates to allow for simplified peer
definitions. It is not mandatory to use a peer template but it can simplify the BGP configuration by
providing reusable blocks of configuration.
Authentication
You can configure authentication for a BGP neighbor session. This authentication method adds an MD5
authentication digest to each TCP segment sent to the neighbor to protect BGP against unauthorized
messages and TCP security attacks.
Note
The MD5 password must be identical between BGP peers.
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About Advanced BGP
Route Policies and Resetting BGP Sessions
You can associate a route policy to a BGP peer. Route policies use route maps to control or modify the
routes that BGP recognizes. You can configure a route policy for inbound or outbound route updates.
The route policies can match on different criteria, such as a prefix or AS_path attribute, and selectively
accept or deny the routes. Route policies can also modify the path attributes.
When you change a route policy applied to a BGP peer, you must reset the BGP sessions for that peer.
Cisco NX-OS supports the following mechanisms to reset BGP peering sessions:
Note
•
Hard reset—A hard reset tears down the specified peering sessions, including the TCP connection,
and deletes routes coming from the specified peer. This option interrupts packet flow through the
BGP network. Hard reset is disabled by default.
•
Soft reconfiguration inbound—A soft reconfiguration inbound triggers routing updates for the
specified peer without resetting the session. You can use this option if you change an inbound route
policy. Soft reconfiguration inbound saves a copy of all routes received from the peer before
processing the routes through the inbound route policy. If you change the inbound route policy,
Cisco NX-OS passes these stored routes through the modified inbound route policy to update the
route table without tearing down existing peering sessions. Soft reconfiguration inbound can use
significant memory resources to store the unfiltered BGP routes. Soft reconfiguration inbound is
disabled by default.
•
Route Refresh—A route refresh updates the inbound routing tables dynamically by sending route
refresh requests to supporting peers when you change an inbound route policy. The remote BGP peer
responds with a new copy of its routes that the local BGP speaker processes with the modified route
policy. Cisco NX-OS automatically sends an outbound route refresh of prefixes to the peer.
•
BGP peers advertise the route refresh capability as part of the BGP capability negotiation when
establishing the BGP peer session. Route refresh is the preferred option and enabled by default.
BGP also uses route maps for route redistribution, route aggregation, route dampening, and other
features. See Chapter 15, “Configuring Route Policy Manager,” for more information on route maps.
eBGP
External BGP (eBGP) allows you to connect BGP peers from different autonomous systems to exchange
routing updates. Connecting to external networks enables traffic from your network to be forwarded to
other networks and across the Internet.
Typically eBGP peerings need to be over directly connected interfaces so that convergence will be faster
when the interface goes down.
iBGP
Internal BGP (iBGP) allows you to connect BGP peers within the same autonomous system. You can use
iBGP for multihomed BGP networks (networks that have more than one connection to the same external
autonomous system).
Figure 10-1 shows an iBGP network within a larger BGP network.
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About Advanced BGP
Figure 10-1
AS10
Z
A
eBGP
C
iBGP
iBGP
iBGP
B
iBGP
iBGP
D
185055
AS20
iBGP Network
iBGP networks are fully meshed. Each iBGP peer has a direct connection to all other iBGP peers to
prevent network loops.
For single-hop iBGP peers with update-source configured under neighbor configuration mode, the peer
supports fast external fallover.
You should use loopback interfaces for establishing eBGP peering sessions because loopback interfaces
are less susceptible to interface flapping. An interface flap occurs when the interface is administratively
brought up or down because of a failure or maintenance issue. See the “Configuring eBGP” section on
page 10-28 for information on multihop, fast external fallovers, and limiting the size of the AS_path
attribute.
Note
You should configure a separate interior gateway protocol in the iBGP network.
This section includes the following topics:
•
AS Confederations, page 10-4
•
Route Reflector, page 10-5
AS Confederations
A fully meshed iBGP network becomes complex as the number of iBGP peers grows. You can reduce
the iBGP mesh by dividing the autonomous system into multiple subautonomous systems and grouping
them into a single confederation. A confederation is a group of iBGP peers that use the same autonomous
system number to communicate to external networks. Each subautonomous system is fully meshed
within itself and has a few connections to other subautonomous systems in the same confederation.
Figure 10-2 shows the BGP network from Figure 10-1, split into two subautonomous systems and one
confederation.
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Figure 10-2
AS10
Z
AS1 A
eBGP
AS2 C
Confederation
peers
iBGP
iBGP
B
D
185056
AS20
AS Confederation
In this example, AS10 is split into two subautonomous systems, AS1 and AS2. Each subautonomous
system is fully meshed, but there is only one link between the subautonomous systems. By using AS
confederations, you can reduce the number of links compared to the fully meshed autonomous system
in Figure 10-1.
Route Reflector
You can alternately reduce the iBGP mesh by using a route reflector configuration where route reflectors
pass learned routes to neighbors so that all iBGP peers do not need to be fully meshed.
Figure 10-1 shows a simple iBGP configuration with four meshed iBGP speakers (routers A, B, C, and
D). Without route reflectors, when router A receives a route from an external neighbor, it advertises the
route to all three iBGP neighbors.
When you configure an iBGP peer to be a route reflector, it becomes responsible for passing iBGP
learned routes to a set of iBGP neighbors.
In Figure 10-3, router B is the route reflector. When the route reflector receives routes advertised from
router A, it advertises (reflects) the routes to routers C and D. Router A no longer has to advertise to both
routers C and D.
Figure 10-3
AS20
Route Reflector
AS10
Z
A
C
eBGP
B
D
185057
iBGP
iBGP
The route reflector and its client peers form a cluster. You do not have to configure all iBGP peers to act
as client peers of the route reflector. You must configure any nonclient peer as fully meshed to guarantee
that complete BGP updates reach all peers.
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Capabilities Negotiation
A BGP speaker can learn about BGP extensions that are supported by a peer by using the capabilities
negotiation feature. Capabilities negotiation allows BGP to use only the set of features supported by both
BGP peers on a link.
If a BGP peer does not support capabilities negotiation, Cisco NX-OS attempts a new session to the peer
without capabilities negotiation if you have configured the address family as IPv4. Any other
multiprotocol configuration (such as IPv6) requires capabilities negotiation.
Route Dampening
Route dampening is a BGP feature that minimizes the propagation of flapping routes across an
internetwork. A route flaps when it alternates between the available and unavailable states in rapid
succession.
For example, consider a network with three BGP autonomous systems: AS1, AS2, and AS3. Suppose
that a route in AS1 flaps (it becomes unavailable). Without route dampening, AS1 sends a withdraw
message to AS2. AS2 propagates the withdrawal message to AS3. When the flapping route reappears,
AS1 sends an advertisement message to AS2, which sends the advertisement to AS3. If the route
repeatedly becomes unavailable, and then available, AS1 sends many withdrawal and advertisement
messages that propagate through the other autonomous systems.
Route dampening can minimize flapping. Suppose that the route flaps. AS2 (in which route dampening
is enabled) assigns the route a penalty of 1000. AS2 continues to advertise the status of the route to
neighbors. Each time that the route flaps, AS2 adds to the penalty value. When the route flaps so often
that the penalty exceeds a configurable suppression limit, AS2 stops advertising the route, regardless of
how many times that it flaps. The route is now dampened.
The penalty placed on the route decays until the reuse limit is reached. At that time, AS2 advertises the
route again. When the reuse limit is at 50 percent, AS2 removes the dampening information for the route.
Note
The router does not apply a penalty to a resetting BGP peer when route dampening is enabled, even
though the peer reset withdraws the route.
Load Sharing and Multipath
BGP can install multiple equal-cost eBGP or iBGP paths into the routing table to reach the same
destination prefix. Traffic to the destination prefix is then shared across all the installed paths.
The BGP best-path algorithm considers the paths as equal-cost paths if the following attributes are
identical:
•
Weight
•
Local preference
•
AS_path
•
Origin code
•
Multi-exit discriminator (MED)
•
IGP cost to the BGP next hop
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About Advanced BGP
BGP supports sending and receiving multiple paths per prefix and advertising such paths. For more
information, see the “BGP Additional Paths” section.
Note
Paths that are received from different AS confederations are considered as equal-cost paths if the
external AS_path values and the other attributes are identical.
Note
When you configure a route reflector for iBGP multipath, and the route reflector advertises the selected
best path to its peers, the next hop for the path is not modified.
BGP Additional Paths
Only one BGP best path is advertised, and the BGP speaker accepts only one path for a given prefix from
a given peer. If a BGP speaker receives multiple paths for the same prefix within the same session, it
uses the most recent advertisement.
BGP supports the additional paths feature, which allows the BGP speaker to propagate and accept
multiple paths for the same prefix without the new paths replacing any previous ones. This feature allows
BGP speaker peers to negotiate whether they support advertising and receiving multiple paths per prefix
and advertising such paths. A special 4-byte path ID is added to the network layer reachability
information (NLRI) to differentiate multiple paths for the same prefix sent across a peer session.
Figure 10-4 illustrates the BGP additional paths capability.
Prefix
BGP Route Advertisement with the Additional Paths Capability
RR
100.0.0.0/24
Path1 via R1
Path2 via R2
Path3 via R3
RR sends all available paths (not just
the best path) to R4, using the path
identifier prepended to the NLRI in
order to distinguish multiple paths.
UPDATE 1:
NLRI: 1:100.0.0.0/24
Path via R1
UPDATE 2:
NLRI: 2:100.0.0.0/24
Path via R2
UPDATE 3:
NLRI: 3:100.0.0.0/24
Path via R3
333817
Figure 10-4
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About Advanced BGP
For information on configuring BGP additional paths, see the “Configuring BGP Additional Paths”
section on page 10-26.
Route Aggregation
You can configure aggregate addresses. Route aggregation simplifies route tables by replacing a number
of more specific addresses with an address that represents all the specific addresses. For example, you
can replace these three more specific addresses, 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one
aggregate address, 10.1.0.0/16.
Aggregate prefixes are present in the BGP route table so that fewer routes are advertised.
Note
Cisco NX-OS does not support automatic route aggregation.
Route aggregation can lead to forwarding loops. To avoid this problem, when BGP generates an
advertisement for an aggregate address, it automatically installs a summary discard route for that
aggregate address in the local routing table. BGP sets the administrative distance of the summary discard
to 220 and sets the route type to discard. BGP does not use discard routes for next-hop resolution.
BGP Conditional Advertisement
BGP conditional advertisement allows you to configure BGP to advertise or withdraw a route based on
whether or not a prefix exists in the BGP table. This feature is useful, for example, in multihomed
networks, in which you want BGP to advertise some prefixes to one of the providers only if information
from the other provider is not present.
Consider an example network with three BGP autonomous systems: AS1, AS2, and AS3, where AS1 and
AS3 connect to the Internet and to AS2. Without conditional advertisement, AS2 propagates all routes
to both AS1 and AS3. With conditional advertisement, you can configure AS2 to advertise certain routes
to AS3 only if routes from AS1 do not exist (if for example, the link to AS1 fails).
BGP conditional advertisement adds an exist or not-exist test to each route that matches the configured
route map. See the “Configuring BGP Conditional Advertisement” section on page 10-38 for more
information.
BGP Next-Hop Address Tracking
BGP monitors the next-hop address of installed routes to verify next-hop reachability and to select,
install, and validate the BGP best path. BGP next-hop address tracking speeds up this next-hop
reachability test by triggering the verification process when routes change in the Routing Information
Base (RIB) that may affect BGP next-hop reachability.
BGP receives notifications from the RIB when the next-hop information changes (event-driven
notifications). BGP is notified when any of the following events occurs:
•
The next hop becomes unreachable.
•
The next hop becomes reachable.
•
The fully recursed Interior Gateway Protocol (IGP) metric to the next hop changes.
•
The first hop IP address or first hop interface changes.
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Note
•
The next hop becomes connected.
•
The next hop becomes unconnected.
•
The next hop becomes a local address.
•
The next hop becomes a nonlocal address.
Reachability and recursed metric events trigger a best-path recalculation.
Event notifications from the RIB are classified as critical and noncritical. Notifications for critical and
noncritical events are sent in separate batches. However, a noncritical event is sent with the critical
events if the noncritical event is pending and there is a request to read the critical events.
•
Critical events are related to next-hop reachability, such as the loss of next hops resulting in a
switchover to a different path. A change in the IGP metric for a next hop resulting in a switchover
to a different path can also be considered a critical event.
•
Non-critical events are related to next hops being added without affecting the best path or changing
the IGP metric to a single next hop.
See the “Configuring BGP Next-Hop Address Tracking” section on page 10-24 for more information.
Route Redistribution
You can configure BGP to redistribute static routes or routes from other protocols. You must configure
a route map with the redistribution to control which routes are passed into BGP. A route map allows you
to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and
so on. See Chapter 15, “Configuring Route Policy Manager,” for more information. iBGP is not
redistributed to IGP by default.
You can use route maps to override the default behavior in both scenarios, but be careful when doing so
as incorrect use of route maps can result in network loops. The following examples show how to use
route maps to change the default behavior.
You can change the default behavior for scenario 1 by modifying the route map as follows:
route-map foo permit 10
match route-type internal
router ospf 1
redistribute bgp 100 route-map foo
Similarly, you can change the default behavior for scenario 2 by modifying the route map as follows:
route-map foo deny 10
match route-type internal
router ospf 1
vrf bar
redistribute bgp 100 route-map foo
BFD
This feature supports bidirectional forwarding detection (BFD) for the IPv4 address families. BFD is a
detection protocol designed to provide fast forwarding-path failure detection times. BFD provides
subsecond failure detection between two adjacent devices and can be less CPU-intensive than protocol
hello messages because some of the BFD load can be distributed onto the data plane on supported
modules.
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About Advanced BGP
BFD for BGP is supported on eBGP peers and iBGP single-hop peers. Configure the update-source
option in neighbor configuration mode for iBGP single-hop peers using BFD.
Note
BFD is not supported on other iBGP peers or for multihop eBGP peers.
See the Cisco Nexus 9000 Series NX-OS Interfaces Configuration Guide for more information.
Tuning BGP
You can modify the default behavior of BGP through BGP timers and by adjusting the best-path
algorithm.
This section includes the following topics:
•
BGP Timers, page 10-10
•
Tuning the Best-Path Algorithm, page 10-10
BGP Timers
BGP uses different types of timers for neighbor session and global protocol events. Each established
session has a minimum of two timers for sending periodic keepalive messages and for timing out
sessions when peer keepalives do not arrive within the expected time. In addition, there are other timers
for handling specific features. Typically, you configure these timers in seconds. The timers include a
random adjustment so that the same timers on different BGP peers trigger at different times.
Tuning the Best-Path Algorithm
You can modify the default behavior of the best-path algorithm through optional configuration
parameters, including changing how the algorithm handles the multi-exit discriminator (MED) attribute
and the router ID.
Multiprotocol BGP
BGP on Cisco NX-OS supports multiple address families. Multiprotocol BGP (MP-BGP) carries
different sets of routes depending on the address family. For example, BGP can carry one set of routes
for IPv4 unicast routing, one set of routes for IPv4 multicast routing, and one set of routes for IPv6
multicast routing.
Note
Because Multicast BGP does not propagate multicast state information, you need a multicast protocol,
such as Protocol Independent Multicast (PIM).
Use the router address-family and neighbor address-family configuration modes to support
multiprotocol BGP configurations. MP-BGP maintains separate RIBs for each configured address
family, such as a unicast RIB and a multicast RIB for BGP.
A multiprotocol BGP network is backward compatible but BGP peers that do not support multiprotocol
extensions cannot forward routing information, such as address family identifier information, that the
multiprotocol extensions carry.
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About Advanced BGP
Graceful Restart and High Availability
Cisco NX-OS supports nonstop forwarding and graceful restart for BGP.
You can use nonstop forwarding (NSF) for BGP to forward data packets along known routes in the
Forward Information Base (FIB) while the BGP routing protocol information is being restored following
a failover. With NSF, BGP peers do not experience routing flaps. During a failover, the data traffic is
forwarded through intelligent modules while the standby supervisor becomes active.
If a Cisco NX-OS router experiences a cold reboot, the network does not forward traffic to the router and
removes the router from the network topology. In this scenario, BGP experiences a nongraceful restart
and removes all routes. When Cisco NX-OS applies the startup configuration, BGP reestablishes peering
sessions and relearns the routes.
A Cisco NX-OS router that has dual supervisors can experience a stateful supervisor switchover. During
the switchover, BGP uses nonstop forwarding to forward traffic based on the information in the FIB, and
the system is not removed from the network topology. A router whose neighbor is restarting is referred
to as a “helper.” After the switchover, a graceful restart operation begins. When it is in progress, both
routers reestablish their neighbor relationship and exchange their BGP routes. The helper continues to
forward prefixes pointing to the restarting peer, and the restarting router continues to forward traffic to
peers even though those neighbor relationships are restarting. When the restarting router has all route
updates from all BGP peers that are graceful restart capable, the graceful restart is complete, and BGP
informs the neighbors that it is operational again.
For single-hop iBGP peers with update-source configured under neighbor configuration mode, the peer
supports fast external fall-over.
With the additional BGP paths feature, if the number of paths advertised for a given prefix is the same
before and after restart, the choice of path ID guarantees the final state and removal of stale paths. If
fewer paths are advertised for a given prefix after a restart, stale paths can occur on the graceful restart
helper peer.
Low Memory Handling
BGP reacts to low memory for the following conditions:
•
Minor alert—BGP does not establish any new eBGP peers. BGP continues to establish new iBGP
peers and confederate peers. Established peers remain, but reset peers are not reestablished.
•
Severe alert—BGP shuts down select established eBGP peers every two minutes until the memory
alert becomes minor. For each eBGP peer, BGP calculates the ratio of total number of paths received
to the number of paths selected as best paths. The peers with the highest ratio are selected to be shut
down to reduce memory usage. You must clear a shutdown eBGP peer before you can bring the
eBGP peer back up to avoid oscillation.
Note
•
You can exempt important eBGP peers from this selection process.
Critical alert—BGP gracefully shuts down all the established peers. You must clear a shutdown BGP
peer before you can bring the BGP peer back up.
See the “Tuning BGP” section on page 10-44 for more information on how to exempt a BGP peer from
a shutdown due to a low memory condition.
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Licensing Requirements for Advanced BGP
Virtualization Support
You can configure one BGP instance. BGP supports virtual routing and forwarding (VRF) instances.
Licensing Requirements for Advanced BGP
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
BGP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Prerequisites for Advanced BGP
Advanced BGP has the following prerequisites:
•
You must enable BGP (see the “Enabling BGP” section on page 9-11).
•
You should have a valid router ID configured on the system.
•
You must have an AS number, either assigned by a Regional Internet Registry (RIR) or locally
administered.
•
You must have reachability (such as an interior gateway protocol [IGP], a static route, or a direct
connection) to the peer that you are trying to make a neighbor relationship with.
•
You must explicitly configure an address family under a neighbor for the BGP session
establishment.
Guidelines and Limitations for Advanced BGP
Advanced BGP has the following configuration guidelines and limitations:
•
The dynamic AS number prefix peer configuration overrides the individual AS number
configuration inherited from a BGP template.
•
If you configure a dynamic AS number for prefix peers in an AS confederation, BGP establishes
sessions with only the AS numbers in the local confederation.
•
BGP sessions created through a dynamic AS number prefix peer ignore any configured eBGP
multihop time-to-live (TTL) value or a disabled check for directly connected peers.
•
Configure a router ID for BGP to avoid automatic router ID changes and session flaps.
•
Use the maximum-prefix configuration option per peer to restrict the number of routes received and
system resources used.
•
Configure the update source to establish a session with eBGP multihop sessions.
•
Specify a BGP route map if you configure a redistribution.
•
Configure the BGP router ID within a VRF.
•
If you decrease the keepalive and hold timer values, the network might experience session flaps.
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Default Settings for Advanced BGP
•
When you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you
must insert an additional deny statement into the route map.
•
Cisco NX-OS does not support multi-hop BFD. BFD for BGP has the following limitations:
– BFD is supported only for eBGP peers and iBGP single-hop peers.
– To enable BFD for iBGP single-hop peers, you must configure the update-source option on the
physical interface.
– BFD is not supported for multi-hop iBGP peers and multi-hop eBGP peers.
– BGP supports prefix-based peers, but BFD is not supported for prefix-based peers.
•
The following guidelines and limitations apply to the remove-private-as command:
– It applies only to eBGP peers.
– It can be configured only in neighbor configuration mode and not in neighbor-address-family
mode.
– If the AS-path includes both private and public AS numbers, the private AS numbers are not
removed.
– If the AS-path contains the AS number of the eBGP neighbor, the private AS numbers are not
removed.
– Private AS numbers are removed only if all AS numbers in that AS-path belong to a private AS
number range. Private AS numbers are not removed if a peer’s AS number or a non-private AS
number is found in the AS-path segment.
•
If you use the aggregate-address command to configure aggregate addresses and the
suppress-fib-pending command to suppress BGP routes, lossless traffic for aggregates cannot be
ensured on BGP or system triggers.
•
When you enable FIB suppression on the switch and route programming fails in the hardware, BGP
advertises routes that are not programmed locally in the hardware.
Default Settings for Advanced BGP
Table 10-1 lists the default settings for advanced BGP parameters.
Table 10-1
Default BGP Parameters
Parameters
Default
BGP feature
Disabled
BGP additional paths
Disabled
Hold timer
180 seconds
Keep alive interval
60 seconds
Dynamic capability
Enabled
Configuring Advanced BGP
This section includes the following topics:
•
Configuring BGP Session Templates, page 10-14
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Note
•
Configuring BGP Peer-Policy Templates, page 10-17
•
Configuring BGP Peer Templates, page 10-19
•
Configuring Prefix Peering, page 10-21
•
Configuring BGP Authentication, page 10-22
•
Resetting a BGP Session, page 10-23
•
Modifying the Next-Hop Address, page 10-23
•
Configuring BGP Next-Hop Address Tracking, page 10-24
•
Configuring Next-Hop Filtering, page 10-24
•
Shrinking Next-Hop Groups When A Session Goes Down, page 10-25
•
Disabling Capabilities Negotiation, page 10-25
•
Disabling Policy Batching, page 10-25
•
Configuring BGP Additional Paths, page 10-26
•
Configuring eBGP, page 10-28
•
Configuring AS Confederations, page 10-30
•
Configuring Route Reflector, page 10-31
•
Configuring Next Hops on Reflected Routes Using an Outbound Route Map, page 10-33
•
Configuring Route Dampening, page 10-35
•
Configuring Load Sharing and ECMP, page 10-36
•
Configuring Maximum Prefixes, page 10-36
•
Configuring Dynamic Capability, page 10-37
•
Configuring Aggregate Addresses, page 10-37
•
Suppressing BGP Routes, page 10-37
•
Configuring BGP Conditional Advertisement, page 10-38
•
Configuring Route Redistribution, page 10-40
•
Advertising the Default Route, page 10-41
•
Configuring Multiprotocol BGP, page 10-43
•
Tuning BGP, page 10-44
•
Configuring a Graceful Restart, page 10-48
•
Configuring Virtualization, page 10-50
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring BGP Session Templates
You can use BGP session templates to simplify the BGP configuration for multiple BGP peers with
similar configuration needs. BGP templates allow you to reuse common configuration blocks. You
configure BGP templates first and then apply these templates to BGP peers.
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With BGP session templates, you can configure session attributes such as inheritance, passwords, timers,
and security.
A peer-session template can inherit from one other peer-session template. You can configure the second
template to inherit from a third template. The first template also inherits this third template. This indirect
inheritance can continue for up to seven peer-session templates.
Any attributes configured for the neighbor take priority over any attributes inherited by that neighbor
from a BGP template.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
Note
When editing a template, you can use the no form of a command at either the peer or template level to
explicitly override a setting in a template. You must use the default form of the command to reset that
attribute to the default state.
SUMMARY STEPS
1.
configure terminal
2.
router bgp autonomous-system-number
3.
template peer-session template-name
4.
(Optional) password number password
5.
(Optional) timers keepalive hold
6.
exit
7.
neighbor ip-address remote-as as-number
8.
inherit peer-session template-name
9.
(Optional) description text
10. (Optional) show bgp peer-session template-name
11. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp autonomous-system-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Enables BGP and assigns the autonomous system
number to the local BGP speaker.
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Step 3
Command
Purpose
template peer-session template-name
Enters peer-session template configuration mode.
Example:
switch(config-router)# template
peer-session BaseSession
switch(config-router-stmp)#
Step 4
password number password
Example:
switch(config-router-stmp)# password 0
test
Step 5
timers keepalive hold
Example:
switch(config-router-stmp)# timers 30 90
Step 6
exit
(Optional) Adds the cleartext password test to the
neighbor. The password is stored and displayed in type
3 encrypted form (3DES).
(Optional) Adds the BGP keepalive and holdtimer
values to the peer-session template.
The default keepalive interval is 60. The default hold
time is 180.
Exits peer-session template configuration mode.
Example:
switch(config-router-stmp)# exit
switch(config-router)#
Step 7
neighbor ip-address remote-as as-number
Example:
switch(config-router)# neighbor
192.168.1.2 remote-as 65535
switch(config-router-neighbor)#
Step 8
inherit peer-session template-name
Places the router in the neighbor configuration mode
for BGP routing and configures the neighbor IP
address.
Applies a peer-session template to the peer.
Example:
switch(config-router-neighbor)# inherit
peer-session BaseSession
switch(config-router-neighbor)
Step 9
description text
(Optional) Adds a description for the neighbor.
Example:
switch(config-router-neighbor)#
description Peer Router A
switch(config-router-neighbor)
Step 10
show bgp peer-session template-name
(Optional) Displays the peer-policy template.
Example:
switch(config-router-neighbor)# show bgp
peer-session BaseSession
Step 11
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor)# copy
running-config startup-config
Use the show bgp neighbor command to see the template applied.
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This example shows how to configure a BGP peer-session template and apply it to a BGP peer:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# template peer-session BaseSession
switch(config-router-stmp)# timers 30 90
switch(config-router-stmp)# exit
switch(config-router)# neighbor 192.168.1.2 remote-as 65535
switch(config-router-neighbor)# inherit peer-session BaseSession
switch(config-router-neighbor)# description Peer Router A
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor)# copy running-config startup-config
Configuring BGP Peer-Policy Templates
You can configure a peer-policy template to define attributes for a particular address family. You assign
a preference to each peer-policy template and these templates are inherited in the order specified, for up
to five peer-policy templates in a neighbor address family.
Cisco NX-OS evaluates multiple peer policies for an address family using the preference value. The
lowest preference value is evaluated first. Any attributes configured for the neighbor take priority over
any attributes inherited by that neighbor from a BGP template.
Peer-policy templates can configure address family-specific attributes such as AS-path filter lists, prefix
lists, route reflection, and soft reconfiguration.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
Note
When editing a template, you can use the no form of a command at either the peer or template level to
explicitly override a setting in a template. You must use the default form of the command to reset that
attribute to the default state.
SUMMARY STEPS
1.
configure terminal
2.
router bgp autonomous-system-number
3.
template peer-policy template-name
4.
(Optional) advertise-active-only
5.
(Optional) maximum-prefix number
6.
exit
7.
neighbor ip-address remote-as as-number
8.
address-family {ipv4 | ipv6} {multicast | unicast}
9.
inherit peer-policy template-name preference
10. (Optional) show bgp peer-policy template-name
11. (Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp autonomous-system-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 3
template peer-policy template-name
Enables BGP and assigns the autonomous system
number to the local BGP speaker.
Creates a peer-policy template.
Example:
switch(config-router)# template
peer-policy BasePolicy
switch(config-router-ptmp)#
Step 4
advertise-active-only
(Optional) Advertises only active routes to the peer.
Example:
switch(config-router-ptmp)#
advertise-active-only
Step 5
maximum-prefix number
Example:
switch(config-router-ptmp)#
maximum-prefix 20
Step 6
exit
(Optional) Sets the maximum number of prefixes
allowed from this peer.
Exits peer-policy template configuration mode.
Example:
switch(config-router-ptmp)# exit
switch(config-router)#
Step 7
neighbor ip-address remote-as as-number
Example:
switch(config-router)# neighbor
192.168.1.2 remote-as 65535
switch(config-router-neighbor)#
Step 8
address-family {ipv4 | ipv6} {multicast
| unicast}
Places the router in neighbor configuration mode for
BGP routing and configures the neighbor IP address.
Enters global address-family configuration mode for
the specified address family.
Example:
switch(config-router-neighbor)#
address-family ipv4 unicast
switch(config-router-neighbor-af)#
Step 9
inherit peer-policy template-name
preference
Example:
switch(config-router-neighbor-af)#
inherit peer-policy BasePolicy 1
Applies a peer-policy template to the peer
address-family configuration and assigns the
preference value for this peer policy.
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Step 10
Command
Purpose
show bgp peer-policy template-name
(Optional) Displays the peer-policy template.
Example:
switch(config-router-neighbor-af)# show
bgp peer-policy BasePolicy
Step 11
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)# copy
running-config startup-config
Use the show bgp neighbor command to see the template applied.
This example shows how to configure a BGP peer-policy template and apply it to a BGP peer:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# template peer-session BasePolicy
switch(config-router-ptmp)# maximum-prefix 20
switch(config-router-ptmp)# exit
switch(config-router)# neighbor 192.168.1.1 remote-as 65535
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# inherit peer-policy BasePolicy
switch(config-router-neighbor-af)# copy running-config startup-config
Configuring BGP Peer Templates
You can configure BGP peer templates to combine session and policy attributes in one reusable
configuration block. Peer templates can also inherit peer-session or peer-policy templates. Any attributes
configured for the neighbor take priority over any attributes inherited by that neighbor from a BGP
template. You configure only one peer template for a neighbor, but that peer template can inherit
peer-session and peer-policy templates.
Peer templates support session and address family attributes, such as eBGP multihop time-to-live,
maximum prefix, next-hop self, and timers.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
Note
When editing a template, you can use the no form of a command at either the peer or template level to
explicitly override a setting in a template. You must use the default form of the command to reset that
attribute to the default state.
SUMMARY STEPS
1.
configure terminal
2.
router bgp autonomous-system-number
3.
template peer template-name
4.
inherit peer-session template-name
5.
address-family {ipv4 | ipv6} {multicast | unicast}
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6.
inherit peer template-name
7.
exit
8.
timers keepalive hold
9.
exit
10. neighbor ip-address remote-as as-number
11. inherit peer template-name
12. timers keepalive hold
13. (Optional) show bgp peer-template template-name
14. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp autonomous-system-number
Example:
switch(config)# router bgp 65535
Step 3
template peer template-name
Enters BGP mode and assigns the autonomous system
number to the local BGP speaker.
Enters peer template configuration mode.
Example:
switch(config-router)# template peer
BasePeer
switch(config-router-neighbor)#
Step 4
inherit peer-session template-name
Example:
switch(config-router-neighbor)# inherit
peer-session BaseSession
Step 5
address-family {ipv4 | ipv6} {multicast
| unicast}
(Optional) Inherits a peer-session template in the peer
template.
(Optional) Configures the global address-family
configuration mode for the specified address family.
Example:
switch(config-router-neighbor)#
address-family ipv4 unicast
switch(config-router-neighbor-af)#
Step 6
inherit peer template-name
Example:
switch(config-router-neighbor-af)#
inherit peer BasePolicy
Step 7
exit
Example:
switch(config-router-neighbor-af)# exit
switch(config-router-neighbor)#
(Optional) Applies a peer template to the neighbor
address-family configuration.
Exits BGP neighbor address-family configuration
mode.
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Step 8
Step 9
Command
Purpose
timers keepalive hold
(Optional) Adds the BGP timer values to the peer.
Example:
switch(config-router-neighbor)# timers
45 100
These values override the timer values in the
peer-session template, BaseSession.
exit
Exits BGP peer template configuration mode.
Example:
switch(config-router-neighbor)# exit
switch(config-router)#
Step 10
neighbor ip-address remote-as as-number
Example:
switch(config-router)# neighbor
192.168.1.2 remote-as 65535
switch(config-router-neighbor)#
Step 11
inherit peer template-name
Places the router in neighbor configuration mode for
BGP routing and configures the neighbor IP address.
Inherits the peer template.
Example:
switch(config-router-neighbor)# inherit
peer BasePeer
Step 12
Step 13
timers keepalive hold
(Optional) Adds the BGP timer values to this neighbor.
Example:
switch(config-router-neighbor)# timers
60 120
These values override the timer values in the peer
template and the peer-session template.
show bgp peer-template template-name
(Optional) Displays the peer template.
Example:
switch(config-router-neighbor-af)# show
bgp peer-template BasePeer
Step 14
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)# copy
running-config startup-config
Use the show bgp neighbor command to see the template applied.
This example shows how to configure a BGP peer template and apply it to a BGP peer:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# template peer BasePeer
switch(config-router-neighbor)# inherit peer-session BaseSession
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# inherit peer-policy BasePolicy 1
switch(config-router-neighbor-af)# exit
switch(config-router-neighbor)# exit
switch(config-router)# neighbor 192.168.1.2 remote-as 65535
switch(config-router-neighbor)# inherit peer BasePeer
switch(config-router-neighbor)# copy running-config startup-config
Configuring Prefix Peering
BGP supports the definition of a set of peers using a prefix for both IPv4 and IPv6. This feature allows
you to not have to add each neighbor to the configuration.
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When defining a prefix peering, you must specify the remote AS number with the prefix. BGP accepts
any peer that connects from that prefix and autonomous system if the prefix peering does not exceed the
configured maximum peers allowed.
When a BGP peer that is part of a prefix peering disconnects, Cisco NX-OS holds its peer structures for
a defined prefix peer timeout value. An established peer can reset and reconnect without danger of being
blocked because other peers have consumed all slots for that prefix peering.
To configure the BGP prefix peering timeout value, use the following command in neighbor
configuration mode:
Command
Purpose
timers prefix-peer-timeout value
Configures the timeout value for prefix peering.
The range is from 0 to 1200 seconds. The default
value is 30.
Example:
switch(config-router-neighbor)# timers
prefix-peer-timeout 120
To configure the maximum number of peers, use the following command in neighbor configuration
mode:
Command
Purpose
maximum-peers value
Configures the maximum number of peers for this
prefix peering. The range is from 1 to 1000.
Example:
switch(config-router-neighbor)#
maximum-peers 120
This example shows how to configure a prefix peering that accepts up to 10 peers:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# timers prefix-peer-timeout 120
switch(config-router)# neighbor 10.100.200.0/24 remote-as 65535
switch(config-router-neighbor)# maximum-peers 10
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)#
Use the show bgp ipv4 unicast neighbors command to show the details of the configuration for that
prefix peering with a list of the currently accepted instances and the counts of active, maximum
concurrent, and total accepted peers.
Configuring BGP Authentication
You can configure BGP to authenticate route updates from peers using MD5 digests.
To configure BGP to use MD5 authentication, use the following command in neighbor configuration
mode:
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Command
Purpose
password [0 | 3 | 7] string
Configures an MD5 password for BGP neighbor
sessions.
Example:
switch(config-router-neighbor)# password
BGPpassword
Resetting a BGP Session
If you modify a route policy for BGP, you must reset the associated BGP peer sessions. If the BGP peers
do not support route refresh, you can configure a soft reconfiguration for inbound policy changes. Cisco
NX-OS automatically attempts a soft reset for the session.
To configure soft reconfiguration inbound, use the following command in neighbor address-family
configuration mode:
Command
Purpose
soft-reconfiguration inbound
Enables soft reconfiguration to store the inbound
BGP route updates. This command triggers an
automatic soft clear or refresh of BGP neighbor
sessions.
Example:
switch(config-router-neighbor-af)#
soft-reconfiguration inbound
To reset a BGP neighbor session, use the following command in any mode:
Command
Purpose
clear bgp {ipv4 | ipv6} {unicast |
multicast} ip-address soft {in | out}
Resets the BGP session without tearing down the
TCP session.
Example:
switch# clear bgp ip unicast 192.0.2.1
soft in
Modifying the Next-Hop Address
You can modify the next-hop address used in a route advertisement in the following ways:
•
Disable next-hop calculation and use the local BGP speaker address as the next-hop address.
•
Set the next-hop address as a third-party address. Use this feature in situations where the original
next-hop address is on the same subnet as the peer that the route is being sent to. Using this feature
saves an extra hop during forwarding.
To modify the next-hop address, use the following commands in address-family configuration mode:
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Command
Purpose
next-hop-self
Uses the local BGP speaker address as the next-hop
address in route updates. This command triggers an
automatic soft clear or refresh of BGP neighbor
sessions.
Example:
switch(config-router-neighbor-af)#
next-hop-self
next-hop-third-party
Example:
switch(config-router-neighbor-af)#
next-hop-third-party
Sets the next-hop address as a third-party address.
Use this command for single-hop EBGP peers that
do not have next-hop-self configured.
Configuring BGP Next-Hop Address Tracking
BGP next-hop address tracking is enabled by default and cannot be disabled.
You can modify the delay interval between RIB checks to increase the performance of BGP next-hop
tracking.
To modify the BGP next-hop address tracking, use the following commands in address-family
configuration mode:
Command
Purpose
nexthop trigger-delay {critical |
non-critical} milliseconds
Specifies the next-hop address tracking delay timer
for critical next-hop reachability routes and for
noncritical routes. The range is from 1 to
4294967295 milliseconds. The critical timer
default is 3000. The noncritical timer default is
10000.
Example:
switch(config-router-af)# nexthop
trigger-delay critical 5000
Configuring Next-Hop Filtering
BGP next-hop filtering allows you to specify that when a next-hop address is checked with the RIB, the
underlying route for that next-hop address is passed through the route map. If the route map rejects the
route, the next-hop address is treated as unreachable.
BGP marks all next hops that are rejected by the route policy as invalid and does not calculate the best
path for the routes that use the invalid next-hop address.
To configure BGP next-hop filtering, use the following command in address-family configuration mode:
Command
Purpose
nexthop route-map name
Specifies a route map to match the BGP next-hop
route to. The name can be any case-sensitive,
alphanumeric string up to 63 characters.
Example:
switch(config-router-af)# nexthop
route-map nextHopLimits
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Shrinking Next-Hop Groups When A Session Goes Down
You can configure BGP to shrink ECMP groups in an accelerated way when a session goes down.
This feature applies to the following BGP path failure events:
•
Any single or multiple Layer 3 link failures
•
Line card failures
•
BFD failure detections for BGP neighbors
Note
•
BFDv6 is currently not supported.
Administrative shutdown of BGP neighbors (using the shutdown command)
The accelerated handling of the first two events (Layer 3 link failures and line card failures) is enabled
by default and does not require a configuration command to be enabled.
To configure the accelerated handling of the last two events, use the following command in router
configuration mode:
Command
Purpose
neighbor-down fib-accelerate
Withdraws the corresponding next hop from all
next-hop groups (ECMP groups and single
next-hop routes) whenever a BGP session goes
down.
Example:
switch(config-router)# neighbor-down
fib-accelerate
Note
This command applies to both IPv4 and
IPv6 address-family routes.
Disabling Capabilities Negotiation
You can disable capabilities negotiations to interoperate with older BGP peers that do not support
capabilities negotiation.
To disable capabilities negotiation, use the following command in neighbor configuration mode:
Command
Purpose
dont-capability-negotiate
Disables capabilities negotiation. You must
manually reset the BGP sessions after configuring
this command.
Example:
switch(config-router-neighbor)#
dont-capability-negotiate
Disabling Policy Batching
In BGP deployments where prefixes have unique attributes, BGP tries to identify routes with similar
attributes to bundle in the same BGP update message. To avoid the overhead of this additional BGP
processing, you can disable batching.
Cisco recommends that you disable policy batching for BGP deployments that have a large number of
routes with unique next hops.
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To disable policy batching, use the following command in router configuration mode:
Command
Purpose
disable-policy-batching
Disables the batching evaluation of prefix
advertisements to all peers.
Example:
switch(config-router)#
disable-policy-batching
Configuring BGP Additional Paths
BGP supports sending and receiving multiple paths per prefix and advertising such paths. This section
includes the following topics:
•
Advertising the Capability of Sending and Receiving Additional Paths, page 10-26
•
Configuring the Sending and Receiving of Additional Paths, page 10-27
•
Configuring Advertised Paths, page 10-27
•
Configuring Additional Path Selection, page 10-28
Advertising the Capability of Sending and Receiving Additional Paths
You can configure BGP to advertise the capability of sending and receiving additional paths to and from
the BGP peers. To do so, use the following commands in neighbor address-family configuration mode:
Command
Purpose
[no] capability additional-paths send
[disable]
Advertises the capability to send additional paths to
the BGP peer. The disable option disables the
advertising capability of sending additional paths.
Example:
switch(config-router-neighbor-af)#
capability additional-paths send
[no] capability additional-paths receive
[disable]
Example:
switch(config-router-neighbor-af)#
capability additional-paths receive
show bgp neighbor
Example:
switch(config-router-neighbor-af)# show
bgp neighbor
The no form of this command disables the
capability of sending additional paths.
Advertises the capability to receive additional
paths from the BGP peer. The disable option
disables the advertising capability of receiving
additional paths.
The no form of this command disables the
capability of receiving additional paths.
Displays whether the local peer has advertised the
additional paths send or receive capability to the
remote peer.
This example shows how to configure BGP to advertise the capability to send and receive additional
paths to the BGP peer:
switch# configure terminal
switch(config)# router bgp 100
switch(config-router)# neighbor 10.131.31.2 remote-as 100
switch(config-router-neighbor)# address-family ipv4 unicast
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switch(config-router-neighbor-af)# capability additional-paths send
switch(config-router-neighbor-af)# capability additional-paths receive
Configuring the Sending and Receiving of Additional Paths
You can configure the capability of sending and receiving additional paths to and from the BGP peers.
To do so, use the following commands in address-family configuration mode:
Command
Purpose
[no] additional-paths send
Enables the send capability of additional paths for
all of the neighbors under this address family for
which the capability has not been disabled.
Example:
switch(config-router-af)# additional-paths
send
[no] additional-paths receive
Example:
switch(config-router-af)# additional-paths
receive
show bgp neighbor
Example:
switch(config-router-af)# show bgp
neighbor
The no form of this command disables the send
capability.
Enables the receive capability of additional paths
for all of the neighbors under this address family
for which the capability has not been disabled.
The no form of this command disables the receive
capability.
Displays whether the local peer has advertised the
additional paths send or receive capability to the
remote peer.
This example shows how to enable the additional paths send and receive capability for all neighbors
under the specified address family for which this capability has not been disabled:
switch# configure terminal
switch(config)# router bgp 100
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# additional-paths send
switch(config-router-af)# additional-paths receive
Configuring Advertised Paths
You can specify the paths that are advertised for BGP. To do so, use the following commands in
route-map configuration mode:
Command
Purpose
[no] set ip next-hop unchanged
Specifies an unchanged next-hop IP address.
Example:
switch(config-route-map)# set ip next-hop
unchanged
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Command
Purpose
[no] set path-selection all advertise
Specifies that all paths be advertised for a given
prefix.
Example:
switch(config-route-map)# set
path-selection all advertise
show bgp {ipv4 | ipv6} unicast [ip-address
| ipv6-prefix] [vrf vrf-name]
Example:
switch(config-route-map)# show bgp ipv4
unicast
The no form of this command specifies that only
the best path be advertised.
Displays the path ID for the additional paths of a
prefix and advertisement information for these
paths.
This example shows how to specify that all paths be advertised for the specified prefix:
switch# configure terminal
switch(config)# route-map PATH_SELECTION_RMAP
switch(config-route-map)# match ip address prefix-list p1
switch(config-route-map)# set path-selection all advertise
Configuring Additional Path Selection
You can configure the capability of selecting additional paths for a prefix. To do so, use the following
commands in address-family configuration mode:
Command
Purpose
[no] additional-paths selection route-map
map-name
Configures the capability of selecting additional
paths for a prefix.
Example:
switch(config-router-af)# additional-paths
selection route-map map1
The no form of this command disables the
additional paths selection capability.
show bgp {ipv4 | ipv6} unicast [ip-address
| ipv6-prefix] [vrf vrf-name]
Displays the path ID for the additional paths of a
prefix and advertisement information for these
paths.
Example:
switch(config-route-af)# show bgp ipv4
unicast
This example shows how to configure the additional paths selection under the specified address family:
switch# configure terminal
switch(config)# router bgp 100
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# additional-paths selection route-map PATH_SELECTION_RMAP
Configuring eBGP
This section includes the following topics:
•
Disabling eBGP Single-Hop Checking, page 10-29
•
Configuring eBGP Multihop, page 10-29
•
Disabling a Fast External Fallover, page 10-29
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•
Limiting the AS-path Attribute, page 10-30
•
Configuring Local AS Support, page 10-30
Disabling eBGP Single-Hop Checking
You can configure eBGP to disable checking whether a single-hop eBGP peer is directly connected to
the local router. Use this option for configuring a single-hop loopback eBGP session between directly
connected switches.
To disable checking whether or not a single-hop eBGP peer is directly connected, use the following
command in neighbor configuration mode:
Command
Purpose
disable-connected-check
Disables checking whether or not a single-hop
eBGP peer is directly connected. You must
manually reset the BGP sessions after using this
command.
Example:
switch(config-router-neighbor)#
disable-connected-check
Configuring eBGP Multihop
You can configure the eBGP time-to-live (TTL) value to support eBGP multihop. In some situations, an
eBGP peer is not directly connected to another eBGP peer and requires multiple hops to reach the remote
eBGP peer. You can configure the eBGP TTL value for a neighbor session to allow these multihop
sessions.
To configure eBGP multihop, use the following command in neighbor configuration mode:
Command
Purpose
ebgp-multihop ttl-value
Configures the eBGP TTL value for eBGP
multihop. The range is from 2 to 255. You must
manually reset the BGP sessions after using this
command.
Example:
switch(config-router-neighbor)#
ebgp-multihop 5
Disabling a Fast External Fallover
By default, the Cisco NX-OS device supports fast external fallover for neighbors in all VRFs and
address-families (IPv4 or IPv6). Typically, when a BGP router loses connectivity to a directly connected
eBGP peer, BGP triggers a fast external fallover by resetting the eBGP session to the peer. You can
disable this fast external fallover to limit the instability caused by link flaps.
To disable fast external fallover, use the following command in router configuration mode:
Command
Purpose
no fast-external-fallover
Disables a fast external fallover for eBGP peers.
This command is enabled by default.
Example:
switch(config-router)# no
fast-external-fallover
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Limiting the AS-path Attribute
You can configure eBGP to discard routes that have excessive AS numbers in the AS-path attribute.
To discard routes that have excessive AS numbers in the AS-path attribute, use the following command
in router configuration mode:
Command
Purpose
maxas-limit number
Discards eBGP routes that have a number of
AS-path segments that exceed the specified limit.
The range is from 1 to 2000.
Example:
switch(config-router)# maxas-limit 50
Configuring Local AS Support
The local AS feature allows a router to appear to be a member of a second autonomous system (AS), in
addition to its real AS. Local AS allows two ISPs to merge without modifying peering arrangements.
Routers in the merged ISP become members of the new autonomous system but continue to use their old
AS numbers for their customers.
This feature can only be used for true eBGP peers. You cannot use this feature for two peers that are
members of different confederation subautonomous systems.
To configure eBGP local AS support, use the following command in neighbor configuration mode:
Command
Purpose
local-as number [no-prepend [replace-as
[dual-as]]]
Configures eBGP to prepend the local AS number
to the AS_PATH attribute.The AS number can be a
16-bit integer or a 32-bit integer in the form of a
higher 16-bit decimal number and a lower 16-bit
decimal number in xx.xx format.
Example:
switch(config-router-neighbor)# local-as
1.1
This example shows how to configure local AS support on a VRF:
switch# configure terminal
switch(config)# router bgp
switch(config-router)# vrf
switch(config-router-vrf)#
switch(config-router-vrf)#
1
test
local-as 1
show running-config bgp
Configuring AS Confederations
To configure an AS confederation, you must specify a confederation identifier. To the outside world, the
group of autonomous systems within the AS confederation look like a single autonomous system with
the confederation identifier as the autonomous system number.
To configure a BGP confederation identifier, use the following command in router configuration mode:
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Command
Purpose
confederation identifier as-number
Configures a confederation identifier for an AS
confederation. This command triggers an
automatic notification and session reset for the
BGP neighbor sessions.
Example:
switch(config-router)# confederation
identifier 4000
To configure the autonomous systems that belong to the AS confederation, use the following command
in router configuration mode:
Command
Purpose
bgp confederation peers as-number
[as-number2...]
Specifies a list of autonomous systems that belong
to the confederation. This command triggers an
automatic notification and session reset for the
BGP neighbor sessions.
Example:
switch(config-router)# bgp confederation
peers 5 33 44
Configuring Route Reflector
You can configure iBGP peers as route reflector clients to the local BGP speaker, which acts as the route
reflector. Together, a route reflector and its clients form a cluster. A cluster of clients usually has a single
route reflector. In such instances, the cluster is identified by the router ID of the route reflector. To
increase redundancy and avoid a single point of failure in the network, you can configure a cluster with
more than one route reflector. You must configure all route reflectors in the cluster with the same 4-byte
cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
SUMMARY STEPS
1.
configure terminal
2.
router bgp as-number
3.
cluster-id cluster-id
4.
address-family {ipv4 | ipv6} {unicast | multicast}
5.
(Optional) client-to-client reflection
6.
exit
7.
neighbor ip-address remote-as as-number
8.
address-family {ipv4 | ipv6} {unicast | multicast}
9.
route-reflector-client
10. (Optional) show bgp {ipv4 | ipv6} {unicast | multicast} neighbors
11. (Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 3
cluster-id cluster-id
Example:
switch(config-router)# cluster-id
192.0.2.1
Step 4
address-family {ipv4 | ipv6} {unicast
| multicast}
Enters BGP mode and assigns the autonomous system
number to the local BGP speaker.
Configures the local router as one of the route reflectors
that serve the cluster. You specify a cluster ID to identify
the cluster. This command triggers an automatic soft
clear or refresh of BGP neighbor sessions.
Enters router address-family configuration mode for the
specified address family.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 5
Step 6
Example:
switch(config-router-af)#
client-to-client reflection
(Optional) Configures client-to-client route reflection.
This feature is enabled by default. This command triggers
an automatic soft clear or refresh of BGP neighbor
sessions.
exit
Exits router address configuration mode.
client-to-client reflection
Example:
switch(config-router-neighbor)# exit
switch(config-router)#
Step 7
neighbor ip-address remote-as
as-number
Configures the IP address and AS number for a remote
BGP peer.
Example:
switch(config-router)# neighbor
192.0.2.10 remote-as 65535
switch(config-router-neighbor)#
Step 8
address-family {ipv4 | ipv6} {unicast
| multicast}
Enters neighbor address-family configuration mode for
the specified address family.
Example:
switch(config-router-neighbor)#
address-family ipv4 unicast
switch(config-router-neighbor-af)#
Step 9
route-reflector-client
Example:
switch(config-router-neighbor-af)#
route-reflector-client
Configures the device as a BGP route reflector and
configures the neighbor as its client. This command
triggers an automatic notification and session reset for
the BGP neighbor sessions.
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Step 10
Command
Purpose
show bgp {ipv4 | ipv6} {unicast |
multicast} neighbors
(Optional) Displays the BGP peers.
Example:
switch(config-router-neighbor-af)#
show bgp ipv4 unicast neighbors
Step 11
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)#
copy running-config startup-config
This example shows how to configure the router as a route reflector and add one neighbor as a client:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# neighbor 192.0.2.10 remote-as 65535
switch(config-router-neighbor)# address-family ip unicast
switch(config-router-neighbor-af)# route-reflector-client
switch(config-router-neighbor-af)# copy running-config startup-config
Configuring Next Hops on Reflected Routes Using an Outbound Route Map
You can change the next hop on reflected routes on a BGP route reflector using an outbound route map.
You can configure the outbound route map to specify the peer’s local address as the next-hop address.
Note
The next-hop-self command does not enable this functionality for routes being reflected to clients by a
route reflector. This functionality can only be enabled using an outbound route map.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
You must enter the set next-hop command to configure an address family specific next-hop address. For
example, for the IPv6 address family, you must enter the set ipv6 next-hop peer-address command.
•
When setting IPv4 next hops using route maps—If set ip next-hop peer-address matches the route
map, the next hop is set to the peer’s local address. If no next hop is set in the route map, the next
hop is set to the one stored in the path.
•
When setting IPv6 next hops using route maps—If set ipv6 next-hop peer-address matches the
route map, the next hop is set as follows:
– For IPv6 peers, the next hop is set to the peer’s local IPv6 address.
– For IPv4 peers, if update-source is configured, the next hop is set to the source interface’s IPv6
address, if any. If no IPv6 address is configured, no next hop is set.
– For IPv4 peers, if update-source is not configured, the next hop is set to the outgoing interface’s
IPv6 address, if any. If no IPv6 address is configured, no next hop is set.
SUMMARY STEPS
1.
configure terminal
2.
router bgp as-number
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3.
neighbor ip-address remote-as as-number
4.
(Optional) update-source interface number
5.
address-family {ipv4 | ipv6} {unicast | multicast}
6.
route-reflector-client
7.
route-map map-name out
8.
(Optional) show bgp {ipv4 | ipv6} {unicast | multicast} neighbors
9.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp as-number
Example:
switch(config)# router bgp 200
switch(config-router)#
Step 3
neighbor ip-address remote-as
as-number
Enters BGP mode and assigns the autonomous system
number to the local BGP speaker.
Configures the IP address and AS number for a remote
BGP peer.
Example:
switch(config-router)# neighbor
192.0.2.12 remote-as 200
switch(config-router-neighbor)#
Step 4
update-source interface number
Example:
switch(config-router-neighbor)#
update-source loopback 300
Step 5
address-family {ipv4 | ipv6} {unicast
| multicast}
(Optional) Specifies and updates the source of the BGP
session.
Enters router address-family configuration mode for the
specified address family.
Example:
switch(config-router-neighbor)#
address-family ipv4 unicast
switch(config-router-neighbor-af)#
Step 6
Step 7
Example:
switch(config-router-neighbor-af)#
route-reflector-client
Configures the device as a BGP route reflector and
configures the neighbor as its client. This command
triggers an automatic notification and session reset for
the BGP neighbor sessions.
route-map map-name out
Applies the configured BGP policy to outgoing routes.
route-reflector-client
Example:
switch(config-router-neighbor-af)#
route-map setrrnh out
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Step 8
Command
Purpose
show bgp {ipv4 | ipv6} {unicast |
multicast} [ip-address | ipv6-prefix]
route-map map-name [vrf vrf-name]
(Optional) Displays the BGP routes that match the route
map.
Example:
switch(config-router-neighbor-af)#
show bgp ipv4 unicast route-map
setrrnh
Step 9
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)#
copy running-config startup-config
This example shows how to configure the next hop on reflected routes on a BGP route reflector using an
outbound route map:
switch# configure terminal
switch(config)# interface loopback 300
switch(config-if)# ip address 192.0.2.11/32
switch(config-if)# ipv6 address 2001::a0c:1a65/64
switch(config-if)# ip router ospf 1 area 0.0.0.0
switch(config-if)# exit
switch(config)# route-map setrrnh permit 10
switch(config-route-map)# set ip next-hop peer-address
switch(config-route-map)# exit
switch(config)# route-map setrrnhv6 permit 10
switch(config-route-map)# set ipv6 next-hop peer-address
switch(config-route-map)# exit
switch(config)# router bgp 200
switch(config-router)# neighbor 192.0.2.12 remote-as 200
switch(config-router-neighbor)# update-source loopback 300
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# route-reflector-client
switch(config-router-neighbor-af)# route-map setrrnh out
switch(config-router-neighbor-af)# exit
switch(config-router-neighbor)# address-family ipv6 unicast
switch(config-router-neighbor-af)# route-reflector-client
switch(config-router-neighbor-af)# route-map setrrnhv6 out
Configuring Route Dampening
You can configure route dampening to minimize route flaps propagating through your iBGP network.
To configure route dampening, use the following command in address-family or VRF address-family
configuration mode:
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Command
Purpose
dampening [{half-life reuse-limit
suppress-limit max-suppress-time |
route-map map-name}]
Disables capabilities negotiation. The parameter
values are as follows:
Example:
switch(config-router-af)# dampening
route-map bgpDamp
•
half-life—The range is from 1 to 45.
•
reuse-limit—The range is from 1 to 20000.
•
suppress-limit—The range is from 1 to 20000.
•
max-suppress-time—The range is from 1 to
255.
Configuring Load Sharing and ECMP
You can configure the maximum number of paths that BGP adds to the route table for equal-cost
multipath load balancing.
To configure the maximum number of paths, use the following command in router address-family
configuration mode:
Command
Purpose
maximum-paths [ibgp] maxpaths
Configures the maximum number of equal-cost
paths for load sharing. The default is 1.
Example:
switch(config-router-af)# maximum-paths 8
Configuring Maximum Prefixes
You can configure the maximum number of prefixes that BGP can receive from a BGP peer. If the
number of prefixes exceeds this value, you can optionally configure BGP to generate a warning message
or tear down the BGP session to the peer.
To configure the maximum allowed prefixes for a BGP peer, use the following command in neighbor
address-family configuration mode:
Command
Purpose
maximum-prefix maximum [threshold]
[restart time | warning-only]
Configures the maximum number of prefixes from
a peer. The parameter ranges are as follows:
Example:
switch(config-router-neighbor-af)#
maximum-prefix 12
•
maximum—The range is from 1 to 300000.
•
Threshold—The range is from 1 to 100
percent. The default is 75 percent.
•
time—The range is from 1 to 65535 minutes.
This command triggers an automatic notification
and session reset for the BGP neighbor sessions if
the prefix limit is exceeded.
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Configuring Dynamic Capability
You can configure dynamic capability for a BGP peer.
To configure dynamic capability, use the following command in neighbor configuration mode:
Command
Purpose
dynamic-capability
Enables dynamic capability. This command
triggers an automatic notification and session reset
for the BGP neighbor sessions.
Example:
switch(config-router-neighbor)#
dynamic-capability
Configuring Aggregate Addresses
You can configure aggregate address entries in the BGP route table.
To configure an aggregate address, use the following command in router address-family configuration
mode:
Command
Purpose
aggregate-address ip-prefix/length
[as-set] [summary-only] [advertise-map
map-name] [attribute-map map-name]
[suppress-map map-name]
Creates an aggregate address. The path advertised
for this route is an autonomous system set that
consists of all elements contained in all paths that
are being summarized:
Example:
switch(config-router-af)#
aggregate-address 192.0.2.0/8 as-set
•
The as-set keyword generates autonomous
system set path information and community
information from contributing paths.
•
The summary-only keyword filters all
more-specific routes from updates.
•
The advertise-map keyword and argument
specify the route map used to select attribute
information from selected routes.
•
The attribute-map keyword and argument
specify the route map used to select attribute
information from the aggregate.
•
The suppress-map keyword and argument
conditionally filter more specific routes.
Suppressing BGP Routes
You can configure Cisco NX-OS to advertise newly learned BGP routes only after these routes are
confirmed by the Forwarding Information Base (FIB) and programmed in the hardware. After the routes
are programmed, subsequent changes to these routes do not require this hardware-programming check.
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To suppress BGP routes, use the following command in router configuration mode:
Command
Purpose
suppress-fib-pending
Suppresses newly learned BGP routes (IPv4 or
IPv6) from being advertised to downstream BGP
neighbors until the routes have been programmed
in the hardware.
Example:
switch(config-router)#
suppress-fib-pending
Configuring BGP Conditional Advertisement
You can configure BGP conditional advertisement to limit the routes that BGP propagates. You define
the following two route maps:
•
Advertise map—Specifies the conditions that the route must match before BGP considers the
conditional advertisement. This route map can contain any appropriate match statements.
•
Exist map or nonexist map—Defines the prefix that must exist in the BGP table before BGP
propagates a route that matches the advertise map. The nonexist map defines the prefix that must not
exist in the BGP table before BGP propagates a route that matches the advertise map. BGP processes
only the permit statements in the prefix list match statements in these route maps.
If the route does not pass the condition, BGP withdraws the route if it exists in the BGP table.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
SUMMARY STEPS
1.
configure terminal
2.
router bgp as-number
3.
neighbor ip-address remote-as as-number
4.
address-family {ipv4 | ipv6} {unicast | multicast}
5.
advertise-map adv-map {exist-map exist-rmap | non-exist-map nonexist-rmap}
6.
(Optional) show bgp {ipv4 | ipv6} {unicast | multicast} neighbors
7.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 3
neighbor ip-address remote-as as-number
Example:
switch(config-router)# neighbor
192.168.1.2 remote-as 65534
switch(config-router-neighbor)#
Step 4
address-family {ipv4 | ipv6} {unicast |
multicast}
Enters BGP mode and assigns the autonomous system
number to the local BGP speaker.
Places the router in neighbor configuration mode for
BGP routing and configures the neighbor IP address.
Enters address-family configuration mode.
Example:
switch(config-router-neighbor)#
address-family ipv4 multicast
switch(config-router-neighbor-af)#
Step 5
advertise-map adv-map {exist-map
exist-rmap | non-exist-map
nonexist-rmap}
Configures BGP to conditionally advertise routes
based on the two configured route maps:
•
adv-map—Specifies a route map with match
statements that the route must pass before BGP
passes the route to the next route map. The
adv-map is a case-sensitive, alphanumeric string
up to 63 characters.
•
exist-rmap—Specifies a route map with match
statements for a prefix list. A prefix in the BGP
table must match a prefix in the prefix list before
BGP advertises the route. The exist-rmap is a
case-sensitive, alphanumeric string up to 63
characters.
•
nonexist-rmap—Specifies a route map with match
statements for a prefix list. A prefix in the BGP
table must not match a prefix in the prefix list
before BGP advertises the route. The
nonexist-rmap is a case-sensitive, alphanumeric
string up to 63 characters.
Example:
switch(config-router-neighbor-af)#
advertise-map advertise exist-map exist
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Step 6
Command
Purpose
show bgp {ipv4 | ipv6} {unicast |
multicast} neighbors
(Optional) Displays information about BGP and the
configured conditional advertisement route maps.
Example:
switch(config-router-neighbor-af)# show
bgp ipv4 unicast neighbors
Step 7
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)# copy
running-config startup-config
This example shows how to configure BGP conditional advertisement:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# neighbor 192.0.2.2 remote-as 65534
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# advertise-map advertise exist-map exist
switch(config-router-neighbor-af)# exit
switch(config-router-neighbor)# exit
switch(config-router)# exit
switch(config)# route-map advertise
switch(config-route-map)# match as-path pathList
switch(config-route-map)# exit
switch(config)# route-map exit
switch(config-route-map)# match ip address prefix-list plist
switch(config-route-map)# exit
switch(config)# ip prefix-list plist permit 172.16.201.0/27
Configuring Route Redistribution
You can configure BGP to accept routing information from another routing protocol and redistribute that
information through the BGP network. Optionally, you can assign a default route for redistributed routes.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
SUMMARY STEPS
1.
configure terminal
2.
router bgp as-number
3.
address-family {ipv4 | ipv6} {unicast | multicast}
4.
redistribute {direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map map-name
5.
(Optional) default-metric value
6.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 3
address-family {ipv4 | ipv6} {unicast |
multicast}
Enters BGP mode and assigns the autonomous system
number to the local BGP speaker.
Enters address-family configuration mode.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
redistribute {direct | {eigrp | isis |
ospf | ospfv3 | rip} instance-tag |
static} route-map map-name
Redistributes routes from other protocols into BGP.
See the “Configuring Route Maps” section on
page 15-11 for more information about route maps.
Example:
switch(config-router-af)# redistribute
eigrp 201 route-map Eigrpmap
Step 5
(Optional) Generates a default route into BGP.
default-metric value
Example:
switch(config-router-af)# default-metric
33
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
This example shows how to redistribute EIGRP into BGP:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# redistribute eigrp 201 route-map Eigrpmap
switch(config-router-af)# copy running-config startup-config
Advertising the Default Route
You can configure BGP to advertise the default route (network 0.0.0.0).
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
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SUMMARY STEPS
1.
configure terminal
2.
route-map allow permit
3.
exit
4.
ip route ip-address network-mask null null-interface-number
5.
router bgp as-number
6.
address-family {ipv4 | ipv6} unicast
7.
default-information originate
8.
redistribute static route-map allow
9.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
route-map allow permit
Example:
switch(config)# route-map allow permit
switch(config-route-map)#
Step 3
exit
Enters router map configuration mode and defines the
conditions for redistributing routes.
Exits router map configuration mode.
Example:
switch(config-route-map)# exit
switch(config)#
Step 4
ip route ip-address network-mask null
null-interface-number
Configures the IP address.
Example:
switch(config)# ip route 192.0.2.1
255.255.255.0 null 0
Step 5
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 6
address-family {ipv4 | ipv6} unicast
Enters BGP mode and assigns the AS number to the
local BGP speaker.
Enters address family configuration mode.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 7
default-information originate
Advertises the default route.
Example:
switch(config-router-af)#
default-information originate
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Step 8
Command
Purpose
redistribute static route-map allow
Redistributes the default route.
Example:
switch(config-router-af)# redistribute
static route-map allow
Step 9
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
Configuring Multiprotocol BGP
You can configure MP-BGP to support multiple address families, including IPv4 and IPv6 unicast and
multicast routes.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
SUMMARY STEPS
1.
configure terminal
2.
router bgp as-number
3.
neighbor ip-address remote-as as-number
4.
address-family {ipv4 | ipv6} {unicast | multicast}
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 3
neighbor ip-address remote-as as-number
Example:
switch(config-router)# neighbor
192.168.1.2 remote-as 65534
switch(config-router-neighbor)#
Enters BGP mode and assigns the autonomous system
number to the local BGP speaker.
Places the router in neighbor configuration mode for
BGP routing and configures the neighbor IP address.
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Step 4
Command
Purpose
address-family {ipv4 | ipv6} {unicast |
multicast}
Enters address family configuration mode.
Example:
switch(config-router-neighbor)#
address-family ipv4 multicast
switch(config-router-neighbor-af)#
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-neighbor-af)# copy
running-config startup-config
This example shows how to enable advertising and receiving IPv4 and IPv6 routes for multicast RPF for
a neighbor:
switch# configure terminal
switch(config)# interface ethernet 2/1
switch(config-if)# ipv6 address 2001:0DB8::1
switch(config-if)# router bgp 65535
switch(config-router)# neighbor 192.168.1.2 remote-as 35537
switch(config-router-neighbor)# address-family ipv4 multicast
switch(config-router-neighbor-af)# exit
switch(config-router-neighbor)# address-family ipv6 multicast
switch(config-router-neighbor-af)# copy running-config startup-config
Tuning BGP
You can tune BGP characteristics through a series of optional parameters.
To tune BGP, use the following optional commands in router configuration mode:
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Command
Purpose
bestpath [always-compare-med | as-path
multipath-relax | compare-routerid |
cost-community ignore | med {confed |
missing-as-worst | non-deterministic}]
Modifies the best-path algorithm. The optional
parameters are as follows:
Example:
switch(config-router)# bestpath
always-compare-med
enforce-first-as
Example:
switch(config-router)# enforce-first-as
•
always-compare-med—Compares MED on
paths from different autonomous systems.
•
as-path multipath-relax—Allows load
sharing across the providers with different (but
equal-length) AS paths. Without this option,
the AS paths must be identical for load sharing.
•
compare-routerid—Compares the router IDs
for identical eBGP paths.
•
cost-community ignore—Ignores the cost
community for BGP best-path calculations.
•
med confed—Forces bestpath to do a MED
comparison only between paths originated
within a confederation.
•
med missing-as-worst—Treats a missing
MED as the highest MED.
•
med non-deterministic—Does not always
pick the best MED path from among the paths
from the same autonomous system.
Enforces the neighbor autonomous system to be the
first AS number listed in the AS_path attribute for
eBGP.
Generates a system message when any neighbor
changes state.
log-neighbor-changes
Example:
switch(config-router)#
log-neighbor-changes
Note
router-id id
Example:
switch(config-router)# router-id
10.165.20.1
To suppress neighbor status change
messages for a specific neighbor, you can
use the log-neighbor-changes disable
command in router address-family
configuration mode.
Manually configures the router ID for this BGP
speaker.
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Command
Purpose
timers [bestpath-delay delay | bgp
keepalive holdtime | prefix-peer-timeout
timeout]
Sets the BGP timer values. The optional parameters
are as follows:
•
delay—Initial best-path timeout value after a
restart. The range is from 0 to 3600 seconds.
The default value is 300.
•
keepalive—BGP session keepalive time. The
range is from 0 to 3600 seconds. The default
value is 60.
•
holdtime—BGP session hold time.The range is
from 0 to 3600 seconds. The default value is
180.
•
timeout—Prefix peer timeout value. The range
is from 0 to 1200 seconds. The default value is
30.
Example:
switch(config-router)# timers bgp 90 270
You must manually reset the BGP sessions after
configuring this command.
To tune BGP, use the following optional commands in router address-family configuration mode:
Command
Purpose
distance ebgp-distance ibgp-distance
local-distance
Sets the administrative distance for BGP. The range
is from 1 to 255. The defaults are as follows:
Example:
switch(config-router-af)# distance 20 100
200
log-neighbor-changes [disable]
Example:
switch(config-router-af)#
log-neighbor-changes disable
•
ebgp-distance—20.
•
ibgp-distance—200.
•
local-distance—220. Local-distance is the
administrative distance used for aggregate
discard routes when they are installed in the
RIB.
Generates a system message when this specific
neighbor changes state.
The disable option suppresses neighbor status
change messages for this specific neighbor.
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To tune BGP, use the following optional commands in neighbor configuration mode:
Command
Purpose
description string
Sets a descriptive string for this BGP peer. The
string can be up to 80 alphanumeric characters.
Example:
switch(config-router-neighbor)#
description main site
low-memory exempt
Example:
switch(config-router-neighbor)# low-memory
exempt
transport connection-mode passive
Example:
switch(config-router-neighbor)# transport
connection-mode passive
[no | default] remove-private-as [all |
replace-as]
Example:
switch(config-router-neighbor)#
remove-private-as
update-source interface-type number
Example:
switch(config-router-neighbor)#
update-source ethernet 2/1
Exempts this BGP neighbor from a possible
shutdown due to a low memory condition.
Allows a passive connection setup only. This BGP
speaker does not initiate a TCP connection to a
BGP peer. You must manually reset the BGP
sessions after configuring this command.
Removes private AS numbers from outbound route
updates to an eBGP peer. This command triggers an
automatic soft clear or refresh of BGP neighbor
sessions.
The optional parameters are as follows:
•
no—Disables the command.
•
default—Moves the command to its default
mode.
•
all—Removes all private-as numbers from the
AS-path.
•
replace-as—Replaces all private AS numbers
with the replace-as AS-path value.
Note
See the “Guidelines and Limitations for
Advanced BGP” section for additional
information on this command.
Configures the BGP speaker to use the source IP
address of the configured interface for BGP
sessions to the peer. This command triggers an
automatic notification and session reset for the
BGP neighbor sessions. Single-hop iBGP peers
support fast external fallover when update-source
is configured.
To tune BGP, use the following optional commands in neighbor address-family configuration mode:
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Command
Purpose
allowas in
Allows routes that have their own AS in the AS
path to be installed in the BRIB.
Example:
switch(config-router-neighbor-af)# allowas
in
default-originate [route-map map-name]
Generates a default route to the BGP peer.
Example:
switch(config-router-neighbor-af)#
default-originate
disable-peer-as-check
Example:
switch(config-router-neighbor-af)#
disable-peer-as-check
filter-list list-name {in | out}
Example:
switch(config-router-neighbor-af)#
filter-list BGPFilter in
prefix-list list-name {in | out}
Example:
switch(config-router-neighbor-af)#
prefix-list PrefixFilter in
send-community
Example:
switch(config-router-neighbor-af)#
send-community
send-community extended
Example:
switch(config-router-neighbor-af)#
send-community extended
suppress-inactive
Example:
switch(config-router-neighbor-af)#
suppress-inactive
Disables peer AS-number checking while the
device advertises routes learned from one node to
another node in the same AS path.
Applies an AS_path filter list to this BGP peer for
inbound or outbound route updates. This command
triggers an automatic soft clear or refresh of BGP
neighbor sessions.
Applies a prefix list to this BGP peer for inbound
or outbound route updates. This command triggers
an automatic soft clear or refresh of BGP neighbor
sessions.
Sends the community attribute to this BGP peer.
This command triggers an automatic soft clear or
refresh of BGP neighbor sessions.
Sends the extended community attribute to this
BGP peer. This command triggers an automatic soft
clear or refresh of BGP neighbor sessions.
Advertises the best (active) routes only to the BGP
peer. This command triggers an automatic soft
clear or refresh of BGP neighbor sessions.
Configuring a Graceful Restart
You can configure a graceful restart and enable the graceful restart helper feature for BGP.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
Create the VRFs.
SUMMARY STEPS
1.
configure terminal
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2.
router bgp as-number
3.
graceful-restart
4.
graceful-restart [restart-time time | stalepath-time time]
5.
graceful-restart-helper
6.
(Optional) show running-config bgp
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 3
graceful-restart
Example:
switch(config-router)# graceful-restart
Creates a new BGP process with the configured
autonomous system number.
Enables a graceful restart and the graceful restart
helper functionality. This command is enabled by
default.
This command triggers an automatic notification and
session reset for the BGP neighbor sessions.
Step 4
graceful-restart [restart-time time |
stalepath-time time]
Configures the graceful restart timers.
The optional parameters are as follows:
Example:
switch(config-router)# graceful-restart
restart-time 300
•
restart-time—Maximum time for a restart sent to
the BGP peer. The range is from 1 to 3600
seconds. The default is 120.
•
stalepath-time—Maximum time that BGP keeps
the stale routes from the restarting BGP peer. The
range is from 1 to 3600 seconds. The default is
300.
This command triggers an automatic notification and
session reset for the BGP neighbor sessions.
Step 5
graceful-restart-helper
Example:
switch(config-router)#
graceful-restart-helper
Enables the graceful restart helper functionality. Use
this command if you have disabled graceful restart but
you still want to enable graceful restart helper
functionality. This command triggers an automatic
notification and session reset for the BGP neighbor
sessions.
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Step 6
Command
Purpose
show running-config bgp
(Optional) Displays the BGP configuration.
Example:
switch(config-router)# show
running-config bgp
Step 7
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to enable a graceful restart:
switch# configure terminal
switch(config)# router bgp 65535
switch(config-router)# graceful-restart
switch(config-router)# copy running-config startup-config
Configuring Virtualization
You can configure one BGP process, create multiple VRFs, and use the same BGP process in each VRF.
BEFORE YOU BEGIN
You must enable BGP (see the “Enabling BGP” section on page 9-11).
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
exit
4.
router bgp as-number
5.
vrf vrf-name
6.
neighbor ip-address remote-as as-number
7.
(Optional) copy running-config startup-config
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Configuring Advanced BGP
Configuring Advanced BGP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context
RemoteOfficeVRF
switch(config-vrf)#
Step 3
Creates a new VRF and enters VRF configuration
mode.
Exits VRF configuration mode.
exit
Example:
switch(config-vrf)# exit
switch(config)#
Step 4
router bgp as-number
Example:
switch(config)# router bgp 65535
switch(config-router)#
Step 5
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
Step 6
neighbor ip-address remote-as as-number
Example:
switch(config-router-vrf)# neighbor
209.165.201.1 remote-as 65535
switch(config-router--vrf-neighbor)#
Step 7
copy running-config startup-config
Creates a new BGP process with the configured
autonomous system number.
Enters the router VRF configuration mode and
associates this BGP instance with a VRF.
Configures the IP address and AS number for a remote
BGP peer.
(Optional) Saves this configuration change.
Example:
switch(config-router-vrf-neighbor)# copy
running-config startup-config
This example shows how to create a VRF and configure the router ID in the VRF:
switch# configure terminal
switch(config)# vrf context NewVRF
switch(config-vrf)# exit
switch(config)# router bgp 65535
switch(config-router)# vrf NewVRF
switch(config-router-vrf)# neighbor 209.165.201.1 remote-as 65535
switch(config-router-vrf-neighbor)# copy running-config startup-config
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Verifying the Advanced BGP Configuration
Verifying the Advanced BGP Configuration
To display the BGP configuration, perform one of the following tasks:
Command
Purpose
show bgp all [summary] [vrf vrf-name]
Displays the BGP information for all address
families.
show bgp convergence [vrf vrf-name]
Displays the BGP information for all address
families.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] community {regexp
expression | [community] [no-advertise]
[no-export] [no-export-subconfed]} [vrf
vrf-name]
Displays the BGP routes that match a BGP
community.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] community-list
list-name [vrf vrf-name]
Displays the BGP routes that match a BGP
community list.
show bgp {ipv4 | ipv6} {unicast | multicast}
Displays the BGP routes that match a BGP
[ip-address | ipv6-prefix] extcommunity {regexp extended community.
expression | generic [non-transitive | transitive]
aa4:nn [exact-match]} [vrf vrf-name]
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] extcommunity-list
list-name [exact-match]} [vrf vrf-name]
Displays the BGP routes that match a BGP
extended community list.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] {dampening
dampened-paths [regexp expression]} [vrf
vrf-name]
Displays the information for BGP route
dampening. Use the clear bgp dampening
command to clear the route flap dampening
information.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] history-paths [regexp
expression] [vrf vrf-name]
Displays the BGP route history paths.
show bgp {ipv4 | ipv6} {unicast | multicast}
Displays the information for the BGP filter list.
[ip-address | ipv6-prefix] filter-list list-name [vrf
vrf-name]
show bgp {ipv4 | ipv6} {unicast | multicast}
Displays the information for BGP peers. Use the
[ip-address | ipv6-prefix] neighbors [ip-address | clear bgp neighbors command to clear these
ipv6-prefix] [vrf vrf-name]
neighbors.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] {nexthop |
nexthop-database} [vrf vrf-name]
Displays the information for the BGP route next
hop.
show bgp paths
Displays the BGP path information.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] policy name [vrf
vrf-name]
Displays the BGP policy information. Use the
clear bgp policy command to clear the policy
information.
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Monitoring BGP Statistics
Command
Purpose
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] prefix-list list-name
[vrf vrf-name]
Displays the BGP routes that match the prefix list.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] received-paths [vrf
vrf-name]
Displays the BGP paths stored for soft
reconfiguration.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] regexp expression [vrf
vrf-name]
Displays the BGP routes that match the AS_path
regular expression.
show bgp {ipv4 | ipv6} {unicast | multicast}
[ip-address | ipv6-prefix] route-map map-name
[vrf vrf-name]
Displays the BGP routes that match the route
map.
show bgp peer-policy name [vrf vrf-name]
Displays the information about BGP peer
policies.
show bgp peer-session name [vrf vrf-name]
Displays the information about BGP peer
sessions.
show bgp peer-template name [vrf vrf-name]
Displays the information about BGP peer
templates. Use the clear bgp peer-template
command to clear all neighbors in a peer template.
show bgp process
Displays the BGP process information.
show {ipv4 | ipv6} bgp options
Displays the BGP status and configuration
information.
show {ipv4 | ipv6} mbgp options
Displays the BGP status and configuration
information.
show running-configuration bgp
Displays the current running BGP configuration.
Monitoring BGP Statistics
To display BGP statistics, use the following commands:
Command
Purpose
show bgp {ipv4 | ipv6} {unicast |
multicast} [ip-address | ipv6-prefix]
flap-statistics [vrf vrf-name]
Displays the BGP route flap statistics. Use the clear bgp
flap-statistics command to clear these statistics.
show bgp {ipv4 | ipv6} unicast
injected-routes
Displays injected routes in the routing table.
show bgp sessions [vrf vrf-name]
Displays the BGP sessions for all peers. Use the clear
bgp sessions command to clear these statistics.
show bgp sessions [vrf vrf-name]
Displays the BGP sessions for all peers. Use the clear
bgp sessions command to clear these statistics.
show bgp statistics
Displays the BGP statistics.
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Configuration Examples
Configuration Examples
This example shows how to configure MD5 authentication for prefix-based neighbors:
template peer BasePeer-V6
description BasePeer-V6
password 3 f4200cfc725bbd28
transport connection-mode passive
address-family ipv6 unicast
template peer BasePeer-V4
bfd
description BasePeer-V4
password 3 f4200cfc725bbd28
address-family ipv4 unicast
-neighbor fc00::10:3:11:0/127 remote-as 65006
inherit peer BasePeer-V6
neighbor 10.3.11.0/31 remote-as 65006
inherit peer BasePeer-V4
This example shows how to enable neighbor status change messages globally and suppress them for a
specific neighbor:
router bgp 65100
log-neighbor-changes
neighbor 209.165.201.1 remote-as 65535
description test
address-family ipv4 unicast
soft-reconfiguration inbound
disable log-neighbor-changes
Related Topics
The following topics can give more information on BGP:
•
Chapter 9, “Configuring Basic BGP”
•
Chapter 15, “Configuring Route Policy Manager”
Additional References
For additional information related to implementing BGP, see the following sections:
•
MIBs, page 10-54
MIBs
MIBs
MIBs Link
MIBs related to BGP
To locate and download supported MIBs, go to the following URL:
ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MI
BSupportList.html
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11
Configuring RIP
This chapter describes how to configure the Routing Information Protocol (RIP) on the Cisco NX-OS
device.
This chapter includes the following sections:
•
About RIP, page 11-1
•
Licensing Requirements for RIP, page 11-4
•
Prerequisites for RIP, page 11-4
•
Guidelines and Limitations, page 11-4
•
Default Settings, page 11-4
•
Configuring RIP, page 11-5
•
Verifying the RIP Configuration, page 11-18
•
Displaying RIP Statistics, page 11-18
•
Configuration Examples for RIP, page 11-19
•
Related Topics, page 11-19
About RIP
This section includes the following topics:
•
RIP Overview, page 11-2
•
RIPv2 Authentication, page 11-2
•
Split Horizon, page 11-2
•
Route Filtering, page 11-3
•
Route Summarization, page 11-3
•
Route Redistribution, page 11-3
•
Load Balancing, page 11-3
•
High Availability, page 11-4
•
Virtualization Support, page 11-4
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About RIP
RIP Overview
RIP uses User Datagram Protocol (UDP) data packets to exchange routing information in small
internetworks. RIPv2 supports IPv4. RIPv2 uses an optional authentication feature supported by the
RIPv2 protocol (see the “RIPv2 Authentication” section on page 11-2).
RIP uses the following two message types:
•
Request—Sent to the multicast address 224.0.0.9 to request route updates from other RIP-enabled
routers.
•
Response—Sent every 30 seconds by default (see the “Verifying the RIP Configuration” section on
page 11-18). The router also sends response messages after it receives a Request message. The
response message contains the entire RIP route table. RIP sends multiple response packets for a
request if the RIP routing table cannot fit in one response packet.
RIP uses a hop count for the routing metric. The hop count is the number of routers that a packet can
traverse before reaching its destination. A directly connected network has a metric of 1; an unreachable
network has a metric of 16. This small range of metrics makes RIP an unsuitable routing protocol for
large networks.
RIPv2 Authentication
You can configure authentication on RIP messages to prevent unauthorized or invalid routing updates in
your network. Cisco NX-OS supports a simple password or an MD5 authentication digest.
You can configure the RIP authentication per interface by using keychain management for the
authentication keys. Keychain management allows you to control changes to the authentication keys
used by an MD5 authentication digest or simple text password authentication. See the Cisco Nexus 9000
Series NX-OS Security Configuration Guide for more details about creating keychains.
To use an MD5 authentication digest, you configure a password that is shared at the local router and all
remote RIP neighbors. Cisco NX-OS creates an MD5 one-way message digest based on the message
itself and the encrypted password and sends this digest with the RIP message (Request or Response).
The receiving RIP neighbor validates the digest by using the same encrypted password. If the message
has not changed, the calculation is identical and the RIP message is considered valid.
An MD5 authentication digest also includes a sequence number with each RIP message to ensure that
no message is replayed in the network.
Split Horizon
You can use split horizon to ensure that RIP never advertises a route out of the interface where it was
learned.
Split horizon is a method that controls the sending of RIP update and query packets. When you enable
split horizon on an interface, Cisco NX-OS does not send update packets for destinations that were
learned from this interface. Controlling update packets in this manner reduces the possibility of routing
loops.
You can use split horizon with poison reverse to configure an interface to advertise routes learned by RIP
as unreachable over the interface that learned the routes. Figure 11-1 shows a sample RIP network with
split horizon and poison reverse enabled.
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Configuring RIP
About RIP
Figure 11-1
RIP with Split Horizon Poison Reverse
route x
route x
route x
185058
route x unreachable
route x unreachable
Router A
Router B
Router C
Router C learns about route X and advertises that route to Router B. Router B in turn advertises route X
to Router A but sends a route X unreachable update back to Router C.
By default, split horizon is enabled on all interfaces.
Route Filtering
You can configure a route policy on a RIP-enabled interface to filter the RIP updates. Cisco NX-OS
updates the route table with only those routes that the route policy allows.
Route Summarization
You can configure multiple summary aggregate addresses for a specified interface. Route summarization
simplifies route tables by replacing a number of more-specific addresses with an address that represents
all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with
one summary address, 10.1.0.0/16.
If more specific routes are in the routing table, RIP advertises the summary address from the interface
with a metric equal to the maximum metric of the more specific routes.
Note
Cisco NX-OS does not support automatic route summarization.
Route Redistribution
You can use RIP to redistribute static routes or routes from other protocols. You must configure a route
map with the redistribution to control which routes are passed into RIP. A route policy allows you to
filter routes based on attributes such as the destination, origination protocol, route type, route tag, and
so on. For more information, see Chapter 15, “Configuring Route Policy Manager.”
Whenever you redistribute routes into a RIP routing domain, Cisco NX-OS does not, by default,
redistribute the default route into the RIP routing domain. You can generate a default route into RIP,
which can be controlled by a route policy.
You also configure the default metric that is used for all imported routes into RIP.
Load Balancing
You can use load balancing to allow a router to distribute traffic over all the router network ports that are
the same distance from the destination address. Load balancing increases the usage of network segments
and increases effective network bandwidth.
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Configuring RIP
Licensing Requirements for RIP
Cisco NX-OS supports the Equal Cost Multiple Path (ECMP) feature with up to 16 equal-cost paths in
the RIP route table and the unicast RIB. You can configure RIP to load balance traffic across some or all
of those paths.
High Availability
Cisco NX-OS supports stateless restarts for RIP. After a reboot or supervisor switchover, Cisco NX-OS
applies the running configuration and RIP immediately sends request packets to repopulate its routing
table.
Virtualization Support
Cisco NX-OS supports multiple instances of the RIP protocol that run on the same system. RIP supports
virtual routing and forwarding (VRF) instances.
Licensing Requirements for RIP
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
RIP requires no license. Any feature not included in a license package is bundled with the nx-os image and
is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see
the Cisco NX-OS Licensing Guide.
Prerequisites for RIP
RIP has the following prerequisites:
•
You must enable RIP (see the “Enabling RIP” section on page 11-5).
Guidelines and Limitations
RIP has the following configuration guidelines and limitations:
•
Cisco NX-OS does not support RIPv1. If Cisco NX-OS receives a RIPv1 packet, it logs a message
and drops the packet.
•
Cisco NX-OS does not establish adjacencies with RIPv1 routers.
•
IPv6 is not supported for RIP.
Default Settings
Table 11-1 lists the default settings for RIP parameters.
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Configuring RIP
Table 11-1
Default RIP Parameters
Parameters
Default
Maximum paths for load balancing
16
RIP feature
Disabled
Split horizon
Enabled
Configuring RIP
This section includes the following topics:
Note
•
Enabling RIP, page 11-5
•
Creating a RIP Instance, page 11-6
•
Restarting a RIP Instance, page 11-8
•
Configuring RIP on an Interface, page 11-8
•
Configuring RIP Authentication, page 11-9
•
Configuring a Passive Interface, page 11-11
•
Configuring Split Horizon with Poison Reverse, page 11-11
•
Configuring Route Summarization, page 11-11
•
Configuring Route Redistribution, page 11-11
•
Configuring Cisco NX-OS RIP for Compatibility with Cisco IOS RIP, page 11-13
•
Configuring Virtualization, page 11-14
•
Tuning RIP, page 11-17
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Enabling RIP
You must enable RIP before you can configure RIP.
SUMMARY STEPS
1.
configure terminal
2.
feature rip
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
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Configuring RIP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
feature rip
Enables the RIP feature.
Example:
switch(config)# feature rip
Step 3
show feature
(Optional) Displays enabled and disabled features.
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To disable the RIP feature and remove all associated configurations, use the following command in
global configuration mode.
Command
Purpose
no feature rip
Disables the RIP feature and removes all associated
configurations.
Example:
switch(config)# no feature rip
Creating a RIP Instance
You can create a RIP instance and configure the address family for that instance.
BEFORE YOU BEGIN
You must enable RIP (see the “Enabling RIP” section on page 11-5).
SUMMARY STEPS
1.
configure terminal
2.
router rip instance-tag
3.
address-family ipv4 unicast
4.
(Optional) show ip rip [instance instance-tag] [vrf vrf-name]
5.
(Optional) copy running-config startup-config
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Configuring RIP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router rip instance-tag
Example:
switch(config)# router RIP Enterprise
switch(config-router)#
Step 3
address-family ipv4 unicast
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
show ip rip [instance instance-tag] [vrf
vrf-name]
Creates a new RIP instance with the configured
instance-tag.
Configures the address family for this RIP instance and
enters address-family configuration mode.
(Optional) Displays a summary of RIP information for
all RIP instances.
Example:
switch(config-router-af)# show ip rip
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
To remove the RIP instance and the associated configurations, use the following command in global
configuration mode.
Command
Purpose
no router rip instance-tag
Deletes the RIP instance and all associated
configuration.
Example:
switch(config)# no router rip Enterprise
Note
You must also remove any RIP commands configured in interface mode.
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Configuring RIP
You can configure the following optional parameters for RIP in address-family configuration mode:
Command
Purpose
distance value
Sets the administrative distance for RIP. The range
is from 1 to 255. The default is 120. See the
“Administrative Distance” section on page 1-7.
Example:
switch(config-router-af)# distance 30
maximum-paths number
Example:
switch(config-router-af)# maximum-paths 6
Configures the maximum number of equal-cost
paths that RIP maintains in the route table. The
range is from 1 to 64. The default is 16.
This example shows how to create a RIP instance for IPv4 and set the number of equal-cost paths for
load balancing:
switch# configure terminal
switch(config)# router rip Enterprise
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# max-paths 10
switch(config-router-af)# copy running-config startup-config
Restarting a RIP Instance
You can restart a RIP instance. This clears all neighbors for the instance.
To restart an RIP instance and remove all associated neighbors, use the following command:
Command
Purpose
restart rip instance-tag
Restarts the RIP instance and removes all
neighbors.
Example:
switch(config)# restart rip Enterprise
Configuring RIP on an Interface
You can add an interface to a RIP instance.
BEFORE YOU BEGIN
You must enable RIP (see the “Enabling RIP” section on page 11-5).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
ip router rip instance-tag
4.
(Optional) show ip rip [instance instance-tag] interface [interface-type slot/port] [vrf vrf-name]
[detail]
5.
(Optional) copy running-config startup-config
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Configuring RIP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ip router rip instance-tag
Associates this interface with a RIP instance.
Example:
switch(config-if)# ip router rip
Enterprise
Step 4
show ip rip [instance instance-tag]
interface [interface-type slot/port]
[vrf vrf-name] [detail]
(Optional) Displays RIP information for an interface.
Example:
switch(config-if)# show ip rip
Enterprise tethernet 1/2
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to add Ethernet 1/2 interface to a RIP instance:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# ip router rip Enterprise
switch(config)# copy running-config startup-config
Configuring RIP Authentication
You can configure authentication for RIP packets on an interface.
BEFORE YOU BEGIN
You must enable RIP (see the “Enabling RIP” section on page 11-5).
Configure a keychain if necessary before enabling authentication. See the Cisco Nexus 9000 Series
NX-OS Security Configuration Guide for details on implementing keychains.
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
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Configuring RIP
3.
ip rip authentication mode{text | md5}
4.
ip rip authentication key-chain key
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ip rip authentication mode {text | md5}
Example:
switch(config-if)# ip rip authentication
mode md5
Step 4
ip rip authentication key-chain key
Example:
switch(config-if)# ip rip authentication
key-chain RIPKey
Step 5
copy running-config startup-config
Sets the authentication type for RIP on this interface as
cleartext or MD5 authentication digest.
Configures the authentication key used for RIP on this
interface.
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
This example shows how to create a keychain and configure MD5 authentication on a RIP interface:
switch# configure terminal
switch(config)# key chain RIPKey
switch(config-keychain)# key 2
switch(config-keychain-key)# accept-lifetime 00:00:00 Jan 01 2000 infinite
switch(config-keychain-key)# send-lifetime 00:00:00 Jan 01 2000 infinite
switch(config-keychain-key)# exit
switch(config-keychain)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# ip rip authentication mode md5
switch(config-if)# ip rip authentication key-chain RIPKey
switch(config-if)# copy running-config startup-config
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Configuring RIP
Configuring a Passive Interface
You can configure a RIP interface to receive routes but not send route updates by setting the interface to
passive mode.
To configure a RIP interface in passive mode, use the following command in interface configuration
mode:
Command
Purpose
ip rip passive-interface
Sets the interface into passive mode.
Example:
switch(config-if)# ip rip
passive-interface
Configuring Split Horizon with Poison Reverse
You can configure an interface to advertise routes learned by RIP as unreachable over the interface that
learned the routes by enabling poison reverse.
To configure split horizon with poison reverse on an interface, use the following command in interface
configuration mode:
Command
Purpose
ip rip poison-reverse
Enables split horizon with poison reverse. Split
horizon with poison reverse is disabled by default.
Example:
switch(config-if)# ip rip poison-reverse
Configuring Route Summarization
You can create aggregate addresses that are represented in the routing table by a summary address. Cisco
NX-OS advertises the summary address metric that is the smallest metric of all the more-specific routes.
To configure a summary address on an interface, use the following command in interface configuration
mode:
Command
Purpose
ip rip summary-address ip-prefix/mask-len
Configures a summary address for RIP for IPv4
addresses.
Example:
switch(config-if)# ip rip summary-address
1.1.1.1/32
Configuring Route Redistribution
You can configure RIP to accept routing information from another routing protocol and redistribute that
information through the RIP network. Redistributed routes can optionally be assigned a default route.
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Configuring RIP
Configuring RIP
BEFORE YOU BEGIN
You must enable RIP (see the “Enabling RIP” section on page 11-5).
Configure a route map before configuring redistribution. See the“Configuring Route Maps” section on
page 15-11 for details on configuring route maps.
SUMMARY STEPS
1.
configure terminal
2.
router rip instance-tag
3.
address-family ipv4 unicast
4.
redistribute {bgp as | direct | eigrp | isis | ospf | ospfv3 | rip} instance-tag | static} route-map
map-name
5.
(Optional) default-information originate [always] [route-map map-name]
6.
(Optional) default-metric value
7.
(Optional) show ip rip route [{ip-prefix [longer-prefixes | shorter-prefixes]] [vrf vrf-name]
[summary]
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router rip instance-tag
Example:
switch(config)# router rip Enterprise
switch(config-router)#
Step 3
address-family ipv4 unicast
Creates a new RIP instance with the configured
instance-tag.
Enters address-family configuration mode.
Example:
switch(config-router)# address-family
ipv4 unicast
switch(config-router-af)#
Step 4
redistribute {bgp as | direct |{eigrp |
isis | ospf | ospfv3 | rip} instance-tag
| static} route-map map-name
Redistributes routes from other protocols into RIP. See
the “Configuring Route Maps” section on page 15-11
for more information about route maps.
Example:
switch(config-router-af)# redistribute
eigrp 201 route-map RIPmap
Step 5
default-information originate [always]
[route-map map-name]
(Optional) Generates a default route into RIP,
optionally controlled by a route map.
Example:
switch(config-router-af)#
default-information originate always
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Configuring RIP
Configuring RIP
Step 6
Command
Purpose
default-metric value
(Optional) Sets the default metric for all redistributed
routes. The range is from 1 to 15. The default is 1.
Example:
switch(config-router-af)# default-metric
2
Step 7
show ip rip route [ip-prefix
[longer-prefixes | shorter-prefixes]
[vrf vrf-name] [summary]
(Optional) Shows the routes in RIP.
Example:
switch(config-router-af)# show ip rip
route
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-router-af)# copy
running-config startup-config
This example shows how to redistribute EIGRP into RIP:
switch# configure terminal
switch(config)# router rip Enterprise
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# redistribute eigrp 201 route-map RIPmap
switch(config-router-af)# copy running-config startup-config
Configuring Cisco NX-OS RIP for Compatibility with Cisco IOS RIP
You can configure Cisco NX-OS RIP to behave like Cisco IOS RIP in the way that routes are advertised
and processed.
Directly connected routes are treated with cost 1 in Cisco NX-OS RIP and with cost 0 in Cisco IOS RIP.
When routes are advertised in Cisco NX-OS RIP, the receiving device adds a minimum cost of +1 to all
received routes and installs the routes in its routing table. In Cisco IOS RIP, this cost increment is done
on the sending router, and the receiving router installs the routes without any modification. This
difference in behavior can cause issues when both Cisco NX-OS and Cisco IOS devices are working
together. You can prevent these compatibility issues by configuring Cisco NX-OS RIP to advertise and
process routes like Cisco IOS RIP.
BEFORE YOU BEGIN
You must enable RIP (see the “Enabling RIP” section on page 11-5).
SUMMARY STEPS
1.
configure terminal
2.
router rip instance-tag
3.
[no] metric direct 0
4.
(Optional) show running-config rip
5.
(Optional) copy running-config startup-config
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Configuring RIP
Configuring RIP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router rip instance-tag
Example:
switch(config)# router rip 100
switch(config-router)#
Step 3
[no] metric direct 0
Example:
switch(config-router)# metric direct 0
Creates a new RIP instance with the configured
instance tag. You can enter 100, 201, or up to 20
alphanumeric chapters for the instance tag.
Configures all directly connected routes with cost 0
instead of the default of cost 1 in order to make Cisco
NX-OS RIP compatible with Cisco IOS RIP in the way
that routes are advertised and processed.
Note
Step 4
show running-config rip
Example:
switch(config-router)# show
running-config rip
Step 5
copy running-config startup-config
This command must be configured on all Cisco
NX-OS devices that are present in any RIP
network that also contains Cisco IOS devices.
(Optional) Displays the current running RIP
configuration.
(Optional) Saves this configuration change.
Example:
switch(config-router)# copy
running-config startup-config
This example shows how to disable Cisco NX-OS RIP compatibility with Cisco IOS RIP by returning
all direct routes from cost 0 to cost 1:
switch# configure terminal
switch(config)# router rip 100
switch(config-router)# no metric direct 0
switch(config-router)# show running-config rip
switch(config-router)# copy running-config startup-config
Configuring Virtualization
You can configure multiple RIP instances, create multiple VRFs, and use the same or multiple RIP
instances in each VRF. You assign a RIP interface to a VRF.
Note
Configure all other parameters for an interface after you configure the VRF for an interface. Configuring
a VRF for an interface deletes all the configurations for that interface.
BEFORE YOU BEGIN
You must enable RIP (see the “Enabling RIP” section on page 11-5).
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Configuring RIP
Configuring RIP
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
exit
4.
router rip instance-tag
5.
vrf vrf-name
6.
(Optional) address-family ipv4 unicast
7.
(Optional) redistribute {bgp as | direct | {eigrp | isis | ospf | ospfv3 | rip} instance-tag | static}
route-map map-name
8.
interface ethernet slot/port
9.
vrf member vrf-name
10. ip-address ip-prefix/length
11. ip router rip instance-tag
12. (Optional) show ip rip [instance instance-tag] interface [interface-type slot/port] [vrf vrf-name]
13. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context
RemoteOfficeVRF
switch(config-vrf)#
Step 3
Creates a new VRF and enters VRF configuration
mode.
Exits VRF configuration mode.
exit
Example:
switch(config-vrf)# exit
switch(config)#
Step 4
router rip instance-tag
Example:
switch(config)# router rip Enterprise
switch(config-router)#
Step 5
Creates a new RIP instance with the configured
instance tag.
Creates a new VRF.
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
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Configuring RIP
Step 6
Command
Purpose
address-family ipv4 unicast
(Optional) Configures the VRF address family for this
RIP instance.
Example:
switch(config-router-vrf)#
address-family ipv4 unicast
switch(config-router-vrf-af)#
Step 7
redistribute {bgp as | direct | {eigrp |
isis | ospf | ospfv3 | rip} instance-tag
| static} route-map map-name
(Optional) Redistributes routes from other protocols
into RIP. See the “Configuring Route Maps” section on
page 15-11 for more information about route maps.
Example:
switch(config-router-vrf-af)#
redistribute eigrp 201 route-map RIPmap
Step 8
interface ethernet slot/port
Enters interface configuration mode.
Example:
switch(config-router-vrf-af)# interface
ethernet 1/2
switch(config-if)#
Step 9
vrf member vrf-name
Adds this interface to a VRF.
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Step 10
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
Step 11
ip router rip instance-tag
Configures an IP address for this interface. You must
do this step after you assign this interface to a VRF.
Associates this interface with a RIP instance.
Example:
switch(config-if)# ip router rip
Enterprise
Step 12
show ip rip [instance instance-tag]
interface [interface-type slot/port]
[vrf vrf-name]
(Optional) Displays RIP information for an interface in
a VRF.
Example:
switch(config-if)# show ip rip
Enterprise ethernet 1/2
Step 13
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if)# copy running-config
startup-config
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Configuring RIP
This example shows how to create a VRF and add an interface to the VRF:
switch# configure terminal
switch(config)# vrf context RemoteOfficeVRF
switch(config-vrf)# exit
switch(config)# router rip Enterprise
switch(config-router)# vrf RemoteOfficeVRF
switch(config-router-vrf)# address-family ipv4 unicast
switch(config-router-vrf-af)# redistribute eigrp 201 route-map RIPmap
switch(config-router-vrf-af)# interface ethernet 1/2
switch(config-if)# vrf member RemoteOfficeVRF
switch(config-if)# ip address 192.0.2.1/16
switch(config-if)# ip router rip Enterprise
switch(config-if)# copy running-config startup-config
Tuning RIP
You can tune RIP to match your network requirements. RIP uses several timers that determine the
frequency of routing updates, the length of time before a route becomes invalid, and other parameters.
You can adjust these timers to tune routing protocol performance to better suit your internetwork needs.
Note
You must configure the same values for the RIP timers on all RIP-enabled routers in your network.
You can use the following optional commands in address-family configuration mode to tune RIP:
Command
Purpose
timers basic update timeout holddown
garbage-collection
Sets the RIP timers in seconds. The parameters are
as follows:
Example:
switch(config-router-af)# timers basic 40
120 120 100
•
update—The range is from 5 to any positive
integer. The default is 30.
•
timeout—The time that Cisco NX-OS waits
before declaring a route as invalid. If Cisco
NX-OS does not receive route update
information for this route before the timeout
interval ends, Cisco NX-OS declares the route
as invalid. The range is from 1 to any positive
integer. The default is 180.
•
holddown—The time during which Cisco
NX-OS ignores better route information for an
invalid route. The range is from 0 to any
positive integer. The default is 180.
•
garbage-collection—The time from when
Cisco NX-OS marks a route as invalid until
Cisco NX-OS removes the route from the
routing table. The range is from 1 to any
positive integer. The default is 120.
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Configuring RIP
Verifying the RIP Configuration
You can use the following optional commands in interface configuration mode to tune RIP:
Command
Purpose
ip rip metric-offset value
Adds a value to the metric for every route received
on this interface. The range is from 1 to 15. The
default is 1.
Example:
switch(config-if)# ip rip metric-offset 10
ip rip route-filter {prefix-list list-name
| route-map map-name| [in | out]
Specifies a route map to filter incoming or outgoing
RIP updates.
Example:
switch(config-if)# ip rip route-filter
route-map InputMap in
Verifying the RIP Configuration
To display RIP configuration, perform one of the following tasks:
Command
Purpose
show ip rip instance [instance-tag] [vrf
vrf-name]
Displays the status for an instance of RIP.
show ip rip [instance instance-tag] interface
slot/port detail [vrf vrf-name]
Displays the RIP status for an interface.
show ip rip [instance instance-tag] neighbor
[interface-type number] [vrf vrf-name]
Displays the RIP neighbor table.
show ip rip [instance instance-tag] route
[ip-prefix/lengh [longer-prefixes |
shorter--prefixes]] [summary] [vrf vrf-name]
Displays the RIP route table.
show running-configuration rip
Displays the current running RIP configuration.
Displaying RIP Statistics
To display RIP statistics, use the following commands:
Command
Purpose
show ip rip [instance instance-tag] policy Displays the RIP policy statistics.
statistics redistribute {bgp as | direct |
{eigrp | isis | ospf | ospfv3 | rip}
instance-tag | static} [vrf vrf-name]
show ip rip [instance instance-tag]
statistics interface-type number] [vrf
vrf-name]
Displays the RIP statistics.
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Configuring RIP
Configuration Examples for RIP
Use the clear ip rip policy statistics redistribute protocol process-tag command to clear policy
statistics.
Use the clear ip rip statistics command to clear RIP statistics.
Configuration Examples for RIP
This example creates the Enterprise RIP instance in a VRF and adds Ethernet interface 1/2 to this RIP
instance. The example also configures authentication for Ethernet interface 1/2 and redistributes EIGRP
into this RIP domain.
vrf context NewVRF
!
feature rip
router rip Enterprise
vrf NewVRF
address-family ipv4 unicast
redistribute eigrp 201 route-map RIPmap
max-paths 10
!
interface ethernet 1/2
vrf member NewVRF
ip address 192.0.2.1/16
ip router rip Enterprise
ip rip authentication mode md5
ip rip authentication key-chain RIPKey
Related Topics
See Chapter 15, “Configuring Route Policy Manager” for more information on route maps.
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Configuring RIP
CH A P T E R
12
Configuring Static Routing
This chapter describes how to configure static routing on the Cisco NX-OS device.
This chapter includes the following sections:
•
About Static Routing, page 12-1
•
Licensing Requirements for Static Routing, page 12-3
•
Prerequisites for Static Routing, page 12-3
•
Default Settings, page 12-4
•
Configuring Static Routing, page 12-4
•
Verifying the Static Routing Configuration, page 12-8
•
Configuration Example for Static Routing, page 12-9
About Static Routing
Routers forward packets using either route information from route table entries that you manually
configure or the route information that is calculated using dynamic routing algorithms.
Static routes, which define explicit paths between two routers, cannot be automatically updated; you
must manually reconfigure static routes when network changes occur. Static routes use less bandwidth
than dynamic routes. No CPU cycles are used to calculate and analyze routing updates.
You can supplement dynamic routes with static routes where appropriate. You can redistribute static
routes into dynamic routing algorithms, but you cannot redistribute routing information calculated by
dynamic routing algorithms into the static routing table.
You should use static routes in environments where network traffic is predictable and where the network
design is simple. You should not use static routes in large, constantly changing networks because static
routes cannot react to network changes. Most networks use dynamic routes to communicate between
routers but might have one or two static routes configured for special cases. Static routes are also useful
for specifying a gateway of last resort (a default router to which all unroutable packets are sent).
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Configuring Static Routing
About Static Routing
This section includes the following topics:
•
Administrative Distance, page 12-2
•
Directly Connected Static Routes, page 12-2
•
Fully Specified Static Routes, page 12-2
•
Floating Static Routes, page 12-2
•
Remote Next Hops for Static Routes, page 12-3
•
BFD, page 12-3
•
Virtualization Support, page 12-3
Administrative Distance
An administrative distance is the metric used by routers to choose the best path when there are two or
more routes to the same destination from two different routing protocols. An administrative distance
guides the selection of one routing protocol (or static route) over another, when more than one protocol
adds the same route to the unicast routing table. Each routing protocol is prioritized in order of most to
least reliable using an administrative distance value.
Static routes have a default administrative distance of 1. A router prefers a static route to a dynamic route
because the router considers a route with a low number to be the shortest. If you want a dynamic route
to override a static route, you can specify an administrative distance for the static route. For example, if
you have two dynamic routes with an administrative distance of 120, you would specify an
administrative distance that is greater than 120 for the static route if you want the dynamic route to
override the static route.
Directly Connected Static Routes
You must specify only the output interface (the interface on which all packets are sent to the destination
network) in a directly connected static route. The router assumes the destination is directly attached to
the output interface and the packet destination is used as the next-hop address. The next hop can be an
interface, only for point-to-point interfaces. For broadcast interfaces, the next hop must be an IPv4/IPv6
address.
Fully Specified Static Routes
You must specify either the output interface (the interface on which all packets are sent to the destination
network) or the next-hop address in a fully specified static route. You can use a fully specified static route
when the output interface is a multi-access interface and you need to identify the next-hop address. The
next-hop address must be directly attached to the specified output interface.
Floating Static Routes
A floating static route is a static route that the router uses to back up a dynamic route. You must configure
a floating static route with a higher administrative distance than the dynamic route that it backs up. In
this instance, the router prefers a dynamic route to a floating static route. You can use a floating static
route as a replacement if the dynamic route is lost.
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Configuring Static Routing
Licensing Requirements for Static Routing
Note
By default, a router prefers a static route to a dynamic route because a static route has a smaller
administrative distance than a dynamic route.
Remote Next Hops for Static Routes
You can specify the next-hop address of a neighboring router that is not directly connected to the router
for static routes with remote (nondirectly attached) next-hops. If a static route has remote next hops
during data forwarding, the next hops are recursively used in the unicast routing table to identify the
corresponding directly attached next hops that have reachability to the remote next hops.
BFD
This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol designed to
provide fast forwarding-path failure detection times. BFD provides subsecond failure detection between
two adjacent devices and can be less CPU-intensive than protocol hello messages because some of the
BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 9000 Series
NX-OS Interfaces Configuration Guide for more information.
Virtualization Support
Static routes support virtual routing and forwarding (VRF) instances.
Licensing Requirements for Static Routing
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
Static routing requires no license. Any feature not included in a license package is bundled with the nx-os
image and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing
scheme, see the Cisco NX-OS Licensing Guide.
Prerequisites for Static Routing
Static routing has the following prerequisites:
•
If the next-hop address for a static route is unreachable, the static route is not added to the unicast
routing table..
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Default Settings
Default Settings
Table 12-1 lists the default settings for static routing parameters.
Table 12-1
Default Static Routing Parameters
Parameters
Default
Administrative distance
1
RIP feature
Disabled
Configuring Static Routing
This section includes the following topics:
Note
•
Configuring a Static Route, page 12-4
•
Configuring a Static Route over a VLAN, page 12-5
•
Configuring Virtualization, page 12-7
•
Verifying the Static Routing Configuration, page 12-8
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring a Static Route
You can configure a static route on the router.
SUMMARY STEPS
1.
configure terminal
2.
ip route {ip-prefix | ip-addr/ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]}
[name nexthop-name] [tag tag-value] [pref]
or
ipv6 route ip6-prefix {nh-prefix | link-local-nh-prefix} | {nh-prefix [interface] | link-local-nh-prefix
[interface]} [name nexthop-name] [tag tag-value] [pref]
3.
(Optional) show {ip | ipv6} static-route
4.
(Optional) copy running-config startup-config
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Configuring Static Routing
Configuring Static Routing
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
ip route {ip-prefix | ip-addr/ip-mask}
{[next-hop | nh-prefix] | [interface
next-hop | nh-prefix]} [name
nexthop-name] [tag tag-value] [pref]
Configures a static route and the interface for this
static route. Use ? to display a list of supported
interfaces. You can specify a null interface by using
null 0.
Example:
switch(config)# ip route 192.0.2.0/8
ethernet 1/2 192.0.2.4
You can optionally configure the next-hop address.
ipv6 route ip6-prefix {nh-prefix |
link-local-nh-prefix} | (nexthop
[interface] | link-local-nexthop
[interface]} [name nexthop-name] [tag
tag-value] [pref]
Configures a static route and the interface for this
static route. Use ? to display a list of supported
interfaces. You can specify a null interface by using
null 0.
Example:
switch(config)# ipv6 route
2001:0DB8::/48 6::6 ethernet 2/1
Step 3
show {ip | ipv6} static-route
The preference value sets the administrative distance.
The range is from 1 to 255. The default is 1.
You can optionally configure the next-hop address.
The preference value sets the administrative distance.
The range is from 1 to 255. The default is 1.
(Optional) Displays information about static routes.
Example:
switch(config)# show ip static-route
Step 4
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure a static route for a null interface:
switch# configure terminal
switch(config)# ip route 1.1.1.1/32 null 0
switch(config)# copy running-config startup-config
Use the no {ip | ipv6} route command to remove the static route.
Configuring a Static Route over a VLAN
You can configure a static route without next hop support over a VLAN.
BEFORE YOU BEGIN
Ensure that the access port is part of the VLAN.
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Configuring Static Routing
SUMMARY STEPS
1.
configure terminal
2.
feature interface-vlan
3.
interface vlan vlan-id
4.
ip address ip-addr/length
5.
ip route ip-addr/length vlan-id
6.
(Optional) show ip route
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
feature interface vlan
Enables VLAN interface mode.
Example:
switch(config)# feature interface-vlan
Step 3
interface-vlan vlan-id
Example:
switch(config)# interface-vlan 10
Step 4
ip address ip-addr/length
Creates an SVI and enters interface configuration
mode.
The range for the vlan-id argument is from 1 to 4094,
except for the VLANs reserved for the internal switch.
Configures an IP address for the VLAN.
Example:
switch(config)# ip address 192.0.2.1/8
Step 5
ip route ip-addr/length vlan-id
Example:
switch(config)# ip route
209.165.200.224/27 vlan 10
Step 6
show ip route
Example:
switch(config)# show ip route
Step 7
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
Adds an interface static route without a next hop on the
switch virtual interface (SVI).
The IP address is the address that is configured on the
interface that is connected to the switch.
(Optional) Displays routes from the Unicast Route
Information Base (URIB).
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure a static route without a next hop over an SVI:
switch# configure terminal
switch(config)# feature interface-vlan
swicth(config)# interface vlan 10
switch(config-if)# ip address 192.0.2.1/8
switch(config-if)# ip route 209.165.200.224/27 vlan 10 <===209,165.200.224 is the IP
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Configuring Static Routing
address of the interface that is configured on the interface that is directly connected to
the switch.
switch(config-if)# copy running-config startup-config
Use the no ip route command to remove the static route.
Configuring Virtualization
You can configure a static route in a VRF.
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
ip route {ip-prefix | ip-addr ip-mask} {next-hop | nh-prefix | interface} [name nexthop-name] [tag
tag-value] [pref]
or
ipv6 route ip6-prefix {nh-prefix | link-local-nh-prefix} | {next-hop [interface] | link-local-next-hop
[interface]} [name nexthop-name] [tag tag-value] [pref]
4.
(Optional) show {ip | ipv6} static-route vrf vrf-name
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Creates a VRF and enters VRF configuration mode.
vrf context vrf-name
Example:
switch(config)# vrf context StaticVrf
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Verifying the Static Routing Configuration
Step 3
Command
Purpose
ip route {ip-prefix | ip-addr ip-mask}
{next-hop | nh-prefix | interface} [name
nexthop-name] [tag tag-value] [pref]
Configures a static route and the interface for this
static route. Use ? to display a list of supported
interfaces. You can specify a null interface by using
null 0.
Example:
switch(config-vrf)# ip route 192.0.2.0/8
ethernet 1/2
You can optionally configure the next-hop address.
The preference value sets the administrative distance.
The range is from 1 to 255. The default is 1.
ipv6 route ip6-prefix {nh-prefix |
link-local-nh-prefix} | (nexthop
[interface] | link-local-nexthop
[interface]} [name nexthop-name] [tag
tag-value] [pref]
Example:
switch(config)# ipv6 route
2001:0DB8::/48 6::6 ethernet 2/1
Step 4
show {ip | ipv6} static-route vrf
vrf-name
Configures a static route and the interface for this
static route. Use ? to display a list of supported
interfaces. You can specify a null interface by using
null 0.
You can optionally configure the next-hop address.
The preference value sets the administrative distance.
The range is from 1 to 255. The default is 1.
(Optional) Displays information on static routes.
Example:
switch(config-vrf)# show ip static-route
Step 5
copy running-config startup-config
Example:
switch(config-vrf)# copy running-config
startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure a static route:
switch# configure terminal
switch(config)# vrf context StaticVrf
switch(config-vrf)# ip route 192.0.2.0/8 192.0.2.10
switch(config-vrf)# copy running-config startup-config
Verifying the Static Routing Configuration
To display the static routing configuration, perform one of the following tasks:
Command
Purpose
show {ip | ipv6} static-route
Displays the configured static routes.
show ipv6 static-route vrf vrf-name
Displays static route information for each VRF.
show {ip | ipv6} static-route track-table
Displays information about the IPv4 or IPv6
static-route track table.
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Configuration Example for Static Routing
Configuration Example for Static Routing
This example shows how to configure static routing:
configure terminal
ip route 192.0.2.0/8 192.0.2.10
copy running-config startup-config
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Configuring Static Routing
CH A P T E R
13
Configuring Layer 3 Virtualization
This chapter describes how to configure Layer 3 virtualization on the Cisco NX-OS device.
This chapter includes the following sections:
•
About Layer 3 Virtualization, page 13-1
•
Licensing Requirements for VRFs, page 13-5
•
Guidelines and Limitations for VRFs, page 13-5
•
Default Settings, page 13-5
•
Configuring VRFs, page 13-6
•
Verifying the VRF Configuration, page 13-12
•
Configuration Examples for VRF, page 13-12
•
Additional References, page 13-15
About Layer 3 Virtualization
Cisco NX-OS supports multiple virtual routing and forwarding instances (VRFs). Each VRF contains a
separate address space with unicast and multicast route tables for IPv4 and IPv6 and makes routing decisions
independent of any other VRF.
Each router has a default VRF and a management VRF:
Management VRF
•
The management VRF is for management purposes only.
•
Only the mgmt 0 interface can be in the management VRF.
•
The mgmt 0 interface cannot be assigned to another VRF.
•
No routing protocols can run in the management VRF (static only).
Default VRF
•
All Layer 3 interfaces exist in the default VRF until they are assigned to another VRF.
•
Routing protocols run in the default VRF context unless another VRF context is specified.
•
The default VRF uses the default routing context for all show commands.
•
The default VRF is similar to the global routing table concept in Cisco IOS.
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About Layer 3 Virtualization
VRF and Routing
All unicast and multicast routing protocols support VRFs. When you configure a routing protocol in a
VRF, you set routing parameters for the VRF that are independent of routing parameters in another VRF
for the same routing protocol instance.
You can assign interfaces and route protocols to a VRF to create virtual Layer 3 networks. An interface
exists in only one VRF. Figure 13-1 shows one physical network split into two virtual networks with two
VRFs. Routers Z, A, and B exist in VRF Red and form one address domain. These routers share route
updates that do not include Router C because Router C is configured in a different VRF.
Figure 13-1
VRFs in a Network
Router B
Router Z
Ethernet 1/1
VRF Red
Ethernet 2/1
VRF Red
Ethernet 2/2
VRF Blue
Router C
186416
Router A
By default, Cisco NX-OS uses the VRF of the incoming interface to select which routing table to use for
a route lookup. You can configure a route policy to modify this behavior and set the VRF that Cisco
NX-OS uses for incoming packets.
Route Leaking and Importing Routes from the Default VRF
Cisco NX-OS supports route leaking (import or export) between VRFs.
You can import IP prefixes from the global routing table (the default VRF) into any other VRF by using
an import policy. The VRF import policy uses a route map to specify the prefixes to be imported into a
VRF. The policy can import IPv4 and IPv6 unicast prefixes.
Note
Routes in the BGP default VRF can be imported directly. Any other routes in the default VRF should be
redistributed into BGP first.
IP prefixes are defined as match criteria for the import route map through standard route policy filtering
mechanisms. For example, you can create an IP prefix list or an as-path filter to define an IP prefix or IP
prefix range and use that prefix list or as-path filter in a match clause for the route map. Prefixes that
pass through the route map are imported into the specified VRF using the import policy. IP prefixes that
are imported into a VRF through this import policy cannot be reimported into another VRF.
For more information, see the “Guidelines and Limitations for VRF Route Leaking” section on
page 13-5.
VRF-Aware Services
A fundamental feature of the Cisco NX-OS architecture is that every IP-based feature is VRF aware.
The following VRF-aware services can select a particular VRF to reach a remote server or to filter
information based on the selected VRF:
•
AAA—See the Cisco Nexus 9000 Series NX-OS Security Configuration Guide for more information.
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About Layer 3 Virtualization
•
Call Home—See the Cisco Nexus 9000 Series NX-OS System Management Configuration Guide for
more information.
•
DNS—See Chapter 4, “Configuring DNS,” for more information.
•
HTTP—See the Cisco Nexus 9000 Series NX-OS Fundamentals Configuration Guide for more
information.
•
HSRP—See Chapter 17, “Configuring HSRP,” for more information.
•
NTP—See the Cisco Nexus 9000 Series NX-OS System Management Configuration Guide for more
information.
•
RADIUS—See the Cisco Nexus 9000 Series NX-OS Security Configuration Guide for more
information.
•
Ping and Traceroute —See the Cisco Nexus 9000 Series NX-OS Fundamentals Configuration Guide
for more information.
•
SSH—See the Cisco Nexus 9000 Series NX-OS Security Configuration Guide for more information.
•
SNMP—See the Cisco Nexus 9000 Series NX-OS System Management Configuration Guide for
more information.
•
Syslog—See the Cisco Nexus 9000 Series NX-OS System Management Configuration Guide for
more information.
•
TACACS+—See the Cisco Nexus 9000 Series NX-OS Security Configuration Guide for more
information.
•
TFTP—See the Cisco Nexus 9000 Series NX-OS Fundamentals Configuration Guide for more
information.
•
VRRP—See Chapter 18, “Configuring VRRP,” for more information.
•
XML—See the Cisco NX-OS XML Management Interface User Guide for more information.
See the appropriate configuration guide for each service for more information on configuring VRF
support in that service.
This section contains the following topics:
•
Reachability, page 13-3
•
Filtering, page 13-4
•
Combining Reachability and Filtering, page 13-4
Reachability
Reachability indicates which VRF contains the routing information needed to get to the server providing
the service. For example, you can configure an SNMP server that is reachable on the management VRF.
When you configure that server address on the router, you also configure which VRF that Cisco NX-OS
must use to reach the server.
Figure 13-2 shows an SNMP server that is reachable over the management VRF. You configure Router
A to use the management VRF for the SNMP server host 192.0.2.1.
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About Layer 3 Virtualization
Figure 13-2
Service VRF Reachability
SNMP Server
192.0.2.1
Router A
mgmt0
186417
VRF management
Filtering
Filtering allows you to limit the type of information that goes to a VRF-aware service based on the VRF.
For example, you can configure a syslog server to support a particular VRF. Figure 13-3 shows two
syslog servers with each server supporting one VRF. syslog server A is configured in VRF Red, so Cisco
NX-OS sends only system messages generated in VRF Red to syslog server A.
Figure 13-3
Service VRF Filtering
Syslog Server A
Ethernet 2/1
VRF Red
Router A
VRF Blue
Syslog Server B
186418
Ethernet 2/2
Combining Reachability and Filtering
You can combine reachability and filtering for VRF-aware services. You can configure the VRF that
Cisco NX-OS uses to connect to that service as well as the VRF that the service supports. If you
configure a service in the default VRF, you can optionally configure the service to support all VRFs.
Figure 13-4 shows an SNMP server that is reachable on the management VRF. You can configure the
SNMP server to support only the SNMP notifications from VRF Red, for example.
Figure 13-4
Service VRF Reachability Filtering
Router B
Router A
mgmt0
VRF management
Ethernet 2/1
VRF Red
Ethernet 2/2
VRF Blue
Router C
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Licensing Requirements for VRFs
Licensing Requirements for VRFs
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
VRFs require no license. Any feature not included in a license package is bundled with the nx-os image and
is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see
the Cisco NX-OS Licensing Guide.
Guidelines and Limitations for VRFs
VRFs have the following configuration guidelines and limitations:
•
When you make an interface a member of an existing VRF, Cisco NX-OS removes all Layer 3
configurations. You should configure all Layer 3 parameters after adding an interface to a VRF.
•
You should add the mgmt0 interface to the management VRF and configure the mgmt0 IP address
and other parameters after you add it to the management VRF.
•
If you configure an interface for a VRF before the VRF exists, the interface is operationally down
until you create the VRF.
•
Cisco NX-OS creates the default and management VRFs by default. You should make the mgmt0
interface a member of the management VRF.
•
The write erase boot command does not remove the management VRF configurations. You must
use the write erase command and then the write erase boot command.
Guidelines and Limitations for VRF Route Leaking
VRF route leaking has the following configuration guidelines and limitations:
•
Route leaking is supported between any two non-default VRFs and from the default VRF to a
non-default VRF.
•
You can restrict route leaking to specific routes using route map filters to match designated IP
addresses.
•
By default, the maximum number of IP prefixes that can be imported from the default VRF into a
non-default VRF is 1000 routes.
•
There is no limit on the number of routes that can be leaked between two non-default VRFs.
•
VRF route leaking requires an Enterprise license, and BGP must be enabled.
Default Settings
Table 13-1 lists the default settings for VRF parameters.
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Table 13-1
Default VRF Parameters
Parameters
Default
Configured VRFs
Default, management
routing context
Default VRF
Configuring VRFs
This section contains the following topics:
Note
•
Creating a VRF, page 13-6
•
Assigning VRF Membership to an Interface, page 13-7
•
Configuring VRF Parameters for a Routing Protocol, page 13-9
•
Configuring a VRF-Aware Service, page 13-10
•
Setting the VRF Scope, page 13-11
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Creating a VRF
You can create a VRF.
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
(Optional) ip route {ip-prefix | ip-addr ip-mask} {[next-hop | nh-prefix] | [interface next-hop |
nh-prefix]} [tag tag-value [pref]
4.
(Optional) show vrf [vrf-name]
5.
(Optional) copy running-config startup-config
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Configuring VRFs
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context name
Example:
switch(config)# vrf context Enterprise
switch(config-vrf)#
Step 3
ip route {ip-prefix | ip-addr ip-mask}
{[next-hop | nh-prefix] | [interface
next-hop | nh-prefix]} [tag tag-value
[pref]
Example:
switch(config-vrf)# ip route 192.0.2.0/8
ethernet 1/2 192.0.2.4
Step 4
Creates a new VRF and enters VRF configuration
mode. The name can be any case-sensitive,
alphanumeric string up to 32 characters.
(Optional) Configures a static route and the interface
for this static route. You can optionally configure the
next-hop address. The preference value sets the
administrative distance. The range is from 1 to 255.
The default is 1.
(Optional) Displays VRF information.
show vrf [vrf-name]
Example:
switch(config-vrf)# show vrf Enterprise
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
To delete the VRF and the associated configuration, use the following command in global configuration
mode:
Command
Purpose
no vrf context name
Deletes the VRF and all associated configurations.
Example:
switch(config)# no vrf context Enterprise
Any commands available in global configuration mode are also available in VRF configuration mode.
This example shows how to create a VRF and add a static route to the VRF:
switch# configure terminal
switch(config)# vrf context Enterprise
switch(config-vrf)# ip route 192.0.2.0/8 ethernet 1/2
switch(config-vrf)# exit
switch(config)# copy running-config startup-config
Assigning VRF Membership to an Interface
You can make an interface a member of a VRF.
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Configuring VRFs
BEFORE YOU BEGIN
Assign the IP address for an interface after you have configured the interface for a VRF.
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrf member vrf-name
4.
ip-address ip-prefix/length
5.
(Optional) show vrf vrf-name interface interface-type number
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
vrf member vrf-name
Adds this interface to a VRF.
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Step 4
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
Step 5
show vrf vrf-name interface
interface-type number
Configures an IP address for this interface. You must
do this step after you assign this interface to a VRF.
(Optional) Displays VRF information.
Example:
switch(config-vrf)# show vrf Enterprise
interface ethernet 1/2
Step 6
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
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Configuring VRFs
This example shows how to add an interface to the VRF:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# vrf member RemoteOfficeVRF
switch(config-if)# ip address 192.0.2.1/16
switch(config-if)# copy running-config startup-config
Configuring VRF Parameters for a Routing Protocol
You can associate a routing protocol with one or more VRFs. See the appropriate chapter for information
on how to configure VRFs for the routing protocol. This section uses OSPFv2 as an example protocol
for the detailed configuration steps.
SUMMARY STEPS
1.
configure terminal
2.
router ospf instance-tag
3.
vrf vrf-name
4.
(Optional) maximum-paths paths
5.
interface interface-type slot/port
6.
vrf member vrf-name
7.
ip address ip-prefix/length
8.
ip router ospf instance-tag area area-id
9.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
router ospf instance-tag
Example:
switch(config-vrf)# router ospf 201
switch(config-router)#
Step 3
Creates a new OSPFv2 instance with the configured
instance tag.
Enters VRF configuration mode.
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
Step 4
maximum-paths paths
Example:
switch(config-router-vrf)# maximum-paths
4
(Optional) Configures the maximum number of equal
OSPFv2 paths to a destination in the route table for this
VRF. Used for load balancing.
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Step 5
Command
Purpose
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 6
vrf member vrf-name
Adds this interface to a VRF.
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
Step 7
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
Step 8
ip router ospf instance-tag area area-id
Example:
switch(config-if)# ip router ospf 201
area 0
Step 9
copy running-config startup-config
Configures an IP address for this interface. You must
do this step after you assign this interface to a VRF.
Assigns this interface to the OSPFv2 instance and area
configured.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to create a VRF and add an interface to the VRF:
switch# configure terminal
switch(config)# vrf context RemoteOfficeVRF
switch(config-vrf)# exit
switch(config)# router ospf 201
switch(config-router)# vrf RemoteOfficeVRF
switch(config-router-vrf)# maximum-paths 4
switch(config-router-vrf)# interface ethernet 1/2
switch(config-if)# vrf member RemoteOfficeVRF
switch(config-if)# ip address 192.0.2.1/16
switch(config-if)# ip router ospf 201 area 0
switch(config-if)# exit
switch(config)# copy running-config startup-config
Configuring a VRF-Aware Service
You can configure a VRF-aware service for reachability and filtering. See the “VRF-Aware Services”
section on page 13-2 for links to the appropriate chapter or configuration guide for information on how
to configure the service for VRFs. This section uses SNMP and IP domain lists as example services for
the detailed configuration steps.
SUMMARY STEPS
1.
configure terminal
2.
snmp-server host ip-address [filter-vrf vrf-name] [use-vrf vrf-name]
3.
vrf context [vrf-name]
4.
ip domain-list domain-name [all-vrfs][use-vrf vrf-name]
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5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
snmp-server host ip-address [filter-vrf
vrf-name] [use-vrf vrf-name]
Example:
switch(config)# snmp-server host
192.0.2.1 use-vrf Red
switch(config-vrf)#
Step 3
Configures a global SNMP server and configures the
VRF that Cisco NX-OS uses to reach the service. Use
the filter-vrf keyword to filter information from the
selected VRF to this server.
Creates a new VRF.
vrf context vrf-name
Example:
switch(config)# vrf context Blue
switch(config-vrf)#
Step 4
ip domain-list domain-name
[all-vrfs][use-vrf vrf-name]
Example:
switch(config-vrf)# ip domain-list List
all-vrfs use-vrf Blue
switch(config-vrf)#
Step 5
copy running-config startup-config
Configures the domain list in the VRF and optionally
configures the VRF that Cisco NX-OS uses to reach
the domain name listed.
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
This example shows how to send SNMP information for all VRFs to SNMP host 192.0.2.1, reachable on
VRF Red:
switch# configure terminal
switch(config)# snmp-server host 192.0.2.1 for-all-vrfs use-vrf Red
switch(config)# copy running-config startup-config
This example shows how to filter SNMP information for VRF Blue to SNMP host 192.0.2.12, reachable
on VRF Red:
switch# configure terminal
switch(config)# vrf context Blue
switch(config-vrf)# snmp-server host 192.0.2.12 use-vrf Red
switch(config)# copy running-config startup-config
Setting the VRF Scope
You can set the VRF scope for all EXEC commands (for example, show commands). This automatically
restricts the scope of the output of EXEC commands to the configured VRF. You can override this scope
by using the VRF keywords available for some EXEC commands.
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Verifying the VRF Configuration
To set the VRF scope, use the following command in EXEC mode:
Command
Purpose
routing-context vrf vrf-name
Sets the routing context for all EXEC commands.
Default routing context is the default VRF.
Example:
switch# routing-context vrf red
switch%red#
To return to the default VRF scope, use the following command in EXEC mode:
Command
Purpose
routing-context vrf default
Sets the default routing context.
Example:
switch%red# routing-context vrf default
switch#
Verifying the VRF Configuration
To display VRF configuration information, perform one of the following tasks:
Command
Purpose
show vrf [vrf-name]
Displays the information for all or one VRF.
show vrf [vrf-name] detail
Displays detailed information for all or one VRF.
show vrf [vrf-name] [interface interface-type
slot/port]
Displays the VRF status for an interface.
Configuration Examples for VRF
This example shows how to configure VRF Red, add an SNMP server to that VRF, and add an instance
of OSPF to VRF Red:
configure terminal
vrf context Red
snmp-server host 192.0.2.12 use-vrf Red
router ospf 201
vrf Red
interface ethernet 1/2
vrf member Red
ip address 192.0.2.1/16
ip router ospf 201 area 0
This example shows how to configure VRF Red and Blue, add an instance of OSPF to each VRF, and
create an SNMP context for each OSPF instance in each VRF:
configure terminal
!Create the VRFs
vrf context Red
vrf context Blue
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Configuration Examples for VRF
vrf context Green
!Create the OSPF instances and associate them with a single VRF or multiple VRFs
(recommended)
feature ospf
router ospf Lab
vrf Red
!
router ospf Production
vrf Blue
router-id 1.1.1.1
vrf Green
router-id 2.2.2.2
!Configure one interface to use ospf Lab on VRF Red
interface ethernet 1/2
vrf member Red
ip address 192.0.2.1/16
ip router ospf Lab area 0
no shutdown
!Configure another interface to use ospf Production on VRF Blue
interface ethernet 10/2
vrf member Blue
ip address 192.0.2.1/16
ip router ospf Production area 0
no shutdown
!
interface ethernet 10/3
vrf member Green
ip address 192.0.2.1/16
ip router ospf Production area 0
no shutdown
!configure the SNMP server
snmp-server user admin network-admin auth md5 nbv-12345
snmp-server community public ro
!Create the SNMP contexts for each VRF
snmp-server context lab instance Lab vrf Red
snmp-server context production instance Production vrf Blue
!Use the SNMP context lab to access the OSPF-MIB values for the OSPF instance Lab in VRF
Red in this example.
Use the SNMP context lab to access the OSPF-MIB values for the OSPF instance Lab in VRF Red in
this example.
This example shows how to configure route leaking between two non-default VRFs and from the
default VRF to a non-default VRF:
feature bgp
vrf context Green
ip route 33.33.33.33/32 35.35.1.254
address-family ipv4 unicast
route-target import 3:3
route-target export 2:2
export map test
import map test
import vrf default map test
interface Ethernet1/7
vrf member Green
ip address 35.35.1.2/24
vrf context Shared
ip route 44.44.44.44/32 45.45.1.254
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Configuration Examples for VRF
address-family ipv4 unicast
route-target import 1:1
route-target import 2:2
route-target export 3:3
export map test
import map test
import vrf default map test
interface Ethernet1/11
vrf member Shared
ip address 45.45.1.2/24
router bgp 100
address-family ipv4
redistribute static
vrf Green
address-family ipv4
redistribute static
vrf Shared
address-family ipv4
redistribute static
unicast
route-map test
unicast
route-map test
unicast
route-map test
ip prefix-list test seq 5 permit 0.0.0.0/0 le 32
route-map test permit 10
match ip address prefix-list test
ip route 100.100.100.100/32 55.55.55.1
switch# show ip route vrf all
IP Route Table for VRF "default"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%<string>' in via output denotes VRF <string>
55.55.55.0/24, ubest/mbest: 1/0, attached
*via 55.55.55.5, Lo0, [0/0], 00:07:59, direct
55.55.55.5/32, ubest/mbest: 1/0, attached
*via 55.55.55.5, Lo0, [0/0], 00:07:59, local
100.100.100.100/32, ubest/mbest: 1/0
*via 55.55.55.1, [1/0], 00:07:42, static
IP Route Table for VRF "management"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%<string>' in via output denotes VRF <string>
0.0.0.0/0, ubest/mbest: 1/0
*via 10.29.176.1, [1/0], 12:53:54, static
10.29.176.0/24, ubest/mbest: 1/0, attached
*via 10.29.176.233, mgmt0, [0/0], 13:11:57, direct
10.29.176.233/32, ubest/mbest: 1/0, attached
*via 10.29.176.233, mgmt0, [0/0], 13:11:57, local
IP Route Table for VRF "Green"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%<string>' in via output denotes VRF <string>
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Chapter 13
Configuring Layer 3 Virtualization
Additional References
33.33.33.33/32, ubest/mbest: 1/0
*via 35.35.1.254, [1/0], 00:23:44, static
35.35.1.0/24, ubest/mbest: 1/0, attached
*via 35.35.1.2, Eth1/7, [0/0], 00:26:46, direct
35.35.1.2/32, ubest/mbest: 1/0, attached
*via 35.35.1.2, Eth1/7, [0/0], 00:26:46, local
44.44.44.44/32, ubest/mbest: 1/0
*via 45.45.1.254%Shared, [20/0], 00:12:08, bgp-100, external, tag 100
100.100.100.100/32, ubest/mbest: 1/0
*via 55.55.55.1%default, [20/0], 00:07:41, bgp-100, external, tag 100
IP Route Table for VRF "Shared"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%<string>' in via output denotes VRF <string>
33.33.33.33/32, ubest/mbest: 1/0
*via 35.35.1.254%Green, [20/0], 00:12:34, bgp-100, external, tag 100
44.44.44.44/32, ubest/mbest: 1/0
*via 45.45.1.254, [1/0], 00:23:16, static
45.45.1.0/24, ubest/mbest: 1/0, attached
*via 45.45.1.2, Eth1/11, [0/0], 00:25:53, direct
45.45.1.2/32, ubest/mbest: 1/0, attached
*via 45.45.1.2, Eth1/11, [0/0], 00:25:53, local
100.100.100.100/32, ubest/mbest: 1/0
*via 55.55.55.1%default, [20/0], 00:07:41, bgp-100, external, tag 100
switch(config)#
Additional References
For additional information related to implementing virtualization, see the following sections:
•
Related Documents, page 13-15
•
Standards, page 13-15
Related Documents
Related Topic
Document Title
VRFs
Cisco Nexus 9000 Series NX-OS Fundamentals Configuration Guide
Cisco Nexus 9000 Series NX-OS System Management Configuration
Guide
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
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Configuring Layer 3 Virtualization
CH A P T E R
14
Managing the Unicast RIB and FIB
This chapter describes how to manage routes in the unicast Routing Information Base (RIB) and the
Forwarding Information Base (FIB) on the Cisco NX-OS device.
This chapter includes the following sections:
•
About the Unicast RIB and FIB, page 14-1
•
Licensing Requirements for the Unicast RIB and FIB, page 14-2
•
Managing the Unicast RIB and FIB, page 14-2
•
Verifying the Unicast RIB and FIB, page 14-10
•
Additional References, page 14-11
About the Unicast RIB and FIB
The unicast RIB (IPv4 RIB and IPv6 RIB) and FIB are part of the Cisco NX-OS forwarding architecture,
as shown in Figure 14-1.
Figure 14-1
Cisco NX-OS Forwarding Architecture
ISIS
BGP
OSPF
ARP
Supervisor components
URIB
Adjacency Manager (AM)
Module components
Unicast Forwarding Information Base (UFIB)
182981
Unicast FIB Distribution Module (uFDM)
The unicast RIB exists on the active supervisor. It maintains the routing table with directly connected
routes, static routes, and routes learned from dynamic unicast routing protocols. The unicast RIB also
collects adjacency information from sources such as the Address Resolution Protocol (ARP). The
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Managing the Unicast RIB and FIB
Licensing Requirements for the Unicast RIB and FIB
unicast RIB determines the best next hop for a given route and populates the unicast forwarding
information bases (FIBs) on the modules by using the services of the unicast FIB distribution module
(FDM).
Each dynamic routing protocol must update the unicast RIB for any route that has timed out. The unicast
RIB then deletes that route and recalculates the best next hop for that route (if an alternate path is
available).
This section includes the following topics:
•
Layer 3 Consistency Checker, page 14-2
Layer 3 Consistency Checker
In rare instances, an inconsistency can occur between the unicast RIB and the FIB on each module. Cisco
NX-OS supports the Layer 3 consistency checker. This feature detects inconsistencies between the
unicast IPv4 RIB on the supervisor module and the FIB on each interface module. Inconsistencies
include the following:
•
Missing prefix
•
Extra prefix
•
Wrong next-hop address
•
Incorrect Layer 2 rewrite string in the ARP or neighbor discovery (ND) cache
The Layer 3 consistency checker compares the FIB entries to the latest adjacency information from the
Adjacency Manager (AM) and logs any inconsistencies. The consistency checker then compares the
unicast RIB prefixes to the module FIB and logs any inconsistencies. See the “Triggering the Layer 3
Consistency Checker” section on page 14-7.
You can then manually clear any inconsistencies. See the “Clearing Forwarding Information in the FIB”
section on page 14-8.
Licensing Requirements for the Unicast RIB and FIB
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
The unicast RIB and FIB require no license. Any feature not included in a license package is bundled with
the nx-os image and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS
licensing scheme, see the Cisco NX-OS Licensing Guide.
Managing the Unicast RIB and FIB
This section includes the following topics:
•
Displaying Module FIB Information, page 14-3
•
Configuring Load Sharing in the Unicast FIB, page 14-3
•
Displaying Routing and Adjacency Information, page 14-5
•
Triggering the Layer 3 Consistency Checker, page 14-7
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Managing the Unicast RIB and FIB
Note
•
Clearing Forwarding Information in the FIB, page 14-8
•
Configuring Maximum Routes for the Unicast RIB, page 14-8
•
Estimating Memory Requirements for Routes, page 14-9
•
Clearing Routes in the Unicast RIB, page 14-9
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Displaying Module FIB Information
You can display the FIB information on a module.
DETAILED STEPS
To display the FIB information on a module, use the following commands in any mode:
Command
Purpose
show forwarding {ipv4 | ipv6}
adjacency module slot
Displays the adjacency information for IPv4 or IPv6.
Example:
switch# show forwarding ipv6
adjacency module 2
show forwarding {ipv4 | ipv6} route
module slot
Displays the route table for IPv4 or IPv6.
Example:
switch# show forwarding ipv6 route
module 2
Configuring Load Sharing in the Unicast FIB
Dynamic routing protocols such as Open Shortest Path First (OSPF) support load balancing with
equal-cost multipath (ECMP). The routing protocol determines its best routes based on the metrics
configured for the protocol and installs up to the protocol-configured maximum paths in the unicast
Routing Information Base (RIB). The unicast RIB compares the administrative distances of all routing
protocol paths in the RIB and selects a best path set from all of the path sets installed by the routing
protocols. The unicast RIB installs this best path set into the Forwarding Information Base (FIB) for use
by the forwarding plane.
The forwarding plane uses a load-sharing algorithm to select one of the installed paths in the FIB to use
for a given data packet.
Note
Load sharing uses the same path for all packets in a given flow. A flow is defined by the load-sharing
method that you configure. For example, if you configure source-destination load sharing, then all
packets with the same source IP address and destination IP address pair follow the same path.
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Managing the Unicast RIB and FIB
To configure the unicast FIB load-sharing algorithm, use the following command in global configuration
mode:
Command
Purpose
ip load-sharing address {destination
port destination | source-destination
[port source-destination]}
[universal-id seed][rotate rotate]
[concatenation]
Configures the unicast FIB load-sharing algorithm for
data traffic.
•
Example:
switch(config)# ip load-sharing
address source-destination
The universal-id option sets the random seed for the
hash algorithm and shifts the flow from one link to
another.
You do not need to configure the universal ID. Cisco
NX-OS chooses the Universal ID if you do not
configure it. The universal-id range is from 1 to
4294967295.
•
The rotate option causes the hash algorithm to rotate
the link picking selection so that it does not
continually choose the same link across all nodes in
the network. It does so by influencing the bit pattern
for the hash algorithm. This option shifts the flow
from one link to another and load balances the
already load-balanced (polarized) traffic from the
first ECMP level across multiple links.
If you specify a rotate value, the 64-bit stream is
interpreted starting from that bit position in a cyclic
rotation. The rotate range is from 1 to 63, and the
default is 32.
Note
With multi-tier Layer 3 topology, polarization is
possible. To avoid polarization, use a different
rotate bit at each tier of the topology.
Note
To configure a rotation value for port channels,
use the port-channel load-balance src-dst
ip-l4port rotate rotate command. For more
information on this command, see the Cisco
Nexus 9000 Series NX-OS Interfaces
Configuration Guide.
•
The concatenation option ties together the hash tag
values for ECMP and the hash tag values for port
channels in order to use a stronger 64-bit hash. If you
do not use this option, you can control ECMP
load-balancing and port-channel load-balancing
independently. The default is disabled.
To display the unicast FIB load-sharing algorithm, use the following command in any mode:
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Managing the Unicast RIB and FIB
Command
Purpose
show ip load-sharing
Displays the unicast FIB load-sharing algorithm for data
traffic.
Example:
switch(config)# show ip load-sharing
address source-destination
To display the route that the unicast RIB and FIB use for a particular source address and destination
address, use the following command in any mode:
Command
Purpose
show routing hash source-addr
dest-addr [source-port dest-port]
[vrf vrf-name]
Displays the route that the unicast RIB FIB use for a
source and destination address pair. The source address
and destination address format is x.x.x.x. The source port
and destination port range is from 1 to 65535. The VRF
name can be any case-sensitive, alphanumeric string up to
64 characters.
Example:
switch# show routing hash 192.0.2.1
10.0.0.1
This example shows how to display the route selected for a source/destination pair:
switch# show routing hash 10.0.0.5 192.0.0.2
Load-share parameters used for software forwarding:
load-share mode: address source-destination port source-destination
Universal-id seed: 0xe05e2e85
Hash for VRF "default"
Hashing to path *172.0.0.2 (hash: 0x0e), for route:
Displaying Routing and Adjacency Information
You can display the routing and adjacency information.
To display the routing and adjacency information, use the following commands in any mode:
Command
Purpose
show {ip | ipv6} route [route-type |
interface int-type number | next-hop]
Displays the unicast route table. The route-type argument
can be a single route prefix, direct, static, or a dynamic
route protocol. Use the ? command to see the supported
interfaces.
Example:
switch# show ip route
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Command
Purpose
show {ip | ipv6} adjacency [prefix |
interface-type number [summary]|
non-best] [detail] [vrf vrf-id]
Displays the adjacency table. The argument ranges are as
follows:
Example:
switch# show ip adjacency
show {ip | ipv6} routing [route-type
| interface int-type number |
next-hop | recursive-next-hop |
summary | updated {since | until}
time]
•
prefix—Any IPv4 or IPv6 prefix address.
•
interface-type number—Use the ? command to see
the supported interfaces.
•
vrf-id—Any case-sensitive, alphanumeric string up
to 64 characters.
Displays the unicast route table. The route-type argument
can be a single route prefix, direct, static, or a dynamic
route protocol. Use the ? command to see the supported
interfaces.
Example:
switch# show routing summary
This example shows how to display the unicast route table:
switch# show ip route
IP Route Table for Context "default"
'*' denotes best ucast next-hop
'[x/y]' denotes [preference/metric]
'**' denotes best mcast next-hop
0.0.0.0/0, 1 ucast next-hops, 0 mcast next-hops
*via 10.1.1.1, mgmt0, [1/0], 5d21h, static
0.0.0.0/32, 1 ucast next-hops, 0 mcast next-hops
*via Null0, [220/0], 1w6d, local, discard
10.1.0.0/22, 1 ucast next-hops, 0 mcast next-hops, attached
*via 10.1.1.55, mgmt0, [0/0], 5d21h, direct
10.1.0.0/32, 1 ucast next-hops, 0 mcast next-hops, attached
*via 10.1.0.0, Null0, [0/0], 5d21h, local
10.1.1.1/32, 1 ucast next-hops, 0 mcast next-hops, attached
*via 10.1.1.1, mgmt0, [2/0], 5d16h, am
10.1.1.55/32, 1 ucast next-hops, 0 mcast next-hops, attached
*via 10.1.1.55, mgmt0, [0/0], 5d21h, local
10.1.1.253/32, 1 ucast next-hops, 0 mcast next-hops, attached
*via 10.1.1.253, mgmt0, [2/0], 5d20h, am
10.1.3.255/32, 1 ucast next-hops, 0 mcast next-hops, attached
*via 10.1.3.255, mgmt0, [0/0], 5d21h, local
255.255.255.255/32, 1 ucast next-hops, 0 mcast next-hops
*via Eth Inband Port, [0/0], 1w6d, local
This example shows how to display the adjacency information:
switch# show ip adjacency
IP Adjacency Table for context default
Total number of entries: 2
Address
Age
MAC Address
10.1.1.1
02:20:54 00e0.b06a.71eb
10.1.1.253
00:06:27 0014.5e0b.81d1
Pref Source
50
arp
50
arp
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Interface
mgmt0
mgmt0
Best
Yes
Yes
Chapter 14
Managing the Unicast RIB and FIB
Managing the Unicast RIB and FIB
Triggering the Layer 3 Consistency Checker
You can manually trigger the Layer 3 consistency checker.
To manually trigger the Layer 3 consistency checker, use the following commands in global
configuration mode:
Command
Purpose
test forwarding [ipv4 | ipv6]
[unicast] inconsistency [vrf
vrf-name] [module {slot| all}]
Starts a Layer 3 consistency check. The vrf-name can be
any case-sensitive, alphanumeric string up to 64
characters. The slot range is from 1 to 26.
Example:
switch(config)# test forwarding
inconsistency
To stop the Layer 3 consistency checker, use the following commands in global configuration mode:
Command
Purpose
test forwarding [ipv4 | ipv6]
[unicast] inconsistency [vrf
vrf-name] [module {slot| all}] stop
Stops a Layer 3 consistency check. The vrf-name can be
any case-sensitive, alphanumeric string up to 64
characters. The slot range is from 1 to 26.
Example:
switch# test forwarding inconsistency
stop
To display the Layer 3 inconsistencies, use the following commands in any mode:
Command
Purpose
show forwarding [ipv4 | ipv6]
inconsistency [vrf vrf-name] [module
{slot| all}]
Displays the results of a Layer 3 consistency check. The
vrf-name can be any case-sensitive, alphanumeric string
up to 64 characters. The slot range is from 1 to 26.
Example:
switch# show forwarding inconsistency
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Clearing Forwarding Information in the FIB
You can clear one or more entries in the FIB. Clearing a FIB entry does not affect the unicast RIB.
Caution
The clear forwarding command disrupts forwarding on the device.
To clear an entry in the FIB, including a Layer 3 inconsistency, use the following command in any mode:
Command
Purpose
clear forwarding {ipv4 | ipv6} route
{* | prefix} [vrf vrf-name] module
{slot| all}
Clears one or more entries from the FIB. The route
options are as follows:
Example:
switch# clear forwarding ipv4 route *
module 1
•
*—All routes.
•
prefix—Any IP or IPv6 prefix.
The vrf-name can be any case-sensitive, alphanumeric
string up to 64 characters. The slot range is from 1 to 26.
Configuring Maximum Routes for the Unicast RIB
You can configure the maximum number of routes allowed in the routing table.
SUMMARY STEPS
1.
configure terminal
2.
vrf context vrf-name
3.
ipv4 unicast
4.
maximum routes max-routes [threshold [reinstall threshold] | warning-only]
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
vrf context vrf-name
Creates a VRF and enters VRF configuration mode.
Example:
switch(config)# vrf context Red
switch(config-vrf)#
Step 3
ipv4 unicast
Enters address-family configuration mode.
Example:
switch(config-vrf)# ipv4 unicast
switch(config-vrf-af-ipv4)#
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Step 4
Step 5
Command
Purpose
maximum routes max-routes [threshold
[reinstall threshold] | warning-only]
Configures the maximum number of routes allowed in
the routing table. The range is from 1 to 4294967295.
Example:
switch(config-vrf-af-ipv4)# maximum
routes 250 90
You can optionally specify the following:
•
threshold—Percentage of maximum routes that
triggers a warning message. The range is from 1 to
100.
•
warning-only—Logs a warning message when
the maximum number of routes is exceeded.
•
reinstall threshold—Reinstalls routes that
previously exceeded the maximum route limit and
were rejected and specifies the threshold value at
which to reinstall them. The threshold range is
from 1 to 100.
(Optional) Saves this configuration change.
copy running-config startup-config
Example:
switch(config-vrf-af-ipv4)# copy
running-config startup-config
Estimating Memory Requirements for Routes
You can estimate the memory that a number of routes and next-hop addresses will use.
To estimate the memory requirements for routes, use the following command in any mode:
Command
Purpose
show routing {ipv6} memory estimate
routes num-routes next-hops
num-nexthops
Displays the memory requirements for routes. The
num-routes range is from 1000 to 1000000. The
num-nexthops range is from 1 to 16.
Example:
switch# show routing memory estimate
routes 5000 next-hops 2
Clearing Routes in the Unicast RIB
You can clear one or more routes from the unicast RIB.
Caution
The * keyword is severely disruptive to routing.
To clear one or more entries in the unicast RIB, use the following commands in any mode:
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Verifying the Unicast RIB and FIB
Command
Purpose
clear {ip | ipv4 | ipv6} route {* |
{route | prefix/length}[next-hop
interface]} [vrf vrf-name]
Clears one or more routes from both the unicast RIB and
all the module FIBs. The route options are as follows:
Example:
switch(config)# clear ip route
10.2.2.2
•
*—All routes.
•
route—An individual IP or IPv6 route.
•
prefix/length—Any IP or IPv6 prefix.
•
next-hop—The next-hop address
•
interface—The interface to reach the next-hop
address.
The vrf-name can be any case-sensitive, alphanumeric
string up to 64 characters.
clear routing [multicast | unicast]
[ip | ipv4 | ipv6] {* | {route |
prefix/length}[next-hop interface]}
[vrf vrf-name]
Example:
switch(config)# clear routing ip
10.2.2.2
Clears one or more routes from the unicast RIB. The
route options are as follows:
•
*—All routes.
•
route—An individual IP or IPv6 route.
•
prefix/length—Any IP or IPv6 prefix.
•
next-hop—The next-hop address
•
interface—The interface to reach the next-hop
address.
The vrf-name can be any case-sensitive, alphanumeric
string up to 64 characters.
Verifying the Unicast RIB and FIB
To display the unicast RIB and FIB information, perform one the following tasks:
Command
Purpose
show forwarding adjacency
Displays the adjacency table on a module.
show forwarding distribution {clients |
fib-state}
Displays the FIB distribution information.
show forwarding interfaces module slot
Displays the FIB information for a module.
show forwarding {ip | ipv4 | ipv6} route
Displays routes in the FIB.
show {ip | ipv6} adjacency
Displays the adjacency table.
show {ip | ipv6} route
Displays IPv4 or IPv6 routes from the unicast RIB.
show routing
Displays routes from the unicast RIB.
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Additional References
Additional References
For additional information related to managing unicast RIB and FIB, see the following sections:
•
Related Documents, page 14-11
Related Documents
Related Topic
Document Title
Configuring EEM
Cisco Nexus 9000 Series NX-OS System Management Configuration
Guide
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Additional References
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Managing the Unicast RIB and FIB
CH A P T E R
15
Configuring Route Policy Manager
This chapter describes how to configure the Route Policy Manager on the Cisco NX-OS device.
This chapter includes the following sections:
•
About Route Policy Manager, page 15-1
•
Licensing Requirements for Route Policy Manager, page 15-5
•
Guidelines and Limitations, page 15-5
•
Default Settings, page 15-5
•
Configuring Route Policy Manager, page 15-6
•
Verifying the Route Policy Manager Configuration, page 15-18
•
Configuration Examples for Route Policy Manager, page 15-18
•
Related Topics, page 15-18
About Route Policy Manager
Route Policy Manager supports route maps and IP prefix lists. These features are used for route
redistribution. A prefix list contains one or more IPv4 or IPv6 network prefixes and the associated prefix
length values. You can use a prefix list by itself in features such as Border Gateway Protocol (BGP)
templates, route filtering, or redistribution of routes that are exchanged between routing domains.
Route maps can apply to both routes and IP packets. Route filtering and redistribution pass a route
through a route map.
This section includes the following topics:
•
Prefix Lists, page 15-1
•
Route Maps, page 15-2
•
Route Redistribution and Route Maps, page 15-4
Prefix Lists
You can use prefix lists to permit or deny an address or range of addresses. Filtering by a prefix list
involves matching the prefixes of routes or packets with the prefixes listed in the prefix list. An implicit
deny is assumed if a given prefix does not match any entries in a prefix list.
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About Route Policy Manager
You can configure multiple entries in a prefix list and permit or deny the prefixes that match the entry.
Each entry has an associated sequence number that you can configure. If you do not configure a sequence
number, Cisco NX-OS assigns a sequence number automatically. Cisco NX-OS evaluates prefix lists
starting with the lowest sequence number. Cisco NX-OS processes the first successful match for a given
prefix. Once a match occurs, Cisco NX-OS processes the permit or deny statement and does not evaluate
the rest of the prefix list.
Note
An empty prefix list permits all routes.
Route Maps
You can use route maps for route redistribution. Route map entries consist of a list of match and set
criteria. The match criteria specify match conditions for incoming routes or packets, and the set criteria
specify the action taken if the match criteria are met.
You can configure multiple entries in the same route map. These entries contain the same route map
name and are differentiated by a sequence number.
You create a route map with one or more route map entries arranged by the sequence number under a
unique route map name. The route map entry has the following parameters:
•
Sequence number
•
Permission—permit or deny
•
Match criteria
•
Set changes
By default, a route map processes routes or IP packets in a linear fashion, that is, starting from the lowest
sequence number. You can configure the route map to process in a different order using the continue
statement, which allows you to determine which route map entry to process next.
Match Criteria
You can use a variety of criteria to match a route or IP packet in a route map. Some criteria, such as BGP
community lists, are applicable only to a specific routing protocol, while other criteria, such as the IP
source or the destination address, can be used for any route or IP packet.
When Cisco NX-OS processes a route or packet through a route map, it compares the route or packet to
each of the match statements configured. If the route or packet matches the configured criteria, Cisco
NX-OS processes it based on the permit or deny configuration for that match entry in the route map and
any set criteria configured.
The match categories and parameters are as follows:
•
BGP parameters—Match based on AS numbers, AS-path, community attributes, or extended
community attributes.
•
Prefix lists—Match based on an address or range of addresses.
•
Multicast parameters—Match based on a rendezvous point, groups, or sources.
•
Other parameters—Match based on an IP next-hop address or packet length.
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About Route Policy Manager
Set Changes
Once a route or packet matches an entry in a route map, the route or packet can be changed based on one
or more configured set statements.
The set changes are as follows:
•
BGP parameters—Change the AS-path, tag, community, extended community, dampening, local
preference, origin, or weight attributes.
•
Metrics—Change the route-metric, the route-tag, or the route-type.
•
Other parameters—Change the forwarding address or the IP next-hop address.
Access Lists
IP access lists can match the packet to a number of IP packet fields such as the following:
•
Source or destination IPv4 or IPv6 address
•
Protocol
•
Precedence
•
ToS
AS Numbers for BGP
You can configure a list of AS numbers to match against BGP peers. If a BGP peer matches an AS
number in the list and matches the other BGP peer configuration, BGP creates a session. If the BGP peer
does not match an AS number in the list, BGP ignores the peer. You can configure the AS numbers as a
list, a range of AS numbers, or you can use an AS-path list to compare the AS numbers against a regular
expression.
AS-Path Lists for BGP
You can configure an AS-path list to filter inbound or outbound BGP route updates. If the route update
contains an AS-path attribute that matches an entry in the AS-path list, the router processes the route
based on the permit or deny condition configured. You can configure AS-path lists within a route map.
You can configure multiple AS-path entries in an AS-path list by using the same AS-path list name. The
router processes the first entry that matches.
Community Lists for BGP
You can filter BGP route updates based on the BGP community attribute by using community lists in a
route map. You can match the community attribute based on a community list, and you can set the
community attribute using a route map.
A community list contains one or more community attributes. If you configure more than one community
attribute in the same community list entry, the BGP route must match all community attributes listed to
be considered a match.
You can also configure multiple community attributes as individual entries in the community list by
using the same community list name. In this case, the router processes the first community attribute that
matches the BGP route, using the permit or deny configuration for that entry.
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You can configure community attributes in the community list in one of the following formats:
•
A named community attribute, such as internet or no-export.
•
In aa:nn format, where the first two bytes represent the two-byte AS number and the last two bytes
represent a user-defined network number.
•
A regular expression.
Extended Community Lists for BGP
Extended community lists support 4-byte AS numbers. You can configure community attributes in the
extended community list in one of the following formats:
•
In aa4:nn format, where the first four bytes represent the four-byte AS number and the last two bytes
represent a a user-defined network number.
•
A regular expression.
Cisco NX-OS supports generic specific extended community lists, which provide similar functionality
to regular community lists for four-byte AS numbers. You can configure generic specific extended
community lists with the following properties:
•
Transitive—BGP propagates the community attributes across autonomous systems.
•
Nontransitive—BGP removes community attributes before propagating the route to another
autonomous system.
Route Redistribution and Route Maps
You can use route maps to control the redistribution of routes between routing domains. Route maps
match on the attributes of the routes to redistribute only those routes that pass the match criteria. The
route map can also modify the route attributes during this redistribution using the set changes.
The router matches redistributed routes against each route map entry. If there are multiple match
statements, the route must pass all of the match criteria. If a route passes the match criteria defined in a
route map entry, the actions defined in the entry are executed. If the route does not match the criteria,
the router compares the route against subsequent route map entries. Route processing continues until a
match is made or the route is processed by all entries in the route map with no match. If the router
processes the route against all entries in a route map with no match, the router accepts the route (inbound
route maps) or forwards the route (outbound route maps).
Note
When you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you must
insert an additional deny statement into the route map.
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Licensing Requirements for Route Policy Manager
Licensing Requirements for Route Policy Manager
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
Route Policy Manager requires no license. Any feature not included in a license package is bundled with
the nx-os image and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS
licensing scheme, see the Cisco NX-OS Licensing Guide.
Guidelines and Limitations
Route Policy Manager has the following configuration guidelines and limitations:
•
An empty route map denies all the routes.
•
An empty prefix list permits all the routes.
•
Without any match statement in a route-map entry, the permission (permit or deny) of the route-map
entry decides the result for all the routes or packets.
•
If referred policies (for example, prefix lists) within a match statement of a route-map entry return
either a no-match or a deny-match, Cisco NX-OS fails the match statement and processes the next
route-map entry.
•
When you change a route map, Cisco NX-OS holds all the changes until you exit from the route-map
configuration submode. Cisco NX-OS then sends all the changes to the protocol clients to take
effect.
•
Cisco recommends that you do not have both IPv4 and IPv6 match statements in the same route-map
sequence. If both are required, they should be specified in different sequences in the same
route-map.
•
Because you can use a route map before you define it, verify that all your route maps exist when you
finish a configuration change.
•
You can view the route-map usage for redistribution and filtering. Each individual routing protocol
provides a way to display these statistics.
•
When you redistribute BGP to IGP, iBGP is redistributed as well. To override this behavior, you
must insert an additional deny statement into the route map.
•
Route Policy Manager does not support MAC lists.
Default Settings
Table 15-1 lists the default settings for Route Policy Manager.
Table 15-1
Default Route Policy Manager Parameters
Parameters
Default
Route Policy Manager
Enabled
Administrative distance
115
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Configuring Route Policy Manager
This section includes the following topics:
Note
•
Configuring IP Prefix Lists, page 15-6
•
Configuring AS-Path Lists, page 15-8
•
Configuring Community Lists, page 15-9
•
Configuring Extended Community Lists, page 15-10
•
Configuring Route Maps, page 15-11
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring IP Prefix Lists
IP prefix lists match the IP packet or route against a list of prefixes and prefix lengths. You can create
an IP prefix list for IPv4 and create an IPv6 prefix list for IPv6.
You can configure the prefix list entry to match the prefix length exactly or to match any prefix with a
length that matches the configured range of prefix lengths.
Use the ge and lt keywords to create a range of possible prefix lengths. The incoming packet or route
matches the prefix list if the prefix matches and if the prefix length is greater than or equal to the ge
keyword value (if configured) and less than or equal to the lt keyword value (if configured).
SUMMARY STEPS
1.
configure terminal
2.
{ip | ipv6} prefix-list name description string
3.
ip prefix-list name [seq number] [{permit | deny} prefix {[eq prefix-length] | [ge prefix-length] [le
prefix-length]}]
or
ipv6 prefix-list name [seq number] [{permit | deny} prefix {[eq prefix-length] | [ge prefix-length]
[le prefix-length]}]
4.
(Optional) show {ip | ipv6} prefix-list name
5.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
{ip | ipv6} prefix-list name description
string
(Optional) Adds an information string about the prefix
list.
Example:
switch(config)# ip prefix-list
AllowPrefix description allows
engineering server
Step 3
ip prefix-list name [seq number]
[{permit | deny} prefix {[eq
prefix-length] | [ge prefix-length] [le
prefix-length]}]
Example:
switch(config)# ip prefix-list
AllowPrefix seq 10 permit 192.0.2.0/24
eq 24
ipv6 prefix-list name [seq number]
[{permit | deny} prefix {[eq
prefix-length] | [ge prefix-length] [le
prefix-length]}]
Example:
switch(config)# ipv6 prefix-list
AllowIPv6Prefix seq 10 permit
2001:0DB8:: le 32
Step 4
show {ip | ipv6} prefix-list name
Creates an IPv4 prefix list or adds a prefix to an
existing prefix list. The prefix length is matched as
follows:
•
eq—Matches the exact prefix length.
•
ge—Matches a prefix length that is equal to or
greater than the configured prefix length.
•
le—Matches a prefix length that is equal to or less
than the configured prefix length.
Creates an IPv6 prefix list or adds a prefix to an
existing prefix list. The prefix length is configured as
follows:
•
eq—Matches the exact prefix length.
•
ge—Matches a prefix length that is equal to or
greater than the configured prefix length.
•
le—Matches a prefix length that is equal to or less
than the configured prefix length.
(Optional) Displays information about prefix lists.
Example:
switch(config)# show ip prefix-list
AllowPrefix
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch# copy running-config
startup-config
This example shows how to create an IPv4 prefix list with two entries and apply the prefix list to a BGP
neighbor:
switch# configure terminal
switch(config)# ip prefix-list allowprefix seq 10 permit 192.0.2.0/24 eq 24
switch(config)# ip prefix-list allowprefix seq 20 permit 209.165.201.0/27 eq 27
switch(config)# router bgp 65535
switch(config-router)# neighbor 192.0.2.1/16 remote-as 65534
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# prefix-list allowprefix in
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Configuring AS-Path Lists
You can specify an AS-path list filter on both inbound and outbound BGP routes. Each filter is an access
list based on regular expressions. If the regular expression matches the representation of the AS-path
attribute of the route as an ASCII string, the permit or deny condition applies.
SUMMARY STEPS
1.
configure terminal
2.
ip as-path access-list name {deny | permit} expression
3.
(Optional) show {ip | ipv6} as-path list name
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
ip as-path access-list name {deny |
permit} expression
Creates a BGP AS-path list using a regular expression.
Example:
switch(config)# ip as-path access-list
Allow40 permit 40
Step 3
show {ip | ipv6} as-path-access-list
name
(Optional) Displays information about as-path access
lists.
Example:
switch(config)# show ip
as-path-access-list Allow40
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch# copy running-config
startup-config
This example shows how to create an AS-path list with two entries and apply the AS path list to a BGP
neighbor:
switch# configure terminal
switch(config)# ip as-path access-list AllowAS permit 64510
switch(config)# ip as-path access-list AllowAS permit 64496
switch(config)# copy running-config startup-config
switch(config)# router bgp 65535:20
switch(config-router)# neighbor 192.0.2.1/16 remote-as 65535:20
switch(config-router-neighbor)# address-family ipv4 unicast
switch(config-router-neighbor-af)# filter-list AllowAS in
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Configuring Community Lists
You can use community lists to filter BGP routes based on the community attribute. The community
number consists of a 4-byte value in the aa:nn format. The first two bytes represent the autonomous
system number, and the last two bytes represent a user-defined network number.
When you configure multiple values in the same community list statement, all community values must
match to satisfy the community list filter. When you configure multiple values in separate community
list statements, the first list that matches a condition is processed.
Use community lists in a match statement to filter BGP routes based on the community attribute.
SUMMARY STEPS
1.
configure terminal
2.
ip community-list standard list-name {deny | permit} [community-list] [internet] [local-AS]
[no-advertise] [no-export]
or
ip community-list expanded list-name {deny | permit} expression
3.
(Optional) show ip community-list name
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
ip community-list standard list-name
{deny | permit} [community-list]
[internet] [local-AS] [no-advertise]
[no-export]
Creates a standard BGP community list. The list-name
can be any case-sensitive, alphanumeric string up to 63
characters. The community-list can be one or more
communities in the aa:nn format.
Example:
switch(config)# ip community-list
standard BGPCommunity permit
no-advertise 65535:20
ip community-list expanded list-name
{deny | permit} expression
Creates an expanded BGP community list using a
regular expression.
Example:
switch(config)# ip community-list
expanded BGPComplex deny
50000:[0-9][0-9]_
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Step 3
Command
Purpose
show ip community-list name
(Optional) Displays information about community
lists.
Example:
switch(config)# show ip community-list
BGPCommunity
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch# copy running-config
startup-config
This example shows how to create a community list with two entries:
switch# configure terminal
switch(config)# ip community-list standard BGPCommunity permit no-advertise 65535:20
switch(config)# ip community-list standard BGPCommunity permit local-AS no-export
switch(config)# copy running-config startup-config
Configuring Extended Community Lists
You can use extended community lists to filter BGP routes based on the community attribute. The
community number consists of a 6-byte value in the aa4:nn format. The first four bytes represent the
autonomous system number, and the last two bytes represent a user-defined network number.
When you configure multiple values in the same extended community list statement, all extended
community values must match to satisfy the extended community list filter. When you configure multiple
values in separate extended community list statements, the first list that matches a condition is processed.
Use extended community lists in a match statement to filter BGP routes based on the extended
community attribute.
SUMMARY STEPS
1.
configure terminal
2.
ip extcommunity-list standard list-name {deny | permit} 4bytegeneric {transitive |
non-transitive} aa4:nn
or
ip extcommunity-list expanded list-name {deny | permit} expression
3.
(Optional) show ip extcommunity-list name
4.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
ip extcommunity-list standard list-name
{deny | permit} 4bytegeneric {transitive
| nontransitive} community1
[community2...]
Creates a standard BGP extended community list. The
community can be one or more extended communities
in the aa4:nn format.
Example:
switch(config)# ip extcommunity-list
standard BGPExtCommunity permit
4bytegeneric transitive 65535:20
ip extcommunity-list expanded list-name
{deny | permit} expression
Creates an expanded BGP extended community list
using a regular expression.
Example:
switch(config)# ip extcommunity-list
expanded BGPExtComplex deny
1.5:[0-9][0-9]_
Step 3
show ip community-list name
Example:
switch(config)# show ip community-list
BGPCommunity
Step 4
copy running-config startup-config
(Optional) Displays information about extended
community lists.
(Optional) Saves this configuration change.
Example:
switch# copy running-config
startup-config
This example shows how to create a generic specific extended community list:
switch# configure terminal
switch(config)# ip extcommunity-list standard test1 permit 4bytegeneric transitive
65535:40 65535:60
switch(config)# copy running-config startup-config
Configuring Route Maps
You can use route maps for route redistribution or route filtering. Route maps can contain multiple match
criteria and multiple set criteria.
Configuring a route map for BGP triggers an automatic soft clear or refresh of BGP neighbor sessions.
SUMMARY STEPS
1.
configure terminal
2.
route-map map-name [permit | deny] [seq]
3.
(Optional) continue seq
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4.
(Optional) exit
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
route-map map-name [permit | deny] [seq]
Example:
switch(config)# route-map Testmap permit
10
switch(config-route-map)#
Step 3
Step 4
Creates a route map or enters route-map configuration
mode for an existing route map. Use seq to order the
entries in a route map.
Example:
switch(config-route-map)# continue 10
(Optional) Determines what sequence statement to
process next in the route map. Used only for filtering
and redistribution.
exit
(Optional) Exits route-map configuration mode.
continue seq
Example:
switch(config-route-map)# exit
Step 5
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
You can configure the following optional match parameters for route maps in route-map configuration
mode:
Note
The default-information originate command ignores match statements in the optional route
map.
Command
Purpose
match as-path name [name...]
Matches against one or more AS-path lists. Create
the AS-path list with the ip as-path access-list
command.
Example:
switch(config-route-map)# match as-path
Allow40
match as-number {number [,number...] |
as-path-list name [name...]}
Example:
switch(config-route-map)# match as-number
33,50-60
Matches against one or more AS numbers or
AS-path lists. Create the AS-path list with the ip
as-path access-list command. The number range is
from 1 to 65535. The AS-path list name can be any
case-sensitive, alphanumeric string up to 63
characters.
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Command
Purpose
match community name
[name...][exact-match]
Matches against one or more community lists.
Create the community list with the ip
community-list command.
Example:
switch(config-route-map)# match community
BGPCommunity
match extcommunity name
[name...][exact-match]
Example:
switch(config-route-map)# match
extcommunity BGPextCommunity
match interface interface-type number
[interface-type number...
Example:
switch(config-route-map)# match interface
e 1/2
match ip address prefix-list name
[name...]
Matches against one or more extended community
lists. Create the community list with the ip
extcommunity-list command.
Matches any routes that have their next hop out one
of the configured interfaces. Use ? to find a list of
supported interface types.
Matches against one or more IPv4 prefix lists. Use
the ip prefix-list command to create the prefix list.
Example:
switch(config-route-map)# match ip address
prefix-list AllowPrefix
match ipv6 address prefix-list name
[name...]
Example:
switch(config-route-map)# match ip address
prefix-list AllowIPv6Prefix
match ip multicast [source ipsource]
[[group ipgroup] [rp iprp]]
Matches against one or more IPv6 prefix lists. Use
the ipv6 prefix-list command to create the prefix
list.
Matches an IPv4 multicast packet based on the
multicast source, group, or rendezvous point.
Example:
switch(config-route-map)# match ip
multicast rp 192.0.2.1
match ipv6 multicast [source ipsource]
[[group ipgroup] [rp iprp]]
Matches an IPv6 multicast packet based on the
multicast source, group, or rendezvous point.
Example:
switch(config-route-map)# match ip
multicast source 2001:0DB8::1
match ip next-hop prefix-list name
[name...]
Example:
switch(config-route-map)# match ip
next-hop prefix-list AllowPrefix
match ipv6 next-hop prefix-list name
[name...]
Example:
switch(config-route-map)# match ipv6
next-hop prefix-list AllowIPv6Prefix
Matches the IPv4 next-hop address of a route to one
or more IP prefix lists. Use the ip prefix-list
command to create the prefix list.
Matches the IPv6 next-hop address of a route to one
or more IP prefix lists. Use the ipv6 prefix-list
command to create the prefix list.
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Command
Purpose
match ip route-source prefix-list name
[name...]
Matches the IPv4 route source address of a route to
one or more IP prefix lists. Use the ip prefix-list
command to create the prefix list.
Example:
switch(config-route-map)# match ip
route-source prefix-list AllowPrefix
match ipv6 route-source prefix-list name
[name...]
Example:
switch(config-route-map)# match ipv6
route-source prefix-list AllowIPv6Prefix
match metric value [+- deviation.]
[value..]
Example:
switch(config-route-map)# match metric 50
+ 10
Matches the IPv6 route-source address of a route to
one or more IP prefix lists. Use the ipv6 prefix-list
command to create the prefix list.
Matches the route metric against one or more
metric values or value ranges. Use +- deviation
argument to set a metric range. The route map
matches any route metric that falls within the
range:
value - deviation to value + deviation.
match route-type route-type
Example:
switch(config-route-map)# match route-type
level 1 level 2
match tag tagid [tagid...]
Example:
switch(config-route-map)# match tag 2
match vlan vlan-id [vlan-range]
Matches against a type of route. The route-type can
be one or more of the following:
•
external—The external route (BGP, EIGRP,
and OSPF type 1 or 2)
•
inter-area—The OSPF inter-area route
•
internal—The internal route (including the
OSPF intra- or inter-area)
•
intra-area—The OSPF intra-area route
•
level-1—The IS-IS level 1 route
•
level-2—The IS-IS level 2 route
•
local—The locally generated route
•
nssa-external—The NSSA external route
(OSPF type 1 or 2).
•
type-1—The OSPF external type 1 route
•
type-2—The OSPF external type 2 route
Matches a route against one or more tags for
filtering or redistribution.
Matches against a VLAN.
Example:
switch(config-route-map)# match vlan 3,
5-10
You can configure the following optional set parameters for route maps in route-map configuration
mode:
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Command
Purpose
set as-path {tag | prepend {last-as number
| as-1 [as-2...]}}
Modifies an AS-path attribute for a BGP route. You
can prepend the configured number of last AS
numbers or a string of particular AS-path values
(as-1 as-2...as-n).
Example:
switch(config-route-map)# set as-path
prepend 10 100 110
set comm-list name delete
Example:
switch(config-route-map)# set comm-list
BGPCommunity delete
set community {none | additive | local-AS
| no-advertise | no-export | community-1
[community-2...]}
Removes communities from the community
attribute of an inbound or outbound BGP route
update. Use the ip community-list command to
create the community list.
Sets the community attribute for a BGP route
update.
Note
When you use both the set community and
set comm-list delete commands in the
same sequence of a route map attribute, the
deletion operation is performed before the
set operation.
Note
Use the send-community command in
BGP neighbor address-family
configuration mode to propagate BGP
community attributes to BGP peers.
Example:
switch(config-route-map)# set community
local-AS
set dampening halflife reuse suppress
duration
Example:
switch(config-route-map)# set dampening 30
1500 10000 120
set distance value
Example:
switch(config-route-map)# set distance 150
set extcomm-list name delete
Example:
switch(config-route-map)# set extcomm-list
BGPextCommunity delete
Sets the following BGP route dampening
parameters:
•
halflife—The range is from 1 to 45 minutes.
The default is 15.
•
reuse—The range is from is 1 to 20000
seconds. The default is 750.
•
suppress—The range is from is 1 to 20000. The
default is 2000.
•
duration—The range is from is 1 to 255
minutes. The default is 60.
Sets the administrative distance of routes for
OSPFv2 or OSPFv3. The range is from 1 to 255.
Removes communities from the extended
community attribute of an inbound or outbound
BGP route update. Use the ip extcommunity-list
command to create the extended community list.
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Configuring Route Policy Manager
Command
Purpose
set extcommunity 4byteas-generic
{transitive | nontransitive} {none |
additive] community-1 [community-2...]}
Sets the extended community attribute for a BGP
route update.
Note
When you use both the set extcommunity
and set extcomm-list delete commands in
the same sequence of a route map attribute,
the deletion operation is performed before
the set operation.
Note
Use the send-community command in
BGP neighbor address-family
configuration mode to propagate BGP
extended community attributes to BGP
peers.
Example:
switch(config-route-map)# set extcommunity
generic transitive 1.0:30
set extcommunity cost community-id1 cost
[igp | pre-bestpath] [community-id2...]}
Example:
switch(config-route-map)# set extcommunity
cost 33 1.0:30
Sets the cost community attribute for a BGP route
update. This attribute allows you to customize the
BGP best-path selection process for a local
autonomous system or confederation. The
community-id range is from 0 to 255. The cost range
is from 0 to 4294967295. The path with the lowest
cost is preferred. For paths with equal cost, the path
with the lowest community ID is preferred.
The igp keyword compares the cost after the IGP
cost comparison. The pre-bestpath keyword
compares before all other steps in the bestpath
algorithm.
Example:
switch(config-route-map)# set extcommunity
rt 1.0:30
Sets the extended community route target attribute
for a BGP route update. The community value can
be a 2-byte AS number:4-byte network number, a
4-byte AS number:2-byte network number, or an
IP address:2-byte network number.
Use the additive keyword to add a route target to an
existing extended community route target attribute.
set forwarding-address
Sets the forwarding address for OSPF.
set extcommunity rt community-1 [additive]
[community-2...]}
Example:
switch(config-route-map)# set
forwarding-address
set ip next-hop unchanged
Example:
switch(config-route-map)# set ip next-hop
unchanged
set level {backbone | level-1 | level-1-2
| level-2}
Example:
switch(config-route-map)# set level
backbone
Specifies an unchanged next-hop IP address. This
command is required for BGP IPv6-over-IPv4
peering.
Sets what area to import routes to for IS-IS. The
options for IS-IS are level-1, level-1-2, or level-2.
The default is level-1.
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Command
Purpose
set local-preference value
Sets the BGP local preference value. The range is
from 0 to 4294967295.
Example:
switch(config-route-map)# set
local-preference 4000
set metric [+ | -]bandwidth-metric
Example:
switch(config-route-map)# set metric +100
set metric bandwidth [delay reliability
load mtu]
Adds or subtracts from the existing metric value.
The metric is in Kb/s. The range is from 0 to
4294967295.
Sets the route metric values.
Metrics are as follows:
Example:
switch(config-route-map)# set metric 33 44
100 200 1500
•
metric0—Bandwidth in Kb/s. The range is
from 0 to 4294967295.
•
metric1—Delay in 10-microsecond units.
•
metric2—Reliability. The range is from 0 to
255 (100 percent reliable).
•
metric3—Loading. The range is from 1 to 255
(100 percent loaded).
•
metric4—MTU of the path. The range is from
1 to 16777215.
set metric-type {external | internal |
type-1 | type-2}
Sets the metric type for the destination routing
protocol. The options are as follows:
Example:
switch(config-route-map)# set metric-type
internal
external—IS-IS external metric
internal— IGP metric as the MED for BGP
type-1—OSPF external type 1 metric
type-2—OSPF external type 2 metric
set nssa-only
Example:
switch(config-route-map)# set nssa-only
set origin {egp as-number | igp |
incomplete}
Sets Type-7 LSA generated on ASBR with no P bit
set. This prevents Type-7 to Type-5 LSA
translation in OSPF.
Sets the BGP origin attribute. The EGP as-number
range is from 0 to 65535.
Example:
switch(config-route-map)# set origin
incomplete
set tag name
Example:
switch(config-route-map)# set tag 33
set weight count
Example:
switch(config-route-map)# set weight 33
Sets the tag value for the destination routing
protocol. The name parameter is an unsigned
integer.
Sets the weight for the BGP route. The range is
from 0 to 65535.
The set metric-type internal command affects an outgoing policy and an eBGP neighbor only. If you
configure both the metric and metric-type internal commands in the same BGP peer outgoing policy,
Cisco NX-OS ignores the metric-type internal command.
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Verifying the Route Policy Manager Configuration
Verifying the Route Policy Manager Configuration
To display route policy manager configuration information, perform one of the following tasks:
Command
Purpose
show ip community-list [name]
Displays information about a community list.
show ip extcommunity-list [name]
Displays information about an extended
community list.
show [ip | ipv6] prefix-list [name]
Displays information about an IPv4 or IPv6 prefix
list.
show route-map [name]
Displays information about a route map.
Configuration Examples for Route Policy Manager
This example shows how to use an address family to configure Route Policy Manager so that any unicast
and multicast routes from neighbor 209.0.2.1 are accepted if they match prefix-list AllowPrefix:
router bgp 64496
neighbor 172.16.0.1 remote-as 64497
address-family ipv4 unicast
route-map filterBGP in
route-map filterBGP
match ip address prefix-list AllowPrefix
ip prefix-list AllowPrefix 10 permit 192.0.2.0/24
ip prefix-list AllowPrefix 20 permit 172.16.201.0/27
Related Topics
The following topics can give more information on Route Policy Manager:
•
Chapter 9, “Configuring Basic BGP”
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CH A P T E R
16
Configuring Policy-Based Routing
This chapter describes how to configure policy-based routing on the Cisco NX-OS device.
This chapter includes the following sections:
•
About Policy-Based Routing, page 16-1
•
Licensing Requirements for Policy-Based Routing, page 16-4
•
Prerequisites for Policy-Based Routing, page 16-4
•
Guidelines and Limitations, page 16-4
•
Default Settings, page 16-5
•
Configuring Policy-Based Routing, page 16-5
•
Verifying the Policy-Based Routing Configuration, page 16-8
•
Configuration Examples for Policy-Based Routing, page 16-8
•
Related Documents, page 16-9
About Policy-Based Routing
With policy-based routing, you can configure a defined policy for IPv4 and IPv6 traffic flows that lessens
the reliance on routes derived from routing protocols. All packets received on an interface with
policy-based routing enabled are passed through enhanced packet filters or route maps. The route maps
dictate the policy that determines where to forward packets.
Policy-based routing includes the following features:
•
Source-based routing—Routes traffic that originates from different sets of users through different
connections across the policy routers.
•
Quality of Service (QoS)—Differentiates traffic by setting the precedence or type of service (ToS)
values in the IP packet headers at the periphery of the network and leveraging queuing mechanisms
to prioritize traffic in the core or backbone of the network (see the Cisco Nexus 9000 Series NX-OS
Quality of Service Configuration Guide).
•
Load sharing—Distributes traffic among multiple paths based on the traffic characteristics.
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About Policy-Based Routing
Policy Route Maps
Each entry in a route map contains a combination of match and set statements. The match statements
define the criteria for whether appropriate packets meet the particular policy (that is, the conditions to
be met). The set clauses explain how the packets should be routed once they have met the match criteria.
You can mark the route-map statements as permit or deny. You can interpret the statements as follows:
Note
•
If the statement is marked as permit and the packets meet the match criteria, the set clause is applied.
One of these actions involves choosing the next hop.
•
If a statement is marked as deny, the packets that meet the match criteria are sent back through the
normal forwarding channels, and destination-based routing is performed.
•
If the statement is marked as permit and the packets do not match any route-map statements, the
packets are sent back through the normal forwarding channels, and destination-based routing is
performed.
Policy-based routing is specified on the interface that receives the packets, not on the interface from
which the packets are sent.
Set Criteria for Policy-Based Routing
The Cisco Nexus 9000 Series switches support the following set commands for route maps used in
policy-based routing:
•
set {ip | ipv6} next-hop address1 [address2...] [load-share]
•
set interface null0
These set commands are mutually exclusive within the route-map sequence.
In the first command, the IP address specifies the adjacent next-hop router in the path toward the
destination to which the packets should be forwarded. The first IP address associated with a currently up
connected interface is used to route the packets.
Note
You can optionally configure this command for next-hop addresses to load balance traffic for up
to 32 IP addresses. In this case, Cisco NX-OS sends all traffic for each IP flow to a particular IP
next-hop address.
If the packets do not meet any of the defined match criteria, those packets are routed through the normal
destination-based routing process.
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About Policy-Based Routing
Route-Map Processing Logic
When a packet is received on an interface that is configured with a route map, the forwarding logic
processes each route-map statement according to the sequence number.
If the route-map statement encountered is a route-map...permit statement, the packet is matched against
the criteria in the match command. This command may refer to an ACL that has one or more access
control entries (ACEs). If the packet matches the permit ACEs in the ACL, the policy-based routing logic
executes the action specified by the set command on the packet.
If the route-map statement encountered is a route-map... deny statement, the packet is matched against
the criteria in the match command. This command may refer to an ACL that has one or more ACEs. If
the packet matches the permit ACEs in the ACL, policy-based routing processing terminates, and the
packet is routed using the default IP routing table.
Note
The set command has no effect inside a route-map... deny statement.
If the route-map configuration does not contain a match statement, the policy-based routing logic
executes the action specified by the set command on the packet. All packets are routed using
policy-based routing.
If the route-map configuration references a match statement but the match statement references a
non-existing ACL or an existing ACL without any access control entries (ACEs), the packet is routed
using the default routing table.
If the next-hop specified in the set {ip | ipv6} next-hop command is down, is not reachable, or is
removed, the packet is routed using the default routing table.
Policy-Based Routing Filtering Options
You can identify traffic by using additional options. The following list includes most but not all
additional filtering options.
Policy-based routing ACLs support the following additional filtering options:
•
Layer 3 source and/or destination address
•
TCP and UDP ports
•
Precedence level
•
Differentiated Services Code Point (DSCP) value
•
TCP packets with the ACK, FIN, PSH, RST, SYN, or URG bit set
•
Established TCP connections
•
Packet length
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Licensing Requirements for Policy-Based Routing
Licensing Requirements for Policy-Based Routing
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
Policy-based routing requires an Enterprise Services license. Any feature not included in a license package
is bundled with the nx-os image and is provided at no extra charge to you. For a complete explanation of the
Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.
Prerequisites for Policy-Based Routing
Policy-based routing has the following prerequisites:
•
Install the correct license.
•
Enable policy-based routing.
•
Assign an IP address on the interface and bring the interface up before you apply a route map on the
interface for policy-based routing.
Guidelines and Limitations
Policy-based routing has the following configuration guidelines and limitations:
•
A policy-based routing route map can have only one match or set statement per route-map statement.
•
A match command cannot refer to more than one ACL in a route map used for policy-based routing.
•
The same route map can be shared among different interfaces for policy-based routing as long as the
interfaces belong to the same virtual routing and forwarding (VRF) instance.
•
Using a prefix list as a match criteria is not supported. Do not use a prefix list in a policy-based
routing route map.
•
Policy-based routing supports only unicast traffic. Multicast traffic is not supported.
•
Policy-based routing is not supported with inbound traffic on FEX ports.
•
Policy-based routing is not supported with Layer 3 port-channel subinterfaces.
•
An ACL used in a policy-based routing route map cannot include deny access control entries
(ACEs).
•
Policy-based routing is supported only in the default system routing mode.
•
The Cisco Nexus 9000 Series switches do not support the set vrf and set default next-hop
commands.
•
Policy-based routing traffic cannot be balanced if the next hop is recursive over ECMP paths.
Instead, use the set {ip | ipv6} next-hop ip-address load-share command to specify the adjacent
next hops.
•
Beginning with Cisco NX-OS Release 6.1(2)I3(2), the Cisco Nexus 9000 Series switches support
policy-based ACLs (PBACLs), also referred to as object-group ACLs. For more information, see the
Cisco Nexus 9000 Series NX-OS Security Configuration Guide.
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Default Settings
•
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this
feature might differ from the Cisco IOS commands that you would use.
Default Settings
Table 16-1 lists the default settings for policy-based routing.
Table 16-1
Default Policy-Based Routing Parameters
Parameters
Default
Policy-based routing
Disabled
Configuring Policy-Based Routing
This section includes the following topics:
•
Enabling the Policy-Based Routing Feature, page 16-5
•
Configuring a Route Policy, page 16-6
Enabling the Policy-Based Routing Feature
You must enable the policy-based routing feature before you can configure a route policy.
SUMMARY STEPS
1.
configure terminal
2.
[no] feature pbr
3.
(Optional) show feature
4.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
[no] feature pbr
Enables the policy-based routing feature.
Example:
switch(config)# feature pbr
Use the no form of this command to disable the
policy-based routing feature.
Note
Step 3
show feature
The no feature pbr command removes the
policies applied under the interfaces. It does
not remove the ACL or route-map
configuration nor does it create a system
checkpoint.
(Optional) Displays enabled and disabled features.
Example:
switch(config)# show feature
Step 4
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config)# copy running-config
startup-config
Configuring a Route Policy
You can use route maps in policy-based routing to assign routing policies to the inbound interface. Cisco
NX-OS routes the packets as soon as it finds a next hop and an interface.
BEFORE YOU BEGIN
You must configure the IPv6 RACL TCAM region (using TCAM carving) before you apply the
policy-based routing policy for IPv6 traffic. For instructions, see the “Configuring ACL TCAM Region
Sizes” and “Configuring TCAM Carving - For Cisco NX-OS Release 6.1(2)I2(1) and Later Releases”
sections in the Cisco Nexus 9000 Series NX-OS Security Configuration Guide.
Note
The switch has an IPv4 RACL TCAM region by default for IPv4 traffic.
SUMMARY STEPS
1.
configure terminal
2.
interface type slot/port
3.
{ip | ipv6} policy route-map map-name
4.
route-map map-name [permit | deny] [seq]
5.
match {ip | ipv6} address access-list-name name [name...]
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6.
(Optional) set ip next-hop address1 [address2...] [load-share]
7.
(Optional) set ipv6 next-hop address1 [address2...] [load-share]
8.
(Optional) set interface null0
9.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
{ip | ipv6} policy route-map map-name
Example:
switch(config-if)# ip policy route-map
Testmap
Step 4
route-map map-name [permit | deny] [seq]
Example:
switch(config-if)# route-map Testmap
switch(config-route-map)#
Step 5
match {ip | ipv6} address
access-list-name name
[name...]
Example:
switch(config-route-map)# match ip
address access-list-name ACL1
Step 6
set ip next-hop address1 [address2...]
[load-share]
Example:
switch(config-route-map)# set ip
next-hop 192.0.2.1
Step 7
set ipv6 next-hop address1 [address2...]
[load-share]
Example:
switch(config-route-map)# set ipv6
next-hop 2001:0DB8::1
Assigns a route map for IPv4 or IPv6 policy-based
routing to the interface.
Creates a route map or enters route-map configuration
mode for an existing route map. Use seq to order the
entries in a route map.
Matches an IPv4 or IPv6 address against one or more
IP or IPv6 access control lists (ACLs). This command
is used for policy-based routing and is ignored by route
filtering or redistribution.
(Optional) Sets the IPv4 next-hop address for
policy-based routing. This command uses the first
valid next-hop address if multiple addresses are
configured.
Use the optional load-share keyword to load balance
traffic across a maximum of 32 next-hop addresses.
(Optional) Sets the IPv6 next-hop address for
policy-based routing. This command uses the first
valid next-hop address if multiple addresses are
configured.
Use the optional load-share keyword to load balance
traffic across a maximum of 32 next-hop addresses.
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Step 8
Step 9
Command
Purpose
set interface null0
(Optional)
Example:
switch(config-route-map)# set interface
null0
Sets the interface used for routing. Use the null0
interface to drop packets.
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-route-map)# copy
running-config startup-config
Verifying the Policy-Based Routing Configuration
To display the policy-based routing configuration information, perform one of the following tasks:
Command
Purpose
show [ip | ipv6] policy [name]
Displays information about an IPv4 or IPv6
policy.
show route-map [name] pbr-statistics
Displays policy statistics.
Use the route-map map-name pbr-statistics command to enable policy statistics. Use the clear
route-map map-name pbr-statistics command to clear these policy statistics.
Configuration Examples for Policy-Based Routing
This example shows how to configure a simple route policy on an interface:
ip access-list pbr-sample
permit tcp host 10.1.1.1 host 192.168.2.1 eq 80
!
route-map pbr-sample
match ip address pbr-sample
set ip next-hop 192.168.1.1
!
route-map pbr-sample pbr-statistics
interface ethernet 1/2
ip policy route-map pbr-sample
The following output verifies this configuration:
switch# show route-map pbr-sample
route-map pbr-sample, permit, sequence 10
Match clauses:
ip address (access-lists): pbr-sample
Set clauses:
ip next-hop 192.168.1.1
switch# show route-map pbr-sample pbr-statistics
route-map pbr-sample, permit, sequence 10
Policy routing matches: 84 packets
Default routing: 233 packets
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Related Documents
switch# show ip policy
Interface
Route-map Status
Ethernet1/2 pbr-sample Active
VRF-Name
--
Related Documents
Related Topic
Document Title
Troubleshooting information
Cisco Nexus 9000 Series NX-OS Troubleshooting Guide
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CH A P T E R
17
Configuring HSRP
This chapter describes how to configure the Hot Standby Router Protocol (HSRP) on the Cisco NX-OS
device.
This chapter includes the following sections:
•
Information About HSRP, page 17-1
•
Licensing Requirements for HSRP, page 17-8
•
Prerequisites for HSRP, page 17-8
•
Guidelines and Limitations for HSRP, page 17-8
•
Default Settings, page 17-9
•
Configuring HSRP, page 17-9
•
Verifying the HSRP Configuration, page 17-23
•
Configuration Examples for HSRP, page 17-23
•
Additional References, page 17-24
Information About HSRP
HSRP is a first-hop redundancy protocol (FHRP) that allows a transparent failover of the first-hop IP
router. HSRP provides first-hop routing redundancy for IP hosts on Ethernet networks configured with
a default router IP address. You use HSRP in a group of routers for selecting an active router and a
standby router. In a group of routers, the active router is the router that routes packets; the standby router
is the router that takes over when the active router fails or when preset conditions are met.
Many host implementations do not support any dynamic router discovery mechanisms but can be
configured with a default router. Running a dynamic router discovery mechanism on every host is not
practical for many reasons, including administrative overhead, processing overhead, and security issues.
HSRP provides failover services to these hosts.
This section includes the following topics:
•
HSRP Overview, page 17-2
•
HSRP Versions, page 17-3
•
HSRP for IPv4, page 17-4
•
HSRP for IPv6, page 17-4
•
HSRP Authentication, page 17-5
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Information About HSRP
•
HSRP Messages, page 17-5
•
HSRP Load Sharing, page 17-6
•
Object Tracking and HSRP, page 17-6
•
vPC and HSRP, page 17-7
•
BFD, page 17-7
•
High Availability and Extended Nonstop Forwarding, page 17-7
•
Virtualization Support, page 17-8
HSRP Overview
When you use HSRP, you configure the HSRP virtual IP address as the host’s default router (instead of
the IP address of the actual router). The virtual IP address is an IPv4 or IPv6 address that is shared among
a group of routers that run HSRP.
When you configure HSRP on a network segment, you provide a virtual MAC address and a virtual IP
address for the HSRP group. You configure the same virtual address on each HSRP-enabled interface in
the group. You also configure a unique IP address and MAC address on each interface that acts as the
real address. HSRP selects one of these interfaces to be the active router. The active router receives and
routes packets destined for the virtual MAC address of the group.
HSRP detects when the designated active router fails. At that point, a selected standby router assumes
control of the virtual MAC and IP addresses of the HSRP group. HSRP also selects a new standby router
at that time.
HSRP uses a priority designator to determine which HSRP-configured interface becomes the default
active router. To configure an interface as the active router, you assign it with a priority that is higher
than the priority of all the other HSRP-configured interfaces in the group. The default priority is 100, so
if you configure just one interface with a higher priority, that interface becomes the default active router.
Interfaces that run HSRP send and receive multicast User Datagram Protocol (UDP)-based hello
messages to detect a failure and to designate active and standby routers. When the active router fails to
send a hello message within a configurable period of time, the standby router with the highest priority
becomes the active router. The transition of packet forwarding functions between the active and standby
router is completely transparent to all hosts on the network.
You can configure multiple HSRP groups on an interface.
Figure 17-1 shows a network configured for HSRP. By sharing a virtual MAC address and a virtual IP
address, two or more interfaces can act as a single virtual router.
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Information About HSRP
Figure 17-1
HSRP Topology with Two Enabled Routers
Internet or
ISP backbone
Active
router
192.0.2.1
Virtual
router
192.0.2.2
Standby
router
192.0.2.3
Host A
Host B
Host C
Host D
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LAN
The virtual router does not physically exist but represents the common default router for interfaces that
are configured to provide backup to each other. You do not need to configure the hosts on the LAN with
the IP address of the active router. Instead, you configure them with the IP address of the virtual router
(virtual IP address) as their default router. If the active router fails to send a hello message within the
configurable period of time, the standby router takes over, responds to the virtual addresses, and becomes
the active router, assuming the active router duties. From the host perspective, the virtual router remains
the same.
Note
Packets received on a routed port destined for the HSRP virtual IP address terminate on the local router,
regardless of whether that router is the active HSRP router or the standby HSRP router. This process
includes ping and Telnet traffic. Packets received on a Layer 2 (VLAN) interface destined for the HSRP
virtual IP address terminate on the active router.
HSRP Versions
Cisco NX-OS supports HSRP version 1 by default. You can configure an interface to use HSRP version
2.
HSRP version 2 has the following enhancements to HSRP version 1:
•
Expands the group number range. HSRP version 1 supports group numbers from 0 to 255. HSRP
version 2 supports group numbers from 0 to 4095.
•
For IPv4, uses the IPv4 multicast address 224.0.0.102 or the IPv6 multicast address FF02::66 to send
hello packets instead of the multicast address of 224.0.0.2, which is used by HSRP version 1.
•
Uses the MAC address range from 0000.0C9F.F000 to 0000.0C9F.FFFF for IPv4 and
0005.73A0.0000 through 0005.73A0.0FFF for IPv6 addresses. HSRP version 1 uses the MAC
address range 0000.0C07.AC00 to 0000.0C07.ACFF.
•
Adds support for MD5 authentication.
When you change the HSRP version, Cisco NX-OS reinitializes the group because it now has a new
virtual MAC address.
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Information About HSRP
HSRP version 2 has a different packet format than HSRP version 1. The packet format uses a
type-length-value (TLV) format. HSRP version 2 packets received by an HSRP version 1 router are
ignored.
HSRP for IPv4
HSRP routers communicate with each other by exchanging HSRP hello packets. These packets are sent
to the destination IP multicast address 224.0.0.2 (reserved multicast address used to communicate to all
routers) on UDP port 1985. The active router sources hello packets from its configured IP address and
the HSRP virtual MAC address while the standby router sources hellos from its configured IP address
and the interface MAC address, which might be the burned-in address (BIA). The BIA is the last six
bytes of the MAC address that is assigned by the manufacturer of the network interface card (NIC).
Because hosts are configured with their default router as the HSRP virtual IP address, hosts must
communicate with the MAC address associated with the HSRP virtual IP address. This MAC address is
a virtual MAC address, 0000.0C07.ACxy, where xy is the HSRP group number in hexadecimal based on
the respective interface. For example, HSRP group 1 uses the HSRP virtual MAC address of
0000.0C07.AC01. Hosts on the adjoining LAN segment use the normal Address Resolution Protocol
(ARP) process to resolve the associated MAC addresses.
HSRP version 2 uses the new IP multicast address 224.0.0.102 to send hello packets instead of the
multicast address of 224.0.0.2, which is used by version 1. HSRP version 2 permits an expanded group
number range of 0 to 4095 and uses a new MAC address range of 0000.0C9F.F000 to 0000.0C9F.FFFF.
HSRP for IPv6
IPv6 hosts learn of available IPv6 routers through IPv6 neighbor discovery (ND) router advertisement
(RA) messages. These messages are multicast periodically, or might be solicited by hosts, but the time
delay for detecting when a default route is down might be 30 seconds or more. HSRP for IPv6 provides
a much faster switchover to an alternate default router than the IPv6 ND protocol provides, which is less
than a second if the milliseconds timers are used. HSRP for IPv6 provides a virtual first hop for IPv6
hosts.
When you configure an IPv6 interface for HSRP, the periodic RAs for the interface link-local address
stop after IPv6 ND sends a final RA with a router lifetime of zero. No restrictions occur for the interface
IPv6 link-local address. Other protocols continue to receive and send packets to this address.
IPv6 ND sends periodic RAs for the HSRP virtual IPv6 link-local address when the HSRP group is
active. These RAs stop after a final RA is sent with a router lifetime of 0 when the HSRP group leaves
the active state. HSRP uses the virtual MAC address for active HSRP group messages only (hello, coup,
and resign).
HSRP for IPv6 uses the following parameters:
•
HSRP version 2
•
UDP port 2029
•
Virtual MAC address range from 0005.73A0.0000 through 0005.73A0.0FFF
•
Multicast link-local IP destination address of FF02::66
•
Hop limit set to 255
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HSRP IPv6 Addresses
An HSRP IPv6 group has a virtual MAC address that is derived from the HSRP group number and a
virtual IPv6 link-local address that is derived, by default, from the HSRP virtual MAC address. The
default virtual MAC address for an HSRP IPv6 group is always used to form the virtual IPv6 link-local
address, regardless of the actual virtual MAC address used by the group.
Table 17-1 shows the MAC and IP addresses used for IPv6 neighbor discovery packets and HSRP
packets.
Table 17-1
HSRP and IPv6 ND Addresses
IPv6
Destination
Address
Link-layer Address Option
Neighbor solicitation (NS) Interface MAC address Interface IPv6 address
—
Interface MAC address
Router solicitation (RS)
Interface MAC address Interface IPv6 address
—
Interface MAC address
Neighbor advertisement
(NA)
Interface MAC address Interface IPv6 address
Virtual IPv6
address
HSRP virtual MAC address
Route advertisement (RA) Interface MAC address Virtual IPv6 address
—
HSRP virtual MAC address
HSRP (inactive)
Interface MAC address Interface IPv6 address
—
—
HSRP (active)
Virtual MAC address
—
—
Packet
MAC Source Address
IPv6 Source Address
Interface IPv6 address
HSRP does not add IPv6 link-local addresses to the Unicast Routing Information Base (URIB).
Link-local addresses have no secondary virtual IP addresses.
For global unicast addresses, HSRP adds the virtual IPv6 address to the URIB and IPv6.
HSRP Authentication
HSRP message digest 5 (MD5) algorithm authentication protects against HSRP-spoofing software and
uses the industry-standard MD5 algorithm for improved reliability and security. HSRP includes the IPv4
or IPv6 address in the authentication TLVs.
HSRP Messages
Routers that are configured with HSRP exchange the following three types of multicast messages:
•
Hello—The hello message conveys the HSRP priority and state information of the router to other
HSRP routers.
•
Coup—When a standby router wants to assume the function of the active router, it sends a coup
message.
•
Resign—A router that is the active router sends this message when it is about to shut down or when
a router that has a higher priority sends a hello or coup message.
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Information About HSRP
HSRP Load Sharing
HSRP allows you to configure multiple groups on an interface. You can configure two overlapping IPv4
HSRP groups to load share traffic from the connected hosts while providing the default router
redundancy expected from HSRP. Figure 17-2 shows an example of a load-sharing HSRP IPv4
configuration.
Figure 17-2
HSRP Load Sharing
User Group A
Default Gateway = 192.0.2.1
Active
Router A
Standby
Standby
Router B
Active
User Group B
Default Gateway = 192.0.2.2
Group B = 192.0.2.2
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Group A = 192.0.2.1
Figure 17-2 shows two routers A and B and two HSRP groups. Router A is the active router for group A
but is the standby router for group B. Similarly, router B is the active router for group B and the standby
router for group A. If both routers remain active, HSRP load balances the traffic from the hosts across
both routers. If either router fails, the remaining router continues to process traffic for both hosts.
Note
HSRP for IPv6 load balances by default. If two HSRP IPv6 groups are on the subnet, hosts learn of both
groups from their router advertisements and choose to use one so that the load is shared between the
advertised routers.
Object Tracking and HSRP
You can use object tracking to modify the priority of an HSRP interface based on the operational state
of another interface. Object tracking allows you to route to a standby router if the interface to the main
network fails.
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Two objects that you can track are the line protocol state of an interface or the reachability of an IP route.
If the specified object goes down, Cisco NX-OS reduces the HSRP priority by the configured amount.
For more information, see the “Configuring HSRP Object Tracking” section on page 17-18.
vPC and HSRP
HSRP interoperates with virtual port channels (vPCs). vPCs allow links that are physically connected to
two different Cisco Nexus 9000 Series devices to appear as a single port channel by a third device. See
the Cisco Nexus 9000 Series NX-OS Layer 2 Switching Configuration Guide for more information on
vPCs.
vPC forwards traffic through both the active HSRP router and the standby HSRP router. For more
information, see the “Configuring the HSRP Priority” section on page 17-20 and the “Configuration
Examples for HSRP” section on page 17-23.
Note
HSRP active can be distributed on both the primary and secondary vPC peers for different SVIs.
vPC Peer Gateway and HSRP
Some third-party devices can ignore the HSRP virtual MAC address and instead use the source MAC
address of an HSRP router. In a vPC environment, the packets that use this source MAC address might
be sent across the vPC peer link, causing a potential dropped packet. Configure the vPC peer gateway to
enable the HSRP routers to directly handle packets sent to the local vPC peer MAC address and the
remote vPC peer MAC address, as well as the HSRP virtual MAC address. See the Cisco Nexus 9000
Series NX-OS Layer 2 Switching Configuration Guide for more information on the vPC peer gateway.
BFD
This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol that
provides fast-forwarding and path-failure detection times. BFD provides subsecond failure detection
between two adjacent devices and can be less CPU-intensive than protocol hello messages because some
of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 9000
Series NX-OS Interfaces Configuration Guide for more information.
High Availability and Extended Nonstop Forwarding
HSRP supports stateful restarts and stateful switchovers. A stateful restart occurs when the HSRP
process fails and is restarted. A stateful switchover occurs when the active supervisor switches to the
standby supervisor. Cisco NX-OS applies the run-time configuration after the switchover.
If HSRP hold timers are configured for short time periods, these timers might expire during a controlled
switchover. HSRP supports extended nonstop forwarding (NSF) to temporarily extend these HSRP hold
timers during a controlled switchover.
With extended NSF configured, HSRP sends hello messages with the extended timers. HSRP peers
update their hold timers with these new values. The extended timers prevent unnecessary HSRP state
changes during the switchover. After the switchover, HSRP restores the hold timers to their original
configured values. If the switchover fails, HSRP restores the hold timers after the extended hold timer
values expire.
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Licensing Requirements for HSRP
See the “Configuring Extended Hold Timers for HSRP” section on page 17-22 for more information.
Virtualization Support
HSRP supports virtual routing and forwarding (VRF) instances.
Licensing Requirements for HSRP
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
HSRP requires no license. Any feature not included in a license package is bundled with the nx-os image
and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme,
see the Cisco NX-OS Licensing Guide.
Prerequisites for HSRP
•
You must enable the HSRP feature in a device before you can configure and enable any HSRP
groups.
Guidelines and Limitations for HSRP
HSRP has the following configuration guidelines and limitations:
•
You must configure an IP address for the interface that you configure HSRP on and enable that
interface before HSRP becomes active.
•
You must configure HSRP version 2 when you configure an IPv6 interface for HSRP.
•
For IPv4, the virtual IP address must be in the same subnet as the interface IP address.
•
We recommend that you do not configure more than one first-hop redundancy protocol on the same
interface.
•
HSRP version 2 does not interoperate with HSRP version 1. An interface cannot operate both
version 1 and version 2 because both versions are mutually exclusive. However, the different
versions can be run on different physical interfaces of the same router.
•
You cannot change from version 2 to version 1 if you have configured groups above the group
number range allowed for version 1 (0 to 255).
•
HSRP for IPv4 is supported with BFD. HSRP for IPv6 is not supported with BFD.
•
If HSRP IPv4 and IPv6 use the same virtual MAC address on an SVI, the HSRP state should be the
same for both HSRP IPv4 and IPv6. The priority and preemption should be configured to result in
the same state after failovers.
•
Cisco NX-OS removes all Layer 3 configurations on an interface when you change the interface
VRF membership, port channel membership, or the port mode to Layer 2.
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Default Settings
•
If you configure virtual MAC addresses with vPC, you must configure the same virtual MAC
address on both vPC peers.
•
You cannot use the HSRP MAC address burned-in option on a VLAN interface that is a vPC
member.
•
Cisco NX-OS does not support having the same HSRP groups on all nodes in a double-sided vPC.
•
If you have not configured authentication, the show hsrp command displays the following string:
Authentication text "cisco"
The default behavior of HSRP is as defined in RFC 2281:
If no authentication data is configured, the RECOMMENDED default
value is 0x63 0x69 0x73 0x63 0x6F 0x00 0x00 0x00.
Default Settings
Table 17-2 lists the default settings for HSRP parameters.
Table 17-2
Default HSRP Parameters
Parameters
Default
HSRP
Disabled
Authentication
Enabled as text for version 1, with cisco as the
password
HSRP version
Version 1
Preemption
Disabled
Priority
100
Virtual MAC address
Derived from HSRP group number
Configuring HSRP
This section includes the following topics:
•
Enabling HSRP, page 17-10
•
Configuring the HSRP Version, page 17-10
•
Configuring an HSRP Group for IPv4, page 17-11
•
Configuring an HSRP Group for IPv6, page 17-12
•
Configuring the HSRP Virtual MAC Address, page 17-14
•
Authenticating HSRP, page 17-15
•
Configuring HSRP Object Tracking, page 17-18
•
Configuring the HSRP Priority, page 17-20
•
Customizing HSRP, page 17-21
•
Configuring Extended Hold Timers for HSRP, page 17-22
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Configuring HSRP
Note
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Enabling HSRP
You must globally enable HSRP before you can configure and enable any HSRP groups.
DETAILED STEPS
To enable the HSRP feature, use the following command in global configuration mode:
Command
Purpose
feature hsrp
Enables HSRP.
Example:
switch(config)# feature hsrp
To disable the HSRP feature and remove all associated configurations, use the following command in
global configuration mode:
Command
Purpose
no feature hsrp
Disables HSRP for all groups.
Example:
switch(config)# no feature hsrp
Configuring the HSRP Version
You can configure the HSRP version. If you change the version for existing groups, Cisco NX-OS
reinitializes HSRP for those groups because the virtual MAC address changes. The HSRP version
applies to all groups on the interface.
Note
IPv6 HSRP groups must be configured as HSRP version 2.
To configure the HSRP version, use the following command in interface configuration mode:
Command
Purpose
hsrp version {1 | 2}
Configures the HSRP version. Version 1 is the
default.
Example:
switch(config-if)# hsrp version 2
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Configuring an HSRP Group for IPv4
You can configure an HSRP group on an IPv4 interface and configure the virtual IP address and virtual
MAC address for the HSRP group.
BEFORE YOU BEGIN
Ensure that you have enabled the HSRP feature (see the “Enabling HSRP” section on page 17-10).
Cisco NX-OS enables an HSRP group once you configure its virtual IP address. You should configure
HSRP attributes such as authentication, timers, and priority before you enable the HSRP group.
SUMMARY STEPS
1.
configure terminal
2.
interface type number
3.
ip address ip-address/length
4.
hsrp group-number [ipv4]
5.
ip [ip-address [secondary]]
6.
exit
7.
no shutdown
8.
(Optional) show hsrp [group group-number] [ipv4]
9.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enters interface configuration mode.
interface type number
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
ip address ip-address/length
Configures the IPv4 address of the interface.
Example:
switch(config-if)# ip 192.0.2.2/8
Step 4
hsrp group-number [ipv4]
Example:
switch(config-if)# hsrp 2
switch(config-if-hsrp)#
Step 5
ip [ip-address [secondary]]
Example:
switch(config-if-hsrp)# ip 192.0.2.1
Creates an HSRP group and enters HSRP
configuration mode. The range for HSRP version 1 is
from 0 to 255. The range is for HSRP version 2 is from
0 to 4095. The default value is 0.
Configures the virtual IP address for the HSRP group
and enables the group. This address should be in the
same subnet as the IPv4 address of the interface.
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Step 6
Command
Purpose
exit
Exits HSRP configuration mode.
Example:
switch(config-if-hsrp)# exit
Step 7
Enables the interface.
no shutdown
Example:
switch(config-if)# no shutdown
Step 8
show hsrp [group group-number] [ipv4]
(Optional) Displays HSRP information.
Example:
switch(config-if)# show hsrp group 2
Step 9
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
Note
(Optional) Copies the running configuration to the
startup configuration.
You should use the no shutdown command to enable the interface after you finish the configuration.
This example shows how to configure an HSRP group on Ethernet 1/2:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# ip 192.0.2.2/8
switch(config-if)# hsrp 2
switch(config-if-hsrp)# ip 192.0.2.1
switch(config-if-hsrp)# exit
switch(config-if)# no shutdown
switch(config-if)# copy running-config startup-config
Configuring an HSRP Group for IPv6
You can configure an HSRP group on an IPv6 interface and configure the virtual MAC address for the
HSRP group.
When you configure an HSRP group for IPv6, HSRP generates a link-local address from the link-local
prefix. HSRP also generates a modified EUI-64 format interface identifier in which the EUI-64 interface
identifier is created from the relevant HSRP virtual MAC address.
BEFORE YOU BEGIN
You must enable HSRP (see the “Enabling HSRP” section on page 17-10).
Ensure that you have enabled HSRP version 2 on the interface that you want to configure an IPv6 HSRP
group on.
Ensure that you have configured HSRP attributes such as authentication, timers, and priority before you
enable the HSRP group.
SUMMARY STEPS
1.
configure terminal
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2.
interface type number
3.
ipv6 address ipv6-address/length
4.
hsrp version 2
5.
hsrp group-number ipv6
6.
ip ipv6-address
7.
ip autoconfig
8.
exit
9.
no shutdown
10. (Optional) show hsrp [group group-number] [ipv6]
11. (Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enters interface configuration mode.
interface type number
Example:
switch(config)# interface ethernet 3/2
switch(config-if)#
Step 3
ipv6 address ipv6-address/length
Configures the IPv6 address of the interface.
Example:
switch(config-if)# ipv6 address
2001:0DB8::0001:0001/64
Step 4
Configures this group for HSRP version 2.
hsrp version 2
Example:
switch(config-if-hsrp)# hsrp version 2
Step 5
hsrp group-number ipv6
Example:
switch(config-if)# hsrp 10 ipv6
switch(config-if-hsrp)#
Step 6
ip ipv6-address
Example:
switch(config-if-hsrp)# ip 2001:DB8::1
Step 7
Step 8
Creates an IPv6 HSRP group and enters HSRP
configuration mode. The range for HSRP version 2 is
from 0 to 4095. The default value is 0.
Configures the virtual IPv6 address for the HSRP
group and enables the group.
Example:
switch(config-if-hsrp)# ip autoconfig
Autoconfigures the virtual IPv6 address for the HSRP
group from the calculated link-local virtual IPv6
address and enables the group.
exit
Exits HSRP configuration mode.
ip autoconfig
Example:
switch(config-if-hsrp)# exit
switch(config-if)#
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Step 9
Command
Purpose
no shutdown
Enables the interface.
Example:
switch(config-if)# no shutdown
Step 10
show hsrp [group group-number] [ipv6]
(Optional) Displays HSRP information.
Example:
switch(config-if)# show hsrp group 10
Step 11
copy running-config startup-config
Example:
switch(config-if)# copy running-config
startup-config
Note
(Optional) Copies the running configuration to the
startup configuration.
You should use the no shutdown command to enable the interface after you finish the configuration.
This example shows how to configure an IPv6 HSRP group on Ethernet 3/2:
switch# configure terminal
switch(config)# interface ethernet 3/2
switch(config-if)# ipv6 address 2001:0DB8::0001:0001/64
switch(config-if-hsrp)# hsrp version 2
switch(config-if)# hsrp 2 ipv6
switch(config-if-hsrp)# ip 2001:DB8::1
switch(config-if-hsrp)# exit
switch(config-if)# no shutdown
switch(config-if)# copy running-config startup-config
Configuring the HSRP Virtual MAC Address
You can override the default virtual MAC address that HSRP derives from the configured group number.
Note
You must configure the same virtual MAC address on both vPC peers of a vPC link.
To manually configure the virtual MAC address for an HSRP group, use the following command in hsrp
configuration mode:
Command
Purpose
mac-address string
Configures the virtual MAC address for an HSRP
group. The string uses the standard MAC address
format (xxxx.xxxx.xxxx).
Example:
switch(config-if-hsrp)# mac-address
5000.1000.1060
To configure HSRP to use the burned-in MAC address of the interface for the virtual MAC address, use
the following command in interface configuration mode:
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Command
Purpose
hsrp use-bia [scope interface]
Configures HSRP to use the burned-in MAC
address of the interface for the HSRP virtual MAC
address. You can optionally configure HSRP to use
the burned-in MAC address for all groups on this
interface by using the scope interface keyword.
Example:
switch(config-if)# hsrp use-bia
Authenticating HSRP
You can configure HSRP to authenticate the protocol using cleartext or MD5 digest authentication. MD5
authentication uses a key chain (see the Cisco Nexus 9000 Series NX-OS Security Configuration Guide).
BEFORE YOU BEGIN
You must enable HSRP (see the “Enabling HSRP” section on page 17-10).
You must configure the same authentication and keys on all members of the HSRP group.
Ensure that you have created the key chain if you are using MD5 authentication.
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
hsrp group-number [ipv4 | ipv6]
4.
authentication text string
or
authentication md5 {key-chain key-chain | key-string {0 | 7} text [timeout seconds]}
5.
(Optional) show hsrp [group group-number]
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
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Step 3
Command
Purpose
hsrp group-number [ipv4 | ipv6]
Creates an HSRP group and enters HSRP
configuration mode.
Example:
switch(config-if)# hsrp 2
switch(config-if-hsrp)#
Step 4
authentication text string
Example:
switch(config-if-hsrp)# authentication
text mypassword
authentication md5 {key-chain key-chain
| key-string {0 | 7} text [timeout
seconds]}
Example:
switch(config-if-hsrp)# authentication
md5 key-chain hsrp-keys
Step 5
show hsrp [group group-number]
Configures cleartext authentication for HSRP on this
interface.
Configures MD5 authentication for HSRP on this
interface. You can use a key chain or key string. If you
use a key string, you can optionally set the timeout for
when HSRP only accepts a new key. The range is from
0 to 32767 seconds.
(Optional) Displays HSRP information.
Example:
switch(config-if-hsrp)# show hsrp group
2
Step 6
copy running-config startup-config
Example:
switch(config-if-hsrp)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure MD5 authentication for HSRP on Ethernet 1/2 after creating the
key chain:
switch# configure terminal
switch(config)# key chain hsrp-keys
switch(config-keychain)# key 0
switch(config-keychain-key)# key-string 7 zqdest
switch(config-keychain-key) accept-lifetime 00:00:00 Jun 01 2013 23:59:59 Sep 12 2013
switch(config-keychain-key) send-lifetime 00:00:00 Jun 01 2013 23:59:59 Aug 12 2013
switch(config-keychain-key) key 1
switch(config-keychain-key) key-string 7 uaeqdyito
switch(config-keychain-key) accept-lifetime 00:00:00 Aug 12 2013 23:59:59 Dec 12 2013
switch(config-keychain-key) send-lifetime 00:00:00 Sep 12 2013 23:59:59 Nov 12 2013
switch(config-keychain-key)# interface ethernet 1/2
switch(config-if)# hsrp 2
switch(config-if-hsrp)# authentication md5 key-chain hsrp-keys
switch(config-if-hsrp)# copy running-config startup-config
Authenticating HSRP
You can configure HSRP to authenticate the protocol using cleartext or MD5 digest authentication. MD5
authentication uses a key chain (see the Cisco Nexus 9000 Series NX-OS Security Configuration Guide).
BEFORE YOU BEGIN
You must enable HSRP (see the “Enabling HSRP” section on page 17-10).
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Configuring HSRP
You must configure the same authentication and keys on all members of the HSRP group.
Ensure that you have created the key chain if you are using MD5 authentication.
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
hsrp group-number [ipv4 | ipv6]
4.
authentication text string
or
authentication md5 {key-chain key-chain | key-string {0 | 7} text [timeout seconds]}
5.
(Optional) show hsrp [group group-number]
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 3
hsrp group-number [ipv4 | ipv6]
Example:
switch(config-if)# hsrp 2
switch(config-if-hsrp)#
Step 4
authentication text string
Example:
switch(config-if-hsrp)# authentication
text mypassword
authentication md5 {key-chain key-chain
| key-string {0 | 7} text [timeout
seconds]}
Example:
switch(config-if-hsrp)# authentication
md5 key-chain hsrp-keys
Creates an HSRP group and enters HSRP
configuration mode.
Configures cleartext authentication for HSRP on this
interface.
Configures MD5 authentication for HSRP on this
interface. You can use a key chain or key string. If you
use a key string, you can optionally set the timeout for
when HSRP only accepts a new key. The range is from
0 to 32767 seconds.
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Configuring HSRP
Step 5
Command
Purpose
show hsrp [group group-number]
(Optional) Displays HSRP information.
Example:
switch(config-if-hsrp)# show hsrp group
2
Step 6
copy running-config startup-config
Example:
switch(config-if-hsrp)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure MD5 authentication for HSRP on Ethernet 1/2 after creating the
key chain:
switch# configure terminal
switch(config)# key chain hsrp-keys
switch(config-keychain)# key 0
switch(config-keychain-key)# key-string 7 zqdest
switch(config-keychain-key) accept-lifetime 00:00:00 Jun 01 2013 23:59:59 Sep 12 2013
switch(config-keychain-key) send-lifetime 00:00:00 Jun 01 2013 23:59:59 Aug 12 2013
switch(config-keychain-key) key 1
Configuring HSRP Object Tracking
You can configure an HSRP group to adjust its priority based on the availability of other interfaces or
routes. The priority of an HSRP group can change dynamically if it has been configured for object
tracking and the object that is being tracked goes down.
The tracking process periodically polls the tracked objects and notes any value change. The value change
triggers HSRP to recalculate the priority. The HSRP interface with the higher priority becomes the active
router if you configure the HSRP interface for preemption.
SUMMARY STEPS
1.
configure terminal
2.
track object-id interface interface-type slot/port {line-protocol | ip routing | ipv6 routing}
3.
track object-id {ip | ipv6} route ip-prefix/length reachability
4.
exit
5.
interface interface-type slot/port
6.
hsrp group-number [ipv4 | ipv6]
7.
priority [value]
8.
track object-id [decrement value]
9.
preempt [delay [minimum seconds] [reload seconds] [sync seconds]]
10. (Optional) show hsrp interface interface-type slot/port
11. (Optional) copy running-config startup-config
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Configuring HSRP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
track object-id interface
interface-type slot/port{line-protocol |
ip routing | ipv6 routing}
Example:
switch(config)# track 1 interface
ethernet 2/2 line-protocol
switch(config-track)#
Step 3
track object-id {ip | ipv6} route
ip-prefix/length reachability
Example:
switch(config-track)# track 2 ip route
192.0.2.0/8 reachability
Step 4
Configures the interface that the track object tracks.
Changes in the state of the interface affect the track
object status as follows:
•
You configure the interface and corresponding
object number that you use with the track
command in global configuration mode.
•
The line-protocol keyword tracks whether the
interface is up. The ip routing or ipv6 routing
keyword also checks that IP routing is enabled on
the interface and an IP address is configured.
Creates a tracked object for a route and enters tracking
configuration mode. The object-id range is from 1 to
500.
Exits track configuration mode.
exit
Example:
switch(config-track)# exit
switch(config)#
Step 5
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
Step 6
hsrp group-number [ipv4 | ipv6]
Example:
switch(config-if)# hsrp 2
switch(config-if-hsrp)#
Step 7
priority [value]
Example:
switch(config-if-hsrp)# priority 254
Step 8
track object-id [decrement value]
Example:
switch(config-if-hsrp)# track 1
decrement 20
Creates an HSRP group and enters HSRP
configuration mode.
Sets the priority level used to select the active router in
an HSRP group. The range is from 0 to 255. The
default is 100.
Specifies an object to be tracked that affects the
weighting of an HSRP interface.
The value argument specifies a reduction in the
priority of an HSRP interface when a tracked object
fails. The range is from 1 to 255. The default is 10.
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Configuring HSRP
Step 9
Command
Purpose
preempt [delay [minimum seconds]
[reload seconds] [sync seconds]]
Configures the router to take over as the active router
for an HSRP group if it has a higher priority than the
current active router. This command is disabled by
default. Optionally, a delay can be configured that
delays the HSRP group preemption by the configured
time. The range is from 0 to 3600 seconds.
Example:
switch(config-if-hsrp)# preempt
delay minimum 60
Step 10
show hsrp interface interface-type
slot/port
(Optional) Displays HSRP information for an
interface.
Example:
switch(config-if-hsrp)# show hsrp
interface ethernet 1/2
Step 11
copy running-config startup-config
Example:
switch(config-if-hsrp)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure HSRP object tracking on Ethernet interface 1/2:
switch# configure terminal
switch(config)# track 1 interface ethernet 2/2 line-protocol
switch(config-track)# track 2 ip route 192.0.2.0/8 reachability
switch(config-track)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# hsrp 2
switch(config-if-hsrp)# priority 254
switch(config-if-hsrp)# track 1 decrement 20
switch(config-if-hsrp)# preempt delay minimum 60
switch(config-if-hsrp)# copy running-config startup-config
Configuring the HSRP Priority
You can configure the priority of an HSRP group. HSRP uses the priority to determine which HSRP
group member acts as the active router. If you configure HSRP on a vPC-enabled interface, you can
optionally configure the upper and lower threshold values to control when to fail over to the vPC trunk.
If the standby router priority falls below the lower threshold, HSRP sends all standby router traffic across
the vPC trunk to forward through the active HSRP router. HSRP maintains this scenario until the standby
HSRP router priority increases above the upper threshold.
For IPv6 HSRP groups, if all group members have the same priority, HSRP selects the active router
based on the IPv6 link-local address.
To configure the HSRP priority, use the following command in the HSRP group configuration mode:
Command
Purpose
priority level [forwarding-threshold
lower lower-value upper upper-value]
Sets the priority level used to select the active router in an
HSRP group. The level range is from 0 to 255. The default
is 100. Optionally, this command sets the upper and lower
threshold values used by vPC to determine when to fail
over to the vPC trunk. The lower-value range is from 1 to
255. The default is 1. The upper-value range is from 1 to
255. The default is 255.
Example:
switch(config-if-hsrp)# priority 60
forwarding-threshold lower 40 upper
50
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Configuring HSRP
Customizing HSRP
You can optionally customize the behavior of HSRP. Be aware that as soon as you enable an HSRP group
by configuring a virtual IP address, that group is now operational. If you first enable an HSRP group
before customizing HSRP, the router could take control over the group and become the active router
before you finish customizing the feature. If you plan to customize HSRP, you should do so before you
enable the HSRP group. To customize HSRP, use the following commands in HSRP configuration mode:
Command
Purpose
name string
Specifies the IP redundancy name for an HSRP group.
The string is from 1 to 255 characters. The default string
has the following format:
Example:
switch(config-if-hsrp)# name HSRP-1
hsrp-interface short-name group-id. For example,
hsrp-Eth2/1-1.
preempt [delay [minimum seconds]
[reload seconds] [sync seconds]]
Example:
switch(config-if-hsrp)# preempt delay
minimum 60
timers [msec] hellotime [msec]
holdtime
Example:
switch(config-if-hsrp)# timers 5 18
Configures the router to take over as an active router for
an HSRP group if it has a higher priority than the current
active router. This command is disabled by default.
Optionally, a delay can be configured that delays the
HSRP group preemption by the configured time. The
range is from 0 to 3600 seconds.
Configures the hello and hold time for this HSRP member
as follows:
•
hellotime—The interval between successive hello
packets sent. The range is from 1 to 254 seconds.
•
holdtime—The interval before the information in the
hello packet is considered invalid. The range is from
3 to 255.
The optional msec keyword specifies that the argument is
expressed in milliseconds instead of the default seconds.
The timer ranges for milliseconds are as follows:
•
hellotime—The interval between successive hello
packets sent. The range is from 255 to 999
milliseconds.
•
holdtime—The interval before the information in the
hello packet is considered invalid. The range is from
750 to 3000 milliseconds.
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Configuring HSRP
To customize HSRP, use the following commands in interface configuration mode:
Command
Purpose
hsrp delay minimum seconds
Specifies the minimum amount of time that HSRP waits
after a group is enabled before participating in the group.
The range is from 0 to 10000 seconds. The default is 0.
Example:
switch(config-if)# hsrp delay minimum
30
hsrp delay reload seconds
Example:
switch(config-if)# hsrp delay reload
30
Specifies the minimum amount of time that HSRP waits
after a reload and before participating in the group. The
range is from 0 to 10000 seconds. The default is 0.
Configuring Extended Hold Timers for HSRP
You can configure HSRP to use extended hold timers to support extended NSF during a controlled
(graceful) switchover. You should configure extended hold timers on all HSRP routers (see the “High
Availability and Extended Nonstop Forwarding” section on page 17-7).
Note
You must configure extended hold timers on all HSRP routers if you configure extended hold timers. If
you configure a nondefault hold timer, you should configure the same value on all HSRP routers when
you configure HSRP extended hold timers.
Note
HSRP extended hold timers are not applied if you configure millisecond hello and hold timers for
HSRPv1. This statement does not apply to HSRPv2.
To configure HSRP extended hold timers, use the following command in global configuration mode:
Command
Purpose
hsrp timers extended-hold [timer]
Sets the HSRP extended hold timer, in seconds, for
both IPv4 and IPv6 groups. The timer range is from
10 to 255. The default is 10.
Example:
switch(config)# hsrp timers extended-hold
Use the show hsrp command or the show running-config hsrp command to display the extended hold
time.
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Verifying the HSRP Configuration
Verifying the HSRP Configuration
To display HSRP configuration information, perform one of the following tasks:
Command
Purpose
show hsrp [group group-number]
Displays the HSRP status for all groups or one
group.
show hsrp delay [interface interface-type
slot/port]
Displays the HSRP delay value for all interfaces
or one interface.
show hsrp [interface interface-type slot/port]
Displays the HSRP status for an interface.
show hsrp [group group-number] [interface
interface-type slot/port] [active] [all] [init]
[learn] [listen] [speak] [standby]
Displays the HSRP status for a group or interface
for virtual forwarders in the active, init, learn,
listen, or standby state. Use the all keyword to see
all states, including disabled.
show hsrp [group group-number] [interface
interface-type slot/port] active] [all] [init]
[learn] [listen] [speak] [standby] brief
Displays a brief summary of the HSRP status for
a group or interface for virtual forwarders in the
active, init, learn, listen, or standby state. Use the
all keyword to see all states, including disabled.
Configuration Examples for HSRP
This example shows how to enable HSRP on an interface with MD5 authentication and interface
tracking:
key chain hsrp-keys
key 0
key-string 7 zqdest
accept-lifetime 00:00:00 Jun 01 2013 23:59:59 Sep 12 2013
send-lifetime 00:00:00 Jun 01 2013 23:59:59 Aug 12 2013
key 1
key-string 7 uaeqdyito
accept-lifetime 00:00:00 Aug 12 2013 23:59:59 Nov 12 2013
send-lifetime 00:00:00 Sep 12 2013 23:59:59 Nov 12 2013
feature hsrp
track 2 interface ethernet 2/2 ip
interface ethernet 1/2
ip address 192.0.2.2/8
hsrp 1
authenticate md5 key-chain hsrp-keys
priority 90
track 2 decrement 20
ip 192.0.2.10
no shutdown
This example shows how to configure the HSRP priority on an interface:
interface vlan 1
hsrp 0
preempt
priority 100 forwarding-threshold lower 80 upper 90
ip 192.0.2.2
track 1 decrement 30
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Additional References
Additional References
For additional information related to implementing HSRP, see the following sections:
•
Related Documents, page 17-24
•
MIBs, page 17-24
Related Documents
Related Topic
Document Title
Configuring the Virtual Router Redundancy Protocol
Chapter 18,“Configuring VRRP”
Configuring high availability
Cisco Nexus 9000 Series NX-OS High Availability and Redundancy
Guide
MIBs
MIBs
MIBs Link
MIBs related to HSRP
To locate and download supported MIBs, go to the following URL:
ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MI
BSupportList.html
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18
Configuring VRRP
This chapter describes how to configure the Virtual Router Redundancy Protocol (VRRP) on the Cisco
NX-OS device.
This chapter includes the following sections:
•
Information About VRRP, page 18-1
•
Licensing Requirements for VRRP, page 18-6
•
Guidelines and Limitations for VRRP, page 18-7
•
Default Settings, page 18-7
•
Configuring VRRP, page 18-7
•
Verifying the VRRP Configuration, page 18-16
•
Monitoring VRRP Statistics, page 18-17
•
Configuration Examples for VRRP, page 18-17
•
Additional References, page 18-18
Information About VRRP
VRRP allows for transparent failover at the first-hop IP router by configuring a group of routers to share
a virtual IP address. VRRP selects a master router in that group to handle all packets for the virtual IP
address. The remaining routers are in standby and take over if the master router fails.
This section includes the following topics:
•
VRRP Operation, page 18-2
•
Multiple VRRP Groups, page 18-3
•
VRRP Router Priority and Preemption, page 18-4
•
vPC and VRRP, page 18-5
•
VRRP Advertisements, page 18-5
•
VRRP Authentication, page 18-5
•
VRRP Tracking, page 18-5
•
BFD, page 18-6
•
Virtualization Support, page 18-6
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Information About VRRP
VRRP Operation
A LAN client can determine which router should be the first hop to a particular remote destination by
using a dynamic process or static configuration. Examples of dynamic router discovery are as follows:
•
Proxy ARP—The client uses the Address Resolution Protocol (ARP) to get the destination it wants
to reach, and a router responds to the ARP request with its own MAC address.
•
Routing protocol—The client listens to dynamic routing protocol updates (for example, from
Routing Information Protocol [RIP]) and forms its own routing table.
•
ICMP Router Discovery Protocol (IRDP) client—The client runs an Internet Control Message
Protocol (ICMP) router discovery client.
The disadvantage to dynamic discovery protocols is that they incur some configuration and processing
overhead on the LAN client. Also, if a router fails, the process of switching to another router can be slow.
An alternative to dynamic discovery protocols is to statically configure a default router on the client.
Although, this approach simplifies client configuration and processing, it creates a single point of
failure. If the default gateway fails, the LAN client is limited to communicating only on the local IP
network segment and is cut off from the rest of the network.
VRRP can solve the static configuration problem by enabling a group of routers (a VRRP group) to share
a single virtual IP address. You can then configure the LAN clients with the virtual IP address as their
default gateway.
Figure 18-1 shows a basic VLAN topology. In this example, Routers A, B, and C form a VRRP group.
The IP address of the group is the same address that was configured for the Ethernet interface of Router
A (10.0.0.1).
Basic VRRP Topology
Router A
Virtual router
master
10.0.0.1
Client 1
Router B
Virtual router
backup
10.0.0.2
Client 2
Router C
Virtual router
backup
Virtual
router group
IP address = 10.0.0.1
10.0.0.3
Client 3
56623
Figure 18-1
Because the virtual IP address uses the IP address of the physical Ethernet interface of Router A, Router
A is the master (also known as the IP address owner). As the master, Router A owns the virtual IP address
of the VRRP group and forwards packets sent to this IP address. Clients 1 through 3 are configured with
the default gateway IP address of 10.0.0.1.
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Information About VRRP
Routers B and C function as backups. If the master fails, the backup router with the highest priority
becomes the master and takes over the virtual IP address to provide uninterrupted service for the LAN
hosts. When router A recovers, it becomes the master again. For more information, see the “VRRP
Router Priority and Preemption” section.
Note
Packets received on a routed port destined for the VRRP virtual IP address terminate on the local router,
regardless of whether that router is the master VRRP router or a backup VRRP router. These packets
include ping and Telnet traffic. Packets received on a Layer 2 (VLAN) interface destined for the VRRP
virtual IP address terminate on the master router.
VRRP Benefits
The benefits of VRRP are as follows:
•
Redundancy—Enables you to configure multiple routers as the default gateway router, which
reduces the possibility of a single point of failure in a network.
•
Load sharing—Allows traffic to and from LAN clients to be shared by multiple routers. The traffic
load is shared more equitably among available routers.
•
Multiple VRRP groups—Supports multiple VRRP groups on a router physical interface if the
platform supports multiple MAC addresses. Multiple VRRP groups enable you to implement
redundancy and load sharing in your LAN topology.
•
Multiple IP addresses—Allows you to manage multiple IP addresses, including secondary IP
addresses. If you have multiple subnets configured on an Ethernet interface, you can configure
VRRP on each subnet.
•
Preemption—Enables you to preempt a backup router that has taken over for a failing master with
a higher priority backup router that has become available.
•
Advertisement protocol—Uses a dedicated Internet Assigned Numbers Authority (IANA) standard
multicast address (224.0.0.18) for VRRP advertisements. This addressing scheme minimizes the
number of routers that must service the multicasts and allows test equipment to accurately identify
VRRP packets on a segment. IANA has assigned the IP protocol number 112 to VRRP.
•
VRRP tracking—Ensures that the best VRRP router is the master for the group by altering VRRP
priorities based on interface states.
Multiple VRRP Groups
You can configure multiple VRRP groups on a physical interface. For the number of supported VRRP
groups, see the Cisco Nexus 9000 Series NX-OS Verified Scalability Guide.
The number of VRRP groups that a router interface can support depends on the following factors:
•
Router processing capability
•
Router memory capability
In a topology where multiple VRRP groups are configured on a router interface, the interface can act as
a master for one VRRP group and as a backup for one or more other VRRP groups.
Figure 18-2 shows a LAN topology in which VRRP is configured so that Routers A and B share the
traffic to and from clients 1 through 4. Routers A and B act as backups to each other if either router fails.
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Information About VRRP
Figure 18-2
Load Sharing and Redundancy VRRP Topology
Router A
Master for virtual router 1
Backup for virtual router 2
10.0.0.2
129284
10.0.0.1
Router B
Backup for virtual router 1
Master for virtual router 2
Client 1
Default gateway =
10.0.0.1
Client 2
Default gateway =
10.0.0.1
Client 3
Default gateway =
10.0.0.2
Client 4
Default gateway =
10.0.0.2
This topology contains two virtual IP addresses for two VRRP groups that overlap. For VRRP group 1,
Router A is the owner of IP address 10.0.0.1 and is the master. Router B is the backup to Router A.
Clients 1 and 2 are configured with the default gateway IP address of 10.0.0.1.
For VRRP group 2, Router B is the owner of IP address 10.0.0.2 and is the master. Router A is the backup
to router B. Clients 3 and 4 are configured with the default gateway IP address of 10.0.0.2.
VRRP Router Priority and Preemption
An important aspect of the VRRP redundancy scheme is the VRRP router priority because the priority
determines the role that each VRRP router plays and what happens if the master router fails.
If a VRRP router owns the virtual IP address and the IP address of the physical interface, this router
functions as the master. The priority of the master is 255.
The priority also determines if a VRRP router functions as a backup router and the order of ascendancy
to becoming a master if the master fails.
For example, if Router A, the master in a LAN topology, fails, VRRP must determine if backups B or C
should take over. If you configure Router B with priority 101 and Router C with the default priority of
100, VRRP selects Router B to become the master because it has the higher priority. If you configure
Routers B and C with the default priority of 100, VRRP selects the backup with the higher IP address to
become the master.
VRRP uses preemption to determine what happens after a VRRP backup router becomes the master.
With preemption enabled by default, VRRP switches to a backup if that backup comes online with a
priority higher than the new master. For example, if Router A is the master and fails, VRRP selects
Router B (next in order of priority). If Router C comes online with a higher priority than Router B, VRRP
selects Router C as the new master, even though Router B has not failed.
If you disable preemption, VRRP switches only if the original master recovers or the new master fails.
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Information About VRRP
vPC and VRRP
VRRP interoperates with virtual port channels (vPCs). vPCs allow links that are physically connected
to two different Cisco Nexus 9000 Series devices to appear as a single port channel by a third device.
See the Cisco Nexus 9000 Series NX-OS Layer 2 Switching Configuration Guide for more information
on vPCs.
vPC forwards traffic through both the master VRRP router as well as the backup VRRP router. See the
“Configuring VRRP Priority” section on page 18-9.
Note
You should configure VRRP on the primary vPC peer device as active and VRRP on the vPC secondary
device as standby.
VRRP Advertisements
The VRRP master sends VRRP advertisements to other VRRP routers in the same group. The
advertisements communicate the priority and state of the master. Cisco NX-OS encapsulates the VRRP
advertisements in IP packets and sends them to the IP multicast address assigned to the VRRP group.
Cisco NX-OS sends the advertisements once every second by default, but you can configure a different
advertisement interval.
VRRP Authentication
VRRP supports the following authentication functions:
•
No authentication
•
Plain text authentication
VRRP rejects packets in any of the following cases:
•
The authentication schemes differ on the router and in the incoming packet.
•
Text authentication strings differ on the router and in the incoming packet.
VRRP Tracking
VRRP supports the following options for tracking:
•
Native interface tracking— Tracks the state of an interface and uses that state to determine the
priority of the VRRP router in a VRRP group. The tracked state is down if the interface is down or
if the interface does not have a primary IP address.
•
Object tracking—Tracks the state of a configured object and uses that state to determine the priority
of the VRRP router in a VRRP group. See Chapter 19, “Configuring Object Tracking” for more
information on object tracking.
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High Availability
If the tracked state (interface or object) goes down, VRRP updates the priority based on what you
configure the new priority to be for the tracked state. When the tracked state comes up, VRRP restores
the original priority for the virtual router group.
For example, you might want to lower the priority of a VRRP group member if its uplink to the network
goes down so another group member can take over as master for the VRRP group. See the “Configuring
VRRP Interface State Tracking” section on page 18-15 for more information.
Note
VRRP does not support Layer 2 interface tracking.
BFD
This feature supports bidirectional forwarding detection (BFD). BFD is a detection protocol that
provides fast-forwarding and path-failure detection times. BFD provides subsecond failure detection
between two adjacent devices and can be less CPU-intensive than protocol hello messages because some
of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 9000
Series NX-OS Interfaces Configuration Guide for more information.
High Availability
VRRP supports high availability through stateful restarts and stateful switchovers. A stateful restart
occurs when the VRRP process fails and is restarted. A stateful switchover occurs when the active
supervisor switches to the standby supervisor. Cisco NX-OS applies the run-time configuration after the
switchover.
Virtualization Support
VRRP supports virtual routing and forwarding (VRF) instances.
Licensing Requirements for VRRP
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
VRRP requires no license. Any feature not included in a license package is bundled with the nx-os image
and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme,
see the Cisco NX-OS Licensing Guide.
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Guidelines and Limitations for VRRP
Guidelines and Limitations for VRRP
VRRP has the following configuration guidelines and limitations:
•
You cannot configure VRRP on the management interface.
•
When VRRP is enabled, you should replicate the VRRP configuration across devices in your
network.
•
We recommend that you do not configure more than one first-hop redundancy protocol on the same
interface.
•
You must configure an IP address for the interface that you configure VRRP on and enable that
interface before VRRP becomes active.
•
Cisco NX-OS removes all Layer 3 configurations on an interface when you change the interface
VRF membership, port channel membership, or when you change the port mode to Layer 2.
•
When you configure VRRP to track a Layer 2 interface, you must shut down the Layer 2 interface
and reenable the interface to update the VRRP priority to reflect the state of the Layer 2 interface.
•
BFD for VRRP can only be configured between two routers.
Default Settings
Table 18-1 lists the default settings for VRRP parameters.
Table 18-1
Default VRRP Parameters
Parameters
Default
VRRP
Disabled
Advertisement interval
1 seconds
Authentication
No authentication
Preemption
Enabled
Priority
100
Configuring VRRP
This section includes the following topics:
•
Enabling the VRRP Feature, page 18-8
•
Configuring VRRP Groups, page 18-8
•
Configuring VRRP Priority, page 18-9
•
Configuring VRRP Authentication, page 18-11
•
Configuring Time Intervals for Advertisement Packets, page 18-12
•
Disabling Preemption, page 18-14
•
Configuring VRRP Interface State Tracking, page 18-15
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Configuring VRRP
Note
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Enabling the VRRP Feature
You must globally enable the VRRP feature before you can configure and enable any VRRP groups.
To enable the VRRP feature, use the following command in global configuration mode:
Command
Purpose
feature vrrp
Enables VRRP.
Example:
switch(config)# feature vrrp
To disable the VRRP feature and remove all associated configurations, use the following command in
global configuration mode:
Command
Purpose
no feature vrrp
Disables the VRRP feature.
Example:
switch(config)# no feature vrrp
Configuring VRRP Groups
You can create a VRRP group, assign the virtual IP address, and enable the group.
You can configure one virtual IPv4 address for a VRRP group. By default, the master VRRP router drops
the packets addressed directly to the virtual IP address because the VRRP master is only intended as a
next-hop router to forward packets. Some applications require that Cisco NX-OS accept packets
addressed to the virtual router IP. Use the secondary option to the virtual IP address to accept these
packets when the local router is the VRRP master.
Once you have configured the VRRP group, you must explicitly enable the group before it becomes
active.
BEFORE YOU BEGIN
Ensure that you configure an IP address on the interface (see the “Configuring IPv4 Addressing” section
on page 2-8).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrrp number
4.
address ip-address [secondary]
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5.
no shutdown
6.
(Optional) show vrrp
7.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/1
switch(config-if)#
Step 3
vrrp number
Example:
switch(config-if)# vrrp 250
switch(config-if-vrrp)#
Step 4
address ip-address [secondary]
Example:
switch(config-if-vrrp)# address 192.0.2.8
Creates a virtual router group. The range
is from 1 to 255.
Configures the virtual IPv4 address for
the specified VRRP group. This address
should be in the same subnet as the IPv4
address of the interface.
Use the secondary option only if
applications require that VRRP routers
accept the packets sent to the virtual
router's IP address and deliver to
applications.
Step 5
no shutdown
Example:
switch(config-if-vrrp)# no shutdown
switch(config-if-vrrp)#
Step 6
Enables the VRRP group. Disabled by
default.
(Optional) Displays VRRP information.
show vrrp
Example:
switch(config-if-vrrp)# show vrrp
Step 7
copy running-config startup-config
Example:
switch(config-if-vrrp)# copy running-config
startup-config
(Optional) Saves this configuration
change.
Configuring VRRP Priority
The valid priority range for a virtual router is from 1 to 254 (1 is the lowest priority and 254 is the
highest). The default priority value for backups is 100. For devices whose interface IP address is the
same as the primary virtual IP address (the master), the default value is 255.
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Configuring VRRP
If you configure VRRP on a vPC-enabled interface, you can optionally configure the upper and lower
threshold values to control when to fail over to the vPC trunk. If the backup router priority falls below
the lower threshold, VRRP sends all backup router traffic across the vPC trunk to forward through the
master VRRP router. VRRP maintains this scenario until the backup VRRP router priority increases
above the upper threshold.
BEFORE YOU BEGIN
You must enable VRRP (see the “Configuring VRRP” section on page 18-7).
Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing”
section on page 2-8).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrrp number
4.
shutdown
5.
priority level [forwarding-threshold lower lower-value upper upper-value]
6.
no shutdown
7.
(Optional) show vrrp
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/1
switch(config-if)#
Step 3
vrrp number
Creates a virtual router group.
Example:
switch(config-if)# vrrp 250
switch(config-if-vrrp)#
Step 4
shutdown
Disables the VRRP group. Disabled by default.
Example:
switch(config-if-vrrp)# shutdown
switch(config-if-vrrp)#
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Step 5
Command
Purpose
priority level [forwarding-threshold lower
lower-value upper upper-value]
Sets the priority level used to select the active
router in an VRRP group. The level range is
from 1 to 254. The default is 100 for backups
and 255 for a master that has an interface IP
address equal to the virtual IP address.
Example:
switch(config-if-vrrp)# priority 60
forwarding-threshold lower 40 upper 50
Optionally, sets the upper and lower threshold
values used by vPC to determine when to fail
over to the vPC trunk. The lower-value range is
from 1 to 255. The default is 1. The upper-value
range is from 1 to 255. The default is 255.
Step 6
Enables the VRRP group. Disabled by default.
no shutdown
Example:
switch(config-if-vrrp)# no shutdown
switch(config-if-vrrp)#
Step 7
show vrrp
Example:
switch(config-if-vrrp)# show vrrp
Step 8
copy running-config startup-config
(Optional) Displays a summary of VRRP
information.
(Optional) Saves this configuration change.
Example:
switch(config-if-vrrp)# copy running-config
startup-config
Configuring VRRP Authentication
You can configure simple text authentication for a VRRP group.
BEFORE YOU BEGIN
Ensure that the authentication configuration is identical for all VRRP devices in the network.
Ensure that you have enabled VRRP (see the “Configuring VRRP” section on page 18-7).
Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing”
section on page 2-8).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrrp number
4.
shutdown
5.
authentication text password
6.
no shutdown
7.
(Optional) show vrrp
8.
(Optional) copy running-config startup-config
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Configuring VRRP
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/1
switch(config-if)#
Step 3
vrrp number
Creates a virtual router group.
Example:
switch(config-if)# vrrp 250
switch(config-if-vrrp)#
Step 4
shutdown
Disables the VRRP group. Disabled by default.
Example:
switch(config-if-vrrp)# shutdown
switch(config-if-vrrp)#
Step 5
authentication text password
Example:
switch(config-if-vrrp)# authentication
text aPassword
Step 6
no shutdown
Assigns the simple text authentication option and
specifies the keyname password. The keyname
range is from 1 to 255 characters. We recommend
that you use at least 16 characters. The text
password is up to eight alphanumeric characters.
Enables the VRRP group. Disabled by default.
Example:
switch(config-if-vrrp)# no shutdown
switch(config-if-vrrp)#
Step 7
show vrrp
Example:
switch(config-if-vrrp)# show vrrp
Step 8
copy running-config startup-config
(Optional) Displays a summary of VRRP
information.
(Optional) Saves this configuration change.
Example:
switch(config-if-vrrp)# copy
running-config startup-config
Configuring Time Intervals for Advertisement Packets
You can configure the time intervals for advertisement packets.
BEFORE YOU BEGIN
You must enable VRRP (see the “Configuring VRRP” section on page 18-7).
Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing”
section on page 2-8).
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SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrrp number
4.
shutdown
5.
advertisement-interval seconds
6.
no shutdown
7.
(Optional) show vrrp
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet 2/1
switch(config-if)#
Step 3
Creates a virtual router group.
vrrp number
Example:
switch(config-if)# vrrp 250
switch(config-if-vrrp)#
Step 4
shutdown
Example:
switch(config-if-vrrp)# shutdown
switch(config-if-vrrp)#
Step 5
advertisement-interval seconds
Example:
switch(config-if-vrrp)# advertisement-interval 15
Step 6
no shutdown
Example:
switch(config-if-vrrp)# no shutdown
switch(config-if-vrrp)#
Step 7
show vrrp
Example:
switch(config-if-vrrp)# show vrrp
Step 8
copy running-config startup-config
Example:
switch(config-if-vrrp)# copy running-config
startup-config
Disables the VRRP group. Disabled by
default.
Sets the interval time in seconds between
sending advertisement frames. The range
is from 1 to 255. The default is 1 second.
Enables the VRRP group. Disabled by
default.
(Optional) Displays a summary of VRRP
information.
(Optional) Saves this configuration
change.
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Configuring VRRP
Disabling Preemption
You can disable preemption for a VRRP group member. If you disable preemption, a higher-priority
backup router does not take over for a lower-priority master router. Preemption is enabled by default.
BEFORE YOU BEGIN
You must enable VRRP (see the “Configuring VRRP” section on page 18-7).
Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing”
section on page 2-8).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrrp number
4.
shutdown
5.
no preempt
6.
no shutdown
7.
(Optional) show vrrp
8.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
interface interface-type slot/port
Enters interface configuration mode.
Example:
switch(config)# interface ethernet
2/1
switch(config-if)#
Step 3
vrrp number
Creates a virtual router group.
Example:
switch(config-if)# vrrp 250
switch(config-if-vrrp)#
Step 4
no shutdown
Enables the VRRP group. Disabled by default.
Example:
switch(config-if-vrrp)# no
shutdown
Step 5
no preempt
Example:
switch(config-if-vrrp)# no preempt
Disables the preempt option and allows the master to remain
when a higher-priority backup appears.
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Configuring VRRP
Step 6
Command
Purpose
no shutdown
Enables the VRRP group. Disabled by default.
Example:
switch(config-if-vrrp)# no
shutdown
Step 7
(Optional) Displays a summary of VRRP information.
show vrrp
Example:
switch(config-if-vrrp)# show vrrp
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if-vrrp)# copy
running-config startup-config
Configuring VRRP Interface State Tracking
Interface state tracking changes the priority of the virtual router based on the state of another interface
in the device. When the tracked interface goes down or the IP address is removed, Cisco NX-OS assigns
the tracking priority value to the virtual router. When the tracked interface comes up and an IP address
is configured on this interface, Cisco NX-OS restores the configured priority to the virtual router (see
the“Configuring VRRP Priority” section on page 18-9).
Note
For interface state tracking to function, you must enable preemption on the interface.
Note
VRRP does not support Layer 2 interface tracking.
BEFORE YOU BEGIN
You must enable VRRP (see the “Configuring VRRP” section on page 18-7).
Ensure that you have configured an IP address on the interface (see the “Configuring IPv4 Addressing”
section on page 2-8).
Ensure that you have enabled the virtual router (see the “Configuring VRRP Groups” section on
page 18-8).
SUMMARY STEPS
1.
configure terminal
2.
interface interface-type slot/port
3.
vrrp number
4.
shutdown
5.
track interface type number priority value
6.
no shutdown
7.
(Optional) show vrrp
8.
(Optional) copy running-config startup-config
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Verifying the VRRP Configuration
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Enters interface configuration mode.
interface interface-type slot/port
Example:
switch(config)# interface ethernet 2/1
switch(config-if)#
Step 3
Creates a virtual router group.
vrrp number
Example:
switch(config-if)# vrrp 250
switch(config-if-vrrp)#
Step 4
Disables the VRRP group. Disabled by default.
shutdown
Example:
switch(config-if-vrrp)# shutdown
switch(config-if-vrrp)#
Step 5
Enables interface priority tracking for a VRRP group.
The priority range is from 1 to 254.
track interface type number priority
value
Example:
switch(config-if-vrrp)# track interface
ethernet 2/10 priority 254
Step 6
no shutdown
Enables the VRRP group. Disabled by default.
Example:
switch(config-if-vrrp)# no shutdown
switch(config-if-vrrp)#
Step 7
show vrrp
(Optional) Displays a summary of VRRP information.
Example:
switch(config-if-vrrp)# show vrrp
Step 8
copy running-config startup-config
(Optional) Saves this configuration change.
Example:
switch(config-if-vrrp)# copy
running-config startup-config
Verifying the VRRP Configuration
To display VRRP configuration information, perform one of the following tasks:
Command
Purpose
show vrrp
Displays the VRRP status for all groups.
show fhrp [interface-type
interface-number] [verbose]
Displays First Hop Redundancy Protocol (FHRP)
information.
show interface interface-type
Displays the virtual router configuration for an interface.
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Monitoring VRRP Statistics
Monitoring VRRP Statistics
To display VRRP statistics, use the following commands:
Command
Purpose
show vrrp statistics
Displays the VRRP statistics.
Use the clear vrrp statistics command to clear all the VRRP statistics for all interfaces in the device.
Use the clear vrrp vr command to clear the IPv4 VRRP statistics for a specified interface.
Use the clear vrrp ipv4 command to clear all the statistics for the specified IPv4 virtual router.
Configuration Examples for VRRP
In this example, Router A and Router B each belong to three VRRP groups. In the configuration, each
group has the following properties:
•
Group 1:
– Virtual IP address is 10.1.0.10.
– Router A will become the master for this group with priority 120.
– Advertising interval is 3 seconds.
– Preemption is enabled.
•
Group 5:
– Router B will become the master for this group with priority 200.
– Advertising interval is 30 seconds.
– Preemption is enabled.
•
Group 100:
– Router A will become the master for this group first because it has a higher IP address
(10.1.0.2).
– Advertising interval is the default of 1 second.
– Preemption is disabled.
Router A
interface ethernet 1/0
ip address 10.1.0.2/16
no shutdown
vrrp 1
priority 120
authentication text cisco
advertisement-interval 3
address 10.1.0.10
no shutdown
vrrp 5
priority 100
advertisement-interval 30
address 10.1.0.50
no shutdown
vrrp 100
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Additional References
no preempt
address 10.1.0.100
no shutdown
Router B
interface ethernet 1/0
ip address 10.2.0.1/2
no shutdown
vrrp 1
priority 100
authentication text cisco
advertisement-interval 3
address 10.2.0.10
no shutdown
vrrp 5
priority 200
advertisement-interval 30
address 10.2.0.50
no shutdown
vrrp 100
no preempt
address 10.2.0.100
no shutdown
Additional References
For additional information related to implementing VRRP, see the following sections:
•
Related Documents, page 18-18
Related Documents
Related Topic
Document Title
Configuring the hot standby routing protocol
Chapter 17, “Configuring HSRP”
Configuring high availability
Cisco Nexus 9000 Series NX-OS High Availability and Redundancy
Guide
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CH A P T E R
19
Configuring Object Tracking
This chapter describes how to configure object tracking on the Cisco NX-OS device.
This chapter includes the following sections:
•
Information About Object Tracking, page 19-1
•
Licensing Requirements for Object Tracking, page 19-3
•
Guidelines and Limitations, page 19-3
•
Default Settings, page 19-3
•
Configuring Object Tracking, page 19-4
•
Verifying the Object Tracking Configuration, page 19-14
•
Configuration Examples for Object Tracking, page 19-14
•
Related Topics, page 19-15
•
Additional References, page 19-15
Information About Object Tracking
Object tracking allows you to track specific objects on the device, such as the interface line protocol
state, IP routing, and route reachability, and to take action when the tracked object’s state changes. This
feature allows you to increase the availability of the network and shorten recovery time if an object state
goes down.
This section includes the following topics:
•
Object Tracking Overview, page 19-1
•
Object Track List, page 19-2
•
High Availability, page 19-3
•
Virtualization Support, page 19-3
Object Tracking Overview
The object tracking feature allows you to create a tracked object that multiple clients can use to modify
the client behavior when a tracked object changes. Several clients register their interest with the tracking
process, track the same object, and take different actions when the object state changes.
Clients include the following features:
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Information About Object Tracking
•
Embedded Event Manager (EEM)
•
Hot Standby Redundancy Protocol (HSRP)
•
Virtual port channel (vPC)
•
Virtual Router Redundancy Protocol (VRRP)
The object tracking monitors the status of the tracked objects and communicates any changes made to
interested clients. Each tracked object is identified by a unique number that clients can use to configure
the action to take when a tracked object changes state.
Cisco NX-OS tracks the following object types:
•
Interface line protocol state—Tracks whether the line protocol state is up or down.
•
Interface IP routing state—Tracks whether the interface has an IPv4 or IPv6 address and if IPv4 or
IPv6 routing is enabled and active.
•
IP route reachability—Tracks whether an IPv4 or IPv6 route exists and is reachable from the local
device.
For example, you can configure HSRP to track the line protocol of the interface that connects one of the
redundant routers to the rest of the network. If that link protocol goes down, you can modify the priority
of the affected HSRP router and cause a switchover to a backup router that has better network
connectivity.
Object Track List
An object track list allows you to track the combined states of multiple objects. Object track lists support
the following capabilities:
•
Boolean "and" function—Each object defined within the track list must be in an up state so that the
track list object can become up.
•
Boolean "or" function—At least one object defined within the track list must be in an up state so
that the tracked object can become up.
•
Threshold percentage—The percentage of up objects in the tracked list must be greater than the
configured up threshold for the tracked list to be in the up state. If the percentage of down objects
in the tracked list is above the configured track list down threshold, the tracked list is marked as
down.
•
Threshold weight—Assign a weight value to each object in the tracked list, and a weight threshold
for the track list. If the combined weights of all up objects exceeds the track list weight up threshold,
the track list is in an up state. If the combined weights of all the down objects exceeds the track list
weight down threshold, the track list is in the down state.
Other entities, such as virtual port channels (vPCs) can use an object track list to modify the state of a
vPC based on the state of the multiple peer links that create the vPC. See the Cisco Nexus 9000 Series
NX-OS Interfaces Configuration Guide for more information on vPCs.
See the “Configuring an Object Track List with a Boolean Expression” section on page 19-7 for more
information on track lists.
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Licensing Requirements for Object Tracking
High Availability
Object tracking supports high availability through stateful restarts. A stateful restart occurs when the
object tracking process crashes. Object tracking also supports a stateful switchover on a dual supervisor
system. Cisco NX-OS applies the runtime configuration after the switchover.
You can also use object tracking to modify the behavior of a client to improve overall network
availability.
Virtualization Support
Object tracking supports virtual routing and forwarding (VRF) instances. By default, Cisco NX-OS
tracks the route reachability state of objects in the default VRF. If you want to track objects in another
VRF, you must configure the object to be a member of that VRF (see the “Configuring Object Tracking
for a Nondefault VRF” section on page 19-13).
Licensing Requirements for Object Tracking
The following table shows the licensing requirements for this feature:
Product
License Requirement
Cisco NX-OS
Object tracking requires no license. Any feature not included in a license package is bundled with the nx-os
image and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing
scheme, see the Cisco NX-OS Licensing Guide.
Guidelines and Limitations
Object tracking has the following configuration guidelines and limitations:
•
Supports Ethernet, subinterfaces, port channels, loopback interfaces, and VLAN interfaces.
•
Supports one tracked object per HSRP group.
Default Settings
Table 19-1 lists the default settings for object tracking parameters.
Table 19-1
Default Object Tracking Parameters
Parameters
Default
Tracked object VRF
Member of default VRF
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Configuring Object Tracking
Configuring Object Tracking
This section includes the following topics:
Note
•
Configuring Object Tracking for an Interface, page 19-4
•
Deleting a Tracked Object, page 19-5
•
Configuring Object Tracking for Route Reachability, page 19-6
•
Configuring an Object Track List with a Boolean Expression, page 19-7
•
Configuring an Object Track List with a Percentage Threshold, page 19-8
•
Configuring an Object Track List with a Weight Threshold, page 19-9
•
Configuring an Object Tracking Delay, page 19-11
•
Configuring Object Tracking for a Nondefault VRF, page 19-13
If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring Object Tracking for an Interface
You can configure Cisco NX-OS to track the line protocol or IPv4 or IPv6 routing state of an interface.
SUMMARY STEPS
1.
configure terminal
2.
track object-id interface interface-type number {ip routing | ipv6 routing | line-protocol}
3.
(Optional) show track [object-id]
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
track object-id interface interface-type
number {ip routing | ipv6 routing |
line-protocol}
Creates a tracked object for an interface and enters
tracking configuration mode. The object-id range is
from 1 to 500.
Example:
switch(config)# track 1 interface
ethernet 1/2 line-protocol
switch(config-track)#
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Step 3
Command
Purpose
show track [object-id]
(Optional) Displays object tracking information.
Example:
switch(config-track)# show track 1
Step 4
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure object tracking for the line protocol state on Ethernet 1/2:
switch# configure terminal
switch(config)# track 1 interface ethernet 1/2 line-protocol
switch(config-track)# copy running-config startup-config
This example shows how to configure object tracking for the IPv4 routing state on Ethernet 1/2:
switch# configure terminal
switch(config)# track 2 interface ethernet 1/2 ip routing
switch(config-track)# copy running-config startup-config
This example shows how to configure object tracking for the IPv6 routing state on Ethernet 1/2:
switch# configure terminal
switch(config)# track 3 interface ethernet 1/2 ipv6 routing
switch(config-track)# copy running-config startup-config
Deleting a Tracked Object
You can delete a tracked object.
SUMMARY STEPS
1.
configure terminal
2.
no track object-id
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
no track object-id
Example:
switch(config)# no track 1
switch(config-track)#
Deletes a tracked object for an interface. The object-id
range is from 1 to 500.
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Configuring Object Tracking
This example shows how to delete a tracked object:
switch# configure terminal
switch(config)# no track 1
switch(config-track)# copy running-config startup-config
Configuring Object Tracking for Route Reachability
You can configure Cisco NX-OS to track the existence and reachability of an IP route or IPv6 route.
SUMMARY STEPS
1.
configure terminal
2.
track object-id {ip | ipv6} route prefix/length reachability
3.
(Optional) show track [object-id]
4.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Step 3
Example:
switch(config)# track 3 ipv6 route
2::5/64 reachability
switch(config-track)#
Creates a tracked object for a route and enters tracking
configuration mode. The object-id range is from 1 to
500. The prefix format for IPv4 is A.B.C.D/length,
where the length range is from 1 to 32. The prefix
format for IPv6 is A:B::C:D/length, where the length
range is from 1 to 128.
show track [object-id]
(Optional) Displays object tracking information.
track object-id {ip | ipv6} route
prefix/length reachability
Example:
switch(config-track)# show track 1
Step 4
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure object tracking for an IPv4 route in the default VRF:
switch# configure terminal
switch(config)# track 4 ip route 192.0.2.0/8 reachability
switch(config-track)# copy running-config startup-config
This example shows how to configure object tracking for an IPv6 route in the default VRF:
switch# configure terminal
switch(config)# track 5 ipv6 route 10::10/128 reachability
switch(config-track)# copy running-config startup-config
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Configuring Object Tracking
Configuring an Object Track List with a Boolean Expression
You can configure an object track list that contains multiple tracked objects. A tracked list contains one
or more objects. The Boolean expression enables two types of calculation by using either "and" or "or"
operators. For example, when tracking two interfaces using the "and" operator, up means that both
interfaces are up, and down means that either interface is down.
SUMMARY STEPS
1.
configure terminal
2.
track track-number list boolean {and | or}
3.
object object-id [not]
4.
(Optional) show track [object-id]
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
Configures a tracked list object and enters tracking
configuration mode. Specifies that the state of the
tracked list is based on a Boolean calculation. The
Example:
switch(config)# track 1 list boolean and keywords are as follows:
switch(config-track)#
• and—Specifies that the list is up if all objects are
up or down if one or more objects are down. For
example, when tracking two interfaces, up means
that both interfaces are up, and down means that
either interface is down.
track track-number list boolean {and |
or}
•
or—Specifies that the list is up if at least one
object is up. For example, when tracking two
interfaces, up means that either interface is up, and
down means that both interfaces are down.
The track-number range is from 1 to 500.
Step 3
object object-id [not]
Example:
switch(config-track)# object 10
Adds a tracked object to the track list. The object-id
range is from 1 to 500. The not keyword optionally
negates the tracked object state.
Note
The example means that when object 10 is up,
the tracked list detects object 10 as down.
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Step 4
Command
Purpose
show track [object-id]
(Optional) Displays object tracking information.
Example:
switch(config-track)# show track
Step 5
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure a track list with multiple objects as a Boolean “and”:
switch# configure terminal
switch(config)# track 1 list boolean and
switch(config-track)# object 10
switch(config-track)# object 20 not
Configuring an Object Track List with a Percentage Threshold
You can configure an object track list that contains a percentage threshold. A tracked list contains one
or more objects. The percentage of up objects must exceed the configured track list up percent threshold
before the track list is in an up state. For example, if the tracked list has three objects and you configure
an up threshold of 60 percent, two of the objects must be in the up state (66 percent of all objects) for
the track list to be in the up state.
SUMMARY STEPS
1.
configure terminal
2.
track track-number list threshold percentage
3.
threshold percentage up up-value down down-value
4.
object object-id
5.
(Optional) show track [object-id]
6.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
track track-number list threshold
percentage
Example:
switch(config)# track 1 list threshold
percentage
switch(config-track)#
Configures a tracked list object and enters tracking
configuration mode. Specifies that the state of the
tracked list is based on a configured threshold percent.
The track-number range is from 1 to 500.
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Step 3
Command
Purpose
threshold percentage up up-value down
down-value
Configures the threshold percentage for the tracked
list. The range from 0 to 100 percent.
Example:
switch(config-track)# threshold
percentage up 70 down 30
Step 4
object object-id
Example:
switch(config-track)# object 10
Step 5
Adds a tracked object to the track list. The object-id
range is from 1 to 500.
(Optional) Displays object tracking information.
show track [object-id]
Example:
switch(config-track)# show track
Step 6
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure a track list with an up threshold of 70 percent and a down threshold
of 30 percent:
switch# configure terminal
switch(config)# track 1 list threshold percentage
switch(config-track)# threshold percentage up 70 down 30
switch(config-track)# object 10
switch(config-track)# object 20
switch(config-track)# object 30
Configuring an Object Track List with a Weight Threshold
You can configure an object track list that contains a weight threshold. A tracked list contains one or
more objects. The combined weight of up objects must exceed the configured track list up weight
threshold before the track list is in an up state. For example, if the tracked list has three objects with the
default weight of 10 each and you configure an up threshold of 15, two of the objects must be in the up
state (combined weight of 20) for the track list to be in the up state.
SUMMARY STEPS
1.
configure terminal
2.
track track-number list threshold weight
3.
threshold weight up up-value down down-value
4.
object object-id weight value
5.
(Optional) show track [object-id]
6.
(Optional) copy running-config startup-config
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DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
track track-number list threshold weight
Example:
switch(config)# track 1 list threshold
weight
switch(config-track)#
Step 3
threshold weight up up-value down
down-value
Configures a tracked list object and enters tracking
configuration mode. Specifies that the state of the
tracked list is based on a configured threshold weight.
The track-number range is from 1 to 500.
Configures the threshold weight for the tracked list.
The range from 1 to 255.
Example:
switch(config-track)# threshold weight
up 30 down 10
Step 4
object object-id weight value
Example:
switch(config-track)# object 10 weight
15
Step 5
show track [object-id]
Adds a tracked object to the track list. The object-id
range is from 1 to 500. The value range is from 1 to
255. The default weight value is 10.
(Optional) Displays object tracking information.
Example:
switch(config-track)# show track
Step 6
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
This example shows how to configure a track list with an up weight threshold of 30 and a down threshold
of 10:
switch# configure terminal
switch(config)# track 1 list threshold
switch(config-track)# threshold weight
switch(config-track)# object 10 weight
switch(config-track)# object 20 weight
switch(config-track)# object 30
weight
up 30 down 10
15
15
In this example, the track list is up if object 10 and object 20 are up, and the track list goes to the down
state if all three objects are down.
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Configuring Object Tracking
Configuring an Object Tracking Delay
You can configure a delay for a tracked object or an object track list that delays when the object or list
triggers a stage change. The tracked object or track list starts the delay timer when a state change occurs
but does not recognize a state change until the delay timer expires. At that point, Cisco NX-OS checks
the object state again and records a state change only if the object or list currently has a changed state.
Object tracking ignores any intermediate state changes before the delay timer expires.
For example, for an interface line-protocol tracked object that is in the up state with a 20-second down
delay, the delay timer starts when the line protocol goes down. The object is not in the down state unless
the line protocol is down 20 seconds later.
You can configure an independent up delay and down delay for a tracked object or track list. When you
delete the delay, object tracking deletes both the up and down delay.
You can change the delay at any point. If the object or list is already counting down the delay timer from
a triggered event, the new delay is computed as follows:
•
If the new configuration value is less than the old configuration value, the timer starts with the new
value.
•
If the new configuration value is more than the old configuration value, the timer is calculated as the
new configuration value minus the current timer countdown minus the old configuration value.
1.
configure terminal
2.
track object-id {parameters}
3.
track track-number list {parameters}
4.
delay {up up-time [down down-time] | down down-time [up up-time]}
5.
(Optional) show track [object-id]
6.
(Optional) copy running-config startup-config
SUMMARY STEPS
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
track object-id {parameters}
Example:
switch(config)# track 2 ip route
192.0.2.0/8 reachability
switch(config-track)#
Step 3
track track-number list {parameters}
Example:
switch(config)# track 1 list threshold
weight
switch(config-track)#
Creates a tracked object for a route and enters tracking
configuration mode. The object-id range is from 1 to
500. The prefix format for IPv4 is A.B.C.D/length,
where the length range is from 1 to 32. The prefix
format for IPv6 is A:B::C:D/length, where the length
range is from 1 to 128.
Configures a tracked list object and enters tracking
configuration mode. Specifies that the state of the
tracked list is based on a configured threshold weight.
The track-number range is from 1 to 500.
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Step 4
Command
Purpose
delay {up up-time [down down-time] |
down down-time [up up-time]}
Configures the object delay timers. The range is from
0 to 180 seconds.
Example:
switch(config-track)# delay up 20 down
30
Step 5
(Optional) Displays object tracking information.
show track [object-id]
Example:
switch(config-track)# show track 3
Step 6
(Optional) Copies the running configuration to the
startup configuration.
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
This example shows how to configure object tracking for a route and use delay timers:
switch# configure terminal
switch(config)# track 2 ip route 209.165.201.0/8 reachability
switch(config-track)# delay up 20 down 30
switch(config-track)# copy running-config startup-config
This example shows how to configure a track list with an up weight threshold of 30 and a down threshold
of 10 with delay timers:
switch# configure terminal
switch(config)# track 1 list threshold
switch(config-track)# threshold weight
switch(config-track)# object 10 weight
switch(config-track)# object 20 weight
switch(config-track)# object 30
switch(config-track)# delay up 20 down
weight
up 30 down 10
15
15
30
This example shows the delay timer in the show track command output before and after an interface is
shut down:
switch(config-track)# show track
Track 1
Interface loopback1 Line Protocol
Line Protocol is UP
1 changes, last change 00:00:13
Delay down 10 secs
switch(config-track)# interface loopback 1
switch(config-if)# shutdown
switch(config-if)# show track
Track 1
Interface loopback1 Line Protocol
Line Protocol is delayed DOWN (8 secs remaining)<------- delay timer counting down
1 changes, last change 00:00:22
Delay down 10 secs
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Configuring Object Tracking
Configuring Object Tracking for a Nondefault VRF
You can configure Cisco NX-OS to track an object in a specific VRF.
BEFORE YOU BEGIN
Ensure that nondefault VRFs are created first.
SUMMARY STEPS
1.
configure terminal
2.
track object-id {ip | ipv6} route prefix/length reachability
3.
vrf member vrf-name
4.
(Optional) show track [object-id]
5.
(Optional) copy running-config startup-config
DETAILED STEPS
Step 1
Command
Purpose
configure terminal
Enters global configuration mode.
Example:
switch# configure terminal
switch(config)#
Step 2
track object-id {ip | ipv6} route
prefix/length reachability
Example:
switch(config)# track 3 ipv6 route
1::2/64 reachability
switch(config-track)#
Step 3
vrf member vrf-name
Example:
switch(config-track)# vrf member Red
Step 4
Creates a tracked object for a route and enters tracking
configuration mode. The object-id range is from 1 to
500. The prefix format for IPv4 is A.B.C.D/length,
where the length range is from 1 to 32. The prefix
format for IPv6 is A:B::C:D/length, where the length
range is from 1 to 128.
Configures the VRF to use for tracking the configured
object.
(Optional) Displays object tracking information.
show track [object-id]
Example:
switch(config-track)# show track 3
Step 5
copy running-config startup-config
Example:
switch(config-track)# copy
running-config startup-config
(Optional) Copies the running configuration to the
startup configuration.
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Verifying the Object Tracking Configuration
This example shows how to configure object tracking for a route and use VRF Red to look up
reachability information for this object:
switch# configure terminal
switch(config)# track 2 ip route 209.165.201.0/8 reachability
switch(config-track)# vrf member Red
switch(config-track)# copy running-config startup-config
This example shows how to configure object tracking for an IPv6 route and use VRF Red to look up
reachability information for this object:
switch# configure terminal
switch(config)# track 3 ipv6 route 1::2/64 reachability
switch(config-track)# vrf member Red
switch(config-track)# copy running-config startup-config
This example shows how to modify tracked object 2 to use VRF Blue instead of VRF Red to look up
reachability information for this object:
switch# configure terminal
switch(config)# track 2
switch(config-track)# vrf member Blue
switch(config-track)# copy running-config startup-config
Verifying the Object Tracking Configuration
To display object tracking configuration information, perform one of the following tasks:
Command
Purpose
show track [object-id] [brief]
Displays the object tracking information for one
or more objects.
show track [object-id] interface [brief]
Displays the interface-based object tracking
information.
show track [object-id] {ip | ipv6} route [brief]
Displays the IPv4 or IPv6 route-based object
tracking information.
Configuration Examples for Object Tracking
This example shows how to configure object tracking for route reachability and use VRF Red to look up
reachability information for this route:
switch# configure terminal
switch(config)# track 2 ip route 209.165.201.0/8 reachability
switch(config-track)# vrf member Red
switch(config-track)# copy running-config startup-config
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Related Topics
Related Topics
See the following topics for information related to object tracking:
•
Chapter 13, “Configuring Layer 3 Virtualization”
•
Chapter 17, “Configuring HSRP”
Additional References
For additional information related to implementing object tracking, see the following sections:
•
Related Documents, page 19-15
Related Documents
Related Topic
Document Title
Configuring the Embedded Event Manager
Cisco Nexus 9000 Series NX-OS System Management Configuration
Guide
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A P P E N D I X
A
IETF RFCs Supported by Cisco NX-OS Unicast
Features
This appendix lists the IETF RFCs supported in Cisco NX-OS.
BGP RFCs
RFCs
Title
RFC 1997
BGP Communities Attribute
RFC 2385
Protection of BGP Sessions via the TCP MD5 Signature Option
RFC 2439
BGP Route Flap Damping
RFC 2519
A Framework for Inter-Domain Route Aggregation
RFC 2545
Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain
Routing
RFC 2858
Multiprotocol Extensions for BGP-4
RFC 2918
Route Refresh Capability for BGP-4
RFC 3065
Autonomous System Confederations for BGP
RFC 3392
Capabilities Advertisement with BGP-4
RFC 4271
A Border Gateway Protocol 4 (BGP-4)
RFC 4273
Definitions of Managed Objects for BGP-4
RFC 4456
BGP Route Reflection: An Alternative to Full Mesh Internal BGP
(IBGP)
RFC 4486
Subcodes for BGP Cease Notification Message
RFC 4724
Graceful Restart Mechanism for BGP
RFC 4893
BGP Support for Four-octet AS Number Space
RFC 5004
RFC 5396
Avoid BGP Best Path Transitions from One External to Another
1
Textual Representation of Autonomous System (AS) Numbers
RFC 5668
4-Octet AS Specific BGP Extended Community
draft-ietf-idr-add-paths-08.txt
Advertisement of Multiple Paths in BGP
draft-ietf-idr-bgp4-mib-15.txt
BGP4-MIB
draft-kato-bgp-ipv6-link-local-00.txt
BGP4+ Peering Using IPv6 Link-local Address
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IETF RFCs Supported by Cisco NX-OS Unicast Features
1. RFC 5396 is partially supported. The asplain and asdot notations are supported, but the asdot+ notation is not.
First-Hop Redundancy Protocol RFCs
RFCs
Title
RFC 2281
Hot Standby Redundancy Protocol
RFC 3768
Virtual Router Redundancy Protocol
IP Services RFCs
RFCs
Title
RFC 786
UDP
RFC 791
IP
RFC 792
ICMP
RFC 793
TCP
RFC 826
ARP
RFC 1027
Proxy ARP
RFC 1591
DNS Client
RFC 1812
IPv4 routers
RFC 4022
TCP-MIB
RFC 4292
IP-FORWARDING-TABLE-MIB
RFC 4293
IP-MIB
IPv6 RFCs
RFCs
Title
RFC 1981
Path MTU Discovery for IP version 6
RFC 2373
IP Version 6 Addressing Architecture
RFC 2374
An Aggregatable Global Unicast Address Format
RFC 2460
Internet Protocol, Version 6 (IPv6) Specification
RFC 2461
Neighbor Discovery for IP Version 6 (IPv6)
RFC 2462
IPv6 Stateless Address Autoconfiguration
RFC 2464
Transmission of IPv6 Packets over Ethernet Networks
RFC 3152
Delegation of IP6.ARPA
RFC 3162
RADIUS and IPv6
RFC 3513
Internet Protocol Version 6 (IPv6) Addressing Architecture
RFC 3596
DNS Extensions to Support IP version 6
RFC 4193
Unique Local IPv6 Unicast Addresses
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IETF RFCs Supported by Cisco NX-OS Unicast Features
IS-IS RFCs
RFCs
Title
RFC 1142
OSI 10589 Intermediate system to intermediate system intra-domain
routing exchange protocol
RFC 1195
Use of OSI IS-IS for routing in TCP/IP and dual environment
RFC 2763, RFC 5301
Dynamic Hostname Exchange Mechanism for IS-IS
RFC 2966, RFC 5302
Domain-wide Prefix Distribution with Two-Level IS-IS
RFC 2972
IS-IS Mesh Groups
RFC 3277
IS-IS Transient Blackhole Avoidance
RFC 3373, RFC 5303
Three-Way Handshake for IS-IS Point-to-Point Adjacencies
RFC 3567, RFC 5304
IS-IS Cryptographic Authentication
RFC 3784, RFC 5305
IS-IS Extensions for Traffic Engineering
RFC 3847, RFC 5306
Restart Signaling for IS-IS
draft-ietf-isis-igp-p2p-over-lan-06.txt
Internet Draft Point-to-point operation over LAN in link-state
routing protocols
OSPF RFCs
RFCs
Title
RFC 2328
OSPF Version 2
RFC 2370
The OSPF Opaque LSA Option
RFC 2740
OSPF for IPv6
RFC 3101
The OSPF Not-So-Stubby Area (NSSA) Option
RFC 3137
OSPF Stub Router Advertisement
RFC 3623
Graceful OSPF Restart
draft-ietf-ospf-ospfv3-graceful-restart-04.txt
OSPFv3 Graceful Restart
RIP RFCs
RFCs
Title
RFC 2082
RIP-2 MD5 Authentication
RFC 2453
RIP Version 2
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
A-3
Appendix A
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
A-4
IETF RFCs Supported by Cisco NX-OS Unicast Features
A P P E N D I X
B
Configuration Limits for Cisco NX-OS Layer 3
Unicast Features
The configuration limits are documented in the Cisco Nexus 9000 Series NX-OS Verified Scalability
Guide.
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
B-1
Appendix B
Configuration Limits for Cisco NX-OS Layer 3 Unicast Features
Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide, Release 6.x
B-2
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