Cisco Network Convergence System 5500 Series Configuration Guide
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Anúncio
Segment Routing Configuration Guide for Cisco NCS 5500 Series
Routers, IOS XR Release 7.2.x
First Published: 2020-08-14
Last Modified: 2021-01-29
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C O N T E N T S
P R E F A C E
C H A P T E R 1
C H A P T E R 2
C H A P T E R 3
Communications, Services, and Additional Information ix
New and Changed Information for Segment Routing Features 1
New and Changed Segment Routing Features 1
Workflow for Deploying Segment Routing 5
Configure Segment Routing over IPv6 (SRv6) 7
Segment Routing over IPv6 Overview 7
Configuring SRv6 under IS-IS 13
Configuring SRv6 IS-IS Flexible Algorithm 14
Configuring SRv6 IS-IS TI-LFA 16
Configuring SRv6 IS-IS Microloop Avoidance 20
SRv6 Services: IPv4 L3VPN Active-Standby Redundancy using Port-Active Mode 33
SRv6 Services for L3VPN Active-Standby Redundancy using Port-Active Mode: Operation 34
Configure SRv6 Services L3VPN Active-Standby Redundancy using Port-Active Mode 34
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
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Contents
C H A P T E R 4
C H A P T E R 5
C H A P T E R 6
SRv6 Services: IPv4 L3VPN Active-Active Redundancy 37
SRv6 Services: BGP Global IPv4 38
SRv6 Services: BGP Global IPv6 39
SRv6 Services: EVPN VPWS — All-Active Multi-Homing 42
SRv6 Services: EVPN VPWS — IPv6 QoS Traffic-Class Marking 44
SRv6 Services: SRv6 Services TLV Type 5 Support 45
SRv6 SID Information in BGP-LS Reporting 45
SRv6 OAM — SID Verification 46
DHCPv4 Relay Agent and Proxy Support over SRv6 48
DHCPv6 Relay Agent Support over SRv6 49
Configure Segment Routing Global Block and Segment Routing Local Block 51
About the Segment Routing Global Block 51
About the Segment Routing Local Block 53
Understanding Segment Routing Label Allocation 54
Setup a Non-Default Segment Routing Global Block Range 57
Setup a Non-Default Segment Routing Local Block Range 58
Configure Segment Routing for IS-IS Protocol 61
Enabling Segment Routing for IS-IS Protocol 61
Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface 64
Configuring an Adjacency SID 66
Manually Configure a Layer 2 Adjacency SID 69
Configuring Bandwidth-Based Local UCMP 73
IS-IS Multi-Domain Prefix SID and Domain Stitching: Example 74
Configure IS-IS Multi-Domain Prefix SID 74
Distribute IS-IS Link-State Data 76
Conditional Prefix Advertisement 76
Segment Routing ECMP-FEC Optimization 78
Configure Segment Routing for OSPF Protocol 81
Enabling Segment Routing for OSPF Protocol 81
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Contents
C H A P T E R 7
C H A P T E R 8
Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface 83
Segment Routing ECMP-FEC Optimization 86
Configure Segment Routing for BGP 87
Configure BGP Prefix Segment Identifiers 88
Segment Routing Egress Peer Engineering 89
Configure Segment Routing Egress Peer Engineering 89
Configuring Manual BGP-EPE Peering SIDs 90
Example: Configuring SR-EPE and BGP-LS 97
Configure BGP Proxy Prefix SID 98
Usage Guidelines and Limitations 104
Instantiation of an SR Policy 104
On-Demand SR Policy – SR On-Demand Next-Hop 104
SR-ODN Configuration Steps 106
Configuring SR-ODN: Examples 108
Configuring SR-ODN for EVPN-VPWS: Use Case 117
Manually Provisioned SR Policy 137
Configure SR Policy with Dynamic Path 141
Anycast SID-Aware Path Computation 143
Configure SR-TE Policy with Explicit Path 143
Configuring Explicit Path with Affinity Constraint Validation 146
Path Computation Element Protocol 148
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Contents
C H A P T E R 9
C H A P T E R 1 0
Configure the Head-End Router as PCEP PCC 148
Configure BGP SR Policy Address Family at SR-TE Head-End 153
Color-Only Automated Steering 156
Address-Family Agnostic Automated Steering 158
Per-Flow Automated Steering 159
Stitching SR-TE Polices Using Binding SID: Example 164
Static Route over Segment Routing Policy 168
LDP over Segment Routing Policy 172
SR-TE MPLS Label Imposition Enhancement 175
SR-TE Head-End IPv4 Unnumbered Interface Support 176
SR-TE Reoptimization Timers 178
Segment Routing Tree Segment Identifier 181
Configure Segment Routing Tree-SID 185
Enabling Segment Routing Flexible Algorithm 189
Prerequisites for Flexible Algorithm 189
Building Blocks of Segment Routing Flexible Algorithm 189
Flexible Algorithm Definition 189
Flexible Algorithm Membership 190
Flexible Algorithm Definition Advertisement 190
Flexible Algorithm Prefix-SID Advertisement 190
Calculation of Flexible Algorithm Path 190
Installation of Forwarding Entries for Flexible Algorithm Paths 191
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C H A P T E R 1 1
C H A P T E R 1 2
C H A P T E R 1 3
Flexible Algorithm Prefix-SID Redistribution 191
Flexible Algorithm Prefix Metric 191
Configuring Flexible Algorithm 192
Example: Configuring IS-IS Flexible Algorithm 193
Example: Configuring OSPF Flexible Algorithm 194
Example: Traffic Steering to Flexible Algorithm Paths 195
BGP Routes on PE – Color Based Steering 195
Configure Segment Routing Path Computation Element 199
Configure the Disjoint Policy (Optional) 203
SR-PCE Flexible Algorithm Multi-Domain Path Computation 206
Example: SR-PCE Flexible Algorithm Multi-Domain Path Computation Use Case 207
ACL Support for PCEP Connection 210
Anycast SID-Aware Path Computation 211
SR-PCE IPv4 Unnumbered Interface Support 214
Inter-Domain Path Computation Using Redistributed SID 216
Example: Inter-Domain Path Computation Using Redistributed SID 218
PCE Support for MPLS-TE LSPs 219
Configuring the North-Bound API on SR-PCE 221
Configure Performance Measurement 225
Usage Guidelines and Limitations 227
SR Policy End-to-End Delay Measurement 241
Configure Topology-Independent Loop-Free Alternate (TI-LFA) 249
Usage Guidelines and Limitations 251
Configuring TI-LFA for IS-IS 252
Configuring TI-LFA for OSPF 254
Contents
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
vii
Contents
C H A P T E R 1 4
C H A P T E R 1 5
C H A P T E R 1 6
TI-LFA Node and SRLG Protection: Examples 256
Configuring Global Weighted SRLG Protection 257
SR-MPLS over GRE as TI-LFA Backup Path 260
Example: SR-MPLS over GRE as TI-LFA Backup Path 263
Configure Segment Routing Microloop Avoidance 273
About Segment Routing Microloop Avoidance 273
Configure Segment Routing Microloop Avoidance for IS-IS 273
Configure Segment Routing Microloop Avoidance for OSPF 274
Configure Segment Routing Mapping Server 277
Segment Routing Mapping Server 277
Usage Guidelines and Restrictions 278
Segment Routing and LDP Interoperability 278
Example: Segment Routing LDP Interoperability 278
Configuring Mapping Server 280
Enable Mapping Advertisement 282
Configure Mapping Advertisement for IS-IS 282
Configure Mapping Advertisement for OSPF 283
MPLS Ping and Traceroute for BGP and IGP Prefix-SID 285
Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID 286
MPLS LSP Ping and Traceroute Nil FEC Target 288
Examples: LSP Ping and Traceroute for Nil_FEC Target 288
Segment Routing Ping and Traceroute 290
Segment Routing Traceroute 292
Segment Routing Ping and Traceroute for Flexible Algorithm 294
Segment Routing Ping for Flexible Algorithm 294
Segment Routing Traceroute for Flexible Algorithm 295
Segment Routing over IPv6 OAM 295
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Preface
The Segment Routing Configuration Guide for for Cisco NCS 5500 Series Routers preface contains these sections:
•
Changes to This Document, on page ix
•
Communications, Services, and Additional Information, on page ix
Changes to This Document
This table lists the changes made to this document since it was first printed.
Date
August 2020
Change Summary
Initial release of this document
January 2021 Replublished for Release 7.2.2
Communications, Services, and Additional Information
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
ix
Communications, Services, and Additional Information
Preface x
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
C H A P T E R
1
New and Changed Information for Segment
Routing Features
This table summarizes the new and changed feature information for the Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers , and lists where they are documented.
•
New and Changed Segment Routing Features, on page 1
New and Changed Segment Routing Features
Segment Routing Features Added or Modified in IOS XR Release 7.2.x
Feature
DHCPv6 Relay Agent
Support over SRv6
Description Introduced/Changed in
Release
This feature is introduced.
Release 7.2.2
SRv6 Services: BGP
Global IPv6
SRv6 Services: IPv6
L3VPN
Per-Flow Automated
Steering
This feature is introduced.
This feature is introduced.
This feature is introduced.
Release 7.2.2
Release 7.2.2
Release 7.2.1
SR-PCE Flexible
Algorithm Multi-Domain
Path Computation
This feature is introduced.
Release 7.2.1
SR-PCE Inter-Domain
Path Computation Using
Redistributed SID
This feature is introduced.
Release 7.2.1
Where Documented
Redistributed SID, on page 216
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
1
New and Changed Information for Segment Routing Features
New and Changed Segment Routing Features
Feature
SR-PCE TCP
Authentication Option
SR-PCE Support for
MPLS-TE LSPs
SRv6 Anycast Locator
SRv6 IS-IS Flex-Algo
Flexible Algorithm Prefix
Summarization
Global Weighted SRLG
Protection for OSPF
TI-LFA
Description Introduced/Changed in
Release
This feature is introduced.
Release 7.2.1
Where Documented
This feature is introduced.
This feature is introduced.
This feature is introduced.
This feature is introduced.
Release 7.2.1
Release 7.2.1
Release 7.2.1
Release 7.2.1
SR-MPLS over GRE as
TI-LFA Backup Path
This feature is introduced.
Release 7.2.1
Manual BGP-EPE Peering
SIDs
This feature is introduced.
Release 7.2.1
Flexible Algorithm, on page 14
#unique_18
BPG Peer Set SID
EVPN (ELAN & ELINE multihoming)
On-Demand Next Hop
DHCPv4 Relay Agent and
Proxy Support for SRv6
IPv4 L3VPN
IS-IS Flexible Algorithm
Prefix Metric
IS-IS Flexible Algorithm
Delay Normalization
This feature is introduced.
This feature is introduced.
This feature is introduced.
This feature is introduced.
This feature is introduced.
Release 7.2.1
Release 7.2.1
Release 7.2.1
Release 7.2.1
Release 7.2.1
BGP-EPE Peering SIDs, on page 90
Proxy Support over SRv6, on page 48
Delay Normalization, on page 238
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
C H A P T E R
2
About Segment Routing
This chapter introduces the concept of segment routing and provides a workflow for configuring segment routing.
•
•
•
•
Workflow for Deploying Segment Routing, on page 5
Scope
Segment routing is a method of forwarding packets on the network based on the source routing paradigm.
The source chooses a path and encodes it in the packet header as an ordered list of segments. Segments are an identifier for any type of instruction. For example, topology segments identify the next hop toward a destination. Each segment is identified by the segment ID (SID) consisting of a flat unsigned 20-bit integer.
Segments
Interior gateway protocol (IGP) distributes two types of segments: prefix segments and adjacency segments.
Each router (node) and each link (adjacency) has an associated segment identifier (SID).
• A prefix SID is associated with an IP prefix. The prefix SID is manually configured from the segment routing global block (SRGB) range of labels, and is distributed by IS-IS or OSPF. The prefix segment steers the traffic along the shortest path to its destination. A node SID is a special type of prefix SID that identifies a specific node. It is configured under the loopback interface with the loopback address of the node as the prefix.
A prefix segment is a global segment, so a prefix SID is globally unique within the segment routing domain.
• An adjacency segment is identified by a label called an adjacency SID, which represents a specific adjacency, such as egress interface, to a neighboring router. An adjacency SID can be allocated dynamically from the dynamic label range or configured manually from the segment routing local block (SRLB) range of labels. The adjacency SID is distributed by IS-IS or OSPF. The adjacency segment steers the traffic to a specific adjacency.
An adjacency segment is a local segment, so the adjacency SID is locally unique relative to a specific router.
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
3
About Segment Routing
Need
By combining prefix (node) and adjacency segment IDs in an ordered list, any path within a network can be constructed. At each hop, the top segment is used to identify the next hop. Segments are stacked in order at the top of the packet header. When the top segment contains the identity of another node, the receiving node uses equal cost multipaths (ECMP) to move the packet to the next hop. When the identity is that of the receiving node, the node pops the top segment and performs the task required by the next segment.
Dataplane
Segment routing can be directly applied to the Multiprotocol Label Switching (MPLS) architecture with no change in the forwarding plane. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. The related label is popped from the stack, after the completion of a segment.
Services
Segment Routing integrates with the rich multi-service capabilities of MPLS, including Layer 3 VPN (L3VPN),
Virtual Private Wire Service (VPWS), Virtual Private LAN Service (VPLS), and Ethernet VPN (EVPN).
Segment Routing for Traffic Engineering
Segment routing for traffic engineering (SR-TE) takes place through a policy between a source and destination pair. Segment routing for traffic engineering uses the concept of source routing, where the source calculates the path and encodes it in the packet header as a segment. Each segment is an end-to-end path from the source to the destination, and instructs the routers in the provider core network to follow the specified path instead of the shortest path calculated by the IGP. The destination is unaware of the presence of the policy.
Need
With segment routing for traffic engineering (SR-TE), the network no longer needs to maintain a per-application and per-flow state. Instead, it simply obeys the forwarding instructions provided in the packet.
SR-TE utilizes network bandwidth more effectively than traditional MPLS-TE networks by using ECMP at every segment level. It uses a single intelligent source and relieves remaining routers from the task of calculating the required path through the network.
Benefits
• Ready for SDN : Segment routing was built for SDN and is the foundation for Application Engineered
Routing (AER). SR prepares networks for business models, where applications can direct network behavior. SR provides the right balance between distributed intelligence and centralized optimization and programming.
• Minimal configuration : Segment routing for TE requires minimal configuration on the source router.
• Load balancing : Unlike in RSVP-TE, load balancing for segment routing can take place in the presence of equal cost multiple paths (ECMPs).
• Supports Fast Reroute (FRR) : Fast reroute enables the activation of a pre-configured backup path within 50 milliseconds of path failure.
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
About Segment Routing
Workflow for Deploying Segment Routing
• Plug-and-Play deployment : Segment routing policies are interoperable with existing MPLS control and data planes and can be implemented in an existing deployment.
Workflow for Deploying Segment Routing
Follow this workflow to deploy segment routing.
1.
Configure the Segment Routing Global Block (SRGB)
2.
Enable Segment Routing and Node SID for the IGP
3.
Configure Segment Routing for BGP
4.
Configure the SR-TE Policy
5.
Configure the SR-PCE
6.
Configure TI-LFA and Microloop Avoidance
7.
Configure the Segment Routing Mapping Server
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
5
Workflow for Deploying Segment Routing
About Segment Routing
6
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
C H A P T E R
3
Configure Segment Routing over IPv6 (SRv6)
Segment Routing for IPv6 (SRv6) is the implementation of Segment Routing over the IPv6 dataplane.
•
Segment Routing over IPv6 Overview, on page 7
•
Configuring SRv6 under IS-IS, on page 13
•
Configuring SRv6 IS-IS Flexible Algorithm, on page 14
•
Configuring SRv6 IS-IS TI-LFA, on page 16
•
Configuring SRv6 IS-IS Microloop Avoidance, on page 20
•
SRv6 Services: IPv4 L3VPN, on page 21
•
SRv6 Services: IPv6 L3VPN, on page 26
•
SRv6 Services: IPv4 L3VPN Active-Standby Redundancy using Port-Active Mode, on page 33
•
SRv6 Services: IPv4 L3VPN Active-Active Redundancy , on page 37
•
SRv6 Services: BGP Global IPv4, on page 38
•
SRv6 Services: BGP Global IPv6, on page 39
•
SRv6 Services: EVPN VPWS — All-Active Multi-Homing , on page 42
•
SRv6 Services: EVPN VPWS — IPv6 QoS Traffic-Class Marking, on page 44
•
SRv6 Services: SRv6 Services TLV Type 5 Support, on page 45
•
SRv6 SID Information in BGP-LS Reporting, on page 45
•
SRv6 OAM — SID Verification, on page 46
•
DHCPv4 Relay Agent and Proxy Support over SRv6, on page 48
•
DHCPv6 Relay Agent Support over SRv6, on page 49
Segment Routing over IPv6 Overview
Segment Routing (SR) can be applied on both MPLS and IPv6 data planes. This feature extends Segment
Routing support with IPv6 data plane. In an SR-MPLS enabled network, an MPLS label is used as the Segment
Identifier (SID) and the source router chooses a path to the destination and encodes the path in the packet header as a stack of labels. However, in a Segment Routing over IPv6 (SRv6) network, an IPv6 address serves as the SID. The source router encodes the path to destination as an ordered list of segments (list of IPv6 addresses) in the IPv6 packet. To encode an ordered list of IPv6 addresses in an IPv6 packet, a new routing header which is an extension header is used. This new header for SRv6 is called Segment Routing Header
(SRH). In an SRv6 enabled network, the active segment is indicated by the destination address of the packet, and the next segment is indicated by a pointer in the SRH.
The following list explains the fields in SRH:
• Next header—Identifies the type of header immediately following the SRH.
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
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Configure Segment Routing over IPv6 (SRv6)
Segment Routing over IPv6 Overview
• Hdr Ext Len (header extension length)—The length of the SRH in 8-octet units, not including the first
8 octets.
• Segments left—Specifies the number of route segments remaining. That means, the number of explicitly listed intermediate nodes still to be visited before reaching the final destination.
• Last Entry—Contains the index (zero based) of the last element of the segment list.
• Flags— Contains 8 bits of flags.
• Tag—Tag a packet as part of a class or group of packets like packets sharing the same set of properties.
• Segment list—128-bit IPv6 addresses representing the n th segment in the segment list. The segment list encoding starts from the last segment of the SR policy (path). That means the first element of the segment list (Segment list [0]) contains the last segment of the SR policy, the second element contains the penultimate segment of the SR policy and so on.
Each node along the SRv6 packet path has a different functionality:
• Source node—A node that can generate an IPv6 packet with an SRH (an SRv6 packet), or an ingress node that can impose an SRH on an IPv6 packet.
• Transit node—A node along the path of the SRv6 packet (IPv6 packet and SRH). The transit node does not inspect the SRH. The destination address of the IPv6 packet does not correspond to the transit node.
• End point node—A node in the SRv6 domain where the SRv6 segment is terminated. The destination address of the IPv6 packet with an SRH corresponds to the end point node. The segment endpoint node executes the function bound to the SID
Table 1: Example of a Segment Routing Header
Next Header
Last Entry
Hdr Ext Len
Flags
Routing Type
Segment List[0]
(128-bit IPv6 address)
. . .
Segment List[ n ]
(128-bit IPv6 address)
Segments Left
Tag
Optional Type Length Value objects (variable)
In SRv6, a SID represents a 128-bit value, consisting of the following three parts:
• Locator: This is the first part of the SID with most significant bits and represents an address of a specific
SRv6 node.
• Function: This is the portion of the SID that is local to the owner node and designates a specific SRv6 function (network instruction) that is executed locally on a particular node, specified by the locator bits.
• Args: This field is optional and represents optional arguments to the function.
The locator part can be further divided into two parts:
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Configure Segment Routing over IPv6 (SRv6)
Segment Routing over IPv6 Overview
• SID Block: This field is the SRv6 network designator and is a fixed or known address space for an SRv6 domain. This is the most significant bit (MSB) portion of a locator subnet.
• Node Id: This field is the node designator in an SRv6 network and is the least significant bit (LSB) portion of a locator subnet.
Configuring SRv6
To enable SRv6 globally, you should first configure a locator with its prefix. The IS-IS protocol announces the locator prefix in IPv6 network and SRv6 applications (like ISIS, BGP) use it to allocate SIDs.
The following usage guidelines and restrictions apply while configuring SRv6.
• All routers in the SRv6 domain should have the same SID block (network designator) in their locator.
• The locator length should be 64-bits long.
• The SID block portion (MSBs) cannot exceed 40 bits. If this value is less than 40 bits, user should use a pattern of zeros as a filler.
• The Node Id portion (LSBs) cannot exceed 24 bits.
• You can configure up to 8 locators to support SRv6 Flexible Algorithm. All locators prefix must share the same SID block (first 40-bits).
Enabling SRv6 with Locator
This example shows how to globally enable SRv6 and configure locator.
Router(config)# segment-routing srv6
Router(config-srv6)# locators
Router(config-srv6-locators)# locator myLoc1
Router(config-srv6-locator)# prefix 2001:db8:0:a2::/64
(Optional) Configuring SRv6 Anycast Locator
An SRv6 Anycast locator is a type of locator that identifies a set of nodes (END SIDs). SRv6 Anycast Locators and their associated END SIDs may be provisioned at multiple places in a topology.
The set of nodes (Anycast group) is configured to advertise a shared Anycast locator and END SID. Anycast routing enables the steering of traffic toward multiple advertising nodes. Packets addressed to an Anycast address are forwarded to the topologically nearest nodes.
One use case is to advertise Anycast END SIDs at exit points from an SRv6 network. Any of the nodes that advertise the common END SID could be used to forward traffic out of the SRv6 portion of the network to the topologically nearest node.
Unlike a normal locator, IS-IS does not program or advertise END.X SIDs associated with an anycast locator.
Note END SIDs allocated from Anycast locators will not be used in constructing TI-LFA backup paths or Microloop
Avoidance primary paths. TI-LFA backup and Microloop Avoidance paths for an Anycast locator prefix may terminate on any node advertising that locator, which may be different from the node terminating the original primary path.
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
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Configure Segment Routing over IPv6 (SRv6)
Segment Routing over IPv6 Overview
Note SRv6 anycast locators may have non-zero algorithm (Flexible Algorithm) values.
The following example shows how to globally enable SRv6 and configure Anycast locator.
Note For Cisco NCS 5500 Series Routers, you must first use the hw-module profile segment-routing srv6 command to enable SRv6 functionality. Then, reload the line card after enabling this command.
Router(config)# hw-module profile segment-routing srv6
Router(config)# segment-routing srv6
Router(config-srv6)# locators
Router(config-srv6-locators)# locator myLoc1 anycast
Router(config-srv6-locator)# prefix 2001:db8:0:a2::/64
Optional: Configuring Encapsulation Parameters
This example shows how to configure encapsulation parameters when configuring SRv6. These optional parameters include:
• Source Address of outer encapsulating IPv6 header: The default source address for encapsulation is one of the loopback addresses.
• The hop limit of outer-encapsulating IPv6 header. The range is from 1 to 254 for NCS 5500 and from 1 to 255 for NCS 5700; the default value for hop-limit is 254.
Router(config)# segment-routing srv6
Router(config-srv6)# encapsulation source-address 1::1
Router(config-srv6)# hop-limit 60
Optional: Enabling Syslog Logging for Locator Status Changes
This example shows how to enable the logging of locator status.
Router(config)# segment-routing srv6
Router(config-srv6)# logging locator status
Verifying SRv6 Manager
This example shows how to verify the overall SRv6 state from SRv6 Manager point of view. The output displays parameters in use, summary information, and platform specific capabilities.
Router# show segment-routing srv6 manager
Parameters:
Parameters:
SRv6 Enabled: Yes
SRv6 Operational Mode:
Base:
SID Base Block: 2001:db8::/40
Encapsulation:
Source Address:
Configured: 1::1
Default: 5::5
Hop-Limit: Default
Traffic-class: Default
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Configure Segment Routing over IPv6 (SRv6)
Segment Routing over IPv6 Overview
Summary:
Number of Locators: 1 (1 operational)
Number of SIDs: 4 (0 stale)
Max SIDs: 64000
OOR:
Thresholds: Green 3200, Warning 1920
Status: Resource Available
History: (0 cleared, 0 warnings, 0 full)
Block 2001:db8:0:a2::/64:
Number of SIDs free: 65470
Max SIDs: 65470
Thresholds: Green 3274, Warning 1965
Status: Resource Available
History: (0 cleared, 0 warnings, 0 full)
Platform Capabilities:
SRv6: Yes
TILFA: Yes
Microloop-Avoidance: Yes
Endpoint behaviors:
End (PSP)
End.X (PSP)
End.DX6
End.DX4
End.DT6
End.DT4
End.DX2
End.OP
uN (PSP/USD) uA (PSP/USD) uDT6 uDT4 uDX2 uB6 (Insert.Red)
Headend behaviors:
T
H.Insert.Red
H.Encaps.Red
Security rules:
SEC-1
SEC-2
SEC-3
Counters:
CNT-1
CNT-3
Signaled parameters:
Max-SL : 3
Max-End-Pop-SRH : 3
Max-H-Insert
Max-H-Encap
: 3 sids
: 3 sids
Max-End-D : 4
Configurable parameters (under srv6):
Encapsulation:
Source Address: Yes
Hop-Limit : value=Yes, propagate=No
Traffic-class : value=Yes, propagate=Yes
Max SIDs: 64000
SID Holdtime: 3 mins
Verifying SRv6 Locator
This example shows how to verify the locator configuration and its operational status.
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Configure Segment Routing over IPv6 (SRv6)
Segment Routing over IPv6 Overview
Router# show segment-routing srv6 locator myLoc1 detail
Name ID Prefix Status
-------------------- ------- ------------------------ ------myLoc1* 5 2001:db8:0:a2::/64 Up
(*): is-default
Interface:
Name: srv6-myLoc1
IFH : 0x00000170
IPv6 address: 2001:db8:0:a2::/64
Chkpt Obj ID: 0x2fc8
Created: Apr 25 06:21:57.077 (00:03:37 ago)
Verifying SRv6 SIDs
This example shows how to verify the allocation of SRv6 local SIDs off locator(s).
Router# show segment-routing srv6 locator myLoc1 sid
SID Function Context
State RW
-----------------------------------------------------------------
------
2001:db8:0:a2:1:: End (PSP) 'default':1
InUse Y
2001:db8:0:a2:40:: End.DT4
'VRF1'
InUse Y
2001:db8:0:a2:41::
InUse Y
End.X (PSP) [Hu0/1/0/1, Link-Local]
Owner
-----------------sidmgr bgp-100 isis-srv6
The following example shows how to display detail information regarding an allocated SRv6 local SID.
Router# show segment-routing srv6 locator myLoc1 sid 2001:db8:0:a2:40:: detail
Owner SID Function Context
State RW
-----------------------------------------------------------------
------
2001:db8:0:a2:40::
InUse Y
End.DT4
'VRF1'
SID context: { table-id=0xe0000011 ('VRF1':IPv4/Unicast) }
Locator: myLoc1'
Allocation type: Dynamic
Created: Feb 1 14:04:02.901 (3d00h ago)
-----------------bgp-100
Similarly, you can display SID information across locators by using the show segment-routing sid command.
show Commands
You can use the following show commands to verify the SRv6 global and locator configuration:
Command show segment-routing srv6 manager
Description
Displays the summary information from SRv6 manager, including platform capabilities.
show segment-routing srv6 locator locator-name
[ detail ]
Displays the SRv6 locator information on the router.
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 under IS-IS
Command
show segment-routing srv6 locator locator-name sid [[ sid-ipv6-address [ detail ]
Description
Displays the information regarding SRv6 local SID(s) allocated from a given locator.
show segment-routing srv6 sid [ sid-ipv6-address | all | stale ] [ detail ]
Displays SID information across locators. By default, only “active” (i.e. non-stale) SIDs are displayed.
show route ipv6 local-srv6 Displays all SRv6 local-SID prefixes in IPv6 RIB.
Configuring SRv6 under IS-IS
Intermediate System-to-Intermediate System (IS-IS) protocol already supports segment routing with MPLS dataplane (SR-MPLS). This feature enables extensions in IS-IS to support Segment Routing with IPv6 data plane (SRv6). The extensions include advertising the SRv6 capabilities of nodes and node and adjacency segments as SRv6 SIDs.
SRv6 IS-IS performs the following functionalities:
1.
Interacts with SID Manager to learn local locator prefixes and announces the locator prefixes in the IGP domain.
2.
Learns remote locator prefixes from other IS-IS neighbor routers and installs the learned remote locator
IPv6 prefix in RIB or FIB.
3.
Allocate or learn prefix SID and adjacency SIDs, create local SID entries, and advertise them in the IGP domain.
Usage Guidelines and Restrictions
The following usage guidelines and restrictions apply for SRv6 IS-IS:
• An IS-IS address-family can support either SR-MPLS or SRv6, but both at the same time is not supported.
Configuring SRv6 under IS-IS
To configure SRv6 IS-IS, use the following command:
• router isis instance address-family ipv6 unicast segment-routing srv6 locator locator [ level { 1 |
2 }]—Enable SRv6 under the IS-IS IPv6 address-family and assign SRv6 locator(s) to it. Use the level
{ 1 | 2 } keywords to advertise the locator only in the specified IS-IS level.
The following example shows how to configure SRv6 under IS-IS.
Router(config)# router isis core
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# segment-routing srv6
Router(config-isis-srv6)# locator myLoc1 level 1
Router(config-isis-srv6-loc)# exit
For more information about configuring IS-IS, refer to the " Implemeting IS-IS " chapter in the Routing
Configuration Guide for Cisco NCS 5500 Series Routers .
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS Flexible Algorithm
Configuring SRv6 IS-IS Flexible Algorithm
This feature introduces support for implementing Flexible Algorithm using IS-IS SRv6.
SRv6 Flexible Algorithm allows operators to customize IGP shortest path computation according to their own needs. An operator can assign custom SRv6 locators to realize forwarding beyond link-cost-based SPF. As a result, Flexible Algorithm provides a traffic engineered path automatically computed by the IGP to any destination reachable by the IGP.
Restrictions and Usage Guidelines
The following restrictions and usage guidelines apply:
• You can configure up to 8 locators to support SRv6 Flexible Algorithm:
• All locators prefix must share the same SID block (first 40-bits).
• The Locator Algorithm value range is 128 to 255.
Configuring SRv6 IS-IS Flexible Algorithm
The following example shows how to configure SRv6 IS-IS Flexible Algorithm.
Note Complete the
before performing these steps.
Note For Cisco NCS5500 Series Routers, you must first use the hw-module profile segment-routing srv6 command to enable SRv6 functionality. Then, reload the line card after enabling this command.
Router(config)# hw-module profile segment-routing srv6
Router(config)# segment-routing srv6
Router(config-srv6)# locators
Router(config-srv6-locators)# locator Loc1-BE // best-effort
Router(config-srv6-locator)# prefix 2001:db8:0:a2::/64
Router(config-srv6-locator)# exit
Router(config-srv6-locators)# locator Loc1-LL // low latency
Router(config-srv6-locator)# prefix 2001:db8:1:a2::/64
Router(config-srv6-locator)# algorithm 128
Router(config-srv6-locator)# exit
Router(config-srv6)# exit
Configuring SRv6 IS-IS
The following example shows how to configure SRv6 IS-IS.
Router(config)# router isis test-igp
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# exit
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# summary-prefix 2001:db8:0::/48
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS Flexible Algorithm
Router(config-isis-af)# summary-prefix 2001:db8:1::/48 algorithm 128 explicit
Router(config-isis-af)# segment-routing srv6
Router(config-isis-srv6)# locator Loc1-BE
Router(config-isis-srv6-loc)# exit
Router(config-isis-srv6)# locator Loc1-LL
Router(config-isis-srv6-loc)# exit
Configuring SRv6 IS-IS Prefix Summarization
SRv6 leverages longest-prefix-match IP forwarding. Massive-scale reachability can be achieved by summarizing locators at ABRs and ASBRs. Use the summary-prefix locator [ algorithm algo ] [ explicit ] command in
IS-IS address-family configuration mode to specify that only locators from the specified algorithm contribute to the summary. The explicit keyword limits the contributing prefixes to only those belonging to the same algorithm.
The following example shows how to configure SRv6 IS-IS Algorithm Summarization for regular algorithm and Flexible Algorithm (128).
Router(config)# router isis test-igp
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# exit
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# summary-prefix 2001:db8:0::/48
Router(config-isis-af)# summary-prefix 2001:db8:1::/48 algorithm 128 explicit
Router(config-isis-af)# segment-routing srv6
Router(config-isis-srv6)# locator Loc1-BE
Router(config-isis-srv6-loc)# exit
Router(config-isis-srv6)# locator Loc1-LL
Router(config-isis-srv6-loc)# exit
Enable Flexible Algorithm for Low Latency
The following example shows how to enable Flexible Algorithm for low-latency:
• IS-IS: Configure Flexible Algorithm definition with delay objective
• Performance-measurement: Configure static delay per interface
Router(config)# router isis test-igp
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# metric-type delay
Router(config-isis-flex-algo)# exit
Router(config-isis)# interface GigabitEthernet0/0/0/0
Router(config-isis-if)# address-family ipv6 unicast
Router(config-isis-if-af)# root
Router(config)# performance-measurement
Router(config-perf-meas)# interface GigabitEthernet0/0/0/0
Router(config-pm-intf)# delay-measurement
Router(config-pm-intf-dm)# advertise-delay 100
Router(config-pm-intf-dm)# commit
Verification
SRv6-LF1# show segment-routing srv6 locator
Mon Aug 12 20:54:15.414 EDT
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS TI-LFA
Name ID Algo Prefix Status
----------------------------------------------------------
Loc1-BE
Loc1-LL
17
18
0
128
2001:db8:0:a2::/64
2001:db8:1:a2::/64
Up
Up
SRv6-LF1# show isis flex-algo 128
Mon Aug 12 21:00:54.282 EDT
IS-IS test-igp Flex-Algo Database
Flex-Algo 128:
Level-2:
Definition Priority: 128
Definition Source: SRv6-LF1.00, (Local)
Definition Equal to Local: Yes
Disabled: No
Level-1:
Definition Priority: 128
Definition Source: SRv6-LF1.00, (Local)
Definition Equal to Local: Yes
Disabled: No
Local Priority: 128
FRR Disabled: No
Microloop Avoidance Disabled: No
Configuring SRv6 IS-IS TI-LFA
This feature introduces support for implementing Topology-Independent Loop-Free Alternate (TI-LFA) using
IS-IS SRv6.
TI-LFA provides link protection in topologies where other fast reroute techniques cannot provide protection.
The goal of TI-LFA is to reduce the packet loss that results while routers converge after a topology change due to a link failure. TI-LFA leverages the post-convergence path which is planned to carry the traffic and ensures link and node protection within 50 milliseconds. TI-LFA with IS-IS SR-MPLS is already supported.
TI-LFA provides link, node, and Shared Risk Link Groups (SRLG) protection in any topology.
For more information, see
Configure Topology-Independent Loop-Free Alternate (TI-LFA), on page 249 .
Usage Guidelines and Restrictions
The following usage guidelines and restrictions apply:
• TI-LFA provides link protection by default. Additional tiebreaker configuration is required to enable node or SRLG protection.
• Usage guidelines for node and SRLG protection:
• TI-LFA node protection functionality provides protection from node failures. The neighbor node is excluded during the post convergence backup path calculation.
• Shared Risk Link Groups (SRLG) refer to situations in which links in a network share a common fiber (or a common physical attribute). These links have a shared risk: when one link fails, other
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS TI-LFA links in the group might also fail. TI-LFA SRLG protection attempts to find the post-convergence backup path that excludes the SRLG of the protected link. All local links that share any SRLG with the protecting link are excluded.
• When you enable link protection, you can also enable node protection, SRLG protection, or both, and specify a tiebreaker priority in case there are multiple LFAs.
• Valid priority values are from 1 to 255. The lower the priority value, the higher the priority of the rule. Link protection always has a lower priority than node or SRLG protection.
Configuring SRv6 IS-IS TI-LFA
The following example shows how to configure SRv6 IS-IS TI-LFA.
Note Complete the
before performing these steps.
Router(config)# router isis core
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# segment-routing srv6
Router(config-isis-srv6)# locator locator1
Router(config-isis-srv6-loc)# exit
Router(config-isis)# interface loopback 0
Router(config-isis-if)# passive
Router(config-isis-if)# address-family ipv6 unicast
Router(config-isis-if-af)# exit
Router(config-isis)# interface bundle-ether 1201
Router(config-isis-if)# address-family ipv6 unicast
Router(config-isis-if-af)# fast-reroute per-prefix
Router(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Router(config-isis-if-af)# exit
Router(config-isis)# interface bundle-ether 1301
Router(config-isis-if)# address-family ipv6 unicast
Router(config-isis-if-af)# fast-reroute per-prefix
Router(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Router(config-isis-if-af)# fast-reroute per-prefix tiebreaker node-protecting index 100
Router(config-isis-if-af)# fast-reroute per-prefix tiebreaker srlg-disjoint index 200
Router(config-isis-if-af)# exit
Configuring SRv6 IS-IS TI-LFA with Flexible Algorithm
TI-LFA backup paths for particular Flexible Algorithm are computed using the same constraints as the calculation of the primary paths for such Flexible Algorithm. These paths use Prefix-SIDs advertised specifically for such Flexible Algorithm in order to enforce a backup path.
The following example shows how to configure SRv6 IS-IS TI-LFA with Flexible Algorithm.
Router(config)# router isis core
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# exit
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# segment-routing srv6
Router(config-isis-srv6)# locator locator1
Router(config-isis-srv6-loc)# exit
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS TI-LFA
Router(config-isis)# interface bundle-ether 1201
Router(config-isis-if)# address-family ipv6 unicast
Router(config-isis-if-af)# fast-reroute per-prefix
Router(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Router(config-isis-if-af)# exit
Use the fast-reroute disable command to disable the LFA calculation on a per-algorithm basis:
Router(config)# router isis core
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# fast-reroute disable
Verification
This example shows how to verify the SRv6 IS-IS TI-LFA configuration using the show isis ipv6 fast-reroute
ipv6-prefix detail command.
Router# show isis ipv6 fast-reroute cafe:0:0:66::/64 detail
Thu Nov 22 16:12:51.983 EST
L1 cafe:0:0:66::/64 [11/115] low priority via fe80::2, TenGigE0/0/0/6, SRv6-HUB6, Weight: 0
Backup path: TI-LFA (link), via fe80::1, Bundle-Ether1201 SRv6-LF1, Weight: 0, Metric:
51
P node: SRv6-TP8.00 [8::8], SRv6 SID: cafe:0:0:88:1:: End (PSP)
Backup-src: SRv6-HUB6.00
P: No, TM: 51, LC: No, NP: No, D: No, SRLG: Yes src SRv6-HUB6.00-00, 6::6
This example shows how to verify the SRv6 IS-IS TI-LFA configuration using the show route ipv6 ipv6-prefix detail command.
Router# show route ipv6 cafe:0:0:66::/64 detail
Thu Nov 22 16:14:07.385 EST
Routing entry for cafe:0:0:66::/64
Known via "isis srv6", distance 115, metric 11, type level-1
Installed Nov 22 09:24:05.160 for 06:50:02
Routing Descriptor Blocks fe80::2, from 6::6, via TenGigE0/0/0/6, Protected
Route metric is 11
Label: None
Tunnel ID: None
Binding Label: None
Extended communities count: 0
Path id:1 Path ref count:0
NHID:0x2000a(Ref:11)
NHID eid:0xffffffffffffffff
SRv6 Headend: H.Insert.Red [base], SRv6 SID-list {cafe:0:0:88:1::}
Backup path id:65 fe80::1, from 6::6, via Bundle-Ether1201, Backup (TI-LFA)
Repair Node(s): 8::8
Route metric is 51
Label: None
Tunnel ID: None
Binding Label: None
Extended communities count: 0
Path id:65 Path ref count:1
NHID:0x2000d(Ref:11)
NHID eid:0xffffffffffffffff
SRv6 Headend: H.Insert.Red [base], SRv6 SID-list {cafe:0:0:88:1::}
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS TI-LFA
MPLS eid:0x1380800000001
This example shows how to verify the SRv6 IS-IS TI-LFA configuration using the show cef ipv6 ipv6-prefix
detail location location command.
Router# show cef ipv6 cafe:0:0:66::/64 detail location 0/0/cpu0
Thu Nov 22 17:01:58.536 EST cafe:0:0:66::/64, version 1356, SRv6 Transit, internal 0x1000001 0x2 (ptr 0x8a4a45cc) [1],
0x0 (0x8a46ae20), 0x0 (0x8c8f31b0)
Updated Nov 22 09:24:05.166
local adjacency fe80::2
Prefix Len 64, traffic index 0, precedence n/a, priority 2 gateway array (0x8a2dfaf0) reference count 4, flags 0x500000, source rib (7), 0 backups
[5 type 3 flags 0x8401 (0x8a395d58) ext 0x0 (0x0)]
LW-LDI[type=3, refc=1, ptr=0x8a46ae20, sh-ldi=0x8a395d58] gateway array update type-time 1 Nov 22 09:24:05.163
LDI Update time Nov 22 09:24:05.163
LW-LDI-TS Nov 22 09:24:05.166
via fe80::2/128, TenGigE0/0/0/6, 8 dependencies, weight 0, class 0, protected [flags
0x400] path-idx 0 bkup-idx 1 NHID 0x2000a [0x8a2c2fd0 0x0] next hop fe80::2/128 via fe80::1/128, Bundle-Ether1201, 8 dependencies, weight 0, class 0, backup (TI-LFA)
[flags 0xb00] path-idx 1 NHID 0x2000d [0x8c2670b0 0x0] next hop fe80::1/128, Repair Node(s): 8::8 local adjacency
SRv6 H.Insert.Red SID-list {cafe:0:0:88:1::}
Load distribution: 0 (refcount 5)
Hash OK Interface
0 Y TenGigE0/0/0/6
Address fe80::2
This example shows how to verify the SRv6 IS-IS TI-LFA configuration using the show cef ipv6 fast-reroute-db command.
Router# show cef ipv6 fast-reroute-db
Sun Dec 9 20:23:08.111 EST
PROTECT-FRR: per-prefix [1, 0x0, 0x0, 0x98c83270] protect-interface: Te0/0/0/6 (0x208) protect-next-hop: fe80::2/128 ipv6 nhinfo [0x977397d0]
Update Time Dec 9 17:29:42.427
BACKUP-FRR: per-prefix [5, 0x0, 0x2, 0x98c83350] backup-interface: BE1201 (0x800002c) backup-next-hop: fe80::1/128 ipv6 nhinfo [0x977396a0 protect-frr: 0x98c83270]
Update Time Dec 9 17:29:42.428
PROTECT-FRR: per-prefix [1, 0x0, 0x0, 0x98c830b0] protect-interface: BE1201 (0x800002c) protect-next-hop: fe80::1/128 ipv6 nhinfo [0x977396a0]
Update Time Dec 9 17:29:42.429
BACKUP-FRR: per-prefix [5, 0x0, 0x1, 0x98c83190] backup-interface: Te0/0/0/6 (0x208) backup-next-hop: fe80::2/128
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Configure Segment Routing over IPv6 (SRv6)
Configuring SRv6 IS-IS Microloop Avoidance ipv6 nhinfo [0x977397d0 protect-frr: 0x98c830b0]
Update Time Dec 9 17:29:42.429
Configuring SRv6 IS-IS Microloop Avoidance
This feature introduces support for implementing microloop avoidance using IS-IS SRv6.
Microloops are brief packet loops that occur in the network following a topology change (link down, link up, or metric change events). Microloops are caused by the non-simultaneous convergence of different nodes in the network. If nodes converge and send traffic to a neighbor node that has not converged yet, traffic may be looped between these two nodes, resulting in packet loss, jitter, and out-of-order packets.
The SRv6 Microloop Avoidance feature detects if microloops are possible following a topology change. If a node computes that a microloop could occur on the new topology, the node creates a loop-free SR-TE policy path to the destination using a list of segments. After the RIB update delay timer expires, the SR-TE policy is replaced with regular forwarding paths.
Restrictions and Usage Guidelines
The following restrictions and usage guidelines apply:
• The Routing Information Base (RIB) update delay value specifies the amount of time the node uses the microloop avoidance policy before updating its forwarding table. The delay-time range is from 1 to 60000 milliseconds; the default value is 5000.
Configuring SRv6 IS-IS Microloop Avoidance
The following example shows how to configure SRv6 IS-IS Microloop Avoidance and set the Routing
Information Base (RIB) update delay value.
Note Complete the
before performing these steps.
Router(config)# router isis test-igp
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# microloop avoidance segment-routing
Router(config-isis-af)# microloop avoidance rib-update-delay 2000
Router(config-isis-af)# commit
Configuring SRv6 IS-IS Microloop Avoidance with Flexible Algorithm
Microloop Avoidance paths for particular Flexible Algorithm are computed using the same constraints as the calculation of the primary paths for such Flexible Algorithm. These paths use Prefix-SIDs advertised specifically for such Flexible Algorithm in order to enforce a microloop avoidance path.
The following example shows how to configure SRv6 IS-IS Microloop Avoidance with Flexible Algorithm.
Router(config)# segment-routing srv6
Router(config-srv6)# locators
Router(config-srv6-locators)# locator myLoc1
Router(config-srv6-locator)# prefix 2001:db8:1:a2::/64
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv4 L3VPN
Router(config-srv6-locator)# algorithm 128
Router(config-srv6-locator)# root
Router(config)# router isis test-uloop
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# exit
Router(config-isis)# address-family ipv6 unicast
Router(config-isis-af)# microloop avoidance segment-routing
Router(config-isis-af)# segment-routing srv6
Router(config-isis-srv6)# locator myLoc1
Router(config-isis-srv6-loc)# commit
Use the microloop avoidance disable command to disable the microloop calculation on a per-algorithm basis:
Router(config)# router isis test-tilfa
Router(config-isis)# flex-algo 128
Router(config-isis-flex-algo)# microloop avoidance disable
SRv6 Services: IPv4 L3VPN
The SRv6-based IPv4 L3VPN feature enables deployment of IPv4 L3VPN over a SRv6 data plane.
Traditionally, it was done over an MPLS-based system. SRv6-based L3VPN uses SRv6 Segment IDs (SIDs) for service segments instead of labels. SRv6-based L3VPN functionality interconnects multiple sites to resemble a private network service over public infrastructure. To use this feature, you must configure SRv6-base.
For this feature, BGP allocates an SRv6 SID from the locator space, configured under SRv6-base and VPNv4 address family. For more information on this, refer
Segment Routing over IPv6 Overview, on page 7
. The
BGP SID can be allocated in the following ways:
• Per-VRF mode that provides End.DT4 support. End.DT4 represents the Endpoint with decapsulation and IPv4 table lookup.
• Per-CE mode that provides End.DX4 cross connect support. End.DX4 represents the Endpoint with decapsulation and IPv4 cross-connect.
BGP encodes the SRv6 SID in the prefix-SID attribute of the IPv4 L3VPN Network Layer Reachability
Information (NLRI) and advertises it to IPv6 peering over an SRv6 network. The Ingress PE (provider edge) router encapsulates the VRF IPv4 traffic with the SRv6 VPN SID and sends it over the SRv6 network.
Usage Guidelines and Limitations
• Equal-Cost Multi-path (ECMP) and Unequal Cost Multipath (UCMP) are supported.
• BGP, OSPF, Static are supported as PE-CE protocol.
• MPLS L3VPN and SRv6 L3VPN interworking gateway is not supported.
Configuring SRv6 based IPv4 L3VPN
To enable SRv6-based L3VPN, you need to configure SRv6 under BGP and SID allocation mode. The following example shows how to configure SRv6-based L3VPN:
/*Configure SRv6 locator name under BGP Global*/
RP/0/0/CPU0:Router(config)# router bgp 100
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
21
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv4 L3VPN
RP/0/0/CPU0:Router(config-bgp)# bgp router-id 10.6.6.6
RP/0/0/CPU0:Router(config-bgp)# segment-routing srv6
RP/0/0/CPU0:Router(config-bgp-srv6)# locator my_locator
RP/0/0/CPU0:Router(config-bgp-srv6)# exit
/*Configure SRv6 locator under VRF All under VPNv4 AFI*/
RP/0/0/CPU0:Router(config)# router bgp 100
RP/0/0/CPU0:Router(config-bgp)# bgp router-id 10.6.6.6
RP/0/0/CPU0:Router(config-bgp)# address-family vpnv4 unicast
RP/0/0/CPU0:Router(config-bgp-af)# vrf all
RP/0/0/CPU0:Router(config-bgp-af-vrfall)# segment-routing srv6
RP/0/0/CPU0:Router(config-bgp-af-vrfall-srv6)# locator my_locator
RP/0/0/CPU0:Router(config-bgp-af-vrfall-srv6)# exit
/*Configure a VRF with per-vrf label allocation mode*/
RP/0/0/CPU0:Router(config-bgp-af)# vrf vrf1
RP/0/0/CPU0:Router(config-bgp-vrf)# rd 106:1
RP/0/0/CPU0:Router(config-bgp-vrf)# address-family ipv4 unicast
RP/0/0/CPU0:Router(config-bgp-vrf-af)# segment-routing srv6
RP/0/0/CPU0:Router(config-bgp-vrf-af-srv6)# alloc mode per-vrf
RP/0/0/CPU0:Router(config-bgp-vrf-af-srv6)# exit
RP/0/0/CPU0:Router(config-bgp-vrf-af)# exit
RP/0/0/CPU0:Router(config-bgp-vrf)# neighbor 10.1.2.2
RP/0/0/CPU0:Router(config-bgp-vrf-nbr)# remote-as 100
RP/0/0/CPU0:Router(config-bgp-vrf-nbr)# address-family ipv4 unicast
/*Configure a VRF with per-ce label allocation mode*/
RP/0/0/CPU0:Router(config-bgp-af)# vrf vrf2
RP/0/0/CPU0:Router(config-bgp-vrf)# rd 106:2
RP/0/0/CPU0:Router(config-bgp-vrf)# address-family ipv4 unicast
RP/0/0/CPU0:Router(config-bgp-vrf-af)# segment-routing srv6
RP/0/0/CPU0:Router(config-bgp-vrf-af-srv6)# alloc mode per-ce
RP/0/0/CPU0:Router(config-bgp-vrf-af-srv6)# exit
RP/0/0/CPU0:Router(config-bgp-vrf-af)# exit
RP/0/0/CPU0:Router(config-bgp-vrf)# neighbor 10.1.2.2
RP/0/0/CPU0:Router(config-bgp-vrf-nbr)# remote-as 100
RP/0/0/CPU0:Router(config-bgp-vrf-nbr)# address-family ipv4 unicast
Verification
The following example shows how to verify the SRv6 based L3VPN configuration using the show segment-routing srv6 sid command.
In this example, End.X represents Endpoint function with Layer-3 cross-connect, End.DT4 represents Endpoint with decapsulation and IPv4 table lookup, and End.DX4 represents Endpoint with decapsulation and IPv4 cross-connect.
RP/0/0/CPU0:SRv6-Hub6# show segment-routing srv6 sid
*** Locator: 'my_locator' ***
SID Function Context
State RW
-----------------------------------------------------------------
-----cafe:0:0:66:1:: End (PSP) 'my_locator':1
InUse Y cafe:0:0:66:40::
InUse Y cafe:0:0:66:41::
InUse Y cafe:0:0:66:42::
InUse Y
End.X (PSP)
End.X (PSP)
End.X (PSP)
[Te0/0/0/2, Link-Local]
[BE6801, Link-Local]
[BE5601, Link-Local]
Owner
-----------------sidmgr isis-srv6 isis-srv6 isis-srv6
22
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv4 L3VPN cafe:0:0:66:43::
InUse Y cafe:0:0:66:44::
InUse Y cafe:0:0:66:45::
InUse Y cafe:0:0:66:46::
InUse Y cafe:0:0:66:47::
InUse Y
End.X (PSP) [BE5602, Link-Local]
End.DT4
End.DT4
End.DX4
End.DX4
'VRF1'
'VRF2'
'VRF2’:3
'VRF2’:4 isis-srv6 bgp-100 bgp-100 bgp-100 bgp-100
The following example shows how to verify the SRv6 based L3VPN configuration using the show
segment-routing srv6SID-prefixdetail command.
RP/0/RP0/CPU0:SRv6-Hub6# show segment-routing srv6 sid cafe:0:0:66:44:: detail
Sun Dec 9 16:52:54.015 EST
*** Locator: ‘my_locator' ***
SID Function Context Owner
State RW
-----------------------------------------------------------------
-----cafe:0:0:66:44:: End.DT4
'VRF1'
-----------------bgp-100
InUse Y
SID context: { table-id=0xe0000001 ('VRF1':IPv4/Unicast) }
Locator: ‘my_locator'
Allocation type: Dynamic
Created: Dec 8 16:34:32.506 (1d00h ago)
RP/0/RP0/CPU0:SRv6-Hub6# show segment-routing srv6 sid cafe:0:0:66:47:: detail
Sun Dec 9 16:54:26.073 EST
*** Locator: 'my_locator' ***
SID Function Context Owner
State RW
-----------------------------------------------------------------
-----cafe:0:0:66:47::
InUse Y
End.DX4
'VRF2’: 4
SID context: { table-id=0xe0000002 ('VRF2':IPv4/Unicast), nh-set-id=4 }
-----------------bgp-100
Locator: ‘my_locator'
Allocation type: Dynamic
Created: Dec 9 16:49:44.714 (00:04:41 ago)
The following example shows how to verify the SRv6 based L3VPN configuration using the show bgp vpnv4
unicast rdroute-distinguisher/prefix command on Egress PE.
RP/0/RP0/CPU0:SRv6-Hub6# show bgp vpnv4 unicast rd 106:1 10.15.0.0/30
Wed Nov 21 16:08:44.765 EST
BGP routing table entry for 10.15.0.0/30, Route Distinguisher: 106:1
Versions:
Process bRIB/RIB SendTblVer
Speaker 2282449 2282449
SRv6-VPN SID: cafe:0:0:66:44::/128
Last Modified: Nov 21 15:50:34.235 for 00:18:10
Paths: (2 available, best #1)
Advertised to peers (in unique update groups):
2::2
Path #1: Received by speaker 0
Advertised to peers (in unique update groups):
2::2
200
10.1.2.2 from 10.1.2.2
(10.7.0.1)
Origin IGP, localpref 200, valid, internal, best, group-best, import-candidate
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
23
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv4 L3VPN
Received Path ID 0, Local Path ID 1, version 2276228
Extended community: RT:201:1
Path #2: Received by speaker 0
Not advertised to any peer
200
10.2.2.2 from 10.2.2.2 (10.20.1.2)
Origin IGP, localpref 100, valid, internal
Received Path ID 0, Local Path ID 0, version 0
Extended community: RT:201:1
The following example shows how to verify the SRv6 based L3VPN configuration using the show bgp vpnv4
unicast rdroute-distinguisher prefix command on Ingress PE.
RP/0/RP0/CPU0:SRv6-LF1# show bgp vpnv4 unicast rd 106:1 10.15.0.0/30
Wed Nov 21 16:11:45.538 EST
BGP routing table entry for 10.15.0.0/30, Route Distinguisher: 106:1
Versions:
Process bRIB/RIB SendTblVer
Speaker 2286222 2286222
Last Modified: Nov 21 15:47:26.288 for 00:24:19
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
200, (received & used)
6::6 (metric 24) from 2::2 (6.6.6.6)
Received Label 3
Origin IGP, localpref 200, valid, internal, best, group-best, import-candidate, not-in-vrf
Received Path ID 1, Local Path ID 1, version 2286222
Extended community: RT:201:1
Originator: 6.6.6.6, Cluster list: 2.2.2.2
SRv6-VPN-SID: T1-cafe:0:0:66:44:: [total 1]
The following example shows how to verify the SRv6 based L3VPN configuration using the show route
vrfvrf-name/prefixdetail command.
RP/0/RP0/CPU0:SRv6-LF1# show route vrf VRF1 10.15.0.0/30 detail
Wed Nov 21 16:35:17.775 EST
Routing entry for 10.15.0.0/30
Known via "bgp 100", distance 200, metric 0
Tag 200, type internal
Installed Nov 21 16:35:14.107 for 00:00:03
Routing Descriptor Blocks
6::6, from 2::2
Nexthop in Vrf: "default", Table: "default", IPv6 Unicast, Table Id: 0xe0800000
Route metric is 0
Label: None
Tunnel ID: None
Binding Label: None
Extended communities count: 0
Source RD attributes: 0x0000:106:1
NHID:0x0(Ref:0)
SRv6 Headend: H.Encaps.Red
[base], SID-list { cafe:0:0:66:44:: }
MPLS eid:0x1380600000001
Route version is 0xd (13)
No local label
IP Precedence: Not Set
QoS Group ID: Not Set
Flow-tag: Not Set
Fwd-class: Not Set
Route Priority: RIB_PRIORITY_RECURSIVE (12) SVD Type RIB_SVD_TYPE_REMOTE
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv4 L3VPN
Download Priority 3, Download Version 3038384
No advertising protos.
The following example shows how to verify the SRv6 based L3VPN configuration for per-ce allocation mode using the show bgp vrfvrf-namenexthop-set command.
RP/0/RP0/CPU0:SRv6-Hub6# show bgp vrf VRF2 nexthop-set
Wed Nov 21 15:52:17.464 EST
Resilient per-CE nexthop set, ID 3
Number of nexthops 1, Label 0, Flags 0x2200
SRv6-VPN SID: cafe:0:0:66:46::/128
Nexthops:
10.1.2.2
Reference count 1,
Resilient per-CE nexthop set, ID 4
Number of nexthops 2, Label 0, Flags 0x2100
SRv6-VPN SID: cafe:0:0:66:47::/128
Nexthops:
10.1.2.2
10.2.2.2
Reference count 2,
The following example shows how to verify the SRv6 based L3VPN configuration using the show cef
vrfvrf-name prefix detail locationline-card command.
RP/0/RP0/CPU0:SRv6-LF1# show cef vrf VRF1 10.15.0.0/30 detail location 0/0/cpu0
Wed Nov 21 16:37:06.894 EST
151.1.0.0/30, version 3038384, SRv6 Transit, internal 0x5000001 0x0 (ptr 0x9ae6474c) [1],
0x0 (0x0), 0x0 (0x8c11b238)
Updated Nov 21 16:35:14.109
Prefix Len 30, traffic index 0, precedence n/a, priority 3 gateway array (0x8cd85190) reference count 1014, flags 0x2010, source rib (7), 0 backups
[1 type 3 flags 0x40441 (0x8a529798) ext 0x0 (0x0)]
LW-LDI[type=0, refc=0, ptr=0x0, sh-ldi=0x0] gateway array update type-time 1 Nov 21 14:47:26.816
LDI Update time Nov 21 14:52:53.073
Level 1 - Load distribution: 0
[0] via cafe:0:0:66::/128 , recursive via cafe:0:0:66::/128, 7 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x8acb53cc 0x0] next hop VRF - 'default', table - 0xe0800000 next hop cafe:0:0:66::/128 via cafe:0:0:66::/64
SRv6 H.Encaps.Red
SID-list { cafe:0:0:66:44:: }
Load distribution: 0 (refcount 1)
Hash OK Interface
0 Y Bundle-Ether1201
Address fe80::2
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
25
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN
SRv6 Services: IPv6 L3VPN
Table 2: Feature History Table
Feature Name
SRv6 Services: IPv6 L3VPN
Release Information
Release 7.2.2
Feature Description
With this feature, the egress PE can signal an SRv6 Service SID with the BGP overlay service route. The ingress PE encapsulates the
IPv4/IPv6 payload in an outer IPv6 header where the destination address is the SRv6 Service SID provided by the egress PE. BGP messages between PEs carry SRv6
Service SIDs as a means to interconnect PEs and form VPNs.
Building on the messages and procedures defined in IETF draft " BGP/MPLS IP Virtual Private Networks
(VPNs) ", this feature provides IPv6 L3VPNs (VPNv6) over an SRv6 network.
In SRv6-based L3VPNs, the egress PE signals an SRv6 Service SID with the BGP overlay service route. The ingress PE encapsulates the IPv4/IPv6 payload in an outer IPv6 header where the destination address is the
SRv6 Service SID provided by the egress PE. BGP messages between PEs carry SRv6 Service SIDs as a means to interconnect PEs and form VPNs.
SRv6 Service SID refers to a segment identifier associated with one of the SRv6 service-specific behaviors on the advertising VPNv6 PE router, such as END.DT6 (Endpoint with decapsulation and IPv6 table lookup) or END.DX6 (cross-connect to a nexthop) behaviors.
Based on the messages and procedures defined in IETF draft " SRv6 BGP based Overlay services ", BGP encodes the SRv6 Service SID in the prefix-SID attribute of the IPv6 L3VPN Network Layer Reachability
Information (NLRI) and advertises it to its IPv6 BGP peers.
BGP allocates an SRv6 Service SID from the locator space, configured under SRv6 and VPNv6 address family. For more information on this, see Segment Routing over IPv6 Overview . The SRv6 Service SID can be allocated in the following ways:
• Per-VRF mode that provides End.DT6 support. End.DT6 represents the Endpoint with decapsulation and IPv6 table lookup.
Usage Guidelines and Restrictions
• Equal-Cost Multi-path (ECMP) and Unequal Cost Multipath (UCMP) are supported.
• BGP, OSPF, Static are supported as PE-CE protocol.
• MPLS L3VPN and SRv6 L3VPN interworking gateway is not supported.
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN
Configuring SRv6-based IPv6 L3VPN
To enable SRv6-based L3VPN, you need to configure SRv6 under BGP, and configure the SID allocation mode.
The following examples show how to configure SRv6-based L3VPN.
Note You can specify the SRv6 locator globally, for all VRFs, or for an individual VRF.
This example shows how to configure the SRv6 locator name under BGP Global:
RP/0/0/CPU0:Node1(config)# router bgp 100
RP/0/0/CPU0:Node1(config-bgp)# segment-routing srv6
RP/0/0/CPU0:Node1(config-bgp-gbl-srv6)# locator Node1-locator
RP/0/0/CPU0:Node1(config-bgp-gbl-srv6)# exit
RP/0/0/CPU0:Node1(config-bgp)# address-family vpnv6 unicast
RP/0/0/CPU0:Node1(config-bgp-af)# exit
RP/0/0/CPU0:Node1(config-bgp)# neighbor 3001::1:1:1:4
RP/0/0/CPU0:Node1(config-bgp-nbr)# remote-as 100
RP/0/0/CPU0:Node1(config-bgp-nbr)# address-family vpnv6 unicast
RP/0/0/CPU0:Node1(config-bgp-nbr-af)# exit
RP/0/0/CPU0:Node1(config-bgp-nbr)# exit
RP/0/0/CPU0:Node1(config-bgp)# vrf vrf_cust6
RP/0/0/CPU0:Node1(config-bgp-vrf)# rd 100:6
RP/0/0/CPU0:Node1(config-bgp-vrf)# address-family ipv6 unicast
RP/0/0/CPU0:Node1(config-bgp-vrf-af)# commit
Running Configuration router bgp 100 segment-routing srv6
!
locator Node1-locator address-family vpnv6 unicast
!
neighbor 3001::1:1:1:4 remote-as 100 address-family vpnv6 unicast
!
!
vrf vrf_cust6
!
!
end rd 100:6 address-family ipv6 unicast
!
This example shows how to configure the SRv6 locator for all VRFs under VPNv6 Address Family, with per-VRF label allocation mode:
RP/0/0/CPU0:Node1(config)# router bgp 100
RP/0/0/CPU0:Node1(config-bgp)# address-family vpnv6 unicast
RP/0/0/CPU0:Node1(config-bgp-af)# vrf all
RP/0/0/CPU0:Node1(config-bgp-af-vrfall)# segment-routing srv6
RP/0/0/CPU0:Node1(config-bgp-af-vrfall-srv6)# locator Node1-locator
RP/0/0/CPU0:Node1(config-bgp-af-vrfall-srv6)# alloc mode per-vrf
RP/0/0/CPU0:Node1(config-bgp-af-vrfall-srv6)# exit
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27
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN
RP/0/0/CPU0:Node1(config-bgp-af-vrfall)# exit
RP/0/0/CPU0:Node1(config-bgp-af)# exit
RP/0/0/CPU0:Node1(config-bgp)# neighbor 3001::1:1:1:4
RP/0/0/CPU0:Node1(config-bgp-nbr)# remote-as 100
RP/0/0/CPU0:Node1(config-bgp-nbr)# address-family vpnv6 unicast
RP/0/0/CPU0:Node1(config-bgp-nbr-af)# exit
RP/0/0/CPU0:Node1(config-bgp-nbr)# exit
RP/0/0/CPU0:Node1(config-bgp)# vrf vrf_cust6
RP/0/0/CPU0:Node1(config-bgp-vrf)# rd 100:6
RP/0/0/CPU0:Node1(config-bgp-vrf)# address-family ipv6 unicast
RP/0/0/CPU0:Node1(config-bgp-vrf-af)# commit
Running Configuration router bgp 100 address-family vpnv6 unicast vrf all segment-routing srv6 locator Node1-locator alloc mode per-vrf
!
!
!
neighbor 3001::1:1:1:4 remote-as 100
!
address-family vpnv6 unicast
!
vrf vrf_cust6 rd 100:6
!
address-family ipv6 unicast
!
!
end
This example shows how to configure the SRv6 locator for an Individual VRF, with per-VRF label allocation mode:
RP/0/0/CPU0:Node1(config)# router bgp 100
RP/0/0/CPU0:Node1(config-bgp)# address-family vpnv6 unicast
RP/0/0/CPU0:Node1(config-bgp-af)# exit
RP/0/0/CPU0:Node1(config-bgp)# neighbor 3001::1:1:1:4
RP/0/0/CPU0:Node1(config-bgp-nbr)# remote-as 100
RP/0/0/CPU0:Node1(config-bgp-nbr)# address-family vpnv6 unicast
RP/0/0/CPU0:Node1(config-bgp-nbr-af)# exit
RP/0/0/CPU0:Node1(config-bgp-nbr)# exit
RP/0/0/CPU0:Node1(config-bgp)# vrf vrf_cust6
RP/0/0/CPU0:Node1(config-bgp-vrf)# rd 100:6
RP/0/0/CPU0:Node1(config-bgp-vrf)# address-family ipv6 unicast
RP/0/0/CPU0:Node1(config-bgp-vrf-af)# segment-routing srv6
RP/0/0/CPU0:Node1(config-bgp-vrf-af-srv6)# locator Node1-locator
RP/0/0/CPU0:Node1(config-bgp-vrf-af-srv6)# alloc mode per-vrf
RP/0/0/CPU0:Node1(config-bgp-vrf-af-srv6)# commit
Running Configuration router bgp 100 address-family vpnv6 unicast
!
neighbor 3001::1:1:1:4 remote-as 100
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN address-family vpnv6 unicast
!
!
vrf vrf_cust6 rd 100:6 address-family ipv6 unicast segment-routing srv6
!
!
!
end
!
locator Node1-locator alloc mode per-vrf
Verification
The following examples shows how to verify the SRv6 based L3VPN configurations for an Individual VRF with per VRF label allocation mode.
In this example, End.X represents Endpoint function with Layer-3 cross-connect, and End.DT6 represents
Endpoint with decapsulation and IPv6 table lookup.
RP/0/RSP0/CPU0:Node1# show segment-routing srv6 sid
Fri Jan 15 18:58:04.911 UTC
*** Locator: 'Node1-locator' ***
SID Behavior Context
State RW
----------------------------------------------------------------------
----------------------cafe:0:0:1:1:: End (PSP) 'default':1
InUse Y cafe:0:0:1:11::
InUse Y cafe:0:0:1:40::
InUse Y
End.OP
End.X (PSP)
'default'
[Hu0/0/0/0, Link-Local]
End.X (PSP) [Hu0/0/0/1, Link-Local] cafe:0:0:1:41::
InUse Y cafe:0:0:1:47::
InUse Y cafe:0:0:1:48::
InUse Y cafe:0:0:1:49::
InUse Y cafe:0:0:1:4a::
InUse Y
End.X (PSP)
End.X (PSP)
End.DT6
End.DT6
[Hu0/0/0/0, Link-Local]:P
[Hu0/0/0/1, Link-Local]:P
'default'
'vrf_cust6'
Owner sidmgr sidmgr isis-1 isis-1 isis-1 isis-1 bgp-100 bgp-100
The following examples show how to verify the SRv6 based L3VPN configuration using the show bgp vpnv6 unicast commands on the Ingress PE.
RP/0/RSP0/CPU0:Node1# show bgp vpnv6 unicast summary
Fri Jan 15 18:37:04.791 UTC
BGP router identifier 1.1.1.1, local AS number 100
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 21
BGP NSR Initial initsync version 4 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
29
Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN
BGP is operating in STANDALONE mode.
Process
Speaker
RcvTblVer bRIB/RIB LabelVer ImportVer SendTblVer StandbyVer
21 21 21 21 21 0
Neighbor
3001::1:1:1:4
3001::1:1:1:5
Spk AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down St/PfxRcd
0 100 1352 1352 21 0 0 01:46:26 1
0 100 1351 1351 21 0 0 01:44:47 1
RP/0/RSP0/CPU0:Node1# show bgp vpnv6 unicast rd 100:6
Fri Jan 15 18:38:02.919 UTC
BGP router identifier 1.1.1.1, local AS number 100
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 21
BGP NSR Initial initsync version 4 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 100:6 (default for vrf vrf_cust6)
*> 3001::12:1:1:1/128 ::
*>i3001::12:1:1:4/128 3001::1:1:1:4
*>i3001::12:1:1:5/128 3001::1:1:1:5
0
0
0
100
100
32768 ?
0 ?
0 ?
Processed 3 prefixes, 3 paths
RP/0/RSP0/CPU0:Node1# show bgp vpnv6 unicast rd 100:6 3001::12:1:1:4/128
Fri Jan 15 18:38:26.492 UTC
BGP routing table entry for 3001::12:1:1:4/128, Route Distinguisher: 100:6
Versions:
Process bRIB/RIB SendTblVer
Speaker 17 17
Last Modified: Jan 15 16:50:44.032 for 01:47:43
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local, (received & used)
3001::1:1:1:4 (metric 30) from 3001::1:1:1:4 (1.1.1.4)
Received Label 0x4900
Origin incomplete, metric 0, localpref 100, valid, internal, best, group-best, import-candidate, imported
Received Path ID 0, Local Path ID 1, version 17
Extended community: RT:100:6
PSID-Type:L3, SubTLV Count:1
SubTLV:
T:1(Sid information), Sid:cafe:0:0:4::, Behavior:18, SS-TLV Count:1
SubSubTLV:
T:1(Sid structure):
Source AFI: VPNv6 Unicast, Source VRF: vrf_cust6, Source Route Distinguisher: 100:6
The following examples show how to verify the BGP prefix information for VRF instances:
RP/0/RSP0/CPU0:Node1# show bgp vrf vrf_cust6 ipv6 unicast
Fri Jan 15 18:38:49.705 UTC
BGP VRF vrf_cust6, state: Active
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN
BGP Route Distinguisher: 100:6
VRF ID: 0x60000008
BGP router identifier 1.1.1.1, local AS number 100
Non-stop routing is enabled
BGP table state: Active
Table ID: 0xe0800017 RD version: 21
BGP main routing table version 21
BGP NSR Initial initsync version 4 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 100:6 (default for vrf vrf_cust6)
*> 3001::12:1:1:1/128 :: 0
*>i3001::12:1:1:4/128 3001::1:1:1:4 0 100
*>i3001::12:1:1:5/128 3001::1:1:1:5 0 100
32768 ?
0 ?
0 ?
Processed 3 prefixes, 3 paths
RP/0/RSP0/CPU0:Node1# show bgp vrf vrf_cust6 ipv6 unicast 3001::12:1:1:4/128
Fri Jan 15 18:39:05.115 UTC
BGP routing table entry for 3001::12:1:1:4/128, Route Distinguisher: 100:6
Versions:
Process bRIB/RIB SendTblVer
Speaker 17 17
Last Modified: Jan 15 16:50:44.032 for 01:48:21
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local, (received & used)
3001::1:1:1:4 (metric 30) from 3001::1:1:1:4 (1.1.1.4)
Received Label 0x4900
Origin incomplete, metric 0, localpref 100, valid, internal, best, group-best, import-candidate, imported
Received Path ID 0, Local Path ID 1, version 17
Extended community: RT:100:6
PSID-Type:L3, SubTLV Count:1
SubTLV:
T:1(Sid information), Sid:cafe:0:0:4::, Behavior:18, SS-TLV Count:1
SubSubTLV:
T:1(Sid structure):
Source AFI: VPNv6 Unicast, Source VRF: vrf_cust6, Source Route Distinguisher: 100:6
The following examples show how to verify the current routes in the Routing Information Base (RIB):
RP/0/RSP0/CPU0:Node1# show route vrf vrf_cust6 ipv6 unicast
Fri Jan 15 18:39:20.619 UTC
Codes: C - connected, S - static, R - RIP, B - BGP, (>) - Diversion path
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - ISIS, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, su - IS-IS summary null, * - candidate default
U - per-user static route, o - ODR, L - local, G - DAGR, l - LISP
A - access/subscriber, a - Application route
M - mobile route, r - RPL, t - Traffic Engineering, (!) - FRR Backup path
Gateway of last resort is not set
L 3001::12:1:1:1/128 is directly connected,
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv6 L3VPN
B
B
21:14:10, Loopback105
3001::12:1:1:4/128
[200/0] via 3001::1:1:1:4 (nexthop in vrf default), 01:48:36
3001::12:1:1:5/128
[200/0] via 3001::1:1:1:5 (nexthop in vrf default), 01:46:56
RP/0/RSP0/CPU0:Node1# show route vrf vrf_cust6 ipv6 unicast 3001::12:1:1:4/128
Fri Jan 15 18:39:39.689 UTC
Routing entry for 3001::12:1:1:4/128
Known via "bgp 100", distance 200, metric 0, type internal
Installed Jan 15 16:50:44.381 for 01:48:55
Routing Descriptor Blocks
3001::1:1:1:4, from 3001::1:1:1:4
Nexthop in Vrf: "default", Table: "default", IPv6 Unicast, Table Id: 0xe0800000
Route metric is 0
No advertising protos.
RP/0/RSP0/CPU0:Node1# show route vrf vrf_cust6 ipv6 unicast 3001::12:1:1:4/128 detail
Fri Jan 15 18:39:51.573 UTC
Routing entry for 3001::12:1:1:4/128
Known via "bgp 100", distance 200, metric 0, type internal
Installed Jan 15 16:50:44.381 for 01:49:07
Routing Descriptor Blocks
3001::1:1:1:4, from 3001::1:1:1:4
Nexthop in Vrf: "default", Table: "default", IPv6 Unicast, Table Id: 0xe0800000
Route metric is 0
Label: None
Tunnel ID: None
Binding Label: None
Extended communities count: 0
Source RD attributes: 0x0000:100:6
NHID:0x0(Ref:0)
SRv6 Headend: H.Encaps.Red [base], SID-list {cafe:0:0:4:49::}
Route version is 0x1 (1)
No local label
IP Precedence: Not Set
QoS Group ID: Not Set
Flow-tag: Not Set
Fwd-class: Not Set
Route Priority: RIB_PRIORITY_RECURSIVE (12) SVD Type RIB_SVD_TYPE_REMOTE
Download Priority 3, Download Version 3
No advertising protos.
The following examples show how to verify the current IPv6 Cisco Express Forwarding (CEF) table:
RP/0/RSP0/CPU0:Node1# show cef vrf vrf_cust6 ipv6
Fri Jan 15 18:40:15.833 UTC
::/0 drop default handler
3001::12:1:1:1/128 receive Loopback105
3001::12:1:1:4/128 recursive cafe:0:0:4::/128
3001::12:1:1:5/128 recursive cafe:0:0:5::/128 fe80::/10 receive ff02::/16 receive ff02::2/128 receive
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SRv6 Services: IPv4 L3VPN Active-Standby Redundancy using Port-Active Mode ff02::1:ff00:0/104 receive ff05::/16 receive ff12::/16 receive
RP/0/RSP0/CPU0:Node1# show cef vrf vrf_cust6 ipv6 3001::12:1:1:4/128
Fri Jan 15 18:40:28.853 UTC
3001::12:1:1:4/128, version 3, SRv6 Headend, internal 0x5000001 0x30 (ptr 0x78f2e0e0) [1],
0x0 (0x0), 0x0 (0x8886b768)
Updated Jan 15 16:50:44.385
Prefix Len 128, traffic index 0, precedence n/a, priority 3 via cafe:0:0:4::/128, 9 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x78a0f504 0x0] next hop VRF - 'default', table - 0xe0800000 next hop cafe:0:0:4::/128 via cafe:0:0:4::/64
SRv6 H.Encaps.Red SID-list {cafe:0:0:4:49::}
RP/0/RSP0/CPU0:Node1# show cef vrf vrf_cust6 ipv6 3001::12:1:1:4/128 detail
Fri Jan 15 18:40:55.327 UTC
3001::12:1:1:4/128, version 3, SRv6 Headend, internal 0x5000001 0x30 (ptr 0x78f2e0e0) [1],
0x0 (0x0), 0x0 (0x8886b768)
Updated Jan 15 16:50:44.385
Prefix Len 128, traffic index 0, precedence n/a, priority 3 gateway array (0x7883b320) reference count 1, flags 0x2010, source rib (7), 0 backups
[1 type 3 flags 0x48441 (0x788e6ad8) ext 0x0 (0x0)]
LW-LDI[type=0, refc=0, ptr=0x0, sh-ldi=0x0] gateway array update type-time 1 Jan 15 16:50:44.385
LDI Update time Jan 15 16:50:44.385
Level 1 - Load distribution: 0
[0] via cafe:0:0:4::/128, recursive via cafe:0:0:4::/128, 9 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x78a0f504 0x0] next hop VRF - 'default', table - 0xe0800000 next hop cafe:0:0:4::/128 via cafe:0:0:4::/64
SRv6 H.Encaps.Red SID-list {cafe:0:0:4:49::}
Load distribution: 0 1 (refcount 1)
Hash OK Interface
0 Y HundredGigE0/0/0/0
1 Y HundredGigE0/0/0/1
Address remote remote
SRv6 Services: IPv4 L3VPN Active-Standby Redundancy using
Port-Active Mode
The Segment Routing IPv6 (SRv6) Services: IPv4 L3VPN Active-Standby Redundancy using Port-Active
Mode feature provides all-active per-port load balancing for multihoming. The forwarding of traffic is determined based on a specific interface rather than per-flow across multiple Provider Edge routers. This feature enables efficient load-balancing and provides faster convergence. In an active-standby scenario, the active PE router is detected using designated forwarder (DF) election by modulo calculation and the interface of the standby PE router brought down. For Modulo calculation, byte 10 of the Ethernet Segment Identifier
(ESI) is used.
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services for L3VPN Active-Standby Redundancy using Port-Active Mode: Operation
Usage Guidelines and Restrictions
• This feature can only be configured for bundle interfaces.
• When an EVPN Ethernet Segment (ES) is configured with port-active load-balancing mode, you cannot configure ACs of that bundle on bridge-domains with a configured EVPN instance (EVI). EVPN Layer
2 bridging service is not compatible with port-active load-balancing.
SRv6 Services for L3VPN Active-Standby Redundancy using Port-Active Mode:
Operation
Under port-active operational mode, EVPN Ethernet Segment (ES) routes are exchanged across BGP for the routers servicing the multihomed ES. Each PE router then builds an ordered list of the IP addresses of all PEs connected to the ES, including itself, and assigns itself an ordinal for its position in the list. The ordinals are used with the modulo calculation to determine which PE will be the Designated Forwarder (DF) for a given
ES. All non-DF PEs will take the respective bundles out of service.
In the case of link or port failure, the active DF PE withdraws its ES route. This re-triggers DF election for all PEs that service the ES and a new PE is elected as DF.
Configure SRv6 Services L3VPN Active-Standby Redundancy using Port-Active
Mode
This section describes how you can configure SRv6 services L3VPN active-standby redundancy using port-active mode under an Ethernet Segment (ES).
Configuration Example
/* Configure Ethernet Link Bundles */
Router# configure
Router(config)# interface Bundle-Ether10
Router(config-if)# ipv4 address 10.0.0.2 255.255.255.0
Router(config-if)# ipv6 address 2001:DB8::1
Router(config-if)# lacp period short
Router(config-if)# mac-address 1.2.3
Router(config-if)# bundle wait-while 0
Router(config-if)# exit
Router(config)# interface GigabitEthernet 0/2/0/5
Router(config-if)# bundle id 14 mode active
Router(config-if)# commit
/* Configure load balancing. */
Router# configure
Router(config)# evpn
Router(config-evpn)# interface Bundle-Ether10
Router(config-evpn-ac)# ethernet-segment
Router(config-evpn-ac-es)# identifier type 0 11.11.11.11.11.11.11.11.14
Router(config-evpn-ac-es)# load-balancing-mode port-active
Router(config-evpn-ac-es)# commit
!
/* Configure address family session in BGP. */
Router# configure
Router(config)# router bgp 100
Router(config-bgp)# bgp router-id 192.168.0.2
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Configure Segment Routing over IPv6 (SRv6)
Running Configuration
Router(config-bgp)# address-family l2vpn evpn
Router(config-bgp)# neighbor 192.168.0.3
Router(config-bgp-nbr)# remote-as 200
Router(config-bgp-nbr)# update-source Loopback 0
Router(config-bgp-nbr)# address-family l2vpn evpn
Router(config-bgp-nbr)# commit
Running Configuration
interface Bundle-Ether14 ipv4 address 14.0.0.2 255.255.255.0
ipv6 address 14::2/64 lacp period short
!
mac-address 1.2.3
bundle wait-while 0 interface GigabitEthernet0/2/0/5 bundle id 14 mode active
!
evpn interface Bundle-Ether14
!
!
ethernet-segment identifier type 0 11.11.11.11.11.11.11.11.14
load-balancing-mode port-active
!
router bgp 100 bgp router-id 192.168.0.2
address-family l2vpn evpn
!
neighbor 192.168.0.3
remote-as 100
!
!
update-source Loopback0 address-family l2vpn evpn
!
Verification
Verify the SRv6 services L3VPN active-standby redundancy using port-active mode configuration.
/* Verify ethernet-segment details on active DF router */
Router# show evpn ethernet-segment interface Bundle-Ether14 detail
Ethernet Segment Id Interface Nexthops
------------------------ ---------------------------------- --------------------
0011.1111.1111.1111.1114 BE14 192.168.0.2
192.168.0.3
ES to BGP Gates : Ready
ES to L2FIB Gates : Ready
Main port :
Interface name : Bundle-Ether14
Interface MAC : 0001.0002.0003
IfHandle : 0x000041d0
State
Redundancy
ESI type
Value
ES Import RT
Source MAC
: Up
: Not Defined
: 0
: 11.1111.1111.1111.1114
: 1111.1111.1111 (from ESI)
: 0000.0000.0000 (N/A)
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Configure Segment Routing over IPv6 (SRv6)
Verification
Topology
Operational
:
: MH
Configured : Port-Active
Service Carving : Auto-selection
Multicast : Disabled
Peering Details :
192.168.0.2 [MOD:P:00]
192.168.0.3 [MOD:P:00]
Service Carving Results:
Forwarders : 0
Permanent : 0
Elected
Not Elected
: 0
: 0
MAC Flushing mode : STP-TCN
Peering timer : 3 sec [not running]
Recovery timer : 30 sec [not running]
Carving timer : 0 sec [not running]
Local SHG label : None
Remote SHG labels : 0
/* Verify bundle Ethernet configuration on active DF router */
Router# show bundle bundle-ether 14
Bundle-Ether14
Status: Up
Local links <active/standby/configured>: 1 / 0 / 1
Local bandwidth <effective/available>: 1000000 (1000000) kbps
MAC address (source):
Inter-chassis link:
Minimum active links / bandwidth:
Maximum active links:
Wait while timer:
0001.0002.0003 (Configured)
No
1 / 1 kbps
64
Off
Load balancing:
Link order signaling:
Hash type:
Locality threshold:
LACP:
Flap suppression timer:
Cisco extensions:
Non-revertive: mLACP:
IPv4 BFD:
IPv6 BFD:
Not configured
Default
None
Operational
Off
Disabled
Disabled
Not configured
Not configured
Not configured
Port Device State Port ID B/W, kbps
------------------------------------------------------------------
Gi0/2/0/5 Local Active 0x8000, 0x0003 1000000
Link is Active
/* Verify ethernet-segment details on standby DF router */
Router# show evpn ethernet-segment interface bundle-ether 10 detail
Router# show evpn ethernet-segment interface Bundle-Ether24 detail
Ethernet Segment Id Interface Nexthops
------------------------ ---------------------------------- --------------------
0011.1111.1111.1111.1114 BE24 192.168.0.2
192.168.0.3
ES to BGP Gates : Ready
ES to L2FIB Gates : Ready
Main port :
Interface name : Bundle-Ether24
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: IPv4 L3VPN Active-Active Redundancy
Interface MAC : 0001.0002.0003
IfHandle : 0x000041b0
State
Redundancy
: Standby
: Not Defined
ESI type
Value
ES Import RT
Source MAC
Topology
: 0
: 11.1111.1111.1111.1114
: 1111.1111.1111 (from ESI)
: 0000.0000.0000 (N/A)
:
Operational
Configured
: MH
: Port-Active
Service Carving : Auto-selection
Multicast : Disabled
Peering Details :
192.168.0.2 [MOD:P:00]
192.168.0.3 [MOD:P:00]
Service Carving Results:
Forwarders : 0
Permanent
Elected
Not Elected
: 0
: 0
: 0
MAC Flushing mode : STP-TCN
Peering timer : 3 sec [not running]
Recovery timer
Carving timer
: 30 sec [not running]
: 0 sec [not running]
Local SHG label : None
Remote SHG labels : 0
/* Verify bundle configuration on standby DF router */
Router# show bundle bundle-ether 24
Bundle-Ether24
Status: LACP OOS (out of service)
Local links <active/standby/configured>: 0 / 1 / 1
Local bandwidth <effective/available>: 0 (0) kbps
MAC address (source):
Inter-chassis link:
0001.0002.0003 (Configured)
No
Minimum active links / bandwidth:
Maximum active links:
Wait while timer:
Load balancing:
Link order signaling:
1 / 1 kbps
64
Off
Hash type:
Locality threshold:
LACP:
Flap suppression timer:
Cisco extensions:
Not configured
Default
None
Operational
Off
Disabled
Non-revertive: mLACP:
IPv4 BFD:
IPv6 BFD:
Disabled
Not configured
Not configured
Not configured
Port Device State Port ID B/W, kbps
------------------------------------------------------------------
Gi0/0/0/4 Local Standby 0x8000, 0x0002 1000000
Link is in standby due to bundle out of service state
SRv6 Services: IPv4 L3VPN Active-Active Redundancy
This feature provides active-active connectivity to a CE device in a L3VPN deployment. The CE device can be Layer-2 or Layer-3 device connecting to the redundant PEs over a single LACP LAG port.
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: BGP Global IPv4
Depending on the bundle hashing, an ARP or IPv6 Network Discovery (ND) packet can be sent to any of the redundant routers. As a result, not all entries will exist on a given PE. In order to provide complete awareness,
Layer-3 local route learning is augmented with remote route-synchronization programming.
Route synchronization between service PEs is required in order to provide minimum interruption to unicast and multicast services after failure on a redundant service PE. The following EVPN route-types are used for
Layer-3 route synchronization:
• EVPN route-type 2 for synchronizing ARP tables
• EVPN route-type 7/8 for synchronizing IGMP JOINS/LEAVES
In a Layer-3 CE scenario, the router that connects to the redundant PEs may establish an IGP adjacency on the bundle port. In this case, the adjacency will be formed to one of the redundant PEs, and IGP customer routes will only be present on that PE. To synchronize Layer-3 customer subnet routes (IP Prefixes), the EVPN route-type 5 is used to carry the ESI and ETAG as well as the gateway address (prefix next-hop address).
Note Gratuitous ARP (GARP) or IPv6 Network Advertisement (NA) replay is not needed for CEs connected to the redundant PEs over a single LAG port.
The below configuration enables Layer-3 route synchronization for routes learned on the Ethernet-segment main-port or any of its sub-interfaces.
evpn route-sync vrf default
!
vrf RED evi route-sync 10
!
vrf BLUE
!
evi route-sync 20
SRv6 Services: BGP Global IPv4
This feature extends support of SRv6-based BGP services to include Internet (IPv4) services by implementing
End.DT4 SRv6 functions at the PE node ( draft-ietf-bess-srv6-services ).
Usage Guidelines and Limitations
• SRv6 locator can be assigned globally or under IPv4 unicast address family
• Equal-Cost Multi-path (ECMP) and Unequal Cost Multipath (UCMP) are supported.
• BGP, OSPF, Static are supported as PE-CE protocol.
BGP Global IPv4 Over SRv6 with Per-VRF SID Allocation Mode (End.DT4)
The following example shows how to configure BGP global IPv4 over SRv6 with per-VRF SID allocation.
router bgp 1 bgp router-id 10.1.0.1
address-family ipv4 unicast
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SRv6 Services: BGP Global IPv6
!
!
segment-routing srv6 alloc mode per-vrf neighbor 60::2 remote-as 1 update-source Loopback1 address-family ipv4 unicast route-policy passall in
!
encapsulation-type srv6 route-policy passall out
!
neighbor 52.52.52.1
remote-as 3 address-family ipv4 unicast route-policy passall in
!
!
!
route-policy passall out
SRv6 Services: BGP Global IPv6
Table 3: Feature History Table
Feature Name
SRv6 Services: BGP Global IPv6
Release Information
Release 7.2.2
Feature Description
With this feature, the egress PE can signal an SRv6 Service SID with the BGP overlay service route. The ingress PE encapsulates the
IPv4/IPv6 payload in an outer IPv6 header where the destination address is the SRv6 Service SID provided by the egress PE. BGP messages between PEs carry SRv6
Service SIDs as a means to interconnect PEs.
This feature extends support of SRv6-based BGP services to include Internet (IPv6) services by implementing
End.DT6 SRv6 functions at the PE node, as defined in IETF draft " SRv6 BGP based Overlay services ".
Usage Guidelines and Limitations
• SRv6 locator can be assigned globally or under IPv4 unicast address family
• Equal-Cost Multi-path (ECMP) and Unequal Cost Multipath (UCMP) are supported.
• BGP, OSPF, Static are supported as PE-CE protocol.
BGP Global IPv6 Over SRv6 with Per-VRF SID Allocation Mode (End.DT6)
The following example shows how to configure BGP global IPv6 over SRv6 with per-VRF SID allocation.
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: BGP Global IPv6 router bgp 100 bgp router-id 1.1.1.1
segment-routing srv6 locator Node1
!
address-family ipv6 unicast segment-routing srv6 locator Node1 alloc mode per-vrf
!
!
neighbor 3001::1:1:1:4 address-family ipv6 unicast encapsulation-type srv6
!
!
neighbor 3001::1:1:1:5 address-family ipv6 unicast encapsulation-type srv6
Verification
The following examples show how to verify the BGP global IPv6 configuration using the show bgp ipv6 unicast commands.
RP/0/RSP0/CPU0:Node1# show bgp ipv6 unicast summary
Fri Jan 15 21:07:04.681 UTC
BGP router identifier 1.1.1.1, local AS number 100
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0xe0800000 RD version: 4
BGP main routing table version 4
BGP NSR Initial initsync version 1 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
BGP is operating in STANDALONE mode.
Process
Speaker
Neighbor
3001::1:1:1:4
3001::1:1:1:5
RcvTblVer bRIB/RIB LabelVer ImportVer SendTblVer StandbyVer
4 4 4 4 4 0
Spk AS MsgRcvd MsgSent
0 100
0 100
1502
1501
1502
1501
TblVer
4
4
InQ OutQ
0
0
Up/Down
0 04:16:26
0 04:14:47
St/PfxRcd
1
1
RP/0/RSP0/CPU0:Node1# show bgp ipv6 unicast
Fri Jan 15 21:07:26.818 UTC
BGP router identifier 1.1.1.1, local AS number 100
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0xe0800000 RD version: 4
BGP main routing table version 4
BGP NSR Initial initsync version 1 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: BGP Global IPv6
Network Next Hop
*> 3001::13:1:1:1/128 ::
*>i3001::13:1:1:4/128 3001::1:1:1:4
*>i3001::13:1:1:5/128 3001::1:1:1:5
Processed 3 prefixes, 3 paths
Metric LocPrf Weight Path
0
0
0
100
100
32768 i
0 i
0 i
RP/0/RSP0/CPU0:Node1# show bgp ipv6 unicast 3001::13:1:1:4/128
Fri Jan 15 21:07:50.309 UTC
BGP routing table entry for 3001::13:1:1:4/128
Versions:
Process
Speaker bRIB/RIB SendTblVer
4 4
Last Modified: Jan 15 17:13:50.032 for 03:54:01
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local
3001::1:1:1:4 (metric 30) from 3001::1:1:1:4 (1.1.1.4)
Origin IGP, metric 0, localpref 100, valid, internal, best, group-best
Received Path ID 0, Local Path ID 1, version 4
PSID-Type:L3, SubTLV Count:1
SubTLV:
T:1(Sid information), Sid:cafe:0:0:4:4b::, Behavior:18, SS-TLV Count:1
SubSubTLV:
T:1(Sid structure):
The following examples show how to verify the current routes in the Routing Information Base (RIB):
RP/0/RSP0/CPU0:Node1# show route ipv6 3001::13:1:1:4/128
Fri Jan 15 21:08:05.499 UTC
Routing entry for 3001::13:1:1:4/128
Known via "bgp 100", distance 200, metric 0, type internal
Installed Jan 15 17:13:50.431 for 03:54:15
Routing Descriptor Blocks
3001::1:1:1:4, from 3001::1:1:1:4
Route metric is 0
No advertising protos.
RP/0/RSP0/CPU0:Node1# show route ipv6 3001::13:1:1:4/128 detail
Fri Jan 15 21:08:22.628 UTC
Routing entry for 3001::13:1:1:4/128
Known via "bgp 100", distance 200, metric 0, type internal
Installed Jan 15 17:13:50.431 for 03:54:32
Routing Descriptor Blocks
3001::1:1:1:4, from 3001::1:1:1:4
Route metric is 0
Label: None
Tunnel ID: None
Binding Label: None
Extended communities count: 0
NHID:0x0(Ref:0)
SRv6 Headend: H.Encaps.Red [base], SID-list {cafe:0:0:4:4b::}
Route version is 0x1 (1)
No local label
IP Precedence: Not Set
QoS Group ID: Not Set
Flow-tag: Not Set
Fwd-class: Not Set
Route Priority: RIB_PRIORITY_RECURSIVE (12) SVD Type RIB_SVD_TYPE_LOCAL
Download Priority 4, Download Version 93
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: EVPN VPWS — All-Active Multi-Homing
No advertising protos.
The following examples show how to verify the current IPv6 Cisco Express Forwarding (CEF) table:
RP/0/RSP0/CPU0:Node1# show cef ipv6 3001::13:1:1:4/128
Fri Jan 15 21:08:41.483 UTC
3001::13:1:1:4/128, version 93, SRv6 Headend, internal 0x5000001 0x40 (ptr 0x78a100d4) [1],
0x0 (0x0), 0x0 (0x8886b840)
Updated Jan 15 17:13:50.433
Prefix Len 128, traffic index 0, precedence n/a, priority 4 via cafe:0:0:4::/128, 9 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x78a0f504 0x0] next hop cafe:0:0:4::/128 via cafe:0:0:4::/64
SRv6 H.Encaps.Red SID-list {cafe:0:0:4:4b::}
RP/0/RSP0/CPU0:Node1# show cef ipv6 3001::13:1:1:4/128 detail
Fri Jan 15 21:08:59.789 UTC
3001::13:1:1:4/128, version 93, SRv6 Headend, internal 0x5000001 0x40 (ptr 0x78a100d4) [1],
0x0 (0x0), 0x0 (0x8886b840)
Updated Jan 15 17:13:50.433
Prefix Len 128, traffic index 0, precedence n/a, priority 4 gateway array (0x7883b5d8) reference count 1, flags 0x2010, source rib (7), 0 backups
[1 type 3 flags 0x48441 (0x788e6c40) ext 0x0 (0x0)]
LW-LDI[type=0, refc=0, ptr=0x0, sh-ldi=0x0] gateway array update type-time 1 Jan 15 17:13:50.433
LDI Update time Jan 15 17:13:50.433
Level 1 - Load distribution: 0
[0] via cafe:0:0:4::/128, recursive via cafe:0:0:4::/128, 9 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x78a0f504 0x0] next hop cafe:0:0:4::/128 via cafe:0:0:4::/64
SRv6 H.Encaps.Red SID-list {cafe:0:0:4:4b::}
Load distribution: 0 1 (refcount 1)
Hash OK Interface
0 Y HundredGigE0/0/0/0
1 Y HundredGigE0/0/0/1
Address remote remote
SRv6 Services: EVPN VPWS — All-Active Multi-Homing
EVPN VPWS All-Active Multi-Homing over SRv6 provides an ELINE (P2P) service with all-active multihoming capability over an SRv6 network.
All-Active Multi-Homing enables an operator to connect a customer edge (CE) device to two or more provider edge (PE) devices to provide load balancing and redundant connectivity. With All-Active Multi-Homing, all the PEs can forward traffic to and from the multi-homed device.
Note For information about EVPN VPWS, refer to the "EVPN Virtual Private Wire Service (VPWS)" chapter in the L2VPN and Ethernet Services Configuration Guide for Cisco NCS 5500 Series Routers .
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SRv6 Services: EVPN VPWS — All-Active Multi-Homing
Configuring EVPN VPWS over SRv6
An SRv6 Locator for an EVPN VPWS service can be configured at 3 different levels independently:
• global_locator is the default locator for all EVPN-VPWS services
• evi_locator is applied to all EVPN-VPWS services for the specific EVI
• evi_service_locator is applied to an individual EVI service
When locators are configured at different levels at the same time, the following priority is implemented:
1.
evi_service_locator
2.
evi_locator
3.
global_locator
This example shows how to configure an EVPN VPWS over SRv6 using a global locator for EVPN: evpn segment-routing srv6 locator sample_global_loc l2vpn xconnect group sample_xcg p2p sample-vpws-12001-2002 interface Bundle-Ether12001.2002
neighbor evpn evi 12001 service 2002 segment-routing srv6
This example shows how to configure EVPN VPWS over SRv6 using specific EVI locator: evpn evi 11001 segment-routing srv6 locator sample_evi_loc l2vpn xconnect group sample_xcg p2p sample-vpws-11001-2002 interface Bundle-Ether11001.2002
neighbor evpn evi 11001 service 2002 segment-routing srv6
This example shows how to configure an EVPN VPWS over SRv6 using a locator for an individual EVI service: l2vpn xconnect group sample_xcg p2p sample-vpws-11001-2001 interface Bundle-Ether11001.2001
neighbor evpn evi 11001 service 2001 segment-routing srv6 locator sample_evi_service_loc
Verification
Router# show segment-routing srv6 locator sample_evi_loc sid
Mon Aug 12 20:57:07.759 EDT
SID Behavior Context
State RW
-----------------------------------------------------------------
-----cafe:0:8:1:1:: End (PSP) 'default':1
Owner
-----------------sidmgr
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Configure Segment Routing over IPv6 (SRv6)
SRv6 Services: EVPN VPWS — IPv6 QoS Traffic-Class Marking
InUse Y cafe:0:8:1:11::
InUse Y cafe:0:8:1:40::
InUse Y cafe:0:8:1:41::
InUse Y cafe:0:8:1:42::
InUse Y cafe:0:8:1:44::
InUse Y
End.OP
End.DX2
End.DX2
End.DX2
End.DX2
'default'
11001:1
11001:2
11001:3
11001:2002
Router# show evpn segment-routing srv6 detail
Tue Aug 13 10:30:46.020 EDT
Configured default locator: sample_global_loc
EVIs with unknown locator config: 0
VPWS with unknown locator config: 0
Locator name
------------
Prefix
-----sample_global_loc cafe:0:0:1::/64
Default locator sample_evi_loc cafe:0:8:1::/64
Configured on EVIs <evi>: 11001
OOR
---
False
False sidmgr l2vpn_srv6 l2vpn_srv6 l2vpn_srv6 l2vpn_srv6
Service count
-------------
1
4
SID count
---------
1
4
SRv6 Services: EVPN VPWS — IPv6 QoS Traffic-Class Marking
This feature allows the ingress EVPN VPWS PE to copy the CoS value from the top-most VLAN header to the traffic-class (TC) field of the outer-most IPv6 header. This functionality enables prioritization of traffic in the IPv6 network.
The following configuration shows how to enable this feature:
Note This command requires you to reload the router for the configuration to take effect.
Router# configure
Router(config)# hw-module profile segment-routing srv6 encapsulation traffic-class propagate
The functionality covers the following scenarios:
• Use case 1: Without additional QoS configuration, the CoS in the outer VLAN tag of incoming Ethernet frames is propagated to the traffic-class field in the encapsulated IPv6 header.
• Use case 2: With additional QoS configuration, DSCP in the IPv4/IPv6 header of incoming IP packets is propagated to the traffic-class field in the encapsulated IPv6 header.
The following configuration shows how to define specific classification criteria: class-map match-any prec-0 match precedence ipv4 0 match precedence ipv6 0 end-class-map
… class-map match-any prec-7 match precedence ipv4 7
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SRv6 Services: SRv6 Services TLV Type 5 Support match precedence ipv6 7 end-class-map
The following configuration shows how to define a QoS policy map: policy-map prec-to-tc class prec-0 set qos-group 0
… class prec-7 set qos-group 7
The following configuration shows how to apply a QoS policy-map to an attachment-circuit (AC) interface: interface Bundle-Ether1.1 l2transport encapsulation untagged service-policy input prec-to-tc
SRv6 Services: SRv6 Services TLV Type 5 Support
IOS XR 6.6.1 supports IETF draft draft-dawra-idr-srv6-vpn-04 , in which the SRv6-VPN SID TLV (TLV
Type 4) carries the SRv6 Service SID information. This SID TLV is inconsistent with the SRv6 SID Structure.
In IOS XR 7.0.2 and later releases, the implementation is compliant with draft-ietf-bess-srv6-services-00 , which defines a new SRv6 Services TLV (TLV Type 5/6) and SRv6 SID Structure Sub-Sub-TLV to address this inconsistency.
SRv6 SID Structure Sub-Sub-TLV describes mechanisms for signaling of the SRv6 Service SID by transposing a variable part of the SRv6 SID value (function and/or the argument parts) and carrying them in existing label fields to achieve more efficient packing of VPN and EVPN service prefix NLRIs in BGP update messages.
In order to allow backward compatibility between the newer software and the older software, use the segment-routing srv6 prefix-sid-type4 command in Router BGP Neighbor VPNv4 Address-Family configuration mode to advertise BGP VPNv4 NLRIs in TLV Type 4 format. The newer software can receive either TLV Type 4 or TLV Type 5 formats.
The following configuration shows how to enable the advertisement of BGP VPNv4 NLRIs in TLV Type 4 format:
RP/0/RSP0/CPU0:Rtr-a(config)# router bgp 65000
RP/0/RSP0/CPU0:Rtr-a(config-bgp)# neighbor 6::6
RP/0/RSP0/CPU0:Rtr-a(config-bgp-nbr)# address-family vpnv4 unicast
RP/0/RSP0/CPU0:Rtr-a(config-bgp-nbr-af)# segment-routing srv6 prefix-sid-type4
RP/0/RSP0/CPU0:Rtr-a(config-bgp-nbr-af)#
SRv6 SID Information in BGP-LS Reporting
BGP Link-State (BGP-LS) is used to report the topology of the domain using nodes, links, and prefixes. This feature adds the capability to report SRv6 Segment Identifier (SID) Network Layer Reachability Information
(NLRI).
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Configure Segment Routing over IPv6 (SRv6)
SRv6 OAM — SID Verification
The following NLRI has been added to the BGP-LS protocol to support SRv6:
• Node NLRI: SRv6 Capabilities, SRv6 MSD types
• Link NLRI: End.X, LAN End.X, and SRv6 MSD types
• Prefix NLRI: SRv6 Locator
• SRv6 SID NLRI (for SIDs associated with the node): Endpoint Function, BGP-EPE Peer Node/Set
This example shows how to distribute IS-IS SRv6 link-state data using BGP-LS:
Router(config)# router isis 200
Router(config-isis)# distribute link-state instance-id 200
Note When you distribute IS-IS SRv6 link-state data, SRv6 ping or traceroute operations using the use-srv6-op-sid keyword can retrieve and use the corresponding END.OP SID automatically. See
for details about SRv6 ping and traceroute.
SRv6 OAM — SID Verification
This feature provides enhanced Operations, Administration, and Maintenance (OAM) in Segment Routing
Networks with IPv6 Data plane (SRv6).
Existing OAM mechanisms to ping and trace a remote IPv6 prefix, along the shortest path, continue to work without any modification in an SRv6 network.
However, classic IPv6 OAM cannot be used to ping or trace a remote SRv6 SID function. This feature augments ping and traceroute operations to target remote SRv6 SIDs. An SRv6-enabled router now allocates a new
SRv6 OAM SID known as END.OP (OAM Endpoint with Punt).
Use the following commands to performs SRv6 ping and traceroute:
ping B : k : F :: [ use-srv6-op-sid [ end.op-sid-value ]]
traceroute B : k : F :: [ use-srv6-op-sid [ end.op-sid-value ]]
Where B : k : F :: is the target SID at node k with locator block B and function F .
Ping/Traceroute to SID Without OAM SID
The user can issue ping or traceroute to an SRv6 SID using the classic CLI. A ping or traceroute to an SRv6
SID does not require the user to enter the “use-end-op” keyword when pinging or tracing a SID function. In this case, and as usual, the packet is pre-routed as an ICMP echo request or UDP packet.
Ping/Traceroute to SID With OAM SID
When ping or traceroute operations include the use-srv6-op-sid keyword, the packet is pre-routed with
END.OP SID as Destination Address (DA) and the target SID in the SRH.
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SRv6 OAM — SID Verification
Note The END.OP SID value is an optional 128 bit value in IPv6 address format. See END.OP SID Derivation below for details on this value.
At the target node, the END.OP SID forces the punt of the packet to the OAM process, which verifies that the next SID is local and valid. If the next SID received by the target node is a local valid address that is not a SID, the target node still replies to indicate ping success. The ping reply contains a subtype to indicate the target was a SID or a local address.
A target remote SID include the following:
• END
• END.DT4/END.DX4 (used by L3 Services over SRv6)
• END.DX2 (used by L2 Services over SRv6)
END.OP SID Derivation
The ingress node can automatically derive the END.OP SID associated with a specified target SID by leveraging the IGP topology database in that node. The database will contain END.OP SIDs from remote nodes.
An END.OP SID associated with a locator will be advertised by IS-IS within an IGP domain in an area/level, which is added to the topology database. However, END.OP SIDs are not redistributed by IS-IS across IGP domains or across different area/level within an IGP domain. In this case, the topology database in a node contains END.OP SIDs only from the nodes within the same IGP domain in an area/level. An END.OP SID cannot be determine automatically if the specified target SID is external to the domain. For target SIDs across
IGP domains or across different area/level within an IGP domain, the end.op-sid-value must be explicitly provided.
If end.op-sid-value is not provided and the END.OP SID cannot be automatically derived, an error is displayed prompting the user to provide the end.op-sid-value .
Configuration Examples
The following example shows using ping to a SID without OAM SID.
Router# ping cafe:0:0:a3:40::
Wed Jul 24 19:24:50.812 UTC
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to cafe:0:0:a3:40::, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
The following example shows using ping to a SID with an OAM SID. Note that the output shows "S" to indicate that this is a response from a SID target.
Router# ping cafe:0:0:a3:40:: use-srv6-op-sid
Wed Jul 24 19:24:50.812 UTC
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to cafe:0:0:a3:40::, timeout is 2 seconds:
SSSSS
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
The following example shows using ping to a SID with an explicit OAM SID. Note that the output shows "S" to indicate that this is a response from a SID target.
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Configure Segment Routing over IPv6 (SRv6)
DHCPv4 Relay Agent and Proxy Support over SRv6
Router# ping cafe:0:0:a3:40:: use-srv6-op-sid cafe:0:0:a3:11::
Wed Jul 24 19:24:50.812 UTC
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to cafe:0:0:a3:40::, timeout is 2 seconds:
SSSSS
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
The following example shows using traceroute to a SID without OAM SID.
Router# traceroute cafe:0:0:a3:1::
Wed Jul 24 19:40:19.192 UTC
Type escape sequence to abort.
Tracing the route to cafe:0:0:a3:1::
1 2001::1:1:1:1 2 msec 2 msec 2 msec
2 2001:10:10:13::2 2 msec 2 msec 2 msec
The following example shows using traceroute to a SID with OAM SID.
Router# traceroute cafe:0:0:a3:40:: use-srv6-op-sid
Type escape sequence to abort.
Tracing the route to cafe:0:0:a3:40::
1 2001::1:1:1:1
[IP tunnel: DA=cafe:0:0:a3:11:: SRH Stack 0 =(cafe:0:0:a3:40:: ,SL=1) msec
2 2001::33:33:33:33
[IP tunnel: DA=cafe:0:0:a3:11:: SRH Stack 0 =(cafe:0:0:a3:40:: ,SL=1) msec
The following example shows using traceroute to a SID with an explicit OAM SID.
Router# traceroute cafe:0:0:a3:40:: use-srv6-op-sid cafe:0:0:a3:11::
Type escape sequence to abort.
Tracing the route to cafe:0:0:a3:40::
1 2001::1:1:1:1
[IP tunnel: DA=cafe:0:0:a3:11:: SRH Stack 0 =(cafe:0:0:a3:40:: ,SL=1) msec
2 2001::33:33:33:33
[IP tunnel: DA=cafe:0:0:a3:11:: SRH Stack 0 =(cafe:0:0:a3:40:: ,SL=1) msec
] 2
] 3
] 2
] 3
DHCPv4 Relay Agent and Proxy Support over SRv6
This feature introduces support for DHCPv4 Relay Agent and Proxy over SRv6.
An IOS XR router can act as a DHCPv4 relay agent/proxy with a DHCPv4 server connected over an SRv6 network.
The following functionality is supported:
• DHCPv4 relay agent/proxy over SRv6 with DHCPv4 server (helper-address) located in default VRF
(global)
• DHCPv4 relay agent/proxy over SRv6 with DHCPv4 server (helper-address) located in non-default VRF
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DHCPv6 Relay Agent Support over SRv6
• DHCPv4 relay agent/proxy on interfaces associated with a default VRF (global)
• DHCPv4 relay agent/proxy on interfaces associated with a non-default VRF
• DHCPv4 relay agent/proxy on Ethernet physical interfaces
• DHCPv4 relay agent/proxy on Ethernet bundle interfaces
For information on configuring DHCPv4 relay agent and proxy, refer to the “Implementing the Dynamic Host
Configuration Protocol” chapter in the IP Addresses and Services Configuration Guide for Cisco NCS 5500
Series Routers.
DHCPv6 Relay Agent Support over SRv6
Table 4: Feature History Table
Feature Name
DHCPv6 Relay Agent Support on
SRv6
Release Information
Release 7.2.2
Feature Description
An IOS XR router can act as a
DHCPv6 relay agent with a
DHCPv6 server connected over an
SRv6 network.
A DHCP relay agent is a host that forwards DHCP packets between clients and servers that do not reside on a shared physical subnet.
This feature introduces support for DHCPv6 Relay Agent over SRv6.
An IOS XR router can act as a DHCPv6 relay agent with a DHCPv6 server connected over an SRv6 network.
The following functionality is supported:
• DHCPv6 relay agent over SRv6 with DHCPv6 server (helper-address) located in default VRF (global)
• DHCPv6 relay agent over SRv6 with DHCPv6 server (helper-address) located in non-default VRF
• DHCPv6 relay agent on interfaces associated with a default VRF (global)
• DHCPv6 relay agent on interfaces associated with a non-default VRF
• DHCPv6 relay agent on Ethernet physical interfaces
• DHCPv6 relay agent on Ethernet bundle interfaces
For information on configuring DHCPv6 relay agent, refer to the “Implementing the Dynamic Host
Configuration Protocol” chapter in the IP Addresses and Services Configuration Guide for Cisco NCS 5500
Series Routers .
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DHCPv6 Relay Agent Support over SRv6
Configure Segment Routing over IPv6 (SRv6)
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C H A P T E R
4
Configure Segment Routing Global Block and
Segment Routing Local Block
Local label allocation is managed by the label switching database (LSD). The Segment Routing Global Block
(SRGB) and Segment Routing Local Block (SRLB) are label values preserved for segment routing in the
LSD.
•
About the Segment Routing Global Block, on page 51
•
About the Segment Routing Local Block, on page 53
•
Understanding Segment Routing Label Allocation, on page 54
•
Setup a Non-Default Segment Routing Global Block Range, on page 57
•
Setup a Non-Default Segment Routing Local Block Range, on page 58
About the Segment Routing Global Block
The Segment Routing Global Block (SRGB) is a range of labels reserved for Segment Routing global segments.
A prefix-SID is advertised as a domain-wide unique index. The prefix-SID index points to a unique label within the SRGB range. The index is zero-based, meaning that the first index is 0. The MPLS label assigned to a prefix is derived from the Prefix-SID index plus the SRGB base. For example, considering an SRGB range of 16,000 to 23,999, a prefix 1.1.1.65/32 with prefix-SID index of 65 is assigned the label value of
16065 .
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About the Segment Routing Global Block
Configure Segment Routing Global Block and Segment Routing Local Block
To keep the configuration simple and straightforward, we strongly recommended that you use a homogenous
SRGB (meaning, the same SRGB range across all nodes). Using a heterogenous SRGB (meaning, a different
SRGB range of the same size across nodes) is also supported but is not recommended.
Behaviors and Limitations
• The default SRGB in IOS XR has a size of 8000 starting from label value 16000. The default range is
16000 to 23,999. With this size, and assuming one loopback prefix per router, an operator can assign prefix SIDs to a network with 8000 routers.
• There are instances when you might need to define a different SRGB range. For example:
• Non-IOS XR nodes with a SRGB range that is different than the default IOS XR SRGB range.
• The default SRGB range is not large enough to accommodate all required prefix SIDs.
• A non-default SRGB can be configured following these guidelines:
• The SRGB starting value can be configured anywhere in the dynamic label range space (16,000 to
1,048,575).
• In Cisco IOS XR release earlier than 6.6.3, the SRGB can have a maximum configurable size of
262,143.
• In Cisco IOS XR release 6.6.3 and later, the SRGB can be configured to any size value that fits within the dynamic label range space.
• Allocating an SRGB label range does not mean that all the labels in this range are programmed in the forwarding table. The label range is just reserved for SR and not available for other purposes. Furthermore, a platform may limit the number of local labels that can be programmed.
• We recommend that the non-default SRGB be configured under the segment-routing global configuration mode. By default, all IGP instances and BGP use this SRGB.
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Configure Segment Routing Global Block and Segment Routing Local Block
About the Segment Routing Local Block
• You can also configure a non-default SRGB under the IGP, but it is not recommended.
SRGB Label Conflicts
When you define a non-default SRGB range, there might be a label conflict (for example, if labels are already allocated, statically or dynamically, in the new SRGB range). The following system log message indicates a label conflict:
%ROUTING-ISIS-4-SRGB_ALLOC_FAIL : SRGB allocation failed: 'SRGB reservation not successful for [16000,80000], SRGB (16000 80000, SRGB_ALLOC_CONFIG_PENDING, 0x2)
(So far 16 attempts). Make sure label range is free'
To remove this conflict, you must reload the router to release the currently allocated labels and to allocate the new SRGB.
After the system reloads, LSD does not accept any dynamic label allocation before IS-IS/OSPF/BGP have registered with LSD. Upon IS-IS/OSPF/BGP registration, LSD allocates the requested SRGB (either the default range or the customized range).
After IS-IS/OSPF/BGP have registered and their SRGB is allocated, LSD starts serving dynamic label requests from other clients.
Note To avoid a potential router reload due to label conflicts, and assuming that the default SRGB size is large enough, we recommend that you use the default IOS XR SRGB range.
Note Allocating a non-default SRGB in the upper part of the MPLS label space increases the chance that the labels are available and a reload can be avoided.
Caution Modifying a SRGB configuration is disruptive for traffic and may require a reboot if the new SRGB is not available entirely.
About the Segment Routing Local Block
A local segment is automatically assigned an MPLS label from the dynamic label range. In most cases, such as TI-LFA backup paths and SR-TE explicit paths defined with IP addresses, this dynamic label allocation is sufficient. However, in some scenarios, it could be beneficial to allocate manually local segment label values to maintain label persistency. For example, an SR-TE policy with a manual binding SID that is performing traffic steering based on incoming label traffic with the binding SID.
The Segment Routing Local Block (SRLB) is a range of label values preserved for the manual allocation of local segments, such as adjacency segment identifiers (adj-SIDs) , Layer 2 adj-SIDs, binding SIDs (BSIDs), and BGP peering SIDs. These labels are locally significant and are only valid on the nodes that allocate the labels.
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Configure Segment Routing Global Block and Segment Routing Local Block
Understanding Segment Routing Label Allocation
Behaviors and Limitations
• The default SRLB has a size of 1000 starting from label value 15000; therefore, the default SRLB range goes from 15000 to 15,999.
• A non-default SRLB can be configured following these guidelines:
• The SRLB starting value can be configured anywhere in the dynamic label range space (16,000 to
1,048,575).
• In Cisco IOS XR release earlier than 6.6.3, the SRLB can have a maximum configurable size of
262,143.
• In Cisco IOS XR release 6.6.3 and later, the SRLB can be configured to any size value that fits within the dynamic label range space.
SRLB Label Conflicts
When you define a non-default SRLB range, there might be a label conflict (for example, if labels are already allocated, statically or dynamically, in the new SRLB range). In this case, the new SRLB range will be accepted, but not applied (pending state). The previous SRLB range (active) will continue to be in use.
To remove this conflict, you must reload the router to release the currently allocated labels and to allocate the new SRLB.
Caution You can use the clear segment-routing local-block discrepancy all command to clear label conflicts.
However, using this command is disruptive for traffic since it forces all other MPLS applications with conflicting labels to allocate new labels.
Note To avoid a potential router reload due to label conflicts, and assuming that the default SRGB size is large enough, we recommend that you use the default IOS XR SRLB range.
Note Allocating a non-default SRLB in the upper part of the MPLS label space increases the chance that the labels are available and a reload can be avoided.
Understanding Segment Routing Label Allocation
In IOS XR, local label allocation is managed by the Label Switching Database (LSD). MPLS applications must register as a client with the LSD to allocate labels. Most MPLS applications (for example: LDP, RSVP,
L2VPN, BGP [LU, VPN], IS-IS and OSPF [Adj-SID], SR-TE [Binding-SID]) use labels allocated dynamically by LSD.
With Segment Routing-capable IOS XR software releases, the LSD preserves the default SRLB label range
(15,000 to 15,999) and default SRGB label range (16,000 to 23,999), even if Segment Routing is not enabled.
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Understanding Segment Routing Label Allocation
This preservation of the default SRLB/SRGB label range makes future Segment Routing activation possible without a reboot. No labels are allocated from this preserved range. When you enable Segment Routing with the default SRLB/SRGB in the future, these label ranges will be available and ready for use.
The LSD allocates dynamic labels starting from 24,000.
Note If an MPLS label range is configured and it overlaps with the default SRLB/SRGB label ranges (for example, mpls label range 15000 1048575 ), then the default SRLB/SRGB preservation is disabled.
Example 1: LSD Label Allocation When SR is not Configured
• Special use: 0-15
• MPLS static: 16 to 14,999
• SRLB (preserved): 15,000 to 15,999
• SRGB (preserved): 16,000 to 23,999
• Dynamic: 24,000 to max
Example 2: LSD Label Allocation When SR is Configured with Default SRGB and Default SRLB
• Special use: 0-15
• MPLS static: 16 to 14,999
• SRLB (reserved): 15,000 to 15,999
• SRGB (reserved): 16,000 to 23,999
• Dynamic: 24,000 to max
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Understanding Segment Routing Label Allocation
Configure Segment Routing Global Block and Segment Routing Local Block
Example 3: LSD Label Allocation When SR is Configured with Non-default SRGB and Non-default SRLB
• Special use: 0-15
• MPLS static: 16 to 14,999
• SRLB (preserved): 15,000 to 15,999
• SRGB (preserved): 16,000 to 23,999
• Dynamic: 24000 to 28,999
• SRLB (reserved): 29,000 to 29,999
• SRGB (reserved): 30,000 to 39,999
• Dynamic: 40,000 to max
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Setup a Non-Default Segment Routing Global Block Range
Setup a Non-Default Segment Routing Global Block Range
This task explains how to configure a non-default SRGB range.
SUMMARY STEPS
1.
configure
2.
segment-routing global-block starting_value ending_value
3.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
Purpose
Enters global configuration mode.
RP/0/RP0/CPU0:router# configure
segment-routing global-block starting_value ending_value
Example:
Enter the lowest value that you want the SRGB range to include as the starting value. Enter the highest value that you want the SRGB range to include as the ending value.
RP/0/RP0/CPU0:router(config)# segment-routing global-block 16000 80000
Step 3 Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
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Command or Action Purpose
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Use the show mpls label table [ label label-value ] command to verify the SRGB configuration:
Router# show mpls label table label 16000 detail
Table Label Owner State Rewrite
----- ------- ------------------------------- ------ -------
0 16000 ISIS(A):1 InUse No
(Lbl-blk SRGB, vers:0, (start_label=16000, size=64001)
What to do next
Configure prefix SIDs and enable segment routing.
Setup a Non-Default Segment Routing Local Block Range
This task explains how to configure a non-default SRLB range.
SUMMARY STEPS
1.
configure
2.
segment-routing local-block starting_value ending_value
3.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
Purpose
Enters global configuration mode.
RP/0/RP0/CPU0:router# configure
segment-routing local-block starting_value ending_value
Example:
Enter the lowest value that you want the SRLB range to include as the starting value. Enter the highest value that you want the SRLB range to include as the ending value.
RP/0/RP0/CPU0:router(config)# segment-routing local-block 30000 30999
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Setup a Non-Default Segment Routing Local Block Range
Step 3
Command or Action
Use the commit or end command.
Purpose commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Use the show mpls label table [ label label-value ] [ detail ] command to verify the SRLB configuration:
Router# show mpls label table label 30000 detail
Table Label Owner State Rewrite
----- ------- ------------------------------- ------ -------
0 30000 LSD(A) InUse No
( Lbl-blk SRLB , vers:0, (start_label= 30000 , size= 1000 , app_notify=0)
Router# show segment-routing local-block inconsistencies
No inconsistencies
The following example shows an SRLB label conflict in the range of 30000 and 30999. Note that the default
SRLB is active and the configured SRLB is pending:
Router(config)# segment-routing local-block 30000 30999
%ROUTING-MPLS_LSD-3-ERR_SRLB_RANGE : SRLB allocation failed: 'SRLB reservation not successfull for [30000,30999]. Use with caution 'clear segment-routing local-block discrepancy all' command to force srlb allocation'
Caution You can use the clear segment-routing local-block discrepancy all command to clear label conflicts.
However, using this command is disruptive for traffic since it forces all other MPLS applications with conflicting labels to allocate new labels.
Router# show mpls label table label 30000 detail
Table Label Owner State Rewrite
----- ------- ------------------------------- ------ -------
0 30000 LSD(A) InUse No
(Lbl-blk SRLB, vers:0, (start_label=30000, size=1000, app_notify=0)
Router# show segment-routing local-block inconsistencies
SRLB inconsistencies range: Start/End: 30000/30999
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Setup a Non-Default Segment Routing Local Block Range
Router# show mpls lsd private | i SRLB
SRLB Lbl Mgr:
Current Active SRLB block = [15000, 15999]
Configured Pending SRLB block = [30000, 30999]
Reload the router to release the currently allocated labels and to allocate the new SRLB:
Router# reload
Proceed with reload? [confirm] yes
After the system is brought back up, verify that there are no label conflicts with the SRLB configuration:
Router# show mpls lsd private | i SRLB
SRLB Lbl Mgr:
Current Active SRLB block = [30000, 30999]
Configured Pending SRLB block = [0, 0]
Router# show segment-routing local-block inconsistencies
No inconsistencies
What to do next
Configure adjacency SIDs and enable segment routing.
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C H A P T E R
5
Configure Segment Routing for IS-IS Protocol
Integrated Intermediate System-to-Intermediate System (IS-IS), Internet Protocol Version 4 (IPv4), is a standards-based Interior Gateway Protocol (IGP). The Cisco IOS XR software implements the IP routing capabilities described in International Organization for Standardization (ISO)/International Engineering
Consortium (IEC) 10589 and RFC 1995, and adds the standard extensions for single topology and multitopology
IS-IS for IP Version 6 (IPv6).
This module provides the configuration information used to enable segment routing for IS-IS.
Note For additional information on implementing IS-IS on your Cisco NCS 5500 Series Router, see the Implementing
IS-IS module in the Routing Configuration Guide for Cisco NCS 5500 Series Routers .
•
Enabling Segment Routing for IS-IS Protocol, on page 61
•
Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface, on page 64
•
Configuring an Adjacency SID, on page 66
•
Configuring Bandwidth-Based Local UCMP, on page 73
•
IS-IS Multi-Domain Prefix SID and Domain Stitching: Example, on page 74
•
Conditional Prefix Advertisement, on page 76
•
Segment Routing ECMP-FEC Optimization, on page 78
Enabling Segment Routing for IS-IS Protocol
Segment routing on the IS-IS control plane supports the following:
• IPv4 and IPv6 control plane
• Level 1, level 2, and multi-level routing
• Prefix SIDs for host prefixes on loopback interfaces
• Adjacency SIDs for adjacencies
• MPLS penultimate hop popping (PHP) and explicit-null signaling
This task explains how to enable segment routing for IS-IS.
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Enabling Segment Routing for IS-IS Protocol
Before you begin
Your network must support the MPLS Cisco IOS XR software feature before you enable segment routing for
IS-IS on your router.
Note You must enter the commands in the following task list on every IS-IS router in the traffic-engineered portion of your network.
SUMMARY STEPS
1.
configure
2.
router isis instance-id
3.
address-family { ipv4 | ipv6 } [ unicast ]
4.
metric-style wide [ level { 1 | 2 }]
5.
mpls traffic-eng level
6.
mpls traffic-eng router-id interface
7.
router-id loopback loopback interface used for prefix-sid
8.
segment-routing mpls
9.
exit
10.
mpls traffic-eng
11.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
Step 3
Step 4
Purpose
Enters global configuration mode.
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
RP/0/RP0/CPU0:router(config)# router isis isp
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
Note You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.
address-family { ipv4 | ipv6 } [ unicast ]
Example:
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast metric-style wide [ level { 1 | 2 }]
Example:
Configures a router to generate and accept only wide link metrics in the Level 1 area.
RP/0/RP0/CPU0:router(config-isis-af)# metric-style wide level 1
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Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Command or Action
mpls traffic-eng level
Example:
RP/0/RP0/CPU0:router(config-isis-af)# mpls traffic-eng level-2-only
mpls traffic-eng router-id interface
Example:
Purpose
Enables RSVP traffic engineering funtionality.
Sets the traffic engineering loopback interface.
RP/0/RP0/CPU0:router(config-isis-af)# mpls traffic-eng router-id Loopback0
router-id loopback loopback interface used for prefix-sid Configures router ID for each address-family (IPv4/IPv6).
Example:
RP/0/RP0/CPU0:router(config-isis-af)#router-id loopback0 segment-routing mpls
Example:
RP/0/RP0/CPU0:router(config-isis-af)# segment-routing mpls
Segment routing is enabled by the following actions:
• MPLS forwarding is enabled on all interfaces where
IS-IS is active.
• All known prefix-SIDs in the forwarding plain are programmed, with the prefix-SIDs advertised by remote routers or learned through local or remote mapping server.
• The prefix-SIDs locally configured are advertised.
exit
Example:
RP/0/RP0/CPU0:router(config-isis-af)# exit
RP/0/RP0/CPU0:router(config-isis)# exit mpls traffic-eng
Example:
RP/0/RP0/CPU0:router(config)# mpls traffic-eng
Use the commit or end command.
Enables traffic engineering functionality on the node. The node advertises the traffic engineering link attributes in
IGP which populates the traffic engineering database
(TED) on the head-end. The RSVP-TE head-end requires the TED to calculate and validate the path of the RSVP-TE policy.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
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Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface
Command or Action Purpose
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
What to do next
Configure the prefix SID.
Configuring a Prefix-SID on the IS-IS Enabled Loopback
Interface
A prefix segment identifier (SID) is associated with an IP prefix. The prefix SID is manually configured from the segment routing global block (SRGB) range of labels. A prefix SID is configured under the loopback interface with the loopback address of the node as the prefix. The prefix segment steers the traffic along the shortest path to its destination.
A prefix SID can be a node SID or an Anycast SID. A node SID is a type of prefix SID that identifies a specific node. An Anycast SID is a type of prefix SID that identifies a set of nodes, and is configured with n-flag clear.
The set of nodes (Anycast group) is configured to advertise a shared prefix address and prefix SID. Anycast routing enables the steering of traffic toward multiple advertising nodes. Packets addressed to an Anycast address are forwarded to the topologically nearest nodes.
The prefix SID is globally unique within the segment routing domain.
This task explains how to configure prefix segment identifier (SID) index or absolute value on the IS-IS enabled Loopback interface.
Before you begin
Ensure that segment routing is enabled on the corresponding address family.
SUMMARY STEPS
1.
configure
2.
router isis instance-id
3.
interface Loopback instance
4.
address-family { ipv4 | ipv6 } [ unicast ]
5.
prefix-sid [ algorithm algorithm-number ] { index SID-index | absolute SID-value } [ n-flag-clear ]
[ explicit-null ]
6.
Use the commit or end command.
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Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
Step 3
Step 4
Step 5
Step 6
RP/0/RP0/CPU0:router(config)# router isis 1
Purpose
Enters global configuration mode.
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
• You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Specifies the loopback interface and instance.
interface Loopback instance
Example:
RP/0/RP0/CPU0:router(config-isis)# interface
Loopback0 address-family { ipv4 | ipv6 } [ unicast ]
Example:
The following is an example for ipv4 address family:
Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.
RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast prefix-sid [ algorithm algorithm-number ] { index SID-index
| absolute SID-value } [ n-flag-clear ] [ explicit-null ]
Configures the prefix-SID index or absolute value for the interface.
Example: Specify algorithm algorithm-number to configure SR
Flexible Algorithm. See
Enabling Segment Routing Flexible
RP/0/RP0/CPU0:router(config-isis-if-af)# prefix-sid index 1001
Specify index SID-index for each node to create a prefix
SID based on the lower boundary of the SRGB + the index.
RP/0/RP0/CPU0:router(config-isis-if-af)# prefix-sid absolute 17001
Specify absolute SID-value for each node to create a specific prefix SID within the SRGB.
By default, the n-flag is set on the prefix-SID, indicating that it is a node SID. For specific prefix-SID (for example,
Anycast prefix-SID), enter the n-flag-clear keyword.
IS-IS does not set the
N flag in the prefix-SID sub Type
Length Value (TLV).
To disable penultimate-hop-popping (PHP) and add explicit-Null label, enter explicit-null keyword. IS-IS sets the
E flag in the prefix-SID sub TLV.
Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
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Configuring an Adjacency SID
Command or Action Purpose end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Verify the prefix-SID configuration:
RP/0/RP0/CPU0:router# show isis database verbose
IS-IS 1 (Level-2) Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
1079 0/0/0 router.00-00 * 0x0000039b 0xfc27
Area Address: 49.0001
NLPID: 0xcc
NLPID:
MT:
0x8e
Standard (IPv4 Unicast)
MT:
Hostname:
IPv6 Unicast router
IP Address: 10.0.0.1
IPv6 Address: 2001:0db8:1234::0a00:0001
Router Cap: 10.0.0.1, D:0, S:0
Segment Routing: I:1 V:1, SRGB Base: 16000 Range: 8000
SR Algorithm:
Algorithm: 0
0/0/0
<...>
Metric: 0 IP-Extended 10.0.0.1/32
Prefix-SID Index: 1001, Algorithm:0 , R:0 N:1 P:0 E:0 V:0 L:0
<...>
What to do next
Configure the SR-TE policy.
Configuring an Adjacency SID
An adjacency SID (Adj-SID) is associated with an adjacency to a neighboring node. The adjacency SID steers the traffic to a specific adjacency. Adjacency SIDs have local significance and are only valid on the node that allocates them.
An adjacency SID can be allocated dynamically from the dynamic label range or configured manually from the segment routing local block (SRLB) range of labels.
Adjacency SIDs that are dynamically allocated do not require any special configuration, however there are some limitations:
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Configuring an Adjacency SID
• A dynamically allocated Adj-SID value is not known until it has been allocated, and a controller will not know the Adj-SID value until the information is flooded by the IGP.
• Dynamically allocated Adj-SIDs are not persistent and can be reallocated after a reload or a process restart.
• Each link is allocated a unique Adj-SID, so the same Adj-SID cannot be shared by multiple links.
Manually allocated Adj-SIDs are persistent over reloads and restarts. They can be provisioned for multiple adjacencies to the same neighbor or to different neighbors. You can specify that the Adj-SID is protected. If the Adj-SID is protected on the primary interface and a backup path is available, a backup path is installed.
By default, manual Adj-SIDs are not protected.
Adjacency SIDs are advertised using the existing IS-IS Adj-SID sub-TLV. The S and P flags are defined for manually allocated Adj-SIDs.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F|B|V|L| S | P | |
+-+-+-+-+-+-+-+-+
Table 5: Adjacency Segment Identifier (Adj-SID) Flags Sub-TLV Fields
Field
S (Set)
Description
This flag is set if the same Adj-SID value has been provisioned on multiple interfaces.
This flag is set if the Adj-SID is persistent (manually allocated).
P (Persistent)
Manually allocated Adj-SIDs are supported on point-to-point (P2P) interfaces.
This task explains how to configure an Adj-SID on an interface.
Before you begin
Ensure that segment routing is enabled on the corresponding address family.
Use the show mpls label table detail command to verify the SRLB range.
SUMMARY STEPS
1.
configure
2.
router isis instance-id
3.
interface type interface-path-id
4.
point-to-point
5.
address-family { ipv4 | ipv6 } [ unicast ]
6.
adjacency-sid { index adj-SID-index | absolute adj-SID-value } [ protected ]
7.
Use the commit or end command.
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Configuring an Adjacency SID
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
Step 3
Step 4
Step 5
Step 6
interface type interface-path-id
Example:
RP/0/RP0/CPU0:router(config-isis)# interface
GigabitEthernet0/0/0/7 point-to-point
Example:
RP/0/RP0/CPU0:router(config-isis-if)# point-to-point address-family { ipv4 | ipv6 } [ unicast ]
Example:
The following is an example for ipv4 address family:
RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast adjacency-sid { index adj-SID-index | absolute adj-SID-value } [ protected ]
Example:
RP/0/RP0/CPU0:router(config-isis-if-af)# adjacency-sid index 10
Step 7
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis-if-af)# adjacency-sid absolute 15010
Use the commit or end command.
Purpose
Enters global configuration mode.
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
• You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Specifies the interface and enters interface configuration mode.
Specifies the interface is a point-to-point interface.
Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.
Configures the Adj-SID index or absolute value for the interface.
Specify index adj-SID-index for each link to create an
Ajd-SID based on the lower boundary of the SRLB + the index.
Specify absolute adj-SID-value for each link to create a specific Ajd-SID within the SRLB.
Specify if the Adj-SID is protected . For each primary path, if the Adj-SID is protected on the primary interface and a backup path is available, a backup path is installed. By default, manual Adj-SIDs are not protected.
commit —Saves the configuration changes and remains within the configuration session.
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Command or Action Purpose end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Verify the Adj-SID configuration:
RP/0/RP0/CPU0:router# show isis segment-routing label adjacency persistent
Mon Jun 12 02:44:07.085 PDT
IS-IS 1 Manual Adjacency SID Table
15010 AF IPv4
GigabitEthernet0/0/0/3: IPv4, Protected 1/65/N, Active
GigabitEthernet0/0/0/7: IPv4, Protected 2/66/N, Active
15100 AF IPv6
GigabitEthernet0/0/0/3: IPv6, Not protected 255/255/N, Active
Verify the labels are added to the MPLS Forwarding Information Base (LFIB):
RP/0/RP0/CPU0:router# show mpls forwarding labels 15010
Mon Jun 12 02:50:12.172 PDT
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
15010 Pop SRLB (idx 10) Gi0/0/0/3 10.0.3.3
0
Pop
16004
16004
SRLB (idx 10)
SRLB (idx 10)
SRLB (idx 10)
Gi0/0/0/7
Gi0/0/0/7
Gi0/0/0/3
10.1.0.5
10.1.0.5
10.0.3.3
0
0
0
(!)
(!)
What to do next
Configure the SR-TE policy.
Manually Configure a Layer 2 Adjacency SID
Typically, an adjacency SID (Adj-SID) is associated with a Layer 3 adjacency to a neighboring node, to steer the traffic to a specific adjacency. If you have Layer 3 bundle interfaces, where multiple physical interfaces form a bundle interface, the individual Layer 2 bundle members are not visible to IGP; only the bundle interface is visible.
You can configure a Layer 2 Adj-SID for the individual Layer 2 bundle interfaces. This configuration allows you to track the availability of individual bundle member links and to verify the segment routing forwarding over the individual bundle member links, for Operational Administration and Maintenance (OAM) purposes.
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Manually Configure a Layer 2 Adjacency SID
A Layer 2 Adj-SID can be allocated dynamically or configured manually.
• IGP dynamically allocates Layer 2 Adj-SIDs from the dynamic label range for each Layer 2 bundle member. A dynamic Layer 2 Adj-SID is not persistent and can be reallocated as the Layer 3 bundle link goes up and down.
• Manually configured Layer 2 Adj-SIDs are persistent if the Layer 3 bundle link goes up and down. Layer
2 Adj-SIDs are allocated from the Segment Routing Local Block (SRLB) range of labels. However, if the configured value of Layer 2 Adj-SID does not fall within the available SRLB, a Layer 2 Adj-SID will not be programmed into forwarding information base (FIB).
Restrictions
• Adj-SID forwarding requires a next-hop, which can be either an IPv4 address or an IPv6 address, but not both. Therefore, manually configured Layer 2 Adj-SIDs are configured per address-family.
• Manually configured Layer 2 Adj-SID can be associated with only one Layer 2 bundle member link.
• A SID value used for Layer 2 Adj-SID cannot be shared with Layer 3 Adj-SID.
• SR-TE using Layer 2 Adj-SID is not supported.
This task explains how to configure a Layer 2 Adj-SID on an interface.
Before you begin
Ensure that segment routing is enabled on the corresponding address family.
Use the show mpls label table detail command to verify the SRLB range.
SUMMARY STEPS
1.
configure
2.
segment-routing
3.
adjacency-sid
4.
interface type interface-path-id
5.
address-family { ipv4 | ipv6 } [ unicast ]
6.
l2-adjacency sid { index adj-SID-index | absolute adj-SID-value } [ next-hop { ipv4_address | ipv6_address } ]
7.
Use the commit or end command.
8.
end
9.
router isis instance-id
10.
address-family { ipv4 | ipv6 } [ unicast ]
11.
segment-routing bundle-member-adj-sid
DETAILED STEPS
Step 1
Command or Action configure
Example:
RP/0/RP0/CPU0:router# configure
Purpose
Enters global configuration mode.
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Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Command or Action segment-routing
Example:
Router(config)# segment-routing
Purpose
Enters segment routing configuration mode.
adjacency-sid
Example:
Router(config-sr)# adjacency-sid
interface type interface-path-id
Example:
Router(config-sr-adj)# interface
GigabitEthernet0/0/0/3 address-family { ipv4 | ipv6 } [ unicast ]
Example:
Enters adjacency SID configuration mode.
Specifies the interface and enters interface configuration mode.
Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.
Router(config-sr-adj-intf)# address-family ipv4 unicast l2-adjacency sid { index adj-SID-index | absolute adj-SID-value } [ next-hop { ipv4_address | ipv6_address
Example:
} ]
Router(config-sr-adj-intf-af)# l2-adjacency sid absolute 15015 next-hop 10.1.1.4
Configures the Adj-SID index or absolute value for the interface.
Specify index adj-SID-index for each link to create an
Ajd-SID based on the lower boundary of the SRLB + the index.
Specify absolute adj-SID-value for each link to create a specific Ajd-SID within the SRLB.
For point-to-point interfaces, you are not required to specify a next-hop. However, if you do specify the next-hop, the Layer 2 Adj-SID will be used only if the specified next-hop matches the neighbor address.
For LAN interfaces, you must configure the next-hop IPv4 or IPv6 address. If you do not configure the next-hop, the
Layer 2 Adj-SID will not be used for LAN interface.
Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
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Step 8
Step 9
Step 10
Command or Action Purpose
• Cancel —Remains in the configuration session, without committing the configuration changes.
end
router isis instance-id
Example:
Router(config)# router isis isp
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
address-family { ipv4 | ipv6 } [ unicast ]
Example:
Router(config-isis)# address-family ipv4 unicast
Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.
Step 11 segment-routing bundle-member-adj-sid
Example:
Router(config-isis-af)# segment-routing bundle-member-adj-sid
Programs the dynamic Layer 2 Adj-SIDs, and advertises both manual and dynamic Layer 2 Adj-SIDs.
Note This command is not required to program manual L2 Adj-SID, but is required to program the dynamic Layer 2 Adj-SIDs and to advertise both manual and dynamic Layer 2 Adj-SIDs.
Verify the configuration:
Router# show mpls forwarding detail | i "Pop|Outgoing Interface|Physical Interface"
Tue Jun 20 06:53:51.876 PDT
. . .
15001 Pop SRLB (idx 1) BE1 10.1.1.4
0
Outgoing Interface: Bundle-Ether1 (ifhandle 0x000000b0)
Physical Interface: GigabitEthernet0/0/0/3 (ifhandle 0x000000b0)
Router# show running-config segment-routing
Tue Jun 20 07:14:25.815 PDT segment-routing adjacency-sid interface GigabitEthernet0/0/0/3 address-family ipv4 unicast l2-adjacency-sid absolute 15015
!
!
!
!
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Configuring Bandwidth-Based Local UCMP
Configuring Bandwidth-Based Local UCMP
Bandwidth-based local Unequal Cost Multipath (UCMP) allows you to enable UCMP functionality locally between Equal Cost Multipath (ECMP) paths based on the bandwidth of the local links.
Bandwidth-based local UCMP is performed for prefixes, segment routing Adjacency SIDs, and Segment
Routing label cross-connects installed by IS-IS, and is supported on any physical or virtual interface that has a valid bandwidth.
For example, if the capacity of a bundle interface changes due to the link or line card up/down event, traffic continues to use the affected bundle interface regardless of the available provisioned bundle members. If some bundle members were not available due to the failure, this behavior could cause the traffic to overload the bundle interface. To address the bundle capacity changes, bandwidth-based local UCMP uses the bandwidth of the local links to load balance traffic when bundle capacity changes.
Before you begin
SUMMARY STEPS
1.
configure
2.
router isis instance-id
3.
address-family { ipv4 | ipv6 } [ unicast ]
4.
apply-weight ecmp-only bandwidth
5.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
RP/0/RP0/CPU0:router(config)# router isis 1
Step 3 address-family { ipv4 | ipv6 } [ unicast ]
Example:
The following is an example for ipv4 address family:
Purpose
Enters global configuration mode.
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Specifies the IPv4 or IPv6 address family, and enters IS-IS address family configuration mode.
Step 4
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast apply-weight ecmp-only bandwidth
Example:
Enables UCMP functionality locally between ECMP paths based on the bandwidth of the local links.
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IS-IS Multi-Domain Prefix SID and Domain Stitching: Example
Step 5
Command or Action Purpose
RP/0/RP0/CPU0:router(config-isis-af)# apply-weight ecmp-only bandwidth
Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
IS-IS Multi-Domain Prefix SID and Domain Stitching: Example
IS-IS Multi-Domain Prefix SID and Domain Stitching allows you to configure multiple IS-IS instances on the same loopback interface for domain border nodes. You specify a loopback interface and prefix SID under multiple IS-IS instances to make the prefix and prefix SID reachable in different domains.
This example uses the following topology. Node 5 and 9 are border nodes between two IS-IS domains (Domain1 and Domain2). Node 10 is configured as the Segment Routing Path Computation Element (SR-PCE) (see
Configure Segment Routing Path Computation Element ).
Figure 1: Multi-Domain Topology
Configure IS-IS Multi-Domain Prefix SID
Specify a loopback interface and prefix SID under multiple IS-IS instances on each border node:
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Configure Common Router ID
Example: Border Node 5 router isis Domain1 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16005 router isis Domain2 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16005
Example: Border Node 9 router isis Domain1 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16009 router isis Domain2 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16009
Border nodes 5 and 9 each run two IS-IS instances (Domain1 and Domain2) and advertise their Loopback0 prefix and prefix SID in both domains.
Nodes in both domains can reach the border nodes by using the same prefix and prefix SID. For example,
Node 3 and Node 22 can reach Node 5 using prefix SID 16005.
Configure Common Router ID
On each border node, configure a common TE router ID under each IS-IS instance:
Example: Border Node 5 router isis Domain1 address-family ipv4 unicast router-id loopback0 router isis Domain2 address-family ipv4 unicast router-id loopback0
Example: Border Node 9 router isis Domain1 address-family ipv4 unicast router-id loopback0 router isis Domain2 address-family ipv4 unicast router-id loopback0
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Distribute IS-IS Link-State Data
Distribute IS-IS Link-State Data
Configure Segment Routing for IS-IS Protocol
Configure BGP Link-state (BGP-LS) on Node 13 and Node 14 to report their local domain to Node 10:
Example: Node 13 router isis Domain1 distribute link-state instance-id instance-id
Example: Node 14 router isis Domain2 distribute link-state instance-id instance-id
Link-state ID starts from 32. One ID is required per IGP domain. Different domain IDs are essential to identify that the SR-TE TED belongs to a particular IGP domain.
Nodes 13 and 14 each reports its local domain in BGP-LS to Node 10.
Node 10 identifies the border nodes (Nodes 5 and 9) by their common advertised TE router ID, then combines
(stitches) the domains on these border nodes for end-to-end path computations.
Conditional Prefix Advertisement
In some situations, it’s beneficial to make the IS-IS prefix advertisement conditional. For example, an Area
Border Router (ABR) or Autonomous System Boundary Router (ASBR) that has lost its connection to one of the areas or autonomous systems (AS) might keep advertising a prefix. If an ABR or ASBR advertises the
Segment Routing (SR) SID with this prefix, the label stack of the traffic routed toward the disconnected area or AS might use this SID, which would result in dropped traffic at the ABR or ASBR.
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Conditional Prefix Advertisement
ABRs or ASBRs are often deployed in pairs for redundancy and advertise a shared Anycast prefix SID.
Conditional Prefix Advertisement allows an ABR or an ASBR to advertise its Anycast SID only when connected to a specific area or domain. If an ABR or ASBR becomes disconnected from the particular area or AS, it stops advertising the address for a specified interface (for example, Loopback).
Configure the conditional prefix advertisement under a specific interface. The prefix advertisement on this interface is associated with the route-policy that tracks the presence of a set of prefixes (prefix-set) in the
Routing Information Base (RIB).
For faster convergence, the route-policy used for conditional prefix advertisement uses the new event-based rib-has-route async condition to notify IS-IS of the following situations:
• When the last prefix from the prefix-set is removed from the RIB.
• When the first prefix from the prefix-set is added to the RIB.
Configuration
To use the conditional prefix advertisement in IS-IS, create a prefix-set to be tracked. Then create a route policy that uses the prefix-set.
Router(config)# prefix-set prefix-set-name
Router(config-pfx)# prefix-address-1 /length [ , prefix-address-2/length ,,, prefix-address-16 /length ]
Router(config-pfx)# end-set
Router(config)# route-policy rpl-name
Router(config-rpl)# if rib-has-route async prefix-set-name then
Router(config-rpl-if)# pass
Router(config-rpl-if)# endif
Router(config-rpl)# end-policy
To advertise the loopback address in IS-IS conditionally, use the advertise prefix route-policy command under IS-IS interface address-family configuration sub-mode.
Router(config)# router isis 1
Router(config-isis)# interface Loopback0
Router(config-isis-if)# address-family ipv4 unicast
Router(config-isis-if-af)# advertise prefix route-policy rpl-name
Router(config-isis-if-af)# commit
Example
Router(config)# prefix-set domain_2
Router(config-pfx)# 2.3.3.3/32, 2.4.4.4/32
Router(config-pfx)# end-set
Router(config)# route-policy track_domain_2
Router(config-rpl)# if rib-has-route async domain_2 then
Router(config-rpl-if)# pass
Router(config-rpl-if)# endif
Router(config-rpl)# end-policy
Router(config)# router isis 1
Router(config-isis)# interface Loopback0
Router(config-isis-if)# address-family ipv4 unicast
Router(config-isis-if-af)# advertise prefix route-policy track_domain-2
Router(config-isis-if-af)# commit
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Running Configuration prefix-set domain_2
2.3.3.3/32,
2.4.4.4/32 end-set
!
route-policy track_domain_2 if rib-has-route async domain_2 then pass endif end-policy
!
router isis 1 interface Loopback0 address-family ipv4 unicast
!
!
advertise prefix route-policy track_domain_2
!
Segment Routing ECMP-FEC Optimization
ECMP-FECs are used for any ECMP programming on the system, such as MPLS LSP ECMP, VPN multipath, and EVPN multi-homing .
The SR ECMP-FEC optimization solution minimizes ECMP-FEC resource consumption during underlay programming for an SR-MPLS network. This feature supports sharing the same ECMP-FEC, regular FEC, and Egress Encapsulation DB (EEDB) entries for all /32 IPv4 Segment Routing prefixes with the same set of next hops. ECMP-FEC optimization is triggered when all the out_labels associated with the ECMP paths for a given prefix have the same value. If this rule is not met, then the prefix is programmed with a dedicated
ECMP-FEC. Other prefixes that meet the rule are candidates for optimization.
Segment Routing Label Edge Router (LER) ECMP-FEC Optimization enables ECMP-FEC optimization originally developed for Label Switched Router (LSR) nodes (MPLS P) to be enabled on LER (Layer 3 MPLS
PE) routers.
Usage Guidelines and Limitations
• SR ECMP-FEC Optimization is not supported on Cisco NCS 5500 series routers that have the Cisco
NC57 line cards installed and operating in the native or compatible modes.
• For prefixes with LFA backup paths, the SR ECMP-FEC Optimization is possible since these backup paths do not require an extra label to be pushed; all paths associated with the prefix (primary and backup) have the same outgoing label value.
• For prefixes with TI-LFA backup paths requiring extra labels to be pushed on to the backup, the SR
ECMP-FEC Optimization is not possible since all the paths associated with the prefix do not have the same outgoing label value.
• For the duration of time that prefixes are programmed to avoid microloops (when SR MicroLoop
Avoidance is triggered), SR ECMP-FEC Optimization is not possible since all the paths associated with the prefix do not have the same outgoing label value. After removal of the microloop-avoidance programming, the SR ECMP-FEC Optimization might be possible again.
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Segment Routing ECMP-FEC Optimization
• For scenarios with prefixes where the SR ECMP-FEC Optimization is not possible, dedicated ECMP-FEC is allocated per prefix. This could potentially lead to ECMP FEC out-of-resource (OOR) considering the baseline usage of ECMP FEC resources at steady state. During ECMP-FEC OOR, prefixes with multiple paths are programmed with a single path in order to avoid traffic disruption.
• SR ECMP-FEC optimization is applicable in the following instances:
• Label Switched Router (LSR) nodes (MPLS P)
• L3VPN Label Edge Router (LER) nodes
• SR ECMP-FEC optimization should not be enabled in the following instances:
• L2VPN LER nodes
• L2VPN/L3VPN LER nodes with VPN over BGP-LU over SR
• BGP PIC is not supported
Enable SR ECMP-FEC Optimization
To enable SR ECMP-FEC optimization, use the hw-module fib mpls label lsr-optimized command in global configuration mode. After enabling this feature, reload the line card.
Router(config)# hw-module fib mpls label lsr-optimized
Router(config)# commit
LC/0/0/CPU0:Oct 11 20:19:12.540 UTC: fia_driver[185]:
%FABRIC-FIA_DRVR-4-MPLS_HW_PROFILE_MISMATCH :
Mismatch found, reload LC to activate the new mpls profile
Router# reload location 0/0/CPU0
Proceed with reload? [ confirm ]
Reloading node 0/0/CPU0
Verification
The following example shows NPU usage before enabling SR ECMP-FEC optimization.
Router# show controllers npu resources ecmpfec location all
HW Resource Information For Location: 0/0/CPU0
HW Resource Information
Name : ecmp_fec
OOR Information
NPU-0
Estimated Max Entries
Red Threshold
Yellow Threshold
OOR State
: 4096
: 95
: 80
: Green
Current Usage
NPU-0
Total In-Use ipnhgroup ip6nhgroup
: 1001
: 1001
: 0
(24 %)
(24 %)
(0 %)
The following example shows NPU usage after enabling SR ECMP-FEC optimization.
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Router# show controllers npu resources ecmpfec location all
HW Resource Information For Location: 0/0/CPU0
HW Resource Information
Name : ecmp_fec
OOR Information
NPU-0
Estimated Max Entries
Red Threshold
Yellow Threshold
OOR State
: 4096
: 95
: 80
: Green
Current Usage
NPU-0
Total In-Use ipnhgroup ip6nhgroup
: 7
: 7
: 0
(0 %)
(0 %)
(0 %)
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C H A P T E R
6
Configure Segment Routing for OSPF Protocol
Open Shortest Path First (OSPF) is an Interior Gateway Protocol (IGP) developed by the OSPF working group of the Internet Engineering Task Force (IETF). Designed expressly for IP networks, OSPF supports IP subnetting and tagging of externally derived routing information. OSPF also allows packet authentication and uses IP multicast when sending and receiving packets.
This module provides the configuration information to enable segment routing for OSPF.
Note For additional information on implementing OSPF on your , see the Implementing OSPF module in the .
•
Enabling Segment Routing for OSPF Protocol, on page 81
•
Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface, on page 83
•
Segment Routing ECMP-FEC Optimization, on page 86
Enabling Segment Routing for OSPF Protocol
Segment routing on the OSPF control plane supports the following:
• OSPFv2 control plane
• Multi-area
• IPv4 prefix SIDs for host prefixes on loopback interfaces
• Adjacency SIDs for adjacencies
• MPLS penultimate hop popping (PHP) and explicit-null signaling
This section describes how to enable segment routing MPLS and MPLS forwarding in OSPF. Segment routing can be configured at the instance, area, or interface level.
Before you begin
Your network must support the MPLS Cisco IOS XR software feature before you enable segment routing for
OSPF on your router.
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Enabling Segment Routing for OSPF Protocol
Note You must enter the commands in the following task list on every OSPF router in the traffic-engineered portion of your network.
SUMMARY STEPS
1.
configure
2.
router ospf process-name
3.
mpls traffic-eng router-id interface
4.
segment-routing mpls
5.
area area
6.
mpls traffic-eng
7.
segment-routing mpls
8.
exit
9.
mpls traffic-eng
10.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router ospf process-name
Example:
Step 3
Step 4
Step 5
Purpose
Enters global configuration mode.
Enables OSPF routing for the specified routing process and places the router in router configuration mode.
RP/0/RP0/CPU0:router(config)# router ospf 1
mpls traffic-eng router-id interface
Example:
Sets the traffic engineering loopback interface.
RP/0/RP0/CPU0:router(config-ospf)# mpls traffic-eng router-id Loopback0 segment-routing mpls
Example:
Enables segment routing using the MPLS data plane on the routing process and all areas and interfaces in the routing process.
RP/0/RP0/CPU0:router(config-ospf)# segment-routing mpls
Enables segment routing fowarding on all interfaces in the routing process and installs the SIDs received by OSPF in the forwarding table.
area area
Example:
RP/0/RP0/CPU0:router(config-ospf)# area 0
Enters area configuration mode.
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Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface
Step 6
Step 7
Step 8
Step 9
Step 10
Command or Action mpls traffic-eng
Example:
RP/0/RP0/CPU0:router(config-ospf-ar)# mpls traffic-eng segment-routing mpls
Example:
RP/0/RP0/CPU0:router(config-ospf-ar)# segment-routing mpls exit
Example:
Purpose
Enables IGP traffic engineering funtionality.
(Optional) Enables segment routing using the MPLS data plane on the area and all interfaces in the area. Enables segment routing fowarding on all interfaces in the area and installs the SIDs received by OSPF in the forwarding table.
RP/0/RP0/CPU0:router(config-ospf-ar)# exit
RP/0/RP0/CPU0:router(config-ospf)# exit mpls traffic-eng
Example:
RP/0/RP0/CPU0:router(config)# mpls traffic-eng
Use the commit or end command.
Enables traffic engineering funtionality on the node. The node advertises the traffic engineering link attributes in
IGP which populates the traffic engineering database
(TED) on the head-end. The SR-TE head-end requires the
TED to calculate and validate the path of the SR-TE policy.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
What to do next
Configure the prefix SID.
Configuring a Prefix-SID on the OSPF-Enabled Loopback
Interface
A prefix segment identifier (SID) is associated with an IP prefix. The prefix SID is manually configured from the segment routing global block (SRGB) range of labels. A prefix SID is configured under the loopback interface with the loopback address of the node as the prefix. The prefix segment steers the traffic along the shortest path to its destination.
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Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface
A prefix SID can be a node SID or an Anycast SID. A node SID is a type of prefix SID that identifies a specific node. An Anycast SID is a type of prefix SID that identifies a set of nodes, and is configured with n-flag clear.
The set of nodes (Anycast group) is configured to advertise a shared prefix address and prefix SID. Anycast routing enables the steering of traffic toward multiple advertising nodes. Packets addressed to an Anycast address are forwarded to the topologically nearest nodes.
The prefix SID is globally unique within the segment routing domain.
This task describes how to configure prefix segment identifier (SID) index or absolute value on the
OSPF-enabled Loopback interface.
Before you begin
Ensure that segment routing is enabled on an instance, area, or interface.
SUMMARY STEPS
1.
configure
2.
router ospf process-name
3.
area value
4.
interface Loopback interface-instance
5.
prefix-sid [ algorithm algorithm-number ] { index SID-index | absolute SID-value } [ n-flag-clear ]
[ explicit-null ]
6.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router ospf process-name
Example:
Step 3
Step 4
Step 5
Purpose
Enters global configuration mode.
Enables OSPF routing for the specified routing process, and places the router in router configuration mode.
RP/0/RP0/CPU0:router(config)# router ospf 1
area value
Example:
Enters area configuration mode.
RP/0/RP0/CPU0:router(config-ospf)# area 0
interface Loopback interface-instance
Example:
Specifies the loopback interface and instance.
RP/0/RP0/CPU0:router(config-ospf-ar)# interface
Loopback0 passive prefix-sid [ algorithm algorithm-number ] { index SID-index
| absolute SID-value } [ n-flag-clear ] [ explicit-null ]
Configures the prefix-SID index or absolute value for the interface.
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Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface
Step 6
Command or Action
Example:
RP/0/RP0/CPU0:router(config-ospf-ar)# prefix-sid index 1001
Purpose
Specify algorithm algorithm-number to configure SR
Flexible Algorithm. See
Enabling Segment Routing Flexible
RP/0/RP0/CPU0:router(config-ospf-ar)# prefix-sid absolute 17001
Specify index SID-index for each node to create a prefix
SID based on the lower boundary of the SRGB + the index.
Specify absolute SID-value for each node to create a specific prefix SID within the SRGB.
By default, the n-flag is set on the prefix-SID, indicating that it is a node SID. For specific prefix-SID (for example,
Anycast prefix-SID), enter the n-flag-clear keyword.
OSPF does not set the
N flag in the prefix-SID sub Type
Length Value (TLV).
To disable penultimate-hop-popping (PHP) and add an explicit-Null label, enter the explicit-null keyword. OSPF sets the
E flag in the prefix-SID sub TLV.
Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Verify the prefix-SID configuration:
RP/0/RP0/CPU0:router# show ospf database opaque-area 7.0.0.1 self-originate
OSPF Router with ID (10.0.0.1) (Process ID 1)
Type-10 Opaque Link Area Link States (Area 0)
<...>
Extended Prefix TLV: Length: 20
Route-type: 1
AF : 0
Flags : 0x40
Prefix : 10.0.0.1/32
SID sub-TLV: Length: 8
Flags : 0x0
MTID : 0
Algo : 0
SID Index : 1001
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Segment Routing ECMP-FEC Optimization
What to do next
Segment Routing ECMP-FEC Optimization
ECMP-FECs are used for any ECMP programming on the system, such as MPLS LSP ECMP, VPN multipath, and EVPN multi-homing .
The SR ECMP-FEC optimization solution minimizes ECMP-FEC resource consumption during underlay programming for an SR-MPLS network. This feature supports sharing the same ECMP-FEC, regular FEC, and Egress Encapsulation DB (EEDB) entries for all /32 IPv4 Segment Routing prefixes with the same set of next hops. ECMP-FEC optimization is triggered when all the out_labels associated with the ECMP paths for a given prefix have the same value. If this rule is not met, then the prefix is programmed with a dedicated
ECMP-FEC. Other prefixes that meet the rule are candidates for optimization.
Segment Routing Label Edge Router (LER) ECMP-FEC Optimization enables ECMP-FEC optimization originally developed for Label Switched Router (LSR) nodes (MPLS P) to be enabled on LER (Layer 3 MPLS
PE) routers.
For usage guidelines, limitations, and configuration options, see
Segment Routing ECMP-FEC Optimization, on page 78
.
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C H A P T E R
7
Configure Segment Routing for BGP
Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-free inter-domain routing between autonomous systems. An autonomous system is a set of routers under a single technical administration. Routers in an autonomous system can use multiple Interior Gateway Protocols (IGPs) to exchange routing information inside the autonomous system and an EGP to route packets outside the autonomous system.
This module provides the configuration information used to enable Segment Routing for BGP.
Note For additional information on implementing BGP on your router, see the BGP Configuration Guide for Cisco
NCS 5500 Series Routers .
•
Segment Routing for BGP, on page 87
•
Configure BGP Prefix Segment Identifiers, on page 88
•
Segment Routing Egress Peer Engineering, on page 89
•
Configure BGP Link-State, on page 92
•
Example: Configuring SR-EPE and BGP-LS, on page 97
•
Configure BGP Proxy Prefix SID, on page 98
Segment Routing for BGP
In a traditional BGP-based data center (DC) fabric, packets are forwarded hop-by-hop to each node in the autonomous system. Traffic is directed only along the external BGP (eBGP) multipath ECMP. No traffic engineering is possible.
In an MPLS-based DC fabric, the eBGP sessions between the nodes exchange BGP labeled unicast (BGP-LU) network layer reachability information (NLRI). An MPLS-based DC fabric allows any leaf (top-of-rack or border router) in the fabric to communicate with any other leaf using a single label, which results in higher packet forwarding performance and lower encapsulation overhead than traditional BGP-based DC fabric.
However, since each label value might be different for each hop, an MPLS-based DC fabric is more difficult to troubleshoot and more complex to configure.
BGP has been extended to carry segment routing prefix-SID index. BGP-LU helps each node learn BGP prefix SIDs of other leaf nodes and can use ECMP between source and destination. Segment routing for BGP simplifies the configuration, operation, and troubleshooting of the fabric. With segment routing for BGP, you can enable traffic steering capabilities in the data center using a BGP prefix SID.
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Configure BGP Prefix Segment Identifiers
Configure BGP Prefix Segment Identifiers
Segments associated with a BGP prefix are known as BGP prefix SIDs. The BGP prefix SID is global within a segment routing or BGP domain. It identifies an instruction to forward the packet over the ECMP-aware best-path computed by BGP to the related prefix. The BGP prefix SID is manually configured from the segment routing global block (SRGB) range of labels.
Each BGP speaker must be configured with an SRGB using the segment-routing global-block command.
See the
About the Segment Routing Global Block
section for information about the SRGB.
Note Because the values assigned from the range have domain-wide significance, we recommend that all routers within the domain be configured with the same range of values.
To assign a BGP prefix SID, first create a routing policy using the set label-index index attribute, then associate the index to the node.
Note A routing policy with the set label-index attribute can be attached to a network configuration or redistribute configuration. Other routing policy language (RPL) configurations are possible. For more information on routing policies, refer to the "Implementing Routing Policy" chapter in the Routing Configuration Guide for
Cisco NCS 5500 Series Routers .
Example
The following example shows how to configure the SRGB, create a BGP route policy using a $SID parameter and set label-index attribute, and then associate the prefix-SID index to the node.
RP/0/RSP0/CPU0:router(config)# segment-routing global-block 16000 23999
RP/0/RSP0/CPU0:router(config)# route-policy SID($SID)
RP/0/RSP0/CPU0:router(config-rpl)# set label-index $SID
RP/0/RSP0/CPU0:router(config-rpl)# end policy
RP/0/RSP0/CPU0:router(config)# router bgp 1
RP/0/RSP0/CPU0:router(config-bgp)# bgp router-id 1.1.1.1
RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router(config-bgp-af)# network 1.1.1.3/32 route-policy SID(3)
RP/0/RSP0/CPU0:router(config-bgp-af)# allocate-label all
RP/0/RSP0/CPU0:router(config-bgp-af)# commit
RP/0/RSP0/CPU0:router(config-bgp-af)# end
RP/0/RSP0/CPU0:router# show bgp 1.1.1.3/32
BGP routing table entry for 1.1.1.3/32
Versions:
Process
Speaker bRIB/RIB SendTblVer
74 74
Local Label: 16003
Last Modified: Sep 29 19:52:18.155 for 00:07:22
Paths: (1 available, best #1)
Advertised to update-groups (with more than one peer):
0.2
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Segment Routing Egress Peer Engineering
Path #1: Received by speaker 0
Advertised to update-groups (with more than one peer):
0.2
3
99.3.21.3 from 99.3.21.3 (1.1.1.3)
Received Label 3
Origin IGP, metric 0, localpref 100, valid, external, best, group-best
Received Path ID 0, Local Path ID 1, version 74
Origin-AS validity: not-found
Label Index: 3
Segment Routing Egress Peer Engineering
Segment routing egress peer engineering (EPE) uses a controller to instruct an ingress provider edge, or a content source (node) within the segment routing domain, to use a specific egress provider edge (node) and a specific external interface to reach a destination. BGP peer SIDs are used to express source-routed inter-domain paths.
Below are the BGP-EPE peering SID types:
• PeerNode SID—To an eBGP peer. Pops the label and forwards the traffic on any interface to the peer.
• PeerAdjacency SID—To an eBGP peer via interface. Pops the label and forwards the traffic on the related interface.
• PeerSet SID—To a set of eBGP peers. Pops the label and forwards the traffic on any interface to the set of peers. All the peers in a set might not be in the same AS.
Multiple PeerSet SIDs can be associated with any combination of PeerNode SIDs or PeerAdjacency
SIDs.
The controller learns the BGP peer SIDs and the external topology of the egress border router through BGP-LS
EPE routes. The controller can program an ingress node to steer traffic to a destination through the egress node and peer node using BGP labeled unicast (BGP-LU).
EPE functionality is only required at the EPE egress border router and the EPE controller.
Configure Segment Routing Egress Peer Engineering
This task explains how to configure segment routing EPE on the EPE egress node.
SUMMARY STEPS
1.
router bgp as-number
2.
neighbor ip-address
3.
remote-as as-number
4.
egress-engineering
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DETAILED STEPS
Step 1
Command or Action
router bgp as-number
Example:
RP/0/RSP0/CPU0:router(config)# router bgp 1
Step 2 neighbor ip-address
Example:
RP/0/RSP0/CPU0:router(config-bgp)# neighbor
192.168.1.3
Step 3
Purpose
Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.
Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.
remote-as as-number
Example:
RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as
3
Creates a neighbor and assigns a remote autonomous system number to it.
Step 4 Configures the egress node with EPE for the eBGP peer.
egress-engineering
Example:
RP/0/RSP0/CPU0:router(config-bgp-nbr)# egress-engineering
Configuring Manual BGP-EPE Peering SIDs
Configuring manual BGP-EPE Peer SIDs allows for persistent EPE label values. Manual BGP-EPE SIDs are advertised through BGP-LS and are allocated from the Segment Routing Local Block (SRLB). See
Segment Routing Global Block and Segment Routing Local Block, on page 51
for information about the
SRLB.
Each PeerNode SID, PeerAdjacency SID, and PeerSet SID is configured with an index value. This index serves as an offset from the configured SRLB start value and the resulting MPLS label (SRLB start label + index) is assigned to these SIDs. This label is used by CEF to perform load balancing across the individual
BGP PeerSet SIDs, BGP PeerNode SID, or ultimately across each first-hop adjacency associated with that
BGP PeerNode SID or BGP PeerSet SID.
Configuring Manual PeerNode SID
Each eBGP peer will be associated with a PeerNode SID index that is configuration driven.
RP/0/0/CPU0:PE1(config)# router bgp 10
RP/0/0/CPU0:PE1(config-bgp)# neighbor 10.10.10.2
RP/0/0/CPU0:PE1(config-bgp-nbr)# remote-as 20
RP/0/0/CPU0:PE1(config-bgp-nbr)# egress-engineering
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Configuring Manual BGP-EPE Peering SIDs
RP/0/0/CPU0:PE1(config-bgp-nbr)# peer-node-sid index 600
Configuring Manual PeerAdjacency SID
Any first-hop for which an adjacency SID is configured needs to be in the resolution chain of at least one eBGP peer that is configured for egress-peer engineering. Otherwise such a kind of “orphan” first-hop with regards to BGP has no effect on this feature. This is because BGP only understands next-hops learnt by the
BGP protocol itself and in addition only the resolving IGP next-hops for those BGP next-hops.
RP/0/0/CPU0:PE1(config)# router bgp 10
RP/0/0/CPU0:PE1(config-bgp)# adjacencies
RP/0/0/CPU0:PE1(config-bgp-adj)# 1.1.1.2
RP/0/0/CPU0:PE1(config-bgp-adj)# adjacency-sid index 500
Configuring Manual PeerSet SID
The PeerSet SID is configured under global Address Family. This configuration results in the creation of a
Peer-Set SID EPE object.
RP/0/0/CPU0:PE1(config)# router bgp 10
RP/0/0/CPU0:PE1(config-bgp)# address-family ipv4 unicast
RP/0/0/CPU0:PE1(config-bgp-afi)# peer-set-id 1
RP/0/0/CPU0:PE1(config-bgp-peer-set)# peer-set-sid 300
Example
Topology
The example in this section uses the following topology.
In this example, BGP-EPE peer SIDs are allocated from the default SRLB label range (15000 – 15999). The
BGP-EPE peer SIDs are configured as follows:
• PeerNode SIDs to 10.10.10.2 with index 600 (label 15600), and for 20.10.10.2 with index 700 (label
15700)
• PeerAdj SID to link 1.1.1.2 with index 500 (label 15500)
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• PeerSet SID 1 to load balance over BGP neighbors 10.10.10.1 and 20.10.10.2 with SID index 300 (label
15300)
• PeerSet SID 2 to load balance over BGP neighbor 20.10.10.2 and link 1.1.1.2 with SID index 400 (label
15400)
Configuration on R1 router bgp 10 address-family ipv4 unicast peer-set-id 1 peer-set-sid index 300
!
peer-set-id 2 peer-set-sid index 400
!
!
adjacencies
1.1.1.2
adjacency-sid index 500
!
peer-set 2
!
neighbor 10.10.10.2
remote-as 20 egress-engineering peer-node-sid index 600
!
peer-set 1 neighbor 20.10.10.2
egress-engineering peer-node-sid index 700
!
peer-set 1 peer-set 2
To further show the load balancing of this example:
• 15600 is load balanced over {1.1.1.1 and 2.1.1.1}
• 15700 is load balanced over {3.1.1.1 and 4.1.1.1}
• 15500 is load balanced over {1.1.1.1}
• 15300 is load balanced over {1.1.1.1, 2.1.1.1, 3.1.1.1 and 4.1.1.1}
• 15400 is load balanced over {1.1.1.1, 3.1.1.1 and 4.1.1.1}
Configure BGP Link-State
BGP Link-State (LS) is an Address Family Identifier (AFI) and Sub-address Family Identifier (SAFI) originally defined to carry interior gateway protocol (IGP) link-state information through BGP. The BGP Network Layer
Reachability Information (NLRI) encoding format for BGP-LS and a new BGP Path Attribute called the
BGP-LS attribute are defined in RFC7752 . The identifying key of each Link-State object, namely a node, link, or prefix, is encoded in the NLRI and the properties of the object are encoded in the BGP-LS attribute.
The BGP-LS Extensions for Segment Routing are documented in RFC9085 .
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Configure BGP Link-State
BGP-LS applications like an SR Path Computation Engine (SR-PCE) can learn the SR capabilities of the nodes in the topology and the mapping of SR segments to those nodes. This can enable the SR-PCE to perform path computations based on SR-TE and to steer traffic on paths different from the underlying IGP-based distributed best-path computation.
The following figure shows a typical deployment scenario. In each IGP area, one or more nodes (BGP speakers) are configured with BGP-LS. These BGP speakers form an iBGP mesh by connecting to one or more route-reflectors. This way, all BGP speakers (specifically the route-reflectors) obtain Link-State information from all IGP areas (and from other ASes from eBGP peers).
Usage Guidelines and Limitations
• BGP-LS supports IS-IS and OSPFv2.
• The identifier field of BGP-LS (referred to as the Instance-ID) identifies the IGP routing domain where the NLRI belongs. The NLRIs representing link-state objects (nodes, links, or prefixes) from the same
IGP routing instance must use the same Instance-ID value.
• When there is only a single protocol instance in the network where BGP-LS is operational, we recommend configuring the Instance-ID value to 0 .
• Assign consistent BGP-LS Instance-ID values on all BGP-LS Producers within a given IGP domain.
• NLRIs with different Instance-ID values are considered to be from different IGP routing instances.
• Unique Instance-ID values must be assigned to routing protocol instances operating in different IGP domains. This allows the BGP-LS Consumer (for example, SR-PCE) to build an accurate segregated
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Configure BGP Link-State multi-domain topology based on the Instance-ID values, even when the topology is advertised via BGP-LS by multiple BGP-LS Producers in the network.
• If the BGP-LS Instance-ID configuration guidelines are not followed, a BGP-LS Consumer may see duplicate link-state objects for the same node, link, or prefix when there are multiple BGP-LS Producers deployed. This may also result in the BGP-LS Consumers getting an inaccurate network-wide topology.
• The following table defines the supported extensions to the BGP-LS address family for carrying IGP topology information (including SR information) via BGP. For more information on the BGP-LS TLVs, refer to Border Gateway Protocol - Link State (BGP-LS) Parameters .
514
515
516
517
266
267
512
513
262
263
264
265
256
257
258
259
260
261
1024
1026
1027
1028
1029
1030
Table 6: IOS XR Supported BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs
TLV Code Point Description
Local Node Descriptors
Remote Node Descriptors
Link Local/Remote Identifiers
IPv4 interface address
IPv4 neighbor address
IPv6 interface address
IPv6 neighbor address
Multi-Topology ID
OSPF Route Type
IP Reachability Information
Node MSD TLV
Link MSD TLV
Autonomous System
BGP-LS Identifier
OSPF Area-ID
IGP Router-ID
BGP Router-ID TLV
BGP Confederation Member TLV
Node Flag Bits
Node Name
IS-IS Area Identifier
IPv4 Router-ID of Local Node
IPv6 Router-ID of Local Node
IPv4 Router-ID of Remote Node
X
X
—
—
X
X
—
—
—
—
—
—
—
—
—
—
—
—
—
X
X
—
—
X
X
—
—
—
—
—
X
X
X
X
—
X
—
X
X
X
—
—
X
X
—
X
X
X
X
X
Produced by
IS-IS
X
X
X
X
X
X
X
X
—
X
—
—
X
X
Produced by
OSPFv2
X
X
Produced by
BGP
—
—
—
—
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1120
1122
1152
1153
1154
1116
1117
1118
1119
1102
1103
1114
1115
1088
1089
1090
1091
1092
1093
1094
1095
TLV Code Point
1031
1034
1035
1036
1039
1044
1096
1099
1100
1101
Description
IPv6 Router-ID of Remote Node
SR Capabilities TLV
SR Algorithm TLV
SR Local Block TLV
Flex Algo Definition (FAD) TLV
Flex Algorithm Prefix Metric (FAPM)
TLV
Administrative group (color)
Maximum link bandwidth
Max. reservable link bandwidth
Unreserved bandwidth
TE Default Metric
Link Protection Type
MPLS Protocol Mask
IGP Metric
Shared Risk Link Group
Adjacency SID TLV
LAN Adjacency SID TLV
PeerNode SID TLV
PeerAdj SID TLV
PeerSet SID TLV
Unidirectional Link Delay TLV X
Min/Max Unidirectional Link Delay TLV X
—
—
X
X
X
—
X
X
X
X
X
X
X
X
X
X
X
X
Produced by
IS-IS
X
X
Unidirectional Delay Variation TLV
Unidirectional Link Loss
Unidirectional Residual Bandwidth
Unidirectional Available Bandwidth
Unidirectional Utilized Bandwidth X
Application-Specific Link Attribute TLV X
IGP Flags
IGP Route Tag
IGP Extended Route Tag
X
X
X
X
X
X
X
X
X
—
—
X
X
X
—
X
X
X
X
X
X
X
X
X
X
X
X
—
X
X
X
X
X
X
X
X
Produced by
OSPFv2
—
X
—
—
—
—
Produced by
BGP
—
—
X
X
—
—
—
—
—
X
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
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TLV Code Point
1155
1156
1158
1159
1161
1170
1171
1172
1173
Description
Prefix Metric
OSPF Forwarding Address
Prefix-SID
Range
SID/Label TLV
Prefix Attribute Flags
Source Router Identifier
L2 Bundle Member Attributes TLV
Extended Administrative Group
X
X
X
X
X
X
X
Produced by
IS-IS
X
—
—
—
X
X
X
X
X
Produced by
OSPFv2
X
X
—
—
—
—
—
—
—
Produced by
BGP
—
—
Exchange Link State Information with BGP Neighbor
The following example shows how to exchange link-state information with a BGP neighbor:
Router# configure
Router(config)# router bgp 1
Router(config-bgp)# neighbor 10.0.0.2
Router(config-bgp-nbr)# remote-as 1
Router(config-bgp-nbr)# address-family link-state link-state
Router(config-bgp-nbr-af)# exit
IGP Link-State Database Distribution
A given BGP node may have connections to multiple, independent routing domains. IGP link-state database distribution into BGP-LS is supported for both OSPF and IS-IS protocols in order to distribute this information on to controllers or applications that desire to build paths spanning or including these multiple domains.
To distribute IS-IS link-state data using BGP-LS, use the distribute link-state command in router configuration mode.
Router# configure
Router(config)# router isis isp
Router(config-isis)# distribute link-state instance-id 32
To distribute OSPFv2 link-state data using BGP-LS, use the distribute link-state command in router configuration mode.
Router# configure
Router(config)# router ospf 100
Router(config-ospf)# distribute link-state instance-id 32
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Example: Configuring SR-EPE and BGP-LS
Example: Configuring SR-EPE and BGP-LS
In the following figure, segment routing is enabled on autonomous system AS1 with ingress node A and egress nodes B and C. In this example, we configure EPE on egress node C.
Figure 2: Topology
Step 1
Step 2
Step 3
Configure node C with EPE for eBGP peers D and E.
Example:
RP/0/RSP0/CPU0:router_C(config)# router bgp 1
RP/0/RSP0/CPU0:router_C(config-bgp)# neighbor 192.168.1.3
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# remote-as 3
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# description to E
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# egress-engineering
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_in in
RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_out out
RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# exit
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# exit
RP/0/RSP0/CPU0:router_C(config-bgp)# neighbor 192.168.1.2
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# remote-as 2
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# description to D
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# egress-engineering
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# address-family ipv4 unicast
RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_in in
RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_out out
RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# exit
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# exit
Configure node C to advertise peer node SIDs to the controller using BGP-LS.
Example:
RP/0/RSP0/CPU0:router_C(config-bgp)# neighbor 172.29.50.71
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# remote-as 1
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# description to EPE_controller
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# address-family link-state link-state
RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# exit
RP/0/RSP0/CPU0:router_C(config-bgp)# exit
Commit the configuration.
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Step 4
Example:
RP/0/RSP0/CPU0:router_C(config)# commit
Verify the configuration.
Example:
RP/0/RSP0/CPU0:router_C# show bgp egress-engineering
Egress Engineering Peer Set: 192.168.1.2/32 (10b87210)
Nexthop: 192.168.1.2
Version: 2, rn_version: 2
Flags: 0x00000002
Local ASN: 1
Remote ASN: 2
Local RID: 1.1.1.3
Remote RID: 1.1.1.4
First Hop: 192.168.1.2
NHID: 3
Label: 24002 , Refcount: 3 rpc_set: 10b9d408
Egress Engineering Peer Set: 192.168.1.3/32 (10be61d4)
Nexthop: 192.168.1.3
Version: 3, rn_version: 3
Flags: 0x00000002
Local ASN: 1
Remote ASN: 3
Local RID: 1.1.1.3
Remote RID: 1.1.1.5
First Hop: 192.168.1.3
NHID: 4
Label: 24003 , Refcount: 3 rpc_set: 10be6250
The output shows that node C has allocated peer SIDs for each eBGP peer.
Example:
RP/0/RSP0/CPU0:router_C# show mpls forwarding labels 24002 24003
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
24002 Unlabelled No ID
24003 Unlabelled No ID
Te0/3/0/0
Te0/1/0/0
192.168.1.2
192.168.1.3
0
0
The output shows that node C installed peer node SIDs in the Forwarding Information Base (FIB).
Configure BGP Proxy Prefix SID
To support segment routing, Border Gateway Protocol (BGP) requires the ability to advertise a segment identifier (SID) for a BGP prefix. A BGP-Prefix-SID is the segment identifier of the BGP prefix segment in a segment routing network. BGP prefix SID attribute is a BGP extension to signal BGP prefix-SIDs. However,
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Configure BGP Proxy Prefix SID there may be routers which do not support BGP extension for segment routing. Hence, those routers also do not support BGP prefix SID attribute and an alternate approach is required.
BGP proxy prefix SID feature allows you to attach BGP prefix SID attributes for remote prefixes learnt from
BGP labeled unicast (LU) neighbours which are not SR-capable and propagate them as SR prefixes. This allows an LSP towards non SR endpoints to use segment routing global block in a SR domain. Since BGP proxy prefix SID uses global label values it minimizes the use of limited resources such as ECMP-FEC and provides more scalability for the networks.
BGP proxy prefix SID feature is implemented using the segment routing mapping server (SRMS). SRMS allows the user to configure SID mapping entries to specify the prefix-SIDs for the prefixes. The mapping server advertises the local SID-mapping policy to the mapping clients. BGP acts as a client of the SRMS and uses the mapping policy to calculate the prefix-SIDs.
Configuration Example:
This example shows how to configure the BGP proxy prefix SID feature for the segment routing mapping server.
RP/0/RSP0/CPU0:router(config)# segment-routing
RP/0/RSP0/CPU0:router(config-sr)# mapping-server
RP/0/RSP0/CPU0:router(config-sr-ms)# prefix-sid-map
RP/0/RSP0/CPU0:router(config-sr-ms-map)# address-family ipv4
RP/0/RSP0/CPU0:router(config-sr-ms-map-af)# 1.1.1.1/32 10 range 200
RP/0/RSP0/CPU0:router(config-sr-ms-map-af)# 192.168.64.1/32 400 range 300
This example shows how to configure the BGP proxy prefix SID feature for the segment-routing mapping client.
RP/0/RSP0/CPU0:router(config)# router bgp 1
RP/0/RSP0/CPU0:router(config-bgp)# address-family ip4 unicast
RP/0/RSP0/CPU0:router(config-bgp-af)# segment-routing prefix-sid-map
Verification
These examples show how to verify the BGP proxy prefix SID feature.
RP/0/RSP0/CPU0:router# show segment-routing mapping-server prefix-sid-map ipv4 detail
Prefix
1.1.1.1/32
SID Index:
Range:
Last Prefix:
10
200
1.1.1.200/32
Last SID Index: 209
Flags:
Number of mapping entries: 1
RP/0/RSP0/CPU0:router# show bgp ipv4 labeled-unicast 192.168.64.1/32
BGP routing table entry for 192.168.64.1/32
Versions:
Process bRIB/RIB SendTblVer
Speaker
Local Label: 16400
117 117
Last Modified: Oct 25 01:02:28.562 for 00:11:45Paths: (2 available, best #1)
Advertised to peers (in unique update groups):
201.1.1.1
Path #1: Received by speaker 0 Advertised to peers (in unique update groups):
201.1.1.1
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Local
20.0.101.1 from 20.0.101.1 (20.0.101.1) Received Label 61
Origin IGP, localpref 100, valid, internal, best, group-best, multipath, labeled-unicast
Received Path ID 0, Local Path ID 0, version 117
Prefix SID Attribute Size: 7
Label Index: 1
RP/0/RSP0/CPU0:router# show route ipv4 unicast 192.68.64.1/32 detail
Routing entry for 192.168.64.1/32
Known via "bgp 65000", distance 200, metric 0, [ei]-bgp, labeled SR, type internal
Installed Oct 25 01:02:28.583 for 00:20:09
Routing Descriptor Blocks
20.0.101.1, from 20.0.101.1, BGP multi path
Route metric is 0
Label: 0x3d (61)
Tunnel ID: None
Binding Label: None
Extended communities count: 0
NHID:0x0(Ref:0)
Route version is 0x6 (6)
Local Label: 0x3e81 (16400)
IP Precedence: Not Set
QoS Group ID: Not Set
Flow-tag: Not Set
Fwd-class: Not Set
Route Priority: RIB_PRIORITY_RECURSIVE (12) SVD Type RIB_SVD_TYPE_LOCAL
Download Priority 4, Download Version 242
No advertising protos.
RP/0/RSP0/CPU0:router# show cef ipv4 192.168.64.1/32 detail
192.168.64.1/32, version 476, labeled SR, drop adjacency, internal 0x5000001 0x80 (ptr
0x71c42b40) [1], 0x0 (0x71c11590), 0x808 (0x722b91e0)
Updated Oct 31 23:23:48.733
Prefix Len 32, traffic index 0, precedence n/a, priority 4
Extensions: context-label:16400 gateway array (0x71ae7e78) reference count 3, flags 0x7a, source rib (7), 0 backups
[2 type 5 flags 0x88401 (0x722eb450) ext 0x0 (0x0)]
LW-LDI[type=5, refc=3, ptr=0x71c11590, sh-ldi=0x722eb450] gateway array update type-time 3 Oct 31 23:49:11.720
LDI Update time Oct 31 23:23:48.733
LW-LDI-TS Oct 31 23:23:48.733
via 20.0.101.1/32, 0 dependencies, recursive, bgp-ext [flags 0x6020] path-idx 0 NHID 0x0 [0x7129a294 0x0] recursion-via-/32 unresolved local label 16400 labels imposed {ExpNullv6}
RP/0/RSP0/CPU0:router# show bgp labels
BGP router identifier 2.1.1.1, local AS number 65000
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0xe0000000 RD version: 245
BGP main routing table version 245
BGP NSR Initial initsync version 16 (Reached)
BGP NSR/ISSU Sync-Group versions 245/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best
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Origin codes: i - IGP, e - EGP, ? - incomplete
Network
*>i1.1.1.1/32
Next Hop
1.1.1.1
Rcvd Label
3
Local Label
16010
*> 2.1.1.1/32
*> 192.68.64.1/32
*> 192.68.64.2/32
0.0.0.0
20.0.101.1
20.0.101.1
nolabel
2
2
3
16400
16401
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C H A P T E R
8
This module provides information about segment routing for traffic engineering (SR-TE) policies, how to configure SR-TE policies, and how to steer traffic into an SR-TE policy.
•
SR-TE Policy Overview, on page 103
•
Usage Guidelines and Limitations, on page 104
•
Instantiation of an SR Policy, on page 104
•
SR-TE Policy Path Types, on page 138
•
•
•
SR-TE Policy Overview
Segment routing for traffic engineering (SR-TE) uses a “policy” to steer traffic through the network. An
SR-TE policy path is expressed as a list of segments that specifies the path, called a segment ID (SID) list.
Each segment is an end-to-end path from the source to the destination, and instructs the routers in the network to follow the specified path instead of following the shortest path calculated by the IGP. If a packet is steered into an SR-TE policy, the SID list is pushed on the packet by the head-end. The rest of the network executes the instructions embedded in the SID list.
An SR-TE policy is identified as an ordered list (head-end, color, end-point):
• Head-end – Where the SR-TE policy is instantiated
• Color – A numerical value that distinguishes between two or more policies to the same node pairs
(Head-end – End point)
• End-point – The destination of the SR-TE policy
Every SR-TE policy has a color value. Every policy between the same node pairs requires a unique color value.
An SR-TE policy uses one or more candidate paths. A candidate path is a single segment list (SID-list) or a set of weighted SID-lists (for weighted equal cost multi-path [WECMP]). A candidate path is either dynamic or explicit. See SR-TE Policy Path Types section for more information.
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Usage Guidelines and Limitations
Usage Guidelines and Limitations
Observe the following guidelines and limitations for the platform.
• SR-TE over BVI is not supported. An SR-TE policy cannot be resolved over an MPLS-enabled BVI interface.
• For NCS 5500 :Counter implications when BVI and SR-TE co-exist in same NPU—Counters for a BVI's logical interface are not allocated when the same NPU hosts layer-2 (sub)interface(s) associated with the BVI alongside other port(s) used as egress interface(s) for an SR policy
• For routers that have Cisco NC57 line cards installed and operate in native or compatible modes :
Counter implications when BVI and SR-TE co-exist in same NPU—Counters for a BVI's logical interface are allocated when the same NPU hosts layer-2 (sub)interface(s) associated with the BVI alongside other port(s) used as egress interface(s) for an SR policy
• GRE tunnel as primary interface for an SR policy is not supported.
• GRE tunnel as backup interface for an SR policy with TI-LFA protection is not supported.
Instantiation of an SR Policy
An SR policy is instantiated, or implemented, at the head-end router.
The following sections provide details on the SR policy instantiation methods:
•
On-Demand SR Policy – SR On-Demand Next-Hop , on page 104
•
Manually Provisioned SR Policy, on page 137
•
PCE-Initiated SR Policy, on page 138
On-Demand SR Policy – SR On-Demand Next-Hop
Segment Routing On-Demand Next Hop (SR-ODN) allows a service head-end router to automatically instantiate an SR policy to a BGP next-hop when required (on-demand). Its key benefits include:
• SLA-aware BGP service – Provides per-destination steering behaviors where a prefix, a set of prefixes, or all prefixes from a service can be associated with a desired underlay SLA. The functionality applies equally to single-domain and multi-domain networks.
• Simplicity – No prior SR Policy configuration needs to be configured and maintained. Instead, operator simply configures a small set of common intent-based optimization templates throughout the network.
• Scalability – Device resources at the head-end router are used only when required, based on service or
SLA connectivity needs.
The following example shows how SR-ODN works:
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On-Demand SR Policy – SR On-Demand Next-Hop
1.
An egress PE (node H) advertises a BGP route for prefix T/t. This advertisement includes an SLA intent encoded with a BGP color extended community. In this example, the operator assigns color purple (example value = 100) to prefixes that should traverse the network over the delay-optimized path.
2.
The route reflector receives the advertised route and advertises it to other PE nodes.
3.
Ingress PEs in the network (such as node F) are pre-configured with an ODN template for color purple that provides the node with the steps to follow in case a route with the intended color appears, for example:
• Contact SR-PCE and request computation for a path toward node H that does not share any nodes with another LSP in the same disjointness group.
• At the head-end router, compute a path towards node H that minimizes cumulative delay.
4.
In this example, the head-end router contacts the SR-PCE and requests computation for a path toward node H that minimizes cumulative delay.
5.
After SR-PCE provides the compute path, an intent-driven SR policy is instantiated at the head-end router.
Other prefixes with the same intent (color) and destined to the same egress PE can share the same on-demand SR policy. When the last prefix associated with a given [intent, egress PE] pair is withdrawn, the on-demand SR policy is deleted, and resources are freed from the head-end router.
An on-demand SR policy is created dynamically for BGP global or VPN (service) routes. The following services are supported with SR-ODN:
• IPv4 BGP global routes
• IPv6 BGP global routes (6PE)
• VPNv4
• VPNv6 (6vPE)
• EVPN-VPWS (single-homing)
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SR-ODN Configuration Steps
• EVPN-VPWS (multi-homing)
• EVPN (single-homing/multi-homing)
Note For EVPN single-homing, you must configure an EVPN Ethernet Segment
Identifier (ESI) with a non-zero value.
Note Colored per-ESI/per-EVI EVPN Ethernet Auto-Discovery route (route-type 1) and Inclusive Multicast Route
(route-type 3) are used to trigger instantiation of ODN SR-TE policies.
Note The following scenarios involving virtual Ethernet Segments (vES) are also supported with EVPN ODN:
• VPLS VFI as vES for single-active Multi-Homing to EVPN
• Active/backup Pseudo-wire (PW) as vES for Single-Homing to EVPN
• Static Pseudo-wire (PW) as vES for active-active Multi-Homing to EVPN
SR-ODN Configuration Steps
To configure SR-ODN, complete the following configurations:
1.
Define the SR-ODN template on the SR-TE head-end router.
(Optional) If using Segment Routing Path Computation Element (SR-PCE) for path computation: a.
Configure SR-PCE. For detailed SR-PCE configuration information, see
b.
Configure the head-end router as Path Computation Element Protocol (PCEP) Path Computation
Client (PCC). For detailed PCEP PCC configuration information, see
Configure the Head-End Router as PCEP PCC .
2.
Define BGP color extended communities. Refer to the "Implementing BGP" chapter in the BGP
Configuration Guide for NCS 5500 Series Routers .
3.
Define routing policies (using routing policy language [RPL]) to set BGP color extended communities.
Refer to the "Implementing Routing Policy" chapter in the Routing Configuration Guide for NCS 5500
Series Routers .
The following RPL attach-points for setting/matching BGP color extended communities are supported:
Note The following table shows the supported RPL match operations; however, routing policies are required primarily to set BGP color extended community. Matching based on BGP color extended communities is performed automatically by ODN's on-demand color template.
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Attach Point
VRF export
VRF import
EVI export
EVI import
Neighbor-in
Neighbor-out
Inter-AFI export
Inter-AFI import
Default-originate
Set
X
–
X
X
X
X
–
–
X
X
X
–
X
X
–
X
Match
X
X
4.
Apply routing policies to a service. Refer to the "Implementing Routing Policy" chapter in the Routing
Configuration Guide for NCS 5500 Series Routers .
Configure On-Demand Color Template
• Use the on-demand color color command to create an ODN template for the specified color value. The head-end router automatically follows the actions defined in the template upon arrival of BGP global or
VPN routes with a BGP color extended community that matches the color value specified in the template.
The color range is from 1 to 4294967295.
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# on-demand color 10
Note Matching based on BGP color extended communities is performed automatically via ODN's on-demand color template. RPL routing policies are not required.
• Use the on-demand color color dynamic command to associate the template with on-demand SR policies with a locally computed dynamic path (by SR-TE head-end router utilizing its TE topology database) or centrally (by SR-PCE). The head-end router will first attempt to install the locally computed path; otherwise, it will use the path computed by the SR-PCE.
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# on-demand color 10 dynamic
• Use the on-demand color color dynamic pcep command to indicate that only the path computed by
SR-PCE should be associated with the on-demand SR policy. With this configuration, local path computation is not attempted; instead the head-end router will only instantiate the path computed by the
SR-PCE.
Router(config-sr-te)# on-demand color 10 dynamic pcep
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Configuring SR-ODN: Examples
Configure Dynamic Path Optimization Objectives
• Use the metric type { igp | te | latency } command to configure the metric for use in path computation.
Router(config-sr-te-color-dyn)# metric type te
• Use the metric margin { absolute value | relative percent } command to configure the On-Demand dynamic path metric margin. The range for value and percent is from 0 to 2147483647.
Router(config-sr-te-color-dyn)# metric margin absolute 5
Configure Dynamic Path Constraints
• Use the disjoint-path group-id group-id type { link | node | srlg | srlg-node } [ sub-id sub-id ] command to configure the disjoint-path constraints. The group-id and sub-id range is from 1 to 65535.
Router(config-sr-te-color-dyn)# disjoint-path group-id 775 type link
• Use the affinity { include-any | include-all | exclude-any } { name WORD } command to configure the affinity constraints.
Router(config-sr-te-color-dyn)# affinity exclude-any name CROSS
• Use the maximum-sid-depth value command to customize the maximum SID depth (MSD) constraints advertised by the router.
The default MSD value is equal to the maximum MSD supported by the platform (12).
Router(config-sr-te-color)# maximum-sid-depth 5
See
Customize MSD Value at PCC, on page 150
for information about SR-TE label imposition capabilities.
• Use the sid-algorithm algorithm-number command to configure the SR Flexible Algorithm constraints.
The algorithm-number range is from 128 to 255.
Router(config-sr-te-color-dyn)# sid-algorithm 128
Configuring SR-ODN: Examples
Configuring SR-ODN: Layer-3 Services Examples
The following examples show end-to-end configurations used in implementing SR-ODN on the head-end router.
Configuring ODN Color Templates: Example
Configure ODN color templates on routers acting as SR-TE head-end nodes. The following example shows various ODN color templates:
• color 10: minimization objective = te-metric
• color 20: minimization objective = igp-metric
• color 21: minimization objective = igp-metric; constraints = affinity
• color 22: minimization objective = te-metric; path computation at SR-PCE; constraints = affinity
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• color 30: minimization objective = delay-metric
• color 128: constraints = flex-algo segment-routing traffic-eng on-demand color 10 dynamic
!
!
!
metric type te on-demand color 20 dynamic metric type igp
!
!
!
on-demand color 21 dynamic metric
!
type igp
!
!
affinity exclude-any name CROSS
!
on-demand color 22 dynamic pcep
!
metric
!
type te affinity exclude-any
!
name CROSS
!
!
on-demand color 30 dynamic metric
!
!
type latency
!
on-demand color 128
!
!
end dynamic sid-algorithm 128
!
Configuring BGP Color Extended Community Set: Example
The following example shows how to configure BGP color extended communities that are later applied to
BGP service routes via route-policies.
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Configuring SR-ODN: Layer-3 Services Examples
Note In most common scenarios, egress PE routers that advertise BGP service routes apply (set) BGP color extended communities. However, color can also be set at the ingress PE router.
extcommunity-set opaque color10-te
10 end-set
!
extcommunity-set opaque color20-igp
20 end-set
!
extcommunity-set opaque color21-igp-excl-cross
21 end-set
!
extcommunity-set opaque color30-delay
30 end-set
!
extcommunity-set opaque color128-fa128
128 end-set
!
Configuring RPL to Set BGP Color (Layer-3 Services): Examples
The following example shows various representative RPL definitions that set BGP color community.
The first 4 RPL examples include the set color action only. The last RPL example performs the set color action for selected destinations based on a prefix-set.
route-policy SET_COLOR_LOW_LATENCY_TE set extcommunity color color10-te pass end-policy
!
route-policy SET_COLOR_HI_BW set extcommunity color color20-igp pass end-policy
!
route-policy SET_COLOR_LOW_LATENCY set extcommunity color color30-delay pass end-policy
!
route-policy SET_COLOR_FA_128 set extcommunity color color128-fa128 pass end-policy
!
prefix-set sample-set
88.1.0.0/24 end-set
!
route-policy SET_COLOR_GLOBAL if destination in sample-set then set extcommunity color color10-te else
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Applying RPL to BGP Services (Layer-3 Services): Example
The following example shows various RPLs that set BGP color community being applied to BGP Layer-3
VPN services (VPNv4/VPNv6) and BGP global.
• The L3VPN examples show the RPL applied at the VRF export attach-point.
• The BGP global example shows the RPL applied at the BGP neighbor-out attach-point.
vrf vrf_cust1 address-family ipv4 unicast
!
export route-policy SET_COLOR_LOW_LATENCY_TE address-family ipv6 unicast export route-policy SET_COLOR_LOW_LATENCY_TE
!
!
vrf vrf_cust2 address-family ipv4 unicast export route-policy SET_COLOR_HI_BW
!
address-family ipv6 unicast export route-policy SET_COLOR_HI_BW
!
!
vrf vrf_cust3 address-family ipv4 unicast export route-policy SET_COLOR_LOW_LATENCY
!
!
!
address-family ipv6 unicast export route-policy SET_COLOR_LOW_LATENCY vrf vrf_cust4 address-family ipv4 unicast
!
export route-policy SET_COLOR_FA_128 address-family ipv6 unicast export route-policy SET_COLOR_FA_128
!
!
router bgp 100 neighbor-group BR-TO-RR address-family ipv4 unicast route-policy SET_COLOR_GLOBAL out
!
!
!
end
Verifying BGP VRF Information
Use the show bgp vrf command to display BGP prefix information for VRF instances. The following output shows the BGP VRF table including a prefix (88.1.1.0/24) with color 10 advertised by router 1.1.1.8.
RP/0/RP0/CPU0:R4# show bgp vrf vrf_cust1
BGP VRF vrf_cust1, state: Active
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BGP Route Distinguisher: 1.1.1.4:101
VRF ID: 0x60000007
BGP router identifier 1.1.1.4, local AS number 100
Non-stop routing is enabled
BGP table state: Active
Table ID: 0xe0000007 RD version: 282
BGP main routing table version 287
BGP NSR Initial initsync version 31 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1.1.1.4:101 (default for vrf vrf_cust1)
*> 44.1.1.0/24 40.4.101.11
*>i55.1.1.0/24 1.1.1.5
100
*>i88.1.1.0/24
*>i99.1.1.0/24
1.1.1.8 C:10
1.1.1.9
100
100
0 400 {1} i
0 500 {1} i
0 800 {1} i
0 800 {1} i
Processed 4 prefixes, 4 paths
The following output displays the details for prefix 88.1.1.0/24. Note the presence of BGP extended color community 10, and that the prefix is associated with an SR policy with color 10 and BSID value of 24036.
RP/0/RP0/CPU0:R4# show bgp vrf vrf_cust1 88.1.1.0/24
BGP routing table entry for 88.1.1.0/24, Route Distinguisher: 1.1.1.4:101
Versions:
Process bRIB/RIB SendTblVer
Speaker 282 282
Last Modified: May 20 09:23:34.112 for 00:06:03
Paths: (1 available, best #1)
Advertised to CE peers (in unique update groups):
40.4.101.11
Path #1: Received by speaker 0
Advertised to CE peers (in unique update groups):
40.4.101.11
800 {1}
1.1.1.8 C:10 (bsid:24036) (metric 20) from 1.1.1.55 (1.1.1.8)
Received Label 24012
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported
Received Path ID 0, Local Path ID 1, version 273
Extended community: Color:10 RT:100:1
Originator: 1.1.1.8, Cluster list: 1.1.1.55
SR policy color 10, up, registered, bsid 24036, if-handle 0x08000024
Source AFI: VPNv4 Unicast, Source VRF: default, Source Route Distinguisher: 1.1.1.8:101
Verifying Forwarding (CEF) Table
Use the show cef vrf command to display the contents of the CEF table for the VRF instance. Note that prefix
88.1.1.0/24 points to the BSID label corresponding to an SR policy. Other non-colored prefixes, such as
55.1.1.0/24, point to BGP next-hop.
RP/0/RP0/CPU0:R4# show cef vrf vrf_cust1
Prefix Next Hop Interface
------------------- ------------------- ------------------
0.0.0.0/0
0.0.0.0/32 drop broadcast default handler
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40.4.101.0/24
40.4.101.0/32
40.4.101.4/32
40.4.101.11/32 attached broadcast receive
40.4.101.11/32
TenGigE0/0/0/0.101
TenGigE0/0/0/0.101
TenGigE0/0/0/0.101
TenGigE0/0/0/0.101
40.4.101.255/32
44.1.1.0/24
55.1.1.0/24
88.1.1.0/24 broadcast
40.4.101.11/32
1.1.1.5/32
TenGigE0/0/0/0.101
<recursive>
<recursive>
99.1.1.0/24
224.0.0.0/4
224.0.0.0/24
24036 (via-label) <recursive>
1.1.1.9/32
0.0.0.0/32 receive
255.255.255.255/32 broadcast
<recursive>
The following output displays CEF details for prefix 88.1.1.0/24. Note that the prefix is associated with an
SR policy with BSID value of 24036.
RP/0/RP0/CPU0:R4# show cef vrf vrf_cust1 88.1.1.0/24
88.1.1.0/24, version 51, internal 0x5000001 0x0 (ptr 0x98c60ddc) [1], 0x0 (0x0), 0x208
(0x98425268)
Updated May 20 09:23:34.216
Prefix Len 24, traffic index 0, precedence n/a, priority 3 via local-label 24036, 5 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x97091ec0 0x0] recursion-via-label next hop VRF - 'default', table - 0xe0000000 next hop via 24036/0/21 next hop srte_c_10_ep labels imposed {ImplNull 24012}
Verifying SR Policy
Use the show segment-routing traffic-eng policy command to display SR policy information.
The following outputs show the details of an on-demand SR policy that was triggered by prefixes with color
10 advertised by node 1.1.1.8.
RP/0/RP0/CPU0:R4# show segment-routing traffic-eng policy color 10 tabular
Color Endpoint Admin Oper
State State
Binding
SID
------ -------------------- ------ ------ --------------------
10 1.1.1.8
up up 24036
The following outputs show the details of the on-demand SR policy for BSID 24036.
Note There are 2 candidate paths associated with this SR policy: the path that is computed by the head-end router
(with preference 200), and the path that is computed by the SR-PCE (with preference 100). The candidate path with the highest preference is the active candidate path (highlighted below) and is installed in forwarding.
RP/0/RP0/CPU0:R4# show segment-routing traffic-eng policy binding-sid 24036
SR-TE policy database
---------------------
Color: 10, End-point: 1.1.1.8
Name: srte_c_10_ep_1.1.1.8
Status:
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Admin: up Operational: up for 4d14h (since Jul 3 20:28:57.840)
Candidate-paths:
Preference: 200 (BGP ODN) (active)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_10_ep_1.1.1.8_discr_200
PLSP-ID: 12
Dynamic (valid)
Metric Type: TE, Path Accumulated Metric: 30
16009 [Prefix-SID, 1.1.1.9]
16008 [Prefix-SID, 1.1.1.8]
Preference: 100 (BGP ODN)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_10_ep_1.1.1.8_discr_100
PLSP-ID: 11
Dynamic (pce 1.1.1.57) (valid)
Metric Type: TE, Path Accumulated Metric: 30
16009 [Prefix-SID, 1.1.1.9]
16008 [Prefix-SID, 1.1.1.8]
Attributes:
Binding SID: 24036
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Verifying SR Policy Forwarding
Use the show segment-routing traffic-eng forwarding policy command to display the SR policy forwarding information.
The following outputs show the forwarding details for an on-demand SR policy that was triggered by prefixes with color 10 advertised by node 1.1.1.8.
RP/0/RP0/CPU0:R4# show segment-routing traffic-eng forwarding policy binding-sid 24036 tabular
Color Endpoint Segment Outgoing Outgoing Next Hop Bytes Pure
List Label Interface Switched Backup
----- --------------- ------------ -------- ------------ ------------ ------------ ------
10 1.1.1.8
dynamic 16009 Gi0/0/0/4 10.4.5.5
0
16001 Gi0/0/0/5 11.4.8.8
0 Yes
RP/0/RP0/CPU0:R4# show segment-routing traffic-eng forwarding policy binding-sid 24036 detail
Mon Jul 8 11:56:46.887 PST
SR-TE Policy Forwarding database
--------------------------------
Color: 10, End-point: 1.1.1.8
Name: srte_c_10_ep_1.1.1.8
Binding SID: 24036
Segment Lists:
SL[0]:
Name: dynamic
Paths:
Path[0]:
Outgoing Label: 16009
Outgoing Interface: GigabitEthernet0/0/0/4
Next Hop: 10.4.5.5
Switched Packets/Bytes: 0/0
FRR Pure Backup: No
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Label Stack (Top -> Bottom): { 16009, 16008 }
Path-id: 1 (Protected), Backup-path-id: 2, Weight: 64
Path[1]:
Outgoing Label: 16001
Outgoing Interface: GigabitEthernet0/0/0/5
Next Hop: 11.4.8.8
Switched Packets/Bytes: 0/0
FRR Pure Backup: Yes
Label Stack (Top -> Bottom): { 16001, 16009, 16008 }
Path-id: 2 (Pure-Backup), Weight: 64
Policy Packets/Bytes Switched: 0/0
Local label: 80013
Configuring SR-ODN: EVPN Services Examples
Configuring BGP Color Extended Community Set: Example
The following example shows how to configure BGP color extended communities that are later applied to
BGP service routes via route-policies.
extcommunity-set opaque color-44
44 end-set extcommunity-set opaque color-55
55 end-set extcommunity-set opaque color-77
77 end-set extcommunity-set opaque color-88
88 end-set
Configuring RPL to Set BGP Color (EVPN Services): Examples
The following examples shows various representative RPL definitions that set BGP color community.
The following RPL examples match on EVPN route-types and then set the BGP color extended community.
route-policy sample-export-rpl if evpn-route-type is 1 then set extcommunity color color-44 endif if evpn-route-type is 3 then set extcommunity color color-55 endif end-policy route-policy sample-import-rpl if evpn-route-type is 1 then set extcommunity color color-77 elseif evpn-route-type is 3 then set extcommunity color color-88 else pass endif end-policy
The following RPL example sets BGP color extended community while matching on the following:
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• Route Distinguisher (RD)
• Ethernet Segment Identifier (ESI)
• Ethernet Tag (ETAG)
• EVPN route-types route-policy sample-bgpneighbor-rpl if rd in (1.1.1.1:3504) then set extcommunity color color3504 elseif rd in (1.1.1.1:3505) then set extcommunity color color3505 elseif rd in (1.1.1.1:3506) then set extcommunity color color99996 elseif esi in (0010.0000.0000.0000.1201) and rd in (1.1.1.1:3508) then set extcommunity color color3508 elseif etag in (30509) and rd in (1.1.1.1:3509) then set extcommunity color color3509 elseif etag in (0) and rd in (1.1.1.1:2001) and evpn-route-type is 1 then set extcommunity color color82001 elseif etag in (0) and rd in (1.1.1.1:2001) and evpn-route-type is 3 then set extcommunity color color92001 endif pass end-policy
Applying RPL to BGP Services (EVPN Services): Example
The following examples show various RPLs that set BGP color community being applied to EVPN services.
The following 2 examples show the RPL applied at the EVI export and import attach-points.
Note RPLs applied under EVI import or export attach-point also support matching on the following:
• Ethernet Segment Identifier (ESI)
• Ethernet Tag (ETAG)
• EVPN-Originator evpn evi 101 bgp route-target 101:1 route-target import 100:1
!
route-target export 101:1 route-policy import sample-import-rpl advertise-mac
!
!
evi 102 bgp route-target 102:1 route-target import 100:2
!
route-target export 102:1 route-policy export sample-export-rpl
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!
!
advertise-mac
!
The following example shows the RPL applied at the BGP neighbor-out attach-point.
Note RPLs defined under BGP neighbor-out attach-point also support matching on the following:
• EVPN-Originator router bgp 100 bgp router-id 1.1.1.1
address-family l2vpn evpn
!
neighbor-group evpn-rr remote-as 100 update-source Loopback0 address-family l2vpn evpn
!
neighbor 10.10.10.10
use neighbor-group evpn-rr address-family l2vpn evpn route-policy sample-bgpneighbor-rpl out
Configuring SR-ODN for EVPN-VPWS: Use Case
This use case shows how to set up a pair of ELINE services using EVPN-VPWS between two sites. Services are carried over SR policies that must not share any common links along their paths (link-disjoint). The SR policies are triggered on-demand based on ODN principles. An SR-PCE computes the disjoint paths.
This use case uses the following topology with 2 sites: Site 1 with nodes A and B, and Site 2 with nodes C and D.
Figure 3: Topology for Use Case: SR-ODN for EVPN-VPWS
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Table 7: Use Case Parameters
IP Addresses of
Loopback0 (Lo0)
Interfaces
EVPN-VPWS Service
Parameters
ODN BGP Color Extended
Communities
SR-PCE Lo0: 1.1.1.207
Site 1:
• Node A Lo0: 1.1.1.5
• Node B Lo0: 1.1.1.6
ELINE-1:
• EVPN-VPWS EVI 100
• Node A: AC-ID = 11
• Node C: AC-ID = 21
Site 1 routers (Nodes A and B):
• set color 10000
• match color 11000
Site 2:
• Node C Lo0: 1.1.1.2
• Node D Lo0: 1.1.1.4
ELINE-2:
• EVPN-VPWS EVI 101
• Node B: AC-ID = 12
• Node D: AC-ID = 22
Site 2 routers (Nodes C and D):
• set color 11000
• match color 10000
Note These colors are associated with the EVPN route-type 1 routes of the EVPN-VPWS services.
PCEP LSP Disjoint-Path
Association Group ID
Site 1 to Site 2 LSPs (from Node A to Node C/from
Node B to Node D):
Site 2 to Site 1 LSPs (from Node C to Node A/from
Node D to Node B):
• group-id = 775 • group-id = 776
The use case provides configuration and verification outputs for all devices.
Configuration Verification
Configuration: SR-PCE, on page 118
Configuration: Site 1 Node A, on page 119
Verification: SR-PCE, on page 123
Verification: Site 1 Node A, on page 127
Configuration: Site 1 Node B, on page 120
Configuration: Site 2 Node C, on page 121
Configuration: Site 2 Node D, on page 122
Verification: Site 1 Node B, on page 129
Verification: Site 2 Node C, on page 132
Verification: Site 2 Node D, on page 135
Configuration: SR-PCE
For cases when PCC nodes support, or signal, PCEP association-group object to indicate the pair of LSPs in a disjoint set, there is no extra configuration required at the SR-PCE to trigger disjoint-path computation.
Note SR-PCE also supports disjoint-path computation for cases when PCC nodes do not support PCEP association-group object. See
Configure the Disjoint Policy (Optional), on page 203
for more information.
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Configuration: Site 1 Node A
This section depicts relevant configuration of Node A at Site 1. It includes service configuration, BGP color extended community, and RPL. It also includes the corresponding ODN template required to achieve the disjointness SLA.
Nodes in Site 1 are configured to set color 10000 on originating EVPN routes, while matching color 11000 on incoming EVPN routes from routers located at Site 2.
Since both nodes in Site 1 request path computation from SR-PCE using the same disjoint-path group-id
(775), the PCE will attempt to compute disjointness for the pair of LSPs originating from Site 1 toward Site
2.
/* EVPN-VPWS configuration */ interface GigabitEthernet0/0/0/3.2500 l2transport encapsulation dot1q 2500
!
rewrite ingress tag pop 1 symmetric l2vpn xconnect group evpn_vpws_group p2p evpn_vpws_100 interface GigabitEthernet0/0/0/3.2500
neighbor evpn evi 100 target 21 source 11
!
!
!
!
/* BGP color community and RPL configuration */ extcommunity-set opaque color-10000
10000 end-set
!
route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 100 )') then set extcommunity color color-10000 endif pass end-policy
!
router bgp 65000 neighbor 1.1.1.253
address-family l2vpn evpn route-policy SET_COLOR_EVPN_VPWS out
!
!
!
/* ODN template configuration */ segment-routing traffic-eng on-demand color 11000 dynamic pcep
!
metric
!
type igp
!
disjoint-path group-id 775 type link
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!
!
!
Configuration: Site 1 Node B
This section depicts relevant configuration of Node B at Site 1.
/* EVPN-VPWS configuration */ interface TenGigE0/3/0/0/8.2500 l2transport encapsulation dot1q 2500 rewrite ingress tag pop 1 symmetric
!
l2vpn xconnect group evpn_vpws_group p2p evpn_vpws_101 interface TenGigE0/3/0/0/8.2500
neighbor evpn evi 101 target 22 source 12
!
!
!
!
/* BGP color community and RPL configuration */ extcommunity-set opaque color-10000
10000 end-set
!
route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 101 )') then set extcommunity color color-10000 endif pass end-policy
!
router bgp 65000
!
!
neighbor 1.1.1.253
address-family l2vpn evpn
!
route-policy SET_COLOR_EVPN_VPWS out
/* ODN template configuration */ segment-routing traffic-eng on-demand color 11000 dynamic pcep
!
!
!
!
metric type igp
!
disjoint-path group-id 775 type link
!
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Configuration: Site 2 Node C
This section depicts relevant configuration of Node C at Site 2. It includes service configuration, BGP color extended community, and RPL. It also includes the corresponding ODN template required to achieve the disjointness SLA.
Nodes in Site 2 are configured to set color 11000 on originating EVPN routes, while matching color 10000 on incoming EVPN routes from routers located at Site 1.
Since both nodes on Site 2 request path computation from SR-PCE using the same disjoint-path group-id
(776), the PCE will attempt to compute disjointness for the pair of LSPs originating from Site 2 toward Site
1.
/* EVPN-VPWS configuration */ interface GigabitEthernet0/0/0/3.2500 l2transport encapsulation dot1q 2500
!
rewrite ingress tag pop 1 symmetric l2vpn xconnect group evpn_vpws_group p2p evpn_vpws_100 interface GigabitEthernet0/0/0/3.2500
neighbor evpn evi 100 target 11 source 21
!
!
!
!
/* BGP color community and RPL configuration */ extcommunity-set opaque color-11000
11000 end-set
!
route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 100 )') then set extcommunity color color-11000 endif pass end-policy
!
router bgp 65000 neighbor 1.1.1.253
address-family l2vpn evpn route-policy SET_COLOR_EVPN_VPWS out
!
!
!
/* ODN template configuration */ segment-routing traffic-eng on-demand color 10000 dynamic pcep
!
!
metric type igp
!
disjoint-path group-id 776 type link
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!
!
!
Configuration: Site 2 Node D
This section depicts relevant configuration of Node D at Site 2.
/* EVPN-VPWS configuration */ interface GigabitEthernet0/0/0/1.2500 l2transport encapsulation dot1q 2500 rewrite ingress tag pop 1 symmetric
!
l2vpn xconnect group evpn_vpws_group p2p evpn_vpws_101 interface GigabitEthernet0/0/0/1.2500
neighbor evpn evi 101 target 12 source 22
!
!
!
!
/* BGP color community and RPL configuration */ extcommunity-set opaque color-11000
11000 end-set
!
route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 101 )') then set extcommunity color color-11000 endif pass end-policy
!
router bgp 65000
!
!
neighbor 1.1.1.253
address-family l2vpn evpn
!
route-policy SET_COLOR_EVPN_VPWS out
/* ODN template configuration */ segment-routing traffic-eng on-demand color 10000 dynamic pcep
!
!
!
!
metric type igp
!
disjoint-path group-id 776 type link
!
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Verification: SR-PCE
Use the show pce ipv4 peer command to display the SR-PCE’s PCEP peers and session status. SR-PCE performs path computation for the 4 nodes depicted in the use-case.
RP/0/0/CPU0:SR-PCE# show pce ipv4 peer
Mon Jul 15 19:41:43.622 UTC
PCE's peer database:
--------------------
Peer address: 1.1.1.2
State: Up
Capabilities: Stateful, Segment-Routing, Update, Instantiation
Peer address: 1.1.1.4
State: Up
Capabilities: Stateful, Segment-Routing, Update, Instantiation
Peer address: 1.1.1.5
State: Up
Capabilities: Stateful, Segment-Routing, Update, Instantiation
Peer address: 1.1.1.6
State: Up
Capabilities: Stateful, Segment-Routing, Update, Instantiation
Use the show pce association group-id command to display information for the pair of LSPs assigned to a given association group-id value.
Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. In particular, disjoint LSPs from site 1 to site 2 are identified by association group-id 775. The output includes high-level information for LSPs associated to this group-id:
• At Node A (1.1.1.5): LSP symbolic name = bgp_c_11000_ep_1.1.1.2_discr_100
• At Node B (1.1.1.6): LSP symbolic name = bgp_c_11000_ep_1.1.1.4_discr_100
In this case, the SR-PCE was able to achieve the desired disjointness level; therefore the Status is shown as
"Satisfied".
RP/0/0/CPU0:SR-PCE# show pce association group-id 775
Thu Jul 11 03:52:20.770 UTC
PCE's association database:
----------------------
Association: Type Link-Disjoint, Group 775 , Not Strict
Associated LSPs:
LSP[0]:
PCC 1.1.1.6, tunnel name bgp_c_11000_ep_1.1.1.4_discr_100
, PLSP ID 18, tunnel ID 17,
LSP ID 3, Configured on PCC
LSP[1]:
PCC 1.1.1.5, tunnel name bgp_c_11000_ep_1.1.1.2_discr_100
, PLSP ID 18, tunnel ID 18,
LSP ID 3, Configured on PCC
Status: Satisfied
Use the show pce lsp command to display detailed information of an LSP present in the PCE's LSP database.
This output shows details for the LSP at Node A (1.1.1.5) that is used to carry traffic of EVPN VPWS EVI
100 towards node C (1.1.1.2).
RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.5 name bgp_c_11000_ep_1.1.1.2_discr_100
Thu Jul 11 03:58:45.903 UTC
PCE's tunnel database:
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----------------------
PCC 1.1.1.5:
Tunnel Name: bgp_c_11000_ep_1.1.1.2_discr_100
Color: 11000
Interface Name: srte_c_11000_ep_1.1.1.2
LSPs:
LSP[0]: source 1.1.1.5, destination 1.1.1.2, tunnel ID 18, LSP ID 3
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 80037
Maximum SID Depth: 10
Absolute Metric Margin: 0
Relative Metric Margin: 0%
Preference: 100
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x12, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Exclude LSP
State-sync PCE: None
PCC: 1.1.1.5
LSP is subdelegated to: None
Reported path:
Metric type: IGP, Accumulated Metric 40
SID[0]: Adj, Label 80003, Address: local 11.5.8.5 remote 11.5.8.8
SID[1]: Node, Label 16007, Address 1.1.1.7
SID[2]: Node, Label 16002, Address 1.1.1.2
Computed path: (Local PCE)
Computed Time: Thu Jul 11 03:49:48 UTC 2019 (00:08:58 ago)
Metric type: IGP, Accumulated Metric 40
SID[0]: Adj, Label 80003, Address: local 11.5.8.5 remote 11.5.8.8
SID[1]: Node, Label 16007, Address 1.1.1.7
SID[2]: Node, Label 16002, Address 1.1.1.2
Recorded path:
None
Disjoint Group Information :
Type Link-Disjoint, Group 775
This output shows details for the LSP at Node B (1.1.1.6) that is used to carry traffic of EVPN VPWS EVI
101 towards node D (1.1.1.4).
RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.6 name bgp_c_11000_ep_1.1.1.4_discr_100
Thu Jul 11 03:58:56.812 UTC
PCE's tunnel database:
----------------------
PCC 1.1.1.6:
Tunnel Name: bgp_c_11000_ep_1.1.1.4_discr_100
Color: 11000
Interface Name: srte_c_11000_ep_1.1.1.4
LSPs:
LSP[0]: source 1.1.1.6, destination 1.1.1.4, tunnel ID 17, LSP ID 3
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 80061
Maximum SID Depth: 10
Absolute Metric Margin: 0
Relative Metric Margin: 0%
Preference: 100
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
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PLSP-ID 0x12, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Disjoint LSP
State-sync PCE: None
PCC: 1.1.1.6
LSP is subdelegated to: None
Reported path:
Metric type: IGP, Accumulated Metric 40
SID[0]: Node, Label 16001, Address 1.1.1.1
SID[1]: Node, Label 16004, Address 1.1.1.4
Computed path: (Local PCE)
Computed Time: Thu Jul 11 03:49:48 UTC 2019 (00:09:08 ago)
Metric type: IGP, Accumulated Metric 40
SID[0]: Node, Label 16001, Address 1.1.1.1
SID[1]: Node, Label 16004, Address 1.1.1.4
Recorded path:
None
Disjoint Group Information :
Type Link-Disjoint, Group 775
Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. In particular, disjoint LSPs from site 2 to site 1 are identified by association group-id 776. The output includes high-level information for LSPs associated to this group-id:
• At Node C (1.1.1.2): LSP symbolic name = bgp_c_10000_ep_1.1.1.5_discr_100
• At Node D (1.1.1.4): LSP symbolic name = bgp_c_10000_ep_1.1.1.6_discr_100
In this case, the SR-PCE was able to achieve the desired disjointness level; therefore, the Status is shown as
"Satisfied".
RP/0/0/CPU0:SR-PCE# show pce association group-id 776
Thu Jul 11 03:52:24.370 UTC
PCE's association database:
----------------------
Association: Type Link-Disjoint, Group 776 , Not Strict
Associated LSPs:
LSP[0]:
PCC 1.1.1.4, tunnel name bgp_c_10000_ep_1.1.1.6_discr_100
, PLSP ID 16, tunnel ID 14,
LSP ID 1, Configured on PCC
LSP[1]:
PCC 1.1.1.2, tunnel name bgp_c_10000_ep_1.1.1.5_discr_100
, PLSP ID 6, tunnel ID 21, LSP
ID 3, Configured on PCC
Status: Satisfied
Use the show pce lsp command to display detailed information of an LSP present in the PCE's LSP database.
This output shows details for the LSP at Node C (1.1.1.2) that is used to carry traffic of EVPN VPWS EVI
100 towards node A (1.1.1.5).
RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.2 name bgp_c_10000_ep_1.1.1.5_discr_100
Thu Jul 11 03:55:21.706 UTC
PCE's tunnel database:
----------------------
PCC 1.1.1.2:
Tunnel Name: bgp_c_10000_ep_1.1.1.5_discr_100
Color: 10000
Interface Name: srte_c_10000_ep_1.1.1.5
LSPs:
LSP[0]: source 1.1.1.2, destination 1.1.1.5, tunnel ID 21, LSP ID 3
State: Admin up, Operation up
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Setup type: Segment Routing
Binding SID: 80052
Maximum SID Depth: 10
Absolute Metric Margin: 0
Relative Metric Margin: 0%
Preference: 100
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x6, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Exclude LSP
State-sync PCE: None
PCC: 1.1.1.2
LSP is subdelegated to: None
Reported path:
Metric type: IGP, Accumulated Metric 40
SID[0]: Node, Label 16007, Address 1.1.1.7
SID[1]: Node, Label 16008, Address 1.1.1.8
SID[2]: Adj, Label 80005, Address: local 11.5.8.8 remote 11.5.8.5
Computed path: (Local PCE)
Computed Time: Thu Jul 11 03:50:03 UTC 2019 (00:05:18 ago)
Metric type: IGP, Accumulated Metric 40
SID[0]: Node, Label 16007, Address 1.1.1.7
SID[1]: Node, Label 16008, Address 1.1.1.8
SID[2]: Adj, Label 80005, Address: local 11.5.8.8 remote 11.5.8.5
Recorded path:
None
Disjoint Group Information :
Type Link-Disjoint, Group 776
This output shows details for the LSP at Node D (1.1.1.4) used to carry traffic of EVPN VPWS EVI 101 towards node B (1.1.1.6).
RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.4 name bgp_c_10000_ep_1.1.1.6_discr_100
Thu Jul 11 03:55:23.296 UTC
PCE's tunnel database:
----------------------
PCC 1.1.1.4:
Tunnel Name: bgp_c_10000_ep_1.1.1.6_discr_100
Color: 10000
Interface Name: srte_c_10000_ep_1.1.1.6
LSPs:
LSP[0]: source 1.1.1.4, destination 1.1.1.6, tunnel ID 14, LSP ID 1
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 80047
Maximum SID Depth: 10
Absolute Metric Margin: 0
Relative Metric Margin: 0%
Preference: 100
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x10, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Disjoint LSP
State-sync PCE: None
PCC: 1.1.1.4
LSP is subdelegated to: None
Reported path:
Metric type: IGP, Accumulated Metric 40
SID[0]: Node, Label 16001, Address 1.1.1.1
SID[1]: Node, Label 16006, Address 1.1.1.6
Computed path: (Local PCE)
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Computed Time: Thu Jul 11 03:50:03 UTC 2019 (00:05:20 ago)
Metric type: IGP, Accumulated Metric 40
SID[0]: Node, Label 16001, Address 1.1.1.1
SID[1]: Node, Label 16006, Address 1.1.1.6
Recorded path:
None
Disjoint Group Information :
Type Link-Disjoint, Group 776
Verification: Site 1 Node A
This section depicts verification steps at Node A.
Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 100 (rd
1.1.1.5:100). The output includes an EVPN route-type 1 route with color 11000 originated at Node C (1.1.1.2).
RP/0/RSP0/CPU0:Node-A# show bgp l2vpn evpn rd 1.1.1.5:100
Wed Jul 10 18:57:57.704 PST
BGP router identifier 1.1.1.5, local AS number 65000
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 360
BGP NSR Initial initsync version 1 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1.1.1.5:100 (default for vrf VPWS:100)
*> [1][0000.0000.0000.0000.0000][11]/120
0.0.0.0
*>i[1][0000.0000.0000.0000.0000][21]/120
1.1.1.2 C:11000 100
0 i
0 i
The following output displays the details for the incoming EVPN RT1. Note the presence of BGP extended color community 11000, and that the prefix is associated with an SR policy with color 11000 and BSID value of 80044.
RP/0/RSP0/CPU0:Node-A# show bgp l2vpn evpn rd 1.1.1.5:100
[1][0000.0000.0000.0000.0000][21]/120
Wed Jul 10 18:57:58.107 PST
BGP routing table entry for [1][0000.0000.0000.0000.0000][21]/120, Route Distinguisher:
1.1.1.5:100
Versions:
Process
Speaker bRIB/RIB SendTblVer
360 360
Last Modified: Jul 10 18:36:18.369 for 00:21:40
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local
1.1.1.2 C:11000 (bsid:80044) (metric 40) from 1.1.1.253 (1.1.1.2)
Received Label 80056
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 358
Extended community: Color:11000 RT:65000:100
Originator: 1.1.1.2, Cluster list: 1.1.1.253
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SR policy color 11000, up, registered, bsid 80044 , if-handle 0x00001b20
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.2:100
Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 100 service.
RP/0/RSP0/CPU0:Node-A# show l2vpn xconnect group evpn_vpws_group
Wed Jul 10 18:58:02.333 PST
Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,
SB = Standby, SR = Standby Ready, (PP) = Partially Programmed
XConnect
Group Name ST
Segment 1
Description ST
Segment 2
Description ST
-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_100
UP Gi0/0/0/3.2500
UP EVPN 100,21,1.1.1.2
UP
----------------------------------------------------------------------------------------
The following output shows the details for the service. Note that the service is associated with the on-demand
SR policy with color 11000 and end-point 1.1.1.2 (node C).
RP/0/RSP0/CPU0:Node-A# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_100 detail
Wed Jul 10 18:58:02.755 PST
Group evpn_vpws_group, XC evpn_vpws_100, state is up; Interworking none
AC: GigabitEthernet0/0/0/3.2500, state is up
Type VLAN; Num Ranges: 1
Rewrite Tags: []
VLAN ranges: [2500, 2500]
MTU 1500; XC ID 0x120000c; interworking none
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 1.1.1.2, PW ID: evi 100, ac-id 21, state is up ( established )
XC ID 0xa0000007
Encapsulation MPLS
Source address 1.1.1.5
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE srte_c_11000_ep_1.1.1.2, On-Demand , fallback enabled
Tunnel : Up
Load Balance Hashing: src-dst-mac
EVPN Local Remote
------------ ------------------------------ -----------------------------
Label
MTU
80040
1500
Control word enabled
AC ID
EVPN type
11
Ethernet
80056
1500 enabled
21
Ethernet
------------ ------------------------------ -----------------------------
Create time: 10/07/2019 18:31:30 (1d17h ago)
Last time status changed: 10/07/2019 19:42:00 (1d16h ago)
Last time PW went down: 10/07/2019 19:40:55 (1d16h ago)
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0
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Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.
The following output shows the on-demand SR policy with BSID 80044 that was triggered by EVPN RT1 prefix with color 11000 advertised by node C (1.1.1.2).
RP/0/RSP0/CPU0:Node-A# show segment-routing traffic-eng policy color 11000 tabular
Wed Jul 10 18:58:00.732 PST
Color Endpoint Admin Oper
State State
Binding
SID
------ -------------------- ------ ------ --------------------
11000 1.1.1.2
up up 80044
The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).
Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. Specifically, from site 1 to site 2, LSP at Node A
(srte_c_11000_ep_1.1.1.2) is link-disjoint from LSP at Node B (srte_c_11000_ep_1.1.1.4).
RP/0/RSP0/CPU0:Node-A# show segment-routing traffic-eng policy color 11000
Wed Jul 10 19:15:47.217 PST
SR-TE policy database
---------------------
Color: 11000, End-point: 1.1.1.2
Name: srte_c_11000_ep_1.1.1.2
Status:
Admin: up Operational: up for 00:39:31 (since Jul 10 18:36:00.471)
Candidate-paths:
Preference: 200 (BGP ODN) (shutdown)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_11000_ep_1.1.1.2_discr_200
PLSP-ID: 19
Dynamic (invalid)
Preference: 100 (BGP ODN) (active)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_11000_ep_1.1.1.2_discr_100
PLSP-ID: 18
Dynamic (pce 1.1.1.207) (valid)
Metric Type: IGP, Path Accumulated Metric: 40
80003 [Adjacency-SID, 11.5.8.5 - 11.5.8.8]
16007 [Prefix-SID, 1.1.1.7]
16002 [Prefix-SID, 1.1.1.2]
Attributes:
Binding SID: 80044
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Verification: Site 1 Node B
This section depicts verification steps at Node B.
Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 101 (rd
1.1.1.6:101). The output includes an EVPN route-type 1 route with color 11000 originated at Node D (1.1.1.4).
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RP/0/RSP0/CPU0:Node-B# show bgp l2vpn evpn rd 1.1.1.6:101
Wed Jul 10 19:08:54.964 PST
BGP router identifier 1.1.1.6, local AS number 65000
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 322
BGP NSR Initial initsync version 7 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1.1.1.6:101 (default for vrf VPWS:101)
*> [1][0000.0000.0000.0000.0000][12]/120
0.0.0.0
*>i[1][0000.0000.0000.0000.0000][22]/120
1.1.1.4 C:11000 100
0 i
0 i
Processed 2 prefixes, 2 paths
The following output displays the details for the incoming EVPN RT1. Note the presence of BGP extended color community 11000, and that the prefix is associated with an SR policy with color 11000 and BSID value of 80061.
RP/0/RSP0/CPU0:Node-B# show bgp l2vpn evpn rd 1.1.1.6:101
[1][0000.0000.0000.0000.0000][22]/120
Wed Jul 10 19:08:55.039 PST
BGP routing table entry for [1][0000.0000.0000.0000.0000][22]/120, Route Distinguisher:
1.1.1.6:101
Versions:
Process bRIB/RIB SendTblVer
Speaker 322 322
Last Modified: Jul 10 18:42:10.408 for 00:26:44
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local
1.1.1.4 C:11000 (bsid:80061) (metric 40) from 1.1.1.253 (1.1.1.4)
Received Label 80045
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 319
Extended community: Color:11000 RT:65000:101
Originator: 1.1.1.4, Cluster list: 1.1.1.253
SR policy color 11000, up, registered, bsid 80061 , if-handle 0x00000560
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.4:101
Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 101 service.
RP/0/RSP0/CPU0:Node-B# show l2vpn xconnect group evpn_vpws_group
Wed Jul 10 19:08:56.388 PST
Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,
SB = Standby, SR = Standby Ready, (PP) = Partially Programmed
XConnect
Group Name
Segment 1
ST Description ST
Segment 2
Description ST
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-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_101
UP Te0/3/0/0/8.2500
UP EVPN 101,22,1.1.1.4
UP
----------------------------------------------------------------------------------------
The following output shows the details for the service. Note that the service is associated with the on-demand
SR policy with color 11000 and end-point 1.1.1.4 (node D).
RP/0/RSP0/CPU0:Node-B# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_101
Wed Jul 10 19:08:56.511 PST
Group evpn_vpws_group, XC evpn_vpws_101, state is up; Interworking none
AC: TenGigE0/3/0/0/8.2500, state is up
Type VLAN; Num Ranges: 1
Rewrite Tags: []
VLAN ranges: [2500, 2500]
MTU 1500; XC ID 0x2a0000e; interworking none
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 1.1.1.4, PW ID: evi 101, ac-id 22, state is up ( established )
XC ID 0xa0000009
Encapsulation MPLS
Source address 1.1.1.6
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE srte_c_11000_ep_1.1.1.4, On-Demand , fallback enabled
Tunnel : Up
Load Balance Hashing: src-dst-mac
EVPN Local Remote
------------ ------------------------------ -----------------------------
Label 80060 80045
MTU 1500
Control word enabled
AC ID
EVPN type
12
Ethernet
1500 enabled
22
Ethernet
------------ ------------------------------ -----------------------------
Create time: 10/07/2019 18:32:49 (00:36:06 ago)
Last time status changed: 10/07/2019 18:42:07 (00:26:49 ago)
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0
Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.
The following output shows the on-demand SR policy with BSID 80061 that was triggered by EVPN RT1 prefix with color 11000 advertised by node D (1.1.1.4).
RP/0/RSP0/CPU0:Node-B# show segment-routing traffic-eng policy color 11000 tabular
Wed Jul 10 19:08:56.146 PST
Color Endpoint Admin Oper Binding
State State SID
------ -------------------- ------ ------ --------------------
11000 1.1.1.4
up up 80061
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The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).
Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. Specifically, from site 1 to site 2, LSP at Node B
(srte_c_11000_ep_1.1.1.4) is link-disjoint from LSP at Node A (srte_c_11000_ep_1.1.1.2).
RP/0/RSP0/CPU0:Node-B# show segment-routing traffic-eng policy color 11000
Wed Jul 10 19:08:56.207 PST
SR-TE policy database
---------------------
Color: 11000, End-point: 1.1.1.4
Name: srte_c_11000_ep_1.1.1.4
Status:
Admin: up Operational: up for 00:26:47 (since Jul 10 18:40:05.868)
Candidate-paths:
Preference: 200 (BGP ODN) (shutdown)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_11000_ep_1.1.1.4_discr_200
PLSP-ID: 19
Dynamic (invalid)
Preference: 100 (BGP ODN) (active)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_11000_ep_1.1.1.4_discr_100
PLSP-ID: 18
Dynamic (pce 1.1.1.207) (valid)
Metric Type: IGP, Path Accumulated Metric: 40
16001 [Prefix-SID, 1.1.1.1]
16004 [Prefix-SID, 1.1.1.4]
Attributes:
Binding SID: 80061
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Verification: Site 2 Node C
This section depicts verification steps at Node C.
Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 100 (rd
1.1.1.2:100). The output includes an EVPN route-type 1 route with color 10000 originated at Node A (1.1.1.5).
RP/0/RSP0/CPU0:Node-C# show bgp l2vpn evpn rd 1.1.1.2:100
BGP router identifier 1.1.1.2, local AS number 65000
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 21
BGP NSR Initial initsync version 1 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1.1.1.2:100 (default for vrf VPWS:100)
*>i[1][0000.0000.0000.0000.0000][11]/120
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1.1.1.5 C:10000
*> [1][0000.0000.0000.0000.0000][21]/120
0.0.0.0
100 0 i
0 i
The following output displays the details for the incoming EVPN RT1. Note the presence of BGP extended color community 10000, and that the prefix is associated with an SR policy with color 10000 and BSID value of 80058.
RP/0/RSP0/CPU0:Node-C# show bgp l2vpn evpn rd 1.1.1.2:100
[1][0000.0000.0000.0000.0000][11]/120
BGP routing table entry for [1][0000.0000.0000.0000.0000][11]/120, Route Distinguisher:
1.1.1.2:100
Versions:
Process
Speaker bRIB/RIB SendTblVer
20 20
Last Modified: Jul 10 18:36:20.503 for 00:45:21
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local
1.1.1.5 C:10000 (bsid:80058) (metric 40) from 1.1.1.253 (1.1.1.5)
Received Label 80040
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 18
Extended community: Color:10000 RT:65000:100
Originator: 1.1.1.5, Cluster list: 1.1.1.253
SR policy color 10000, up, registered, bsid 80058 , if-handle 0x000006a0
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.5:100
Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 100 service.
RP/0/RSP0/CPU0:Node-C# show l2vpn xconnect group evpn_vpws_group
Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,
SB = Standby, SR = Standby Ready, (PP) = Partially Programmed
XConnect Segment 1 Segment 2
Group Name ST Description ST Description ST
-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_100
UP Gi0/0/0/3.2500
UP EVPN 100,11,1.1.1.5
UP
----------------------------------------------------------------------------------------
The following output shows the details for the service. Note that the service is associated with the on-demand
SR policy with color 10000 and end-point 1.1.1.5 (node A).
RP/0/RSP0/CPU0:Node-C# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_100
Group evpn_vpws_group, XC evpn_vpws_100, state is up; Interworking none
AC: GigabitEthernet0/0/0/3.2500, state is up
Type VLAN; Num Ranges: 1
Rewrite Tags: []
VLAN ranges: [2500, 2500]
MTU 1500; XC ID 0x1200008; interworking none
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 1.1.1.5, PW ID: evi 100, ac-id 11, state is up ( established )
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XC ID 0xa0000003
Encapsulation MPLS
Source address 1.1.1.2
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE srte_c_10000_ep_1.1.1.5, On-Demand , fallback enabled
Tunnel : Up
Load Balance Hashing: src-dst-mac
EVPN Local Remote
------------ ------------------------------ -----------------------------
Label
MTU
80056
1500
80040
1500
Control word enabled
AC ID 21
EVPN type Ethernet enabled
11
Ethernet
------------ ------------------------------ -----------------------------
Create time: 10/07/2019 18:36:16 (1d19h ago)
Last time status changed: 10/07/2019 19:41:59 (1d18h ago)
Last time PW went down: 10/07/2019 19:40:54 (1d18h ago)
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0
Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.
The following output shows the on-demand SR policy with BSID 80058 that was triggered by EVPN RT1 prefix with color 10000 advertised by node A (1.1.1.5).
RP/0/RSP0/CPU0:Node-C# show segment-routing traffic-eng policy color 10000 tabular
Color Endpoint Admin Oper
State State
Binding
SID
------ -------------------- ------ ------ --------------------
10000 1.1.1.5
up up 80058
The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).
Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. Specifically, from site 2 to site 1, LSP at Node C
(srte_c_10000_ep_1.1.1.5) is link-disjoint from LSP at Node D (srte_c_10000_ep_1.1.1.6).
RP/0/RSP0/CPU0:Node-C# show segment-routing traffic-eng policy color 10000
SR-TE policy database
---------------------
Color: 10000, End-point: 1.1.1.5
Name: srte_c_10000_ep_1.1.1.5
Status:
Admin: up Operational: up for 00:12:35 (since Jul 10 19:49:21.890)
Candidate-paths:
Preference: 200 (BGP ODN) (shutdown)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_10000_ep_1.1.1.5_discr_200
PLSP-ID: 7
Dynamic (invalid)
Preference: 100 (BGP ODN) (active)
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Configuring SR-ODN for EVPN-VPWS: Use Case
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_10000_ep_1.1.1.5_discr_100
PLSP-ID: 6
Dynamic (pce 1.1.1.207) (valid)
Metric Type: IGP, Path Accumulated Metric: 40
16007 [Prefix-SID, 1.1.1.7]
16008 [Prefix-SID, 1.1.1.8]
80005 [Adjacency-SID, 11.5.8.8 - 11.5.8.5]
Attributes:
Binding SID: 80058
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Verification: Site 2 Node D
This section depicts verification steps at Node D.
Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 101 (rd
1.1.1.4:101). The output includes an EVPN route-type 1 route with color 10000 originated at Node B (1.1.1.6).
RP/0/RSP0/CPU0:Node-D# show bgp l2vpn evpn rd 1.1.1.4:101
BGP router identifier 1.1.1.4, local AS number 65000
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 570
BGP NSR Initial initsync version 1 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1.1.1.4:101 (default for vrf VPWS:101)
*>i[1][0000.0000.0000.0000.0000][12]/120
1.1.1.6 C:10000
*> [1][0000.0000.0000.0000.0000][22]/120
0.0.0.0
100 0 i
0 i
Processed 2 prefixes, 2 paths
The following output displays the details for the incoming EVPN RT1. Note the presence of BGP extended color community 10000, and that the prefix is associated with an SR policy with color 10000 and BSID value of 80047.
RP/0/RSP0/CPU0:Node-D# show bgp l2vpn evpn rd 1.1.1.4:101
[1][0000.0000.0000.0000.0000][12]/120
BGP routing table entry for [1][0000.0000.0000.0000.0000][12]/120, Route Distinguisher:
1.1.1.4:101
Versions:
Process bRIB/RIB SendTblVer
Speaker 569 569
Last Modified: Jul 10 18:42:12.455 for 00:45:38
Paths: (1 available, best #1)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local
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1.1.1.6 C:10000 (bsid:80047) (metric 40) from 1.1.1.253 (1.1.1.6)
Received Label 80060
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 568
Extended community: Color:10000 RT:65000:101
Originator: 1.1.1.6, Cluster list: 1.1.1.253
SR policy color 10000, up, registered, bsid 80047 , if-handle 0x00001720
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.6:101
Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 101 service.
RP/0/RSP0/CPU0:Node-D# show l2vpn xconnect group evpn_vpws_group
Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,
SB = Standby, SR = Standby Ready, (PP) = Partially Programmed
XConnect
Group Name
Segment 1
ST Description ST
Segment 2
Description ST
-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_101
UP Gi0/0/0/1.2500
UP EVPN 101,12,1.1.1.6
UP
----------------------------------------------------------------------------------------
The following output shows the details for the service. Note that the service is associated with the on-demand
SR policy with color 10000 and end-point 1.1.1.6 (node B).
RP/0/RSP0/CPU0:Node-D# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_101
Group evpn_vpws_group, XC evpn_vpws_101, state is up; Interworking none
AC: GigabitEthernet0/0/0/1.2500, state is up
Type VLAN; Num Ranges: 1
Rewrite Tags: []
VLAN ranges: [2500, 2500]
MTU 1500; XC ID 0x120000c; interworking none
Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 1.1.1.6, PW ID: evi 101, ac-id 12, state is up ( established )
XC ID 0xa000000d
Encapsulation MPLS
Source address 1.1.1.4
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE srte_c_10000_ep_1.1.1.6, On-Demand , fallback enabled
Tunnel : Up
Load Balance Hashing: src-dst-mac
EVPN Local Remote
------------ ------------------------------ -----------------------------
Label
MTU
80045
1500
80060
1500
Control word enabled
AC ID 22
EVPN type Ethernet enabled
12
Ethernet
------------ ------------------------------ -----------------------------
Create time: 10/07/2019 18:42:07 (00:45:49 ago)
Last time status changed: 10/07/2019 18:42:09 (00:45:47 ago)
Statistics: packets: received 0, sent 0
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Manually Provisioned SR Policy bytes: received 0, sent 0
Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.
The following output shows the on-demand SR policy with BSID 80047 that was triggered by EVPN RT1 prefix with color 10000 advertised by node B (1.1.1.6).
RP/0/RSP0/CPU0:Node-D# show segment-routing traffic-eng policy color 10000 tabular
Color Endpoint Admin Oper Binding
State State SID
------ -------------------- ------ ------ --------------------
10000 1.1.1.6
up up 80047
The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).
Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. Specifically, from site 2 to site 1, LSP at Node D
(srte_c_10000_ep_1.1.1.6) is link-disjoint from LSP at Node C (srte_c_10000_ep_1.1.1.5).
RP/0/RSP0/CPU0:Node-D# show segment-routing traffic-eng policy color 10000
SR-TE policy database
---------------------
Color: 10000, End-point: 1.1.1.6
Name: srte_c_10000_ep_1.1.1.6
Status:
Admin: up Operational: up for 01:23:04 (since Jul 10 18:42:07.350)
Candidate-paths:
Preference: 200 (BGP ODN) (shutdown)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_10000_ep_1.1.1.6_discr_200
PLSP-ID: 17
Dynamic (invalid)
Preference: 100 (BGP ODN) (active)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_10000_ep_1.1.1.6_discr_100
PLSP-ID: 16
Dynamic (pce 1.1.1.207) (valid)
Metric Type: IGP, Path Accumulated Metric: 40
16001 [Prefix-SID, 1.1.1.1]
16006 [Prefix-SID, 1.1.1.6]
Attributes:
Binding SID: 80047
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Manually Provisioned SR Policy
Manually provisioned SR policies are configured on the head-end router. These policies can use dynamic paths or explicit paths. See the
SR-TE Policy Path Types, on page 138
section for information on manually provisioning an SR policy using dynamic or explicit paths.
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PCE-Initiated SR Policy
PCE-Initiated SR Policy
An SR-TE policy can be configured on the path computation element (PCE) to reduce link congestion or to minimize the number of network touch points.
The PCE collects network information, such as traffic demand and link utilization. When the PCE determines that a link is congested, it identifies one or more flows that are causing the congestion. The PCE finds a suitable path and deploys an SR-TE policy to divert those flows, without moving the congestion to another part of the network. When there is no more link congestion, the policy is removed.
To minimize the number of network touch points, an application, such as a Network Services Orchestrator
(NSO), can request the PCE to create an SR-TE policy. PCE deploys the SR-TE policy using PCC-PCE communication protocol (PCEP).
For more information, see the
PCE-Initiated SR Policies, on page 204
section.
SR-TE Policy Path Types
A dynamic path is based on an optimization objective and a set of constraints. The head-end computes a solution, resulting in a SID-list or a set of SID-lists. When the topology changes, a new path is computed. If the head-end does not have enough information about the topology, the head-end might delegate the computation to a Segment Routing Path Computation Element (SR-PCE). For information on configuring SR-PCE, see
Configure Segment Routing Path Computation Element chapter.
An explicit path is a specified SID-list or set of SID-lists.
An SR-TE policy initiates a single (selected) path in RIB/FIB. This is the preferred valid candidate path.
A candidate path has the following characteristics:
• It has a preference – If two policies have same {color, endpoint} but different preferences, the policy with the highest preference is selected.
• It is associated with a single binding SID (BSID) – A BSID conflict occurs when there are different SR policies with the same BSID. In this case, the policy that is installed first gets the BSID and is selected.
• It is valid if it is usable.
A path is selected when the path is valid and its preference is the best among all candidate paths for that policy.
Note The protocol of the source is not relevant in the path selection logic.
Dynamic Paths
Behaviors and Limitations
For a dynamic path that traverses a specific interface between nodes (segment), the algorithm may encode this segment using an Adj-SID. The SR-TE process prefers the protected Adj-SID of the link, if one is available.
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Optimization Objectives
Optimization Objectives
Optimization objectives allow the head-end router to compute a SID-list that expresses the shortest dynamic path according to the selected metric type:
• IGP metric — Refer to the "Implementing IS-IS" and "Implementing OSPF" chapters in the Routing
Configuration Guide for Cisco NCS 5500 Series Routers .
• TE metric — See the
Configure Interface TE Metrics, on page 139
section for information about configuring
TE metrics.
This example shows a dynamic path from head-end router 1 to end-point router 3 that minimizes IGP or TE metric:
• The blue path uses the minimum IGP metric: Min-Metric (1 → 3, IGP) = SID-list <16003>; cumulative
IGP metric: 20
• The green path uses the minimum TE metric: Min-Metric (1 → 3, TE) = SID-list <16005, 16004, 16003>; cumulative TE metric: 23
Configure Interface TE Metrics
Use the metric value command in SR-TE interface submode to configure the TE metric for interfaces. The value range is from 0 to 2147483647.
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# interface type interface-path-id
Router(config-sr-te-if)# metric value
Configuring TE Metric: Example
The following configuration example shows how to set the TE metric for various interfaces: segment-routing traffic-eng interface TenGigE0/0/0/0 metric 100
!
interface TenGigE0/0/0/1 metric 1000
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Constraints
!
end
!
interface TenGigE0/0/2/0
!
metric 50
Constraints
Constraints allow the head-end router to compute a dynamic path according to the selected metric type:
• Affinity — You can apply a color or name to links or interfaces by assigning affinity bit-maps to them.
You can then specify an affinity (or relationship) between an SR policy path and link colors. SR-TE computes a path that includes or excludes links that have specific colors,or combinations of colors. See the
Named Interface Link Admin Groups and SR-TE Affinity Maps, on page 140
section for information on named interface link admin groups and SR-TE Affinity Maps.
• Disjoint — SR-TE computes a path that is disjoint from another path in the same disjoint-group. Disjoint paths do not share network resources. Path disjointness may be required for paths between the same pair of nodes, between different pairs of nodes, or a combination (only same head-end or only same end-point).
• Flexible Algorithm — Flexible Algorithm allows for user-defined algorithms where the IGP computes paths based on a user-defined combination of metric type and constraint.
Named Interface Link Admin Groups and SR-TE Affinity Maps
Named Interface Link Admin Groups and SR-TE Affinity Maps provide a simplified and more flexible means of configuring link attributes and path affinities to compute paths for SR-TE policies.
In the traditional TE scheme, links are configured with attribute-flags that are flooded with TE link-state parameters using Interior Gateway Protocols (IGPs), such as Open Shortest Path First (OSPF).
Named Interface Link Admin Groups and SR-TE Affinity Maps let you assign, or map, up to 256 color names for affinity and attribute-flag attributes instead of 32-bit hexadecimal numbers. After mappings are defined, the attributes can be referred to by the corresponding color name in the CLI. Furthermore, you can define constraints using include-any , include-all , and exclude-any arguments, where each statement can contain up to 10 colors.
Note You can configure affinity constraints using attribute flags or the Flexible Name Based Policy Constraints scheme; however, when configurations for both schemes exist, only the configuration pertaining to the new scheme is applied.
Configure Named Interface Link Admin Groups and SR-TE Affinity Maps
Use the affinity name NAME command in SR-TE interface submode to assign affinity to interfaces. Configure this on routers with interfaces that have an associated admin group attribute.
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# interface TenGigE0/0/1/2
Router(config-sr-if)# affinity
Router(config-sr-if-affinity)# name RED
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Configure SR Policy with Dynamic Path
Use the affinity-map name NAME bit-position bit-position command in SR-TE sub-mode to define affinity maps. The bit-position range is from 0 to 255.
Configure affinity maps on the following routers:
• Routers with interfaces that have an associated admin group attribute.
• Routers that act as SR-TE head-ends for SR policies that include affinity constraints.
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# affinity-map
Router(config-sr-te-affinity-map)# name RED bit-position 23
Configuring Link Admin Group: Example
The following example shows how to assign affinity to interfaces and to define affinity maps. This configuration is applicable to any router (SR-TE head-end or transit node) with colored interfaces.
segment-routing traffic-eng interface TenGigE0/0/1/1 affinity name CROSS
!
name RED
!
interface TenGigE0/0/1/2 affinity
!
name RED
!
interface TenGigE0/0/2/0 affinity
!
name BLUE
!
affinity-map name RED bit-position 23
!
end name BLUE bit-position 24 name CROSS bit-position 25
Configure SR Policy with Dynamic Path
To configure a SR-TE policy with a dynamic path, optimization objectives, and affinity constraints, complete the following configurations:
1.
Define the optimization objectives. See the
Optimization Objectives, on page 139
section.
2.
Define the constraints. See the
section.
3.
Create the policy.
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Configure SR Policy with Dynamic Path
Behaviors and Limitations
For a dynamic path that traverses a specific interface between nodes (segment), the algorithm may encode this segment using an Adj-SID. The SR-TE process prefers the protected Adj-SID of the link, if one is available.
Examples
The following example shows a configuration of an SR policy at an SR-TE head-end router. The policy has a dynamic path with optimization objectives and affinity constraints computed by the head-end router.
segment-routing traffic-eng policy foo color 100 end-point ipv4 1.1.1.2
candidate-paths preference 100 dynamic metric type te
!
!
constraints affinity exclude-any
!
!
name RED
!
!
!
!
The following example shows a configuration of an SR policy at an SR-TE head-end router. The policy has a dynamic path with optimization objectives and affinity constraints computed by the SR-PCE.
segment-routing traffic-eng policy baa color 101 end-point ipv4 1.1.1.2
candidate-paths preference 100 dynamic
!
!
!
!
pcep
!
metric type te
!
!
constraints affinity exclude-any
!
!
name BLUE
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Anycast SID-Aware Path Computation
Anycast SID-Aware Path Computation
This feature allows the SR-TE head-end or SR-PCE to compute a path that is encoded using Anycast prefix
SIDs of nodes along the path.
An Anycast SID is a type of prefix SID that identifies a set of nodes and is configured with n-flag clear. The set of nodes (Anycast group) is configured to advertise a shared prefix address and prefix SID. Anycast routing enables the steering of traffic toward multiple advertising nodes, providing load-balancing and redundancy.
Packets addressed to an Anycast address are forwarded to the topologically nearest nodes.
For more information about this feature, see the Anycast SID-Aware Path Computation topic in the Configure
Segment Routing Path Computation Element chapter.
Note For information on configuring Anycast SID, see
Configuring a Prefix-SID on the IS-IS Enabled Loopback
and
Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface, on page 83
.
Explicit Paths
Configure SR-TE Policy with Explicit Path
To configure a SR-TE policy with an explicit path, complete the following configurations:
1.
Create the segment lists.
2.
Create the SR-TE policy.
Behaviors and Limitations
A segment list can use IP addresses or MPLS labels, or a combination of both.
• The IP address can be link or a Loopback address.
• Once you enter an MPLS label, you cannot enter an IP address.
When configuring an explicit path using IP addresses of links along the path, the SR-TE process prefers the protected Adj-SID of the link, if one is available.
Configure Local SR-TE Policy Using Explicit Paths
Create a segment list with IP addresses:
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list name SIDLIST1
Router(config-sr-te-sl)# index 10 mpls adjacency 1.1.1.2
Router(config-sr-te-sl)# index 20 mpls adjacency 1.1.1.3
Router(config-sr-te-sl)# index 30 mpls adjacency 1.1.1.4
Router(config-sr-te-sl)# exit
Create a segment list with MPLS labels:
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Router(config-sr-te)# segment-list name SIDLIST2
Router(config-sr-te-sl)# index 10 mpls label 16002
Router(config-sr-te-sl)# index 20 mpls label 16003
Router(config-sr-te-sl)# index 30 mpls label 16004
Router(config-sr-te-sl)# exit
Create a segment list with IP addresses and MPLS labels:
Router(config-sr-te)# segment-list name SIDLIST3
Router(config-sr-te-sl)# index 10 mpls adjacency 1.1.1.2
Router(config-sr-te-sl)# index 20 mpls label 16003
Router(config-sr-te-sl)# index 30 mpls label 16004
Router(config-sr-te-sl)# exit
Create the SR-TE policy:
Router(config-sr-te)# policy POLICY1
Router(config-sr-te-policy)# color 10 end-point ipv4 1.1.1.4
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST1
Router(config-sr-te-pp-info)# exit
Router(config-sr-te-policy-path-pref)# exit
Router(config-sr-te-pp-info)# exit
Router(config-sr-te)# policy POLICY2
Router(config-sr-te-policy)# color 20 end-point ipv4 1.1.1.4
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST2
Router(config-sr-te-pp-info)# exit
Router(config-sr-te)# policy POLICY3
Router(config-sr-te-policy)# color 30 end-point ipv4 1.1.1.4
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST3
Router(config-sr-te-policy-path-pref)# commit
Running Configuration
Router# show running-configuration segment-routing traffic-eng segment-list SIDLIST1 index 10 mpls adjacency 1.1.1.2
index 20 mpls adjacency 1.1.1.3
!
index 30 mpls adjacency 1.1.1.4
segment-list SIDLIST2 index 10 mpls label 16002 index 20 mpls label 16003
!
index 30 mpls label 16004 segment-list SIDLIST3 index 10 mpls adjacency 1.1.1.2
index 20 mpls label 16003
!
index 30 mpls label 16004 policy POLICY1
Configure SR-TE Policies
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Configure SR-TE Policy with Explicit Path color 10 end-point ipv4 1.1.1.4
candidate-paths preference 100 explicit segment-list SIDLIST1
!
!
!
policy POLICY1 color 10 end-point ipv4 1.1.1.4
candidate-paths preference 100
!
explicit segment-list SIDLIST1
!
!
policy POLICY2 color 20 end-point ipv4 1.1.1.4
candidate-paths preference 100 explicit segment-list SIDLIST2
!
!
!
policy POLICY3 color 30 end-point ipv4 1.1.1.4
candidate-paths
!
!
preference 100 explicit segment-list SIDLIST3
!
Verification
Router# show segment-routing traffic-eng policy name srte_c_20_ep_1.1.1.4
SR-TE policy database
---------------------
Color: 20, End-point: 1.1.1.4
Name: srte_c_20_ep_1.1.1.4
Status:
Admin: up Operational: up for 00:02:47 (since Mar 26 16:05:21.857)
Candidate-paths:
Preference: 100 (configuration)
Name: POLICY2
Requested BSID: dynamic
Explicit: segment-list SIDLIST2 (active)
Weight: 1, Metric Type: TE
Attributes:
Forward Class: 0
Steering labeled-services disabled: no
Steering BGP disabled: no
IPv6 caps enable: no
Invalidation drop enabled: no
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Configuring Explicit Path with Affinity Constraint Validation
Configuring Explicit Path with Affinity Constraint Validation
To fully configure SR-TE flexible name-based policy constraints, you must complete these high-level tasks in order:
1.
Assign Color Names to Numeric Values
2.
Associate Affinity-Names with SR-TE Links
3.
Associate Affinity Constraints for SR-TE Policies
/* Enter the global configuration mode and assign color names to numeric values
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# affinity-map
Router(config-sr-te-affinity-map)# blue bit-position 0
Router(config-sr-te-affinity-map)# green bit-position 1
Router(config-sr-te-affinity-map)# red bit-position 2
Router(config-sr-te-affinity-map)# exit
/* Associate affinity-names with SR-TE links
Router(config-sr-te)# interface Gi0/0/0/0
Router(config-sr-te-if)# affinity
Router(config-sr-te-if-affinity)# blue
Router(config-sr-te-if-affinity)# exit
Router(config-sr-te-if)# exit
Router(config-sr-te)# interface Gi0/0/0/1
Router(config-sr-te-if)# affinity
Router(config-sr-te-if-affinity)# blue
Router(config-sr-te-if-affinity)# green
Router(config-sr-te-if-affinity)# exit
Router(config-sr-te-if)# exit
Router(config-sr-te)#
/* Associate affinity constraints for SR-TE policies
Router(config-sr-te)# segment-list name SIDLIST1
Router(config-sr-te-sl)# index 10 mpls adjacency 1.1.1.2
Router(config-sr-te-sl)# index 20 mpls adjacency 2.2.2.23
Router(config-sr-te-sl)# index 30 mpls adjacency 1.1.1.4
Router(config-sr-te-sl)# exit
Router(config-sr-te)# segment-list name SIDLIST2
Router(config-sr-te-sl)# index 10 mpls adjacency 1.1.1.2
Router(config-sr-te-sl)# index 30 mpls adjacency 1.1.1.4
Router(config-sr-te-sl)# exit
Router(config-sr-te)# segment-list name SIDLIST3
Router(config-sr-te-sl)# index 10 mpls adjacency 1.1.1.5
Router(config-sr-te-sl)# index 30 mpls adjacency 1.1.1.4
Router(config-sr-te-sl)# exit
Router(config-sr-te)# policy POLICY1
Router(config-sr-te-policy)# color 20 end-point ipv4 1.1.1.4
Router(config-sr-te-policy)# binding-sid mpls 1000
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 200
Router(config-sr-te-policy-path-pref)# constraints affinity exclude-any red
Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST1
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Router(config-sr-te-pp-info)# exit
Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST2
Router(config-sr-te-pp-info)# exit
Router(config-sr-te-policy-path-pref)# exit
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST3
Running Configuration
Router# show running-configuration segment-routing traffic-eng interface GigabitEthernet0/0/0/0 affinity blue
!
!
interface GigabitEthernet0/0/0/1
!
!
affinity blue green segment-list name SIDLIST1 index 10 mpls adjacency 1.1.1.2
index 20 mpls adjacency 2.2.2.23
index 30 mpls adjacency 1.1.1.4
!
segment-list name SIDLIST2 index 10 mpls adjacency 1.1.1.2
index 30 mpls adjacency 1.1.1.4
!
segment-list name SIDLIST3 index 10 mpls adjacency 1.1.1.5
!
index 30 mpls adjacency 1.1.1.4
policy POLICY1 binding-sid mpls 1000 color 20 end-point ipv4 1.1.1.4
candidate-paths preference 100
!
explicit segment-list SIDLIST3
!
preference 200 explicit segment-list SIDLIST1
!
explicit segment-list SIDLIST2
!
constraints affinity
!
!
exclude-any red
!
!
!
!
affinity-map
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Protocols
!
!
blue bit-position 0 green bit-position 1
!
red bit-position 2
Protocols
Path Computation Element Protocol
The path computation element protocol (PCEP) describes a set of procedures by which a path computation client (PCC) can report and delegate control of head-end label switched paths (LSPs) sourced from the PCC to a PCE peer. The PCE can request the PCC to update and modify parameters of LSPs it controls. The stateful model also enables a PCC to allow the PCE to initiate computations allowing the PCE to perform network-wide orchestration.
Configure the Head-End Router as PCEP PCC
Configure the head-end router as PCEP Path Computation Client (PCC) to establish a connection to the PCE.
The PCC and PCE addresses must be routable so that TCP connection (to exchange PCEP messages) can be established between PCC and PCE.
Configure the PCC to Establish a Connection to the PCE
Use the segment-routing traffic-eng pcc command to configure the PCC source address, the SR-PCE address, and SR-PCE options.
A PCE can be given an optional precedence. If a PCC is connected to multiple PCEs, the PCC selects a PCE with the lowest precedence value. If there is a tie, a PCE with the highest IP address is chosen for computing path. The precedence value range is from 0 to 255.
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# pcc
Router(config-sr-te-pcc)# source-address ipv4 local-source-address
Router(config-sr-te-pcc)# pce address ipv4 PCE-address [ precedence value ]
Router(config-sr-te-pcc)# pce address ipv4 PCE-address [ keychain WORD ]
Configure PCEP Authentication
TCP Message Digest 5 (MD5) authentication has been used for authenticating PCEP (TCP) sessions by using a clear text or encrypted password. This feature introduces support for TCP Authentication Option (TCP-AO), which replaces the TCP MD5 option.
TCP-AO uses Message Authentication Codes (MACs), which provides the following:
• Protection against replays for long-lived TCP connections
• More details on the security association with TCP connections than TCP MD5
• A larger set of MACs with minimal system and operational changes
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TCP-AO is compatible with Master Key Tuple (MKT) configuration. TCP-AO also protects connections when using the same MKT across repeated instances of a connection. TCP-AO protects the connections by using traffic key that are derived from the MKT, and then coordinates changes between the endpoints.
Note TCP-AO and TCP MD5 are never permitted to be used simultaneously. TCP-AO supports IPv6, and is fully compatible with the proposed requirements for the replacement of TCP MD5.
TCP Message Digest 5 (MD5) Authentication
Use the password { clear | encrypted } LINE command to enable TCP MD5 authentication for all PCEP peers.
Any TCP segment coming from the PCC that does not contain a MAC matching the configured password will be rejected. Specify if the password is encrypted or clear text
Router(config-sr-te-pcc)# pce address ipv4 PCE-address [ password {clear | encrypted} LINE ]
TCP Authentication Option (TCP-AO)
Use the tcp-ao key-chain [ include-tcp-options ] command to enable TCP Authentication Option (TCP-AO) authentication for all PCEP peers. Any TCP segment coming from the PCC that does not contain a MAC matching the configured key chain will be rejected. Use the include-tcp-options keyword to include other
TCP options in the header for MAC calculation.
Router(config-sr-te-pcc)# pce address ipv4 PCE-address tcp-ao key-chain [ include-tcp-options ]
Configure PCEP-Related Timers
Use the timers keepalive command to specify how often keepalive messages are sent from PCC to its peers.
The range is from 0 to 255 seconds; the default value is 30.
Router(config-sr-te-pcc)# timers keepalive seconds
Use the timers deadtimer command to specify how long the remote peers wait before bringing down the
PCEP session if no PCEP messages are received from this PCC. The range is from 1 to 255 seconds; the default value is 120.
Router(config-sr-te-pcc)# timers deadtimer seconds
Use the timers delegation-timeout command to specify how long a delegated SR policy can remain up without an active connection to a PCE. The range is from 0 to 3600 seconds; the default value is 60.
Router(config-sr-te-pcc)# timers delegation-timeout seconds
PCE-Initiated SR Policy Timers
Use the timers initiated orphans command to specify the amount of time that a PCE-initiated SR policy will remain delegated to a PCE peer that is no longer reachable by the PCC. The range is from 10 to 180 seconds; the default value is 180.
Router(config-sr-te-pcc)# timers initiated orphans seconds
Use the timers initiated state command to specify the amount of time that a PCE-initiated SR policy will remain programmed while not being delegated to any PCE. The range is from 15 to 14440 seconds (24 hours); the default value is 600.
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Router(config-sr-te-pcc)# timers initiated state seconds
To better understand how the PCE-initiated SR policy timers operate, consider the following example:
• PCE A instantiates SR policy P at head-end N.
• Head-end N delegates SR policy P to PCE A and programs it in forwarding.
• If head-end N detects that PCE A is no longer reachable, then head-end N starts the PCE-initiated orphan and state timers for SR policy P.
• If PCE A reconnects before the orphan timer expires, then SR policy P is automatically delegated back to its original PCE (PCE A).
• After the orphan timer expires, SR policy P will be eligible for delegation to any other surviving PCE(s).
• If SR policy P is not delegated to another PCE before the state timer expires, then head-end N will remove SR policy P from its forwarding.
Enable SR-TE SYSLOG Alarms
Use the logging policy status command to enable SR-TE related SYSLOG alarms.
Router(config-sr-te)# logging policy status
Enable PCEP Reports to SR-PCE
Use the report-all command to enable the PCC to report all SR policies in its database to the PCE.
Router(config-sr-te-pcc)# report-all
Customize MSD Value at PCC
Use the maximum-sid-depth value command to customize the Maximum SID Depth (MSD) signaled by
PCC during PCEP session establishment.
The default MSD value is equal to the maximum MSD supported by the platform (12).
Router(config-sr-te)# maximum-sid-depth value
Note The platform's SR-TE label imposition capabilities are as follows:
• Up to 12 transport labels when no service labels are imposed
• Up to 9 transport labels when service labels are imposed
For cases with path computation at PCE, a PCC can signal its MSD to the PCE in the following ways:
• During PCEP session establishment – The signaled MSD is treated as a node-wide property.
• MSD is configured under segment-routing traffic-eng maximum-sid-depth value command
• During PCEP LSP path request – The signaled MSD is treated as an LSP property.
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• On-demand (ODN) SR Policy: MSD is configured using the segment-routing traffic-eng
on-demand color color maximum-sid-depth value command
• Local SR Policy: MSD is configured using the segment-routing traffic-eng policy WORD
candidate-paths preference preference dynamic metric sid-limit value command.
Note If the configured MSD values are different, the per-LSP MSD takes precedence over the per-node MSD.
After path computation, the resulting label stack size is verified against the MSD requirement.
• If the label stack size is larger than the MSD and path computation is performed by PCE, then the PCE returns a "no path" response to the PCC.
• If the label stack size is larger than the MSD and path computation is performed by PCC, then the PCC will not install the path.
Note A sub-optimal path (if one exists) that satisfies the MSD constraint could be computed in the following cases:
• For a dynamic path with TE metric, when the PCE is configured with the pce segment-routing te-latency command or the PCC is configured with the segment-routing traffic-eng te-latency command.
• For a dynamic path with LATENCY metric
• For a dynamic path with affinity constraints
For example, if the PCC MSD is 4 and the optimal path (with an accumulated metric of 100) requires 5 labels, but a sub-optimal path exists (with accumulated metric of 110) requiring 4 labels, then the sub-optimal path is installed.
Customize the SR-TE Path Calculation
Use the te-latency command to enable ECMP-aware path computation for TE metric.
Router(config-sr-te)# te-latency
Note ECMP-aware path computation is enabled by default for IGP and LATENCY metrics.
Configure PCEP Redundancy Type
Use the redundancy pcc-centric command to enable PCC-centric high-availability model. The PCC-centric model changes the default PCC delegation behavior to the following:
• After LSP creation, LSP is automatically delegated to the PCE that computed it.
• If this PCE is disconnected, then the LSP is redelegated to another PCE.
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• If the original PCE is reconnected, then the delegation fallback timer is started. When the timer expires, the LSP is redelegated back to the original PCE, even if it has worse preference than the current PCE.
Router(config-sr-te-pcc)# redundancy pcc-centric
Configuring Head-End Router as PCEP PCC and Customizing SR-TE Related Options: Example
The following example shows how to configure an SR-TE head-end router with the following functionality:
• Enable the SR-TE head-end router as a PCEP client (PCC) with 3 PCEP servers (PCE) with different precedence values. The PCE with IP address 1.1.1.57 is selected as BEST.
• Enable SR-TE related syslogs.
• Set the Maximum SID Depth (MSD) signaled during PCEP session establishment to 5.
• Enable PCEP reporting for all policies in the node.
segment-routing traffic-eng pcc source-address ipv4 1.1.1.2
pce address ipv4 1.1.1.57
precedence 150
!
password clear <password> pce address ipv4 1.1.1.58
precedence 200 password clear <password>
!
pce address ipv4 1.1.1.59
!
precedence 250 password clear <password>
!
logging
!
!
!
end
!
policy status maximum-sid-depth 5 pcc report-all
Verification
RP/0/RSP0/CPU0:Router# show segment-routing traffic-eng pcc ipv4 peer
PCC's peer database:
--------------------
Peer address: 1.1.1.57
, Precedence: 150 , ( best PCE )
State up
Capabilities: Stateful, Update, Segment-Routing, Instantiation
Peer address: 1.1.1.58
, Precedence: 200
State up
Capabilities: Stateful, Update, Segment-Routing, Instantiation
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BGP SR-TE
Peer address: 1.1.1.59
, Precedence: 250
State up
Capabilities: Stateful, Update, Segment-Routing, Instantiation
BGP SR-TE
BGP may be used to distribute SR Policy candidate paths to an SR-TE head-end. Dedicated BGP SAFI and
NLRI have been defined to advertise a candidate path of an SR Policy. The advertisement of Segment Routing policies in BGP is documented in the IETF draft https://datatracker.ietf.org/doc/ draft-ietf-idr-segment-routing-te-policy/
SR policies with IPv4 and IPv6 end-points can be advertised over BGPv4 or BGPv6 sessions between the
SR-TE controller and the SR-TE headend.
The Cisco IOS-XR implementation supports the following combinations:
• IPv4 SR policy advertised over BGPv4 session
• IPv6 SR policy advertised over BGPv4 session
• IPv4 SR policy advertised over BGPv6 session
• IPv6 SR policy advertised over BGPv6 session
Configure BGP SR Policy Address Family at SR-TE Head-End
Perform this task to configure BGP SR policy address family at SR-TE head-end:
SUMMARY STEPS
1.
configure
2.
router bgp as-number
3.
bgp router-id ip-address
4.
address-family { ipv4 | ipv6 } sr-policy
5.
exit
6.
neighbor ip-address
7.
remote-as as-number
8.
address-family { ipv4 | ipv6 } sr-policy
9.
route-policy route-policy-name { in | out }
DETAILED STEPS
Step 1
Step 2
Command or Action configure
router bgp as-number
Example:
RP/0/RSP0/CPU0:router(config)# router bgp 65000
Purpose
Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.
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Step 3
Command or Action
bgp router-id ip-address
Example:
RP/0/RSP0/CPU0:router(config-bgp)# bgp router-id
1.1.1.1
Purpose
Configures the local router with a specified router ID.
Step 4
Step 5
Step 6 address-family { ipv4 | ipv6 } sr-policy
Example:
RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 sr-policy
Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.
exit
neighbor ip-address
Example:
RP/0/RSP0/CPU0:router(config-bgp)# neighbor
10.10.0.1
Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.
Step 7
Step 8
remote-as as-number
Example:
RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as
1
Creates a neighbor and assigns a remote autonomous system number to it.
Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.
Step 9 address-family { ipv4 | ipv6 } sr-policy
Example:
RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 sr-policy
route-policy route-policy-name { in | out }
Example:
RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy pass out
Applies the specified policy to IPv4 or IPv6 unicast routes.
Example: BGP SR-TE with BGPv4 Neighbor to BGP SR-TE Controller
The following configuration shows the an SR-TE head-end with a BGPv4 session towards a BGP SR-TE controller. This BGP session is used to signal both IPv4 and IPv6 SR policies.
router bgp 65000 bgp router-id 1.1.1.1
!
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Traffic Steering address-family ipv4 sr-policy
!
address-family ipv6 sr-policy
!
neighbor 10.1.3.1
remote-as 10 description *** eBGP session to BGP SRTE controller *** address-family ipv4 sr-policy route-policy pass in
!
!
!
route-policy pass out
!
address-family ipv6 sr-policy route-policy pass in route-policy pass out
Example: BGP SR-TE with BGPv6 Neighbor to BGP SR-TE Controller
The following configuration shows an SR-TE head-end with a BGPv6 session towards a BGP SR-TE controller.
This BGP session is used to signal both IPv4 and IPv6 SR policies.
router bgp 65000 bgp router-id 1.1.1.1
address-family ipv4 sr-policy
!
address-family ipv6 sr-policy
!
neighbor 3001::10:1:3:1 remote-as 10 description *** eBGP session to BGP SRTE controller *** address-family ipv4 sr-policy route-policy pass in route-policy pass out
!
!
!
address-family ipv6 sr-policy route-policy pass in
!
route-policy pass out
Traffic Steering
Automated Steering
Automated steering (AS) allows service traffic to be automatically steered onto the required transport SLA path programmed by an SR policy.
With AS, BGP automatically steers traffic onto an SR Policy based on the next-hop and color of a BGP service route. The color of a BGP service route is specified by a color extended community attribute. This color is used as a transport SLA indicator, such as min-delay or min-cost.
When the next-hop and color of a BGP service route matches the end-point and color of an SR Policy, BGP automatically installs the route resolving onto the BSID of the matching SR Policy. Recall that an SR Policy on a head-end is uniquely identified by an end-point and color.
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Color-Only Automated Steering
When a BGP route has multiple extended-color communities, each with a valid SR Policy, the BGP process installs the route on the SR Policy giving preference to the color with the highest numerical value.
The granularity of AS behaviors can be applied at multiple levels, for example:
• At a service level—When traffic destined to all prefixes in a given service is associated to the same transport path type. All prefixes share the same color.
• At a destination/prefix level—When traffic destined to a prefix in a given service is associated to a specific transport path type. Each prefix could be assigned a different color.
• At a flow level—When flows destined to the same prefix are associated with different transport path types
AS behaviors apply regardless of the instantiation method of the SR policy, including:
• On-demand SR policy
• Manually provisioned SR policy
• PCE-initiated SR policy
See the
Verifying BGP VRF Information, on page 111
and
Verifying Forwarding (CEF) Table, on page 112
sections for sample output that shows AS implementation.
Color-Only Automated Steering
Color-only steering is a traffic steering mechanism where a policy is created with given color, regardless of the endpoint.
You can create an SR-TE policy for a specific color that uses a NULL end-point (0.0.0.0 for IPv4 NULL, and
::0 for IPv6 NULL end-point). This means that you can have a single policy that can steer traffic that is based on that color and a NULL endpoint for routes with a particular color extended community, but different destinations (next-hop).
Note Every SR-TE policy with a NULL end-point must have an explicit path-option. The policy cannot have a dynamic path-option (where the path is computed by the head-end or PCE) since there is no destination for the policy.
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Setting CO Flag
You can also specify a color-only (CO) flag in the color extended community for overlay routes. The CO flag allows the selection of an SR-policy with a matching color, regardless of endpoint Sub-address Family Identifier
(SAFI) (IPv4 or IPv6). See
Setting CO Flag, on page 157 .
Configure Color-Only Steering
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy P1
Router(config-sr-te-policy)# color 1 end-point ipv4 0.0.0.0
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy P2
Router(config-sr-te-policy)# color 2 end-point ipv6 ::0
Router# show running-configuration segment-routing traffic-eng policy P1 color 1 end-point ipv4 0.0.0.0
!
policy P2 color 2 end-point ipv6 ::
!
!
!
end
Setting CO Flag
The BGP-based steering mechanism matches BGP color and next-hop with that of an SR-TE policy. If the policy does not exist, BGP requests SR-PCE to create an SR-TE policy with the associated color, end-point, and explicit paths. For color-only steering (NULL end-point), you can configure a color-only (CO) flag as part of the color extended community in BGP.
Note See
Color-Only Automated Steering, on page 156
for information about color-only steering (NULL end-point).
The behavior of the steering mechanism is based on the following values of the CO flags: co-flag 00 1.
The BGP next-hop and color <N, C> is matched with an SR-TE policy of same
<N, C>.
2.
If a policy does not exist, then IGP path for the next-hop N is chosen.
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Address-Family Agnostic Automated Steering co-flag 01 1.
The BGP next-hop and color <N, C> is matched with an SR-TE policy of same
<N, C>.
2.
If a policy does not exist, then an SR-TE policy with NULL end-point with the same address-family as N and color C is chosen.
3.
If a policy with NULL end-point with same address-family as N does not exist, then an SR-TE policy with any NULL end-point and color C is chosen.
4.
If no match is found, then IGP path for the next-hop N is chosen.
Configuration Example
Router(config)# extcommunity-set opaque overlay-color
Router(config-ext)# 1 co-flag 01
Router(config-ext)# end-set
Router(config)#
Router(config)# route-policy color
Router(config-rpl)# if destination in (5.5.5.1/32) then
Router(config-rpl-if)# set extcommunity color overlay-color
Router(config-rpl-if)# endif
Router(config-rpl)# pass
Router(config-rpl)# end-policy
Router(config)#
Address-Family Agnostic Automated Steering
Address-family agnostic steering uses an SR-TE policy to steer both labeled and unlabeled IPv4 and IPv6 traffic. This feature requires support of IPv6 encapsulation (IPv6 caps) over IPV4 endpoint policy.
IPv6 caps for IPv4 NULL end-point is enabled automatically when the policy is created in Segment Routing
Path Computation Element (SR-PCE). The binding SID (BSID) state notification for each policy contains an
"ipv6_caps" flag that notifies SR-PCE clients (PCC) of the status of IPv6 caps (enabled or disabled).
An SR-TE policy with a given color and IPv4 NULL end-point could have more than one candidate path. If any of the candidate paths has IPv6 caps enabled, then all of the remaining candidate paths need IPv6 caps enabled. If IPv6 caps is not enabled on all candidate paths of same color and end-point, traffic drops can occur.
You can disable IPv6 caps for a particular color and IPv4 NULL end-point using the ipv6 disable command on the local policy. This command disables IPv6 caps on all candidate paths that share the same color and
IPv4 NULL end-point.
Disable IPv6 Encapsulation
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy P1
Router(config-sr-te-policy)# color 1 end-point ipv4 0.0.0.0
Router(config-sr-te-policy)# ipv6 disable
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Per-Flow Automated Steering
Per-Flow Automated Steering
The steering of traffic through a Segment Routing (SR) policy is based on the candidate paths of that policy.
For a given policy, a candidate path specifies the path to be used to steer traffic to the policy’s destination.
The policy determines which candidate path to use based on the candidate path’s preference and state. The candidate path that is valid and has the highest preference is used to steer all traffic using the given policy.
This type of policy is called a Per-Destination Policy (PDP).
Per-Flow Automated Traffic Steering using SR-TE Policies introduces a way to steer traffic on an SR policy based on the attributes of the incoming packets, called a Per-Flow Policy (PFP).
A PFP provides up to 8 "ways" or options to the endpoint. With a PFP, packets are classified by a classification policy and marked using internal tags called forward classes (FCs). The FC setting of the packet selects the
“way”. For example, this “way” can be a traffic-engineered SR path, using a low-delay path to the endpoint.
The FC is represented as a numeral with a value of 0 to 7.
A PFP defines an array of FC-to-PDP mappings. A PFP can then be used to steer traffic into a given PDP based on the FC assigned to a packet.
As with PDPs, PFPs are identified by a {headend, color, endpoint} tuple. The color associated with a given
FC corresponds to a valid PDP policy of that color and same endpoint as the parent PFP. So PFP policies contain mappings of different FCs to valid PDP policies of different colors. Every PFP has an FC designated as its default FC. The default FC is associated to packets with a FC undefined under the PFP or for packets with a FC with no valid PDP policy.
The following example shows a per-flow policy from Node1 to Node4:
Figure 4: PFP Example
• FC=0 -> shortest path to Node4
• IGP shortest path = 16004
• FC=1 -> Min-delay path to Node4
• SID list = {16002,16004}
The same on-demand instantiation behaviors of PDPs apply to PFPs. For example, an edge node automatically
(on demand) instantiates Per-Flow SR Policy paths to an endpoint by service route signaling. Automated
Steering steers the service route in the matching SR Policy.
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Figure 5: PFP with ODN Example
Like PDPs, PFPs have a binding SID (BSID). Existing SR-TE automated steering (AS) mechanisms for labeled traffic (via BSID) and unlabeled traffic (via BGP) onto a PFP is similar to that of a PDP. For example, a packet having the BSID of a PFP as the top label is steered onto that PFP. The classification policy on the ingress interface marks the packet with an FC based on the configured class-map. The packet is then steered to the PDP that corresponds to that FC.
Usage Guidelines and Limitations
The following guidelines and limitations apply to the platform when acting as a head-end of a PFP policy:
• BGP IPv4 unicast over PFP (steered via ODN/AS) is supported
• BGP IPv6 unicast (with IPv4 next-hop [6PE]) over PFP (steered via ODN/AS) is supported
• BGP IPv6 unicast (with IPv6 next-hop) over PFP (steered via ODN/AS) is supported
• BGP VPNv4 over PFP is not supported
• BGP VPNv6 (6VPE) over PFP is not supported
• BGP EVPN over PFP is not supported
• Pseudowire and VPLS over PFP are not supported
• BGP multipath is not supported
• BGP PIC is not supported
• Labeled traffic (Binding SID) steered over PFP is not supported
• When not explicitly configured, FC 0 is the default FC.
• A PFP is considered valid as long as its default FC has a valid PDP.
• An ingress QoS policy applied to an input interface is used to classify flows and set corresponding forward-class (FC) values.
• The following counters are supported:
• PFP’s BSID counter (packet, bytes)
• Per-FC counters (packet, byte)
• Collected from the PDP’s segment-list-per-path egress counters
• If an SR policy is used for more than one purpose (as a regular policy as well as a PDP under one or more PFPs), then the collected counters will represent the aggregate of all contributions.
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Per-Flow Automated Steering
To preserve independent counters, it is recommended that an SR policy be used only for one purpose.
• Inbound packet classification, based on the following fields, is supported:
• IP precedence
• IP DSCP
• L3 ACL-based (L3 source/destination IP; L4 source/destination port)
• A color associated with a PFP SR policy cannot be used by a non-PFP SR policy. For example, if a per-flow ODN template for color 100 is configured, then the system will reject the configuration of any non-PFP SR policy using the same color. You must assign different color value ranges for PFP and non-PFP SR policies.
Configuring ODN Template for PFP Policies: Example
The following example depicts an ODN template for PFP policies that includes three FCs.
The example also includes the corresponding ODN templates for PDPs as follows:
• FC0 (default FC) mapped to color 10 = Min IGP path
• FC1 mapped to color 20 = Flex Algo 128 path
• FC2 mapped to color 30 = Flex Algo 129 path segment-routing traffic-eng on-demand color 10 dynamic metric type igp
!
!
!
on-demand color 20
!
!
dynamic sid-algorithm 128 on-demand color 30 dynamic
!
sid-algorithm 129
!
on-demand color 1000 per-flow forward-class 0 color 10 forward-class 1 color 20 forward-class 2 color 30
Manually Configuring a PFP and PDPs: Example
The following example depicts a manually defined PFP that includes three FCs and corresponding manually defined PDPs.
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The example also includes the corresponding PDPs as follows:
• FC0 (default FC) mapped to color 10 = Min IGP path
• FC1 mapped to color 20 = Min TE path
• FC2 mapped to color 30 = Min delay path segment-routing traffic-eng policy MyPerFlow color 1000 end-point ipv4 1.1.1.4
candidate-paths preference 100 per-flow forward-class 0 color 10 forward-class 1 color 20 forward-class 2 color 30
!
policy MyLowIGP color 10 end-point ipv4 1.1.1.4
!
candidate-paths preference 100 dynamic metric type igp policy MyLowTE color 20 end-point ipv4 1.1.1.4
candidate-paths preference 100 dynamic metric type te
!
policy MyLowDelay color 30 end-point ipv4 1.1.1.4
candidate-paths preference 100 dynamic metric type delay
Configuring Ingress Classification: Example
An MQC QoS policy is used to classify and mark traffic to a corresponding fowarding class.
The following shows an example of such ingress classification policy: class-map match-any MinDelay match dscp 46 end-class-map
!
class-map match-any PremiumHosts match access-group ipv4 PrioHosts end-class-map
!
!
policy-map MyPerFlowClassificationPolicy class MinDelay set forward-class 2
!
class PremiumHosts set forward-class 1
!
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Using Binding Segments class class-default
!
end-policy-map
!
interface GigabitEthernet0/0/0/0 description PE_Ingress_Interface
!
service-policy input MyPerFlowClassificationPolicy
Determining Per-Flow Policy State
A PFP is brought down for the following reasons:
• The PDP associated with the default FC is in a down state.
• All FCs are associated with PDPs in a down state.
• The FC assigned as the default FC is missing in the forward class mapping.
Scenario 1—FC 0 (default FC) is not configured in the FC mappings below: policy foo color 1 end-point ipv4 1.1.1.1
per-flow forward-class 1 color 10 forward-class 2 color 20
Scenario 2—FC 1 is configured as the default FC, however it is not present in the FC mappings: policy foo color 1 end-point ipv4 1.1.1.1
per-flow forward-class 0 color 10 forward-class 2 color 20 forward-class default 1
Using Binding Segments
The binding segment is a local segment identifying an SR-TE policy. Each SR-TE policy is associated with a binding segment ID (BSID). The BSID is a local label that is automatically allocated for each SR-TE policy when the SR-TE policy is instantiated.
Note In Cisco IOS XR 6.3.2 and later releases, you can specify an explicit BSID for an SR-TE policy. See the following Explicit Binding SID section.
BSID can be used to steer traffic into the SR-TE policy and across domain borders, creating seamless end-to-end inter-domain SR-TE policies. Each domain controls its local SR-TE policies; local SR-TE policies can be validated and rerouted if needed, independent from the remote domain’s head-end. Using binding segments isolates the head-end from topology changes in the remote domain.
Packets received with a BSID as top label are steered into the SR-TE policy associated with the BSID. When the BSID label is popped, the SR-TE policy’s SID list is pushed.
BSID can be used in the following cases:
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• Multi-Domain (inter-domain, inter-autonomous system)—BSIDs can be used to steer traffic across domain borders, creating seamless end-to-end inter-domain SR-TE policies.
• Large-Scale within a single domain—The head-end can use hierarchical SR-TE policies by nesting the end-to-end (edge-to-edge) SR-TE policy within another layer of SR-TE policies
(aggregation-to-aggregation). The SR-TE policies are nested within another layer of policies using the
BSIDs, resulting in seamless end-to-end SR-TE policies.
• Label stack compression—If the label-stack size required for an SR-TE policy exceeds the platform capability, the SR-TE policy can be seamlessly stitched to, or nested within, other SR-TE policies using a binding segment.
Explicit Binding SID
Use the binding-sid mpls label command in SR-TE policy configuration mode to specify the explicit BSID.
Explicit BSIDs are allocated from the segment routing local block (SRLB) or the dynamic range of labels. A best-effort is made to request and obtain the BSID for the SR-TE policy. If requested BSID is not available
(if it does not fall within the available SRLB or is already used by another application or SR-TE policy), the policy stays down.
Use the binding-sid explicit { fallback-dynamic | enforce-srlb } command to specify how the BSID allocation behaves if the BSID value is not available.
• Fallback to dynamic allocation – If the BSID is not available, the BSID is allocated dynamically and the policy comes up:
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# binding-sid explicit fallback-dynamic
• Strict SRLB enforcement – If the BSID is not within the SRLB, the policy stays down:
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# binding-sid explicit enforce-srlb
This example shows how to configure an SR policy to use an explicit BSID of 1000. If the BSID is not available, the BSID is allocated dynamically and the policy comes up.
segment-routing traffic-eng binding-sid explicit fallback-dynamic
!
!
policy goo binding-sid mpls 1000
!
Stitching SR-TE Polices Using Binding SID: Example
In this example, three SR-TE policies are stitched together to form a seamless end-to-end path from node 1 to node 10. The path is a chain of SR-TE policies stitched together using the binding-SIDs of intermediate policies, providing a seamless end-to-end path.
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Figure 6: Stitching SR-TE Polices Using Binding SID
Stitching SR-TE Polices Using Binding SID: Example
5
6
Table 8: Router IP Address
Router
3
4
9
10
Prefix Address
Loopback0 - 1.1.1.3
Loopback0 - 1.1.1.4
Link node 4 to node 6 - 10.4.6.4
Loopback0 - 1.1.1.5
Loopback0 - 1.1.1.6
Link node 4 to node 6 - 10.4.6.6
Loopback0 - 1.1.1.9
Loopback0 - 1.1.1.10
Prefix SID/Adj-SID
Prefix SID - 16003
Prefix SID - 16004
Adjacency SID - dynamic
Prefix SID - 16005
Prefix SID - 16006
Adjacency SID - dynamic
Prefix SID - 16009
Prefix SID - 16010
Step 1 On node 5, do the following: a) Define an SR-TE policy with an explicit path configured using the loopback interface IP addresses of node 9 and node 10.
b) Define an explicit binding-SID ( mpls label 15888 ) allocated from SRLB for the SR-TE policy.
Example:
Node 5 segment-routing traffic-eng segment-list PATH-9_10 index 10 address ipv4 1.1.1.9
!
index 20 address ipv4 1.1.1.10
policy foo binding-sid mpls 15888 color 777 end-point ipv4 1.1.1.10
candidate-paths preference 100 explicit segment-list PATH5-9_10
!
!
!
!
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Step 2
!
!
RP/0/RSP0/CPU0:Node-5# show segment-routing traffic-eng policy color 777
SR-TE policy database
---------------------
Color: 777, End-point: 1.1.1.10
Name: srte_c_777_ep_1.1.1.10
Status:
Admin: up Operational: up for 00:00:52 (since Aug 19 07:40:12.662)
Candidate-paths:
Preference: 100 (configuration) (active)
Name: foo
Requested BSID: 15888
PCC info:
Symbolic name: cfg_foo_discr_100
PLSP-ID: 70
Explicit: segment-list PATH-9_10 (valid)
Weight: 1, Metric Type: TE
16009 [Prefix-SID, 1.1.1.9]
16010 [Prefix-SID, 1.1.1.10]
Attributes:
Binding SID: 15888 (SRLB)
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
On node 3, do the following: a) Define an SR-TE policy with an explicit path configured using the following:
• Loopback interface IP address of node 4
• Interface IP address of link between node 4 and node 6
• Loopback interface IP address of node 5
• Binding-SID of the SR-TE policy defined in Step 1 ( mpls label 15888 )
Note This last segment allows the stitching of these policies.
b) Define an explicit binding-SID ( mpls label 15900 ) allocated from SRLB for the SR-TE policy.
Example:
Node 3 segment-routing traffic-eng segment-list PATH-4_4-6_5_BSID index 10 address ipv4 1.1.1.4
index 20 address ipv4 10.4.6.6
index 30 address ipv4 1.1.1.5
index 40 mpls label 15888
!
policy baa binding-sid mpls 15900 color 777 end-point ipv4 1.1.1.5
candidate-paths preference 100 explicit segment-list PATH-4_4-6_5_BSID
!
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!
!
!
!
!
RP/0/RSP0/CPU0:Node-3# show segment-routing traffic-eng policy color 777
SR-TE policy database
---------------------
Color: 777, End-point: 1.1.1.5
Name: srte_c_777_ep_1.1.1.5
Status:
Admin: up Operational: up for 00:00:32 (since Aug 19 07:40:32.662)
Candidate-paths:
Preference: 100 (configuration) (active)
Name: baa
Requested BSID: 15900
PCC info:
Symbolic name: cfg_baa_discr_100
PLSP-ID: 70
Explicit: segment-list PATH-4_4-6_5_BSID (valid)
Weight: 1, Metric Type: TE
16004 [Prefix-SID, 1.1.1.4]
80005 [Adjacency-SID, 10.4.6.4 - 10.4.6.6]
16005 [Prefix-SID, 1.1.1.5]
15888
Attributes:
Binding SID: 15900 (SRLB)
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Step 3 On node 1, define an SR-TE policy with an explicit path configured using the loopback interface IP address of node 3 and the binding-SID of the SR-TE policy defined in step 2 ( mpls label 15900 ). This last segment allows the stitching of these policies.
Example:
Node 1 segment-routing traffic-eng segment-list PATH-3_BSID index 10 address ipv4 1.1.1.3
index 20 mpls label 15900
!
policy bar
!
!
!
color 777 end-point ipv4 1.1.1.3
candidate-paths
!
!
preference 100 explicit segment-list PATH-3_BSID
!
RP/0/RSP0/CPU0:Node-1# show segment-routing traffic-eng policy color 777
SR-TE policy database
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L2VPN Preferred Path
---------------------
Color: 777, End-point: 1.1.1.3
Name: srte_c_777_ep_1.1.1.3
Status:
Admin: up Operational: up for 00:00:12 (since Aug 19 07:40:52.662)
Candidate-paths:
Preference: 100 (configuration) (active)
Name: bar
Requested BSID: dynamic
PCC info:
Symbolic name: cfg_bar_discr_100
PLSP-ID: 70
Explicit: segment-list PATH-3_BSID (valid)
Weight: 1, Metric Type: TE
16003 [Prefix-SID, 1.1.1.3]
15900
Attributes:
Binding SID: 80021
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
L2VPN Preferred Path
EVPN VPWS Preferred Path over SR-TE Policy feature allows you to set the preferred path between the two end-points for EVPN VPWS pseudowire (PW) using SR-TE policy.
L2VPN VPLS or VPWS Preferred Path over SR-TE Policy feature allows you to set the preferred path between the two end-points for L2VPN Virtual Private LAN Service (VPLS) or Virtual Private Wire Service (VPWS) using SR-TE policy.
Refer to the EVPN VPWS Preferred Path over SR-TE Policy and L2VPN VPLS or VPWS Preferred Path over SR-TE Policy sections in the "L2VPN Services over Segment Routing for Traffic Engineering Policy" chapter of the L2VPN and Ethernet Services Configuration Guide .
Static Route over Segment Routing Policy
This feature allows you to specify a Segment Routing (SR) policy as an interface type when configuring static routes for MPLS data planes.
For information on configuring static routes, see the "Implementing Static Routes" chapter in the Routing
Configuration Guide for Cisco NCS 5500 Series Routers .
Configuration Example
The following example depicts a configuration of a static route for an IPv4 destination over an SR policy according to following parameters:
• Target SR policy:
• Color = 200
• End-point = 1.1.1.4
• Auto-generated SR policy name = srte_c_200_ep_1.1.1.4
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Static Route over Segment Routing Policy
Note Use the auto-generated SR-TE policy name to attach the SR policy to the static route. Auto-generated SR policy names use the following naming convention:
srte_c_color_val_ep_endpoint-address .
Use the show segment-routing traffic-eng policy color <color_val> endpoint ipv4
<ip_addr> command to display the auto-generated policy name.
• Admin distance = 40
• Load metric = 150
• Install the route in RIB regardless of reachability
Router(config)# router static
Router(config-static)# address-family ipv4 unicast
Router(config-static-afi)# 1.1.1.4/32 sr-policy srte_c_200_ep_1.1.1.4 40 permanent metric
150
Running Configuration router static
!
address-family ipv4 unicast
1.1.1.4/32 sr-policy srte_c_200_ep_1.1.1.4 40 permanent metric 150
!
Verification
RP/0/RP0/CPU0:RTR-1# show run segment-routing traffic-eng policy sample-policy-foo
Tue Feb 16 17:40:16.759 PST segment-routing traffic-eng policy sample-policy-foo color 200 end-point ipv4 1.1.1.4
candidate-paths preference 100 dynamic metric type te
!
!
!
!
!
!
!
RP/0/RP0/CPU0:RTR-1# show segment-routing traffic-eng policy color 200 endpoint ipv4 1.1.1.4
Tue Feb 16 17:17:45.724 PST
SR-TE policy database
---------------------
Color: 200, End-point: 1.1.1.4
Name: srte_c_200_ep_1.1.1.4
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Status:
Admin: up Operational: up for 5d04h (since Feb 11 12:22:59.054)
Candidate-paths:
Preference: 100 (configuration) (active)
Name: sample-policy-foo
Requested BSID: dynamic
Protection Type: protected-preferred
Maximum SID Depth: 10
Dynamic (valid)
Metric Type: TE, Path Accumulated Metric: 14
16005 [Prefix-SID, 1.1.1.5]
16004 [Prefix-SID, 1.1.1.4]
Attributes:
Binding SID: 24014
Forward Class: Not Configured
Steering labeled-services disabled: no
Steering BGP disabled: no
IPv6 caps enable: yes
Invalidation drop enabled: no
RP/0/RP0/CPU0:RTR-1# show static sr-policy srte_c_200_ep_1.1.1.4
Tue Feb 16 17:50:19.932 PST
Paths
1.1.1.4/32
Interface VRF State srte_c_200_ep_1.1.1.4
default Up
Reference Count(in path with both intf<-->NH):0
Last IM notification was Up at Feb 16 17:09:08.325
Global ifh
IM state
RSI registration
Table IDs
: 0x0000007c
: up
: Yes
: 0xe0000000
Address Info:
1.1.1.1/32
Route tag: 0x00000000 Flags: 0x00000000 Prefix SID: False [Active]
IP-STATIC-IDB-CLASS
Total entries : 1
Interface
| Event Name
| idb-create
: sr-srte_c_200_ep_1.1.1.4
| Time Stamp | S, M
| Feb 16 17:09:08.352
| 0, 0
RP/0/RP0/CPU0:RTR-1# show route 1.1.1.4/32
Tue Feb 16 17:09:21.164 PST
Routing entry for 1.1.1.4/32
Known via "static", distance 40, metric 0 (connected)
Installed Feb 16 17:09:08.325 for 00:00:13
Routing Descriptor Blocks directly connected, via srte_c_200_ep_1.1.1.4
, permanent
Route metric is 0, Wt is 150
No advertising protos.
RP/0/RP0/CPU0:RTR-1# show route 1.1.1.4/32 detail
Tue Feb 16 17:09:36.718 PST
Routing entry for 1.1.1.4/32
Known via "static", distance 40, metric 0 (connected)
Installed Feb 16 17:09:08.325 for 00:00:28
Routing Descriptor Blocks directly connected, via srte_c_200_ep_1.1.1.4
, permanent
Route metric is 0, Wt is 150
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Label: None
Tunnel ID: None
Binding Label: None
Extended communities count: 0
NHID:0x0(Ref:0)
Route version is 0x4a (74)
Local Label: 0x3e84 (16004)
IP Precedence: Not Set
QoS Group ID: Not Set
Flow-tag: Not Set
Fwd-class: Not Set
Route Priority: RIB_PRIORITY_RECURSIVE (9) SVD Type RIB_SVD_TYPE_LOCAL
Download Priority 3, Download Version 258
No advertising protos.
RP/0/RP0/CPU0:RTR-1# show cef 1.1.1.4/32 detail
Tue Feb 16 17:10:06.956 PST
1.1.1.4/32, version 258, attached, internal 0x1000441 0x30 (ptr 0xd3f0d30) [1], 0x0
(0xe46f960), 0xa20 (0xe9694e0)
Updated Feb 16 17:09:08.328
Prefix Len 32, traffic index 0, precedence n/a, priority 3 gateway array (0xe2d9a08) reference count 2, flags 0x8068, source rib (7), 0 backups
[3 type 4 flags 0x108401 (0xe9aeb98) ext 0x0 (0x0)]
LW-LDI[type=1, refc=1, ptr=0xe46f960, sh-ldi=0xe9aeb98] gateway array update type-time 1 Feb 16 17:07:59.946
LDI Update time Feb 16 17:07:59.946
LW-LDI-TS Feb 16 17:07:59.946
via srte_c_200_ep_1.1.1.4, 5 dependencies, weight 0, class 0 [flags 0xc] path-idx 0 NHID 0x0 [0xf3b1a30 0x0] local adjacency local label 16004 labels imposed {None}
Load distribution: 0 (refcount 3)
Hash OK Interface
0 Y srte_c_200_ep_1.1.1.4
Address point2point
RP/0/RP0/CPU0:RTR-1# show mpls forwarding labels 16004 detail
Tue Feb 16 17:27:59.831 PST
Local
Label
Outgoing
Label
Prefix or ID
Outgoing
Interface
Next Hop Bytes
Switched
------ ----------- ------------------ ------------ --------------- ------------
16004 Unlabelled SR Pfx (idx 4) srte_c_200_e point2point 990
Updated: Feb 16 17:07:59.945
Path Flags: 0xc [ ]
Version: 258, Priority: 3
Label Stack (Top -> Bottom): { Unlabelled Unlabelled }
NHID: 0x0, Encap-ID: N/A, Path idx: 0, Backup path idx: 0, Weight: 0
MAC/Encaps: 0/0, MTU: 0
Outgoing Interface: srte_c_200_ep_1.1.1.4
(ifhandle 0x0000007c)
Packets Switched: 20
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Miscellaneous
Miscellaneous
LDP over Segment Routing Policy
The LDP over Segment Routing Policy feature enables an LDP-targeted adjacency over a Segment Routing
(SR) policy between two routers. This feature extends the existing MPLS LDP address family neighbor configuration to specify an SR policy as the targeted end-point.
LDP over SR policy is supported for locally configured SR policies with IPv4 end-points.
For more information about MPLS LDP, see the "Implementing MPLS Label Distribution Protocol" chapter in the MPLS Configuration Guide .
For more information about Autoroute, see the Autoroute Announce for SR-TE section.
Note Before you configure an LDP targeted adjacency over SR policy name, you need to create the SR policy under
Segment Routing configuration. The SR policy interface names are created internally based on the color and endpoint of the policy. LDP is non-operational if SR policy name is unknown.
The following functionality applies:
1.
Configure the SR policy – LDP receives the associated end-point address from the interface manager (IM) and stores it in the LDP interface database (IDB) for the configured SR policy.
2.
Configure the SR policy name under LDP – LDP retrieves the stored end-point address from the IDB and uses it. Use the auto-generated SR policy name assigned by the router when creating an LDP targeted adjacency over an SR policy. Auto-generated SR policy names use the following naming convention:
srte_c_color_val_ep_endpoint-address . For example, srte_c_1000_ep_1.1.1.2
Configuration Example
/* Enter the SR-TE configuration mode and create the SR policy. This example corresponds to a local SR policy with an explicit path. */
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list sample-sid-list
Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.7
Router(config-sr-te-sl)# index 20 address ipv4 1.1.1.2
Router(config-sr-te-sl)# exit
Router(config-sr-te)# policy sample_policy
Router(config-sr-te-policy)# color 1000 end-point ipv4 1.1.1.2
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# explicit segment-list sample-sid-list
Router(config-sr-te-pp-info)# end
/* Configure LDP over an SR policy */
Router(config)# mpls ldp
Router(config-ldp)# address-family ipv4
Router(config-ldp-af)# neighbor sr-policy srte_c_1000_ep_1.1.1.2 targeted
Router(config-ldp-af)#
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LDP over Segment Routing Policy
Note Do one of the following to configure LDP discovery for targeted hellos:
• Active targeted hellos (SR policy head end): mpls ldp interface GigabitEthernet0/0/0/0
!
!
• Passive targeted hellos (SR policy end-point): mpls ldp address-family ipv4 discovery targeted-hello accept
!
!
Running Configuration segment-routing traffic-eng segment-list sample-sid-list index 10 address ipv4 1.1.1.7
index 20 address ipv4 1.1.1.2
!
policy sample_policy
!
!
color 1000 end-point ipv4 1.1.1.2
candidate-paths preference 100
!
!
!
explicit segment-list sample-sid-list
!
mpls ldp address-family ipv4 neighbor sr-policy srte_c_1000_ep_1.1.1.2 targeted discovery targeted-hello accept
!
!
Verification
Router# show mpls ldp interface brief
Interface VRF Name Config Enabled IGP-Auto-Cfg TE-Mesh-Grp cfg
--------------- ------------------- ------ ------- ------------ ---------------
Te0/3/0/0/3 default Y Y 0 N/A
Te0/3/0/0/6
Te0/3/0/0/7
Te0/3/0/0/8
Te0/3/0/0/9 srte_c_1000_ default default default default default
Y
Y
N
N
Y
Y
Y
N
N
Y
0
0
0
0
0
N/A
N/A
N/A
N/A
N/A
Router# show mpls ldp interface
Interface TenGigE0/3/0/0/3 (0xa000340)
VRF: 'default' (0x60000000)
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Enabled via config: LDP interface
Interface TenGigE0/3/0/0/6 (0xa000400)
VRF: 'default' (0x60000000)
Enabled via config: LDP interface
Interface TenGigE0/3/0/0/7 (0xa000440)
VRF: 'default' (0x60000000)
Enabled via config: LDP interface
Interface TenGigE0/3/0/0/8 (0xa000480)
VRF: 'default' (0x60000000)
Disabled:
Interface TenGigE0/3/0/0/9 (0xa0004c0)
VRF: 'default' (0x60000000)
Disabled:
Interface srte_c_1000_ep_1.1.1.2 (0x520)
VRF: 'default' (0x60000000)
Enabled via config: LDP interface
Router# show segment-routing traffic-eng policy color 1000
SR-TE policy database
---------------------
Color: 1000, End-point: 1.1.1.2
Name: srte_c_1000_ep_1.1.1.2
Status:
Admin: up Operational: up for 00:02:00 (since Jul 2 22:39:06.663)
Candidate-paths:
Preference: 100 (configuration) (active)
Name: sample_policy
Requested BSID: dynamic
PCC info:
Symbolic name: cfg_sample_policy_discr_100
PLSP-ID: 17
Explicit: segment-list sample-sid-list (valid)
Weight: 1, Metric Type: TE
16007 [Prefix-SID, 1.1.1.7]
16002 [Prefix-SID, 1.1.1.2]
Attributes:
Binding SID: 80011
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: yes
Router# show mpls ldp neighbor 1.1.1.2 detail
Peer LDP Identifier: 1.1.1.2:0
TCP connection: 1.1.1.2:646 - 1.1.1.6:57473
Graceful Restart: No
Session Holdtime: 180 sec
State: Oper; Msgs sent/rcvd: 421/423; Downstream-Unsolicited
Up time: 05:22:02
LDP Discovery Sources:
IPv4: (1)
Targeted Hello (1.1.1.6 -> 1.1.1.2, active/passive)
IPv6: (0)
Addresses bound to this peer:
IPv4: (9)
1.1.1.2
10.2.4.2
2.2.2.99
10.2.22.2
10.1.2.2
10.2.222.2
10.2.3.2
10.30.110.132
11.2.9.2
IPv6: (0)
Peer holdtime: 180 sec; KA interval: 60 sec; Peer state: Estab
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SR-TE MPLS Label Imposition Enhancement
NSR: Disabled
Clients: LDP over SR Policy
Capabilities:
Sent:
0x508 (MP: Point-to-Multipoint (P2MP))
0x509 (MP: Multipoint-to-Multipoint (MP2MP))
0x50a (MP: Make-Before-Break (MBB))
0x50b (Typed Wildcard FEC)
Received:
0x508 (MP: Point-to-Multipoint (P2MP))
0x509 (MP: Multipoint-to-Multipoint (MP2MP))
0x50a (MP: Make-Before-Break (MBB))
0x50b (Typed Wildcard FEC)
SR-TE MPLS Label Imposition Enhancement
The SR-TE MPLS Label Imposition Enhancement feature increases the maximum label imposition capabilities of the platform.
In previous releases, the platform supported:
• Up to 5 MPLS transport labels when no MPLS service labels are imposed
• Up to 3 MPLS transport labels when MPLS service labels are imposed
With the SR-TE MPLS Label Imposition Enhancement feature, the platform supports the following:
• Up to 12 MPLS transport labels when no MPLS service labels are imposed
• Up to 9 MPLS transport labels when MPLS service labels are imposed
This enhancement is enabled and disabled dynamically, as the label count changes. For example, if a path requires only 3 MPLS transport labels, the MPLS Label Imposition Enhancement feature is not enabled.
You can disable labeled services for SR-TE policies. The label switching database (LSD) needs to know if labeled services are disabled on top of an SR-TE policy to perform proper label stack splitting.
Disable Labeled Services per Local Policy
Use the labeled-services disable command to disable steering for labeled services for a configured policy.
This configuration applies per policy.
segment-routing traffic-eng policy policy name steering labeled-services disable
Disable Labeled Services per ODN color
Use the labeled-services disable command to disable steering of labeled-services for on-demand color policies.
This configuration applies for a specific ODN color.
segment-routing traffic-eng on-demand color color steering labeled-services disable
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Disable Labeled Services per Policy Type
Use the labeled-services disable command to disable steering of labeled services for all policies for the following policy types:
• all — all policies
• local — all locally configured policies
• on-demand — all BGP on-demand color policies
• bgp-srte — all controller-initiated BGP SR-TE policies
• pcep — all PCE-initiated policies
Note You can specify more than one policy type.
segment-routing traffic-eng steering labeled-services disable { all | local | on-demand | bgp-srte | pcep }
Verification
Use the show segment-routing traffic-eng policy command to display SR policy information. The following output shows that steering of labeled services for the on-demand SR policy are disabled.
Router# show segment-routing traffic-eng policy color 10
Thu Jul 18 11:35:25.124 PDT
SR-TE policy database
---------------------
Color: 10, End-point: 1.1.1.8
Name: srte_c_10_ep_1.1.1.8
Status:
Admin: up Operational: up for 00:00:06 (since Jul 18 11:35:19.350)
Candidate-paths:
Preference: 1 (configuration) (active)
Name: test_pol_2
Requested BSID: dynamic
Dynamic (valid)
Metric Type: TE, Path Accumulated Metric: 10
24004 [Adjacency-SID, 1.1.1.1 - 1.1.1.2]
Attributes:
Binding SID: 24011
Forward Class: 0
Steering labeled-services disabled: yes
Steering BGP disabled: no
IPv6 caps enable: yes
SR-TE Head-End IPv4 Unnumbered Interface Support
This feature allows IPv4 unnumbered interfaces to be part of an SR-TE head-end router topology database.
An unnumbered IPv4 interface is not identified by its own unique IPv4 address. Instead, it is identified by the router ID of the node where this interfaces resides and the local SNMP index assigned for this interface.
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SR-TE Head-End IPv4 Unnumbered Interface Support
This feature provides enhancements to the following components:
• IGPs (IS-IS and OSPF):
• Support the IPv4 unnumbered interfaces in the SR-TE context by flooding the necessary interface information in the topology
• SR-PCE:
Note SR-PCE and path computation clients (PCCs) need to be running Cisco IOS XR
7.0.2 or later.
• Compute and return paths from a topology containing IPv4 unnumbered interfaces.
• Process reported SR policies from a head-end router that contain hops with IPv4 unnumbered adjacencies.
PCEP extensions for IPv4 unnumbered interfaces adhere to IETF RFC8664 “PCEP Extensions for
Segment Routing” ( https://datatracker.ietf.org/doc/rfc8664/ ). The unnumbered hops use a Node or
Adjacency Identifier (NAI) of type 5. This indicates that the segment in the explicit routing object
(ERO) is an unnumbered adjacency with an IPv4 ID and an interface index.
• SR-TE process at the head-end router:
• Compute its own local path over a topology, including unnumbered interfaces.
• Process PCE-computed paths that contain hops with IPv4 unnumbered interfaces.
• Report a path that contains hops with IPv4 unnumbered interfaces to the PCE.
Configuration Example
The following example shows how to configure an IPv4 unnumbered interface:
RP/0/0/CPU0:rtrA(config)# interface GigabitEthernet0/0/0/0
RP/0/0/CPU0:rtrA(config-if)# ipv4 point-to-point
RP/0/0/CPU0:rtrA(config-if)# ipv4 unnumbered Loopback0
To bring up the IPv4 unnumbered adjacency under the IGP, configure the link as point-to-point under the
IGP configuration. The following example shows how to configure the link as point-to-point under the IGP configuration:
RP/0/0/CPU0:rtrA(config)# router ospf one
RP/0/0/CPU0:rtrA(config-ospf)# area 0
RP/0/0/CPU0:rtrA(config-ospf-ar)# interface GigabitEthernet0/0/0/0
RP/0/0/CPU0:rtrA(config-ospf-ar-if)# network point-to-point
Verification
Use the show ipv4 interface command to display information about the interface:
RP/0/0/CPU0:rtrA# show ipv4 interface GigabitEthernet0/0/0/0 brief
Tue Apr 2 12:59:53.140 EDT
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Interface
GigabitEthernet0/0/0/0
IP-Address
192.168.0.1
RP/0/0/CPU0:rtrA# show snmp interface
Tue Apr 2 13:02:49.190 EDT ifName : Null0 ifName : Loopback0 ifIndex : 3 ifIndex : 10 ifName : GigabitEthernet0/0/0/0 ifIndex : 6
Status
Up
This interface shows the IPv4 address of Loopback0.
Use the show snmp interface command to find the SNMP index for this interface:
Protocol
Up
The interface is identified with the pair (IPv4:192.168.0.1, index:6).
Use the show ospf neighbor command to display the adjacency:
RP/0/0/CPU0:rtrA# show ospf neighbor gigabitEthernet 0/0/0/0 detail
…
Neighbor 192.168.0.4, interface address 192.168.0.4
In the area 0 via interface GigabitEthernet0/0/0/0
Neighbor priority is 1, State is FULL, 6 state changes
…
Adjacency SIDs:
Label: 24001, Dynamic, Unprotected
Neighbor Interface ID: 4
The output of the show segment-routing traffic-eng ipv4 topology command is enhanced to display the interface index instead of the IP address for unnumbered interfaces:
RP/0/0/CPU0:rtrA# show segment-routing traffic-eng ipv4 topology
…
Link[2]: Unnumbered local index 6, remote index 4
Local node:
OSPF router ID: 192.168.0.1 area ID: 0 ASN: 0
Remote node:
TE router ID: 192.168.0.4
OSPF router ID: 192.168.0.4 area ID: 0 ASN: 0
Metric: IGP 1, TE 1, Latency 1 microseconds
Bandwidth: Total 125000000 Bps, Reservable 0 Bps
Admin-groups: 0x00000000
Adj SID: 24001 (unprotected)
The output of the show segment-routing traffic-eng policy detail command includes unnumbered hops:
RP/0/0/CPU0:rtrA# show segment-routing traffic-eng policy detail
…
Dynamic (pce 192.168.0.5) (valid)
Metric Type: TE, Path Accumulated Metric: 3
24001 [Adjacency-SID, unnumbered 192.168.0.1(6) - 192.168.0.4(4)]
24002 [Adjacency-SID, unnumbered 192.168.0.4(7) - 192.168.0.3(7)]
24000 [Adjacency-SID, unnumbered 192.168.0.3(5) - 192.168.0.2(5)]
…
SR-TE Reoptimization Timers
SR-TE path re-optimization occurs when the head-end determines that there is a more optimal path available than the one currently used. For example, in case of a failure along the SR-TE LSP path, the head-end could detect and revert to a more optimal path by triggering re-optimization.
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SR-TE Reoptimization Timers
Re-optimization can occur due to the following events:
• The explicit path hops used by the primary SR-TE LSP explicit path are modified
• The head-end determines the currently used path-option are invalid due to either a topology path disconnect, or a missing SID in the SID database that is specified in the explicit-path
• A more favorable path-option (lower index) becomes available
For event-based re-optimization, you can specify various delay timers for path re-optimization. For example, you can specify how long to wait before switching to a reoptimized path
Additionally, you can configure a timer to specify how often to perform reoptimization of policies. You can also trigger an immediate reoptimization for a specific policy or for all policies.
SR-TE Reoptimization
To trigger an immediate SR-TE reoptimization, use the segment-routing traffic-eng reoptimization command in Exec mode:
Router# segment-routing traffic-eng reoptimization { all | name policy }
Use the all option to trigger an immediate reoptimization for all policies. Use the name policy option to trigger an immediate reoptimization for a specific policy.
Configuring SR-TE Reoptimization Timers
Use these commands in SR-TE configuration mode to configure SR-TE reoptimization timers:
• timers candidate-path cleanup-delay seconds —Specifies the delay before cleaning up candidate paths, in seconds. The range is from 0 (immediate clean-up) to 86400; the default value is 120
• timers cleanup-delay seconds —Specifies the delay before cleaning up previous path, in seconds. The range is from 0 (immediate clean-up) to 300; the default value is 10.
• timers init-verify-restart seconds —Specifies the delay for topology convergence after the topology starts populating due to a restart, in seconds. The range is from 10 to 10000; the default is 40.
• timers init-verify-startup seconds —Specifies the delay for topology convergence after topology starts populating for due to startup, in seconds. The range is from 10 to 10000; the default is 300
• timers init-verify-switchover seconds —Specifies the delay for topology convergence after topology starts populating due to a switchover, in seconds. The range is from 10 to 10000; the default is 60.
• timers install-delay seconds —Specifies the delay before switching to a reoptimized path, in seconds.
The range is from 0 (immediate installation of new path) to 300; the default is 10.
• timers periodic-reoptimization seconds —Specifies how often to perform periodic reoptimization of policies, in seconds. The range is from 0 to 86400; the default is 600.
Example Configuration
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# timers
Router(config-sr-te-timers)# candidate-path cleanup-delay 600
Router(config-sr-te-timers)# cleanup-delay 60
Router(config-sr-te-timers)# init-verify-restart 120
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Router(config-sr-te-timers)# init-verify-startup 600
Router(config-sr-te-timers)# init-verify-switchover 30
Router(config-sr-te-timers)# install-delay 60
Router(config-sr-te-timers)# periodic-reoptimization 3000
Running Config segment-routing traffic-eng timers install-delay 60 periodic-reoptimization 3000 cleanup-delay 60 candidate-path cleanup-delay 600 init-verify-restart 120 init-verify-startup 600
!
!
init-verify-switchover 30
!
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9
Segment Routing Tree Segment Identifier
Tree Segment Identifier (Tree-SID) is a tree-building solution that uses a Segment Routing Path Computation
Element (SR-PCE) using path computation element protocol (PCEP) to calculate the point-to-multipoint
(P2MP) tree using SR policies. Tree-SID uses a single MPLS label for building a multicast replication tree in an SR network. Tree-SID does not require multicast control protocols such as RSVP, mLDP, and PIM.
A P2MP SR policy provides an SR-based TE solution for transporting multicast traffic. It works on existing data-plane (MPLS and IP) and supports TE capabilities and single/multi routing domains. At each node of the tree, the forwarding state is represented by the same segment (using a global Tree-SID specified from the
SRLB range of labels). P2MP SR policy prevents transient loop and packet loss when updating the path of a
P2MP SR policy.
A P2MP SR policy request contains the following:
• Policy name
• SID for the P2MP Tree (Tree-SID)
• Address of the root node
• Addresses of the leaf nodes
• Optimization objectives (TE, IGP, delay metric)
• Constraints (affinity)
Tree SID Workflow Overview
This sections shows a basic workflow using a Tree SID policy:
1.
User creates a Tree-SID policy.
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2.
SR-PCE computes the P2MP Tree.
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Segment Routing Tree Segment Identifier
3.
SR-PCE instantiates the Tree-SID state at each node in the tree.
4.
The Root node encapsulates the multicast traffic, replicates it, and forwards it to the Transit nodes.
5.
The Transit nodes replicate the multicast traffic and forward it to the Leaf nodes.
6.
The Leaf nodes decapsulate the multicast traffic and forward it to the multicast receivers.
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Behaviors and Limitations
Segment Routing Tree Segment Identifier
•
Behaviors and Limitations, on page 184
•
•
Configure Segment Routing Tree-SID, on page 185
•
Behaviors and Limitations
PCE redundancy is not supported for Tree-SID. Tree-SID can only be controlled by a single PCE. Configure only one PCE on each PCC in the Tree-SID path.
Bud Node Support
In a multicast distribution tree, a Bud node is a node that acts as a leaf (egress) node as well as a mid-point
(transit) node toward the downstream sub-tree.
In the below multicast distribution tree topology with Root node {A} and Leaf nodes set {B, C, D}, node D is a Bud node. Similarly, if node E is later added to the Leaf set, it would also become a Bud node.
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The tree computation algorithm on SR-PCE has been enhanced to detect a Bud node based on knowledge of the Leaf set, and to handle Leaf/Transit node transitions to Bud node. The role of the Bud node is also explicitly signaled in PCEP.
Configure Segment Routing Tree-SID
To configure Segment Routing Tree-SID for Point-to-Multipoint (P2MP) SR policies, complete the following configurations:
1.
Configure Path Computation Element Protocol (PCEP) Path Computation Client (PCC) on all nodes involved in the Tree-SID path (root, mid-point, leaf)
2.
Configure Affinity Maps on the SR-PCE
3.
Configure P2MP SR Policy on SR-PCE
4.
Configure Multicast on the Root and Leaf Nodes
Configure PCEP PCC on All Nodes in Tree-SID Path
Configure all nodes involved in the Tree-SID path (root, mid-point, leaf) as PCEP PCC. For detailed PCEP
PCC configuration information, see
Configure the Head-End Router as PCEP PCC, on page 148
.
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Configure Affinity Maps on the SR-PCE
Use the affinity bit-map COLOR bit-position command in PCE SR-TE sub-mode to define affinity maps.
The bit-position range is from 0 to 255.
Router# configure
Router(config)# pce
Router(config-pce)# segment-routing traffic-eng
Router(config-pce-sr-te)# affinity bit-map RED 23
Router(config-pce-sr-te)# affinity bit-map BLUE 24
Router(config-pce-sr-te)# affinity bit-map CROSS 25
Router(config-pce-sr-te)#
Configure P2MP SR Policy on SR-PCE
Configure the end-point name and addresses, Tree-SID label, and constraints for the P2MP policy.
Use the endpoint-set NAME command in SR-PCE P2MP sub-mode to enter the name of the end-point set and to define the set of end-point addresses.
Router(config-pce-sr-te)# p2mp
Router(config-pce-sr-te-p2mp)# endpoint-set BAR
Router(config-pce-p2mp-ep-set)# ipv4 1.1.1.2
Router(config-pce-p2mp-ep-set)# ipv4 1.1.1.3
Router(config-pce-p2mp-ep-set)# ipv4 1.1.1.4
Router(config-pce-p2mp-ep-set)# exit
Router(config-pce-sr-te-p2mp)#
Use the policy policy command to configure the P2MP policy name and enter P2MP Policy sub-mode.
Configure the source address, endpoint-set color, Tree-SID label, affinity constraints, and metric type.
Router(config-pce-sr-te-p2mp)# policy FOO
Router(config-pce-p2mp-policy)# source ipv4 1.1.1.6
Router(config-pce-p2mp-policy)# color 10 endpoint-set BAR
Router(config-pce-p2mp-policy)# treesid mpls 15200
Router(config-pce-p2mp-policy)# candidate-paths
Router(config-pce-p2mp-policy-path)# constraints
Router(config-pce-p2mp-path-const)# affinity
Router(config-pce-p2mp-path-affinity)# exclude BLUE
Router(config-pce-p2mp-path-affinity)# exit
Router(config-pce-p2mp-path-const)# exit
Router(config-pce-p2mp-policy-path)# preference 100
Router(config-pce-p2mp-policy-path-preference)# dynamic
Router(config-pce-p2mp-path-info)# metric type te
Router(config-pce-p2mp-path-info)# root
Router(config)#
Configure Multicast on the Root and Leaf Nodes
On the root node of the SR P2MP segment, use the router pim command to enter Protocol Independent
Multicast (PIM) configuration mode to statically steer multicast flows into an SR P2MP policy.
Note Enter this configuration only on an SR P2MP segment. Multicast traffic cannot be steered into a P2P policy.
Router(config)# router pim
Router(config-pim)# vrf name
Router(config-pim-name)# address-family ipv4
Router(config-pim-name-ipv4)# sr-p2mp-policy FOO
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Running Config
Router(config-pim-name-ipv4-srp2mp)# static-group 235.1.1.5 1.1.1.6
Router(config-pim-name-ipv4-srp2mp)# root
Router(config)#
On the root and leaf nodes of the SR P2MP tree, use the mdt static segment-routing command to configure the multicast distribution tree (MDT) core as Tree-SID from the multicast VRF configuration submode.
Router(config)# multicast-routing
Router(config-mcast)# vrf TEST
Router(config-mcast-TEST)# address-family ipv4
Router(config-mcast-TEST-ipv4)# mdt static segment-routing
On the leaf nodes of an SR P2MP segment, use the static sr-policy p2mp-policy command to configure the static SR P2MP Policy from the multicast VRF configuration submode to statically decapsulate multicast flows.
Router(config)# multicast-routing
Router(config-mcast)# vrf TEST
Router(config-mcast-TEST)# address-family ipv4
Router(config-mcast-TEST-ipv4)# static sr-policy FOO
Running Config
The following example shows how to configure the end point addresses and P2MP SR policy with affinity constraints on SR-PCE.
pce segment-routing traffic-eng affinity bit-map
RED 23
BLUE 24
!
CROSS 25 p2mp endpoint-set BAR ipv4 1.1.1.2
!
ipv4 1.1.1.3
ipv4 1.1.1.4
policy FOO source ipv4 1.1.1.6
color 10 endpoint-set BAR treesid mpls 15200 candidate-paths preference 100 dynamic metric type te
!
!
!
constraints affinity exclude
!
BLUE
!
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Running Config
Segment Routing Tree Segment Identifier
!
!
!
!
!
!
!
The following example shows how to statically decapsulate multicast flows on the leaf nodes.
multicast-routing vrf TEST address-family ipv4 static sr-policy FOO
!
!
!
The following example shows to configure the multicast distribution tree (MDT) core as Tree-SID on the root and leaf nodes.
multicast-routing vrf TEST address-family ipv4
!
mdt static segment-routing
!
!
The following example shows how to steer traffic to the SR P2MP policy on the root node.
router pim vrf TEST address-family ipv4
!
!
sr-p2mp-policy FOO static-group 232.1.1.5 1.1.1.6
!
!
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Enabling Segment Routing Flexible Algorithm
Segment Routing Flexible Algorithm allows operators to customize IGP shortest path computation according to their own needs. An operator can assign custom SR prefix-SIDs to realize forwarding beyond link-cost-based
SPF. As a result, Flexible Algorithm provides a traffic engineered path automatically computed by the IGP to any destination reachable by the IGP.
The SR architecture associates prefix-SIDs to an algorithm which defines how the path is computed. Flexible
Algorithm allows for user-defined algorithms where the IGP computes paths based on a user-defined combination of metric type and constraint.
This document describes the IS-IS and OSPF extensions to support Segment Routing Flexible Algorithm on an MPLS data-plane.
•
Prerequisites for Flexible Algorithm, on page 189
•
Building Blocks of Segment Routing Flexible Algorithm, on page 189
•
Configuring Flexible Algorithm, on page 192
•
Example: Configuring IS-IS Flexible Algorithm, on page 193
•
Example: Configuring OSPF Flexible Algorithm, on page 194
•
Example: Traffic Steering to Flexible Algorithm Paths, on page 195
Prerequisites for Flexible Algorithm
Segment routing must be enabled on the router before the Flexible Algorithm functionality is activated.
Building Blocks of Segment Routing Flexible Algorithm
This section describes the building blocks that are required to support the SR Flexible Algorithm functionality in IS-IS and OSPF.
Flexible Algorithm Definition
Many possible constraints may be used to compute a path over a network. Some networks are deployed with multiple planes. A simple form of constraint may be to use a particular plane. A more sophisticated form of constraint can include some extended metric, like delay, as described in [RFC7810]. Even more advanced case could be to restrict the path and avoid links with certain affinities. Combinations of these are also possible.
To provide a maximum flexibility, the mapping between the algorithm value and its meaning can be defined
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Flexible Algorithm Membership by the user. When all the routers in the domain have the common understanding what the particular algorithm value represents, the computation for such algorithm is consistent and the traffic is not subject to looping.
Here, since the meaning of the algorithm is not defined by any standard, but is defined by the user, it is called a Flexible Algorithm.
Flexible Algorithm Membership
An algorithm defines how the best path is computed by IGP. Routers advertise the support for the algorithm as a node capability. Prefix-SIDs are also advertised with an algorithm value and are tightly coupled with the algorithm itself.
An algorithm is a one octet value. Values from 128 to 255 are reserved for user defined values and are used for Flexible Algorithm representation.
Flexible Algorithm Definition Advertisement
To guarantee the loop free forwarding for paths computed for a particular Flexible Algorithm, all routers in the network must share the same definition of the Flexible Algorithm. This is achieved by dedicated router(s) advertising the definition of each Flexible Algorithm. Such advertisement is associated with the priority to make sure that all routers will agree on a single and consistent definition for each Flexible Algorithm.
Definition of Flexible Algorithm includes:
• Metric type
• Affinity constraints
To enable the router to advertise the definition for the particular Flexible Algorithm, advertise-definition command is used. At least one router in the area, preferably two for redundancy, must advertise the Flexible
Algorithm definition. Without the valid definition being advertised, the Flexible Algorithm will not be functional.
Flexible Algorithm Prefix-SID Advertisement
To be able to forward traffic on a Flexible Algorithm specific path, all routers participating in the Flexible
Algorithm will install a MPLS labeled path for the Flexible Algorithm specific SID that is advertised for the prefix. Only prefixes for which the Flexible Algorithm specific Prefix-SID is advertised is subject to Flexible
Algorithm specific forwarding.
Calculation of Flexible Algorithm Path
A router may compute path for multiple Flexible Algorithms. A router must be configured to support particular
Flexible Algorithm before it can compute any path for such Flexible Algorithm. A router must have a valid definition of the Flexible Algorithm before Flexible Algorithm is used.
When computing the shortest path tree for particular Flexible Algorithm:
• All nodes that don't advertise support for Flexible Algorithm are pruned from the topology.
• If the Flexible Algorithm definition includes affinities that are excluded, then all links for which any of such affinities are advertised will be pruned from the topology.
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Installation of Forwarding Entries for Flexible Algorithm Paths
• Router uses the metric that is part of the Flexible Algorithm definition. If the metric isn't advertised for the particular link, the link is pruned from the topology.
Configuring Microloop Avoidance for Flexible Algorithm
By default, Microloop Avoidance per Flexible Algorithm instance follows Microloop Avoidance configuration for algo-0. For information about configuring Microloop Avoidance, see
Configure Segment Routing Microloop
You can disable Microloop Avoidance for Flexible Algorithm using the following commands:
router isis instance flex-algo algo microloop avoidance disable
router ospf process flex-algo algo microloop avoidance disable
Configuring LFA / TI-LFA for Flexible Algorithm
By default, LFA/TI-LFA per Flexible Algorithm instance follows LFA/TI-LFA configuration for algo-0. For information about configuring TI-LFA, see
Configure Topology-Independent Loop-Free Alternate (TI-LFA), on page 249
.
You can disable TI-LFA for Flexible Algorithm using the following commands:
router isis instance flex-algo algo fast-reroute disable
router ospf process flex-algo algo fast-reroute disable
Installation of Forwarding Entries for Flexible Algorithm Paths
Flexible Algorithm path to any prefix must be installed in the forwarding using the Prefix-SID that was advertised for such Flexible Algorithm. If the Prefix-SID for Flexible Algorithm is not known, such Flexible
Algorithm path is not installed in forwarding for such prefix..
Only MPLS to MPLS entries are installed for a Flexible Algorithm path. No IP to IP or IP to MPLS entries are installed. These follow the native IPG paths computed based on the default algorithm and regular IGP metrics.
Flexible Algorithm Prefix-SID Redistribution
Previously, prefix redistribution from IS-IS to another IS-IS instance or protocol was limited to SR algorithm
0 (regular SPF) prefix SIDs; SR algorithm 1 (Strict SPF) and SR algorithms 128-255 (Flexible Algorithm) prefix SIDs were not redistributed along with the prefix. The Segment Routing IS-IS Flexible Algorithm
Prefix SID Redistribution feature allows redistribution of strict and flexible algorithms prefix SIDs from IS-IS to another IS-IS instance or protocols. This feature is enabled automatically when you configure redistribution of IS-IS Routes with strict or Flexible Algorithm SIDs.
Flexible Algorithm Prefix Metric
A limitation of the existing Flexible Algorithm functionality in IS-IS is the inability to compute the best path to a prefix in a remote area or remote IGP domain. Prefixes are advertised between IS-IS areas or between protocol domains, but the existing prefix metric does not reflect any of the constraints used for Flexible
Algorithm path. Although the best Flexible Algorithm path can be computed to the inter-area or redistributed prefix inside the area, the path may not represent the overall best path through multiple areas or IGP domains.
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Configuring Flexible Algorithm
The Flexible Algorithm Prefix Metric feature introduces a Flexible Algorithm-specific prefix-metric in the
IS-IS prefix advertisement. The prefix-metric provides a way to compute the best end-to-end Flexible Algorithm optimized paths across multiple areas or domains.
Note The Flexible Algorithm definition must be consistent between domains or areas. Refer to section 8 in IETF draft https://datatracker.ietf.org/doc/draft-ietf-lsr-flex-algo/ .
Configuring Flexible Algorithm
The following ISIS and OSPF configuration sub-mode is used to configure Flexible Algorithm:
router isis instance flex-algo algo
router ospf process flex-algo algo algo —value from 128 to 255
Configuring Flexible Algorithm Definitions
The following commands are used to configure Flexible Algorithm definition under the flex-algo sub-mode:
• IS-IS metric-type delay
Note By default the regular IGP metric is used. If delay metric is enabled, the advertised delay on the link is used as a metric for Flexible Algorithm computation.
OSPF metric-type { delay | te-metric }
Note By default the regular IGP metric is used. If delay or TE metric is enabled, the advertised delay or TE metric on the link is used as a metric for Flexible Algorithm computation.
• affinity { include-any | include-all | exclude-any } name1, name2, … name —name of the affinity map
•
priority priority value priority value —priority used during the Flexible Algorithm definition election.
The following command is used to to include the Flexible Algorithm prefix metric in the advertised Flexible
Algorithm definition in IS-IS :
router isis instance flex-algo algo prefix-metric
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Example: Configuring IS-IS Flexible Algorithm
The following command is used to enable advertisement of the Flexible Algorithm definition in IS-IS:
router isis instance flex-algo algo advertise-definition
Configuring Affinity
The following command is used for defining the affinity-map. Affinity-map associates the name with the particular bit positions in the Extended Admin Group bitmask.
router isis instance flex-algo algo affinity-map name bit-position bit number
router ospf process flex-algo algo affinity-map name bit-position bit number
• name —name of the affinity-map.
• bit number —bit position in the Extended Admin Group bitmask.
The following command is used to associate the affinity with an interface:
router isis instance interface type interface-path-id affinity flex-algo name 1, name 2, …
router ospf process area area interface type interface-path-id affinity flex-algo name 1, name 2, … name —name of the affinity-map
Configuring Prefix-SID Advertisement
The following command is used to advertise prefix-SID for default and strict-SPF algorithm:
router isis instance interface type interface-path-id address-family { ipv4 | ipv6 } [ unicast ] prefix-sid [ strict-spf | algorithm algorithm-number ] [ index | absolute ] sid value
router ospf process area area interface Loopback interface-instance prefix-sid [ strict-spf
| algorithm algorithm-number ] [ index | absolute ] sid value
• algorithm-number —Flexible Algorithm number
• sid value —SID value
Example: Configuring IS-IS Flexible Algorithm
router isis 1 affinity-map red bit-position 65 affinity-map blue bit-position 8 affinity-map green bit-position 201 flex-algo 128 advertise-definition
!
affinity exclude-any red affinity include-any blue flex-algo 129
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Example: Configuring OSPF Flexible Algorithm
!
affinity exclude-any green
!
address-family ipv4 unicast segment-routing mpls
!
interface Loopback0 address-family ipv4 unicast prefix-sid algorithm 128 index 100 prefix-sid algorithm 129 index 101
!
!
interface GigabitEthernet0/0/0/0 affinity flex-algo red
!
interface GigabitEthernet0/0/0/1 affinity flex-algo blue red
!
interface GigabitEthernet0/0/0/2
!
affinity flex-algo blue
Example: Configuring OSPF Flexible Algorithm
router ospf 1 flex-algo 130 priority 200 affinity exclude-any red
!
blue
!
metric-type delay flex-algo 140 affinity include-all green
!
!
!
affinity include-any red interface Loopback0 prefix-sid index 10 prefix-sid strict-spf index 40 prefix-sid algorithm 128 absolute 16128
!
!
prefix-sid algorithm 129 index 129 prefix-sid algorithm 200 index 20 prefix-sid algorithm 210 index 30 interface GigabitEthernet0/0/0/0 flex-algo affinity color red color blue
!
!
affinity-map color red bit-position 10
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Example: Traffic Steering to Flexible Algorithm Paths
!
color blue bit-position 11
Example: Traffic Steering to Flexible Algorithm Paths
BGP Routes on PE – Color Based Steering
SR-TE On Demand Next-Hop (ODN) feature can be used to steer the BGP traffic towards the Flexible
Algorithm paths.
The following example configuration shows how to setup BGP steering local policy, assuming two router:
R1 (2.2.2.2) and R2 (4.4.4.4), in the topology.
Configuration on router R1: vrf Test address-family ipv4 unicast import route-target
1:150
!
export route-policy SET_COLOR_RED_HI_BW export route-target
1:150
!
!
!
interface Loopback0 ipv4 address 2.2.2.2 255.255.255.255
!
interface Loopback150 vrf Test ipv4 address 2.2.2.222 255.255.255.255
!
interface TenGigE0/1/0/3/0 description exr1 to cxr1 ipv4 address 10.0.20.2 255.255.255.0
!
extcommunity-set opaque color129-red-igp
129 end-set
!
route-policy PASS pass end-policy
!
route-policy SET_COLOR_RED_HI_BW set extcommunity color color129-red-igp pass end-policy
!
router isis 1 is-type level-2-only net 49.0001.0000.0000.0002.00
log adjacency changes affinity-map RED bit-position 28 flex-algo 128 priority 228
!
address-family ipv4 unicast metric-style wide
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BGP Routes on PE – Color Based Steering
!
!
advertise link attributes router-id 2.2.2.2
segment-routing mpls
!
interface Loopback0 address-family ipv4 unicast prefix-sid index 2
!
prefix-sid algorithm 128 index 282
!
interface TenGigE0/1/0/3/0 point-to-point address-family ipv4 unicast
!
!
!
router bgp 65000 bgp router-id 2.2.2.2
address-family ipv4 unicast
!
address-family vpnv4 unicast retain route-target all
!
neighbor-group RR-services-group remote-as 65000 update-source Loopback0 address-family ipv4 unicast
!
address-family vpnv4 unicast
!
!
neighbor 4.4.4.4
use neighbor-group RR-services-group
!
vrf Test rd auto address-family ipv4 unicast
!
redistribute connected segment-routing traffic-eng logging
!
policy status segment-list sl-cxr1 index 10 mpls label 16294
!
policy pol-foo color 129 end-point ipv4 4.4.4.4
candidate-paths preference 100 explicit segment-list sl-cxr1
!
!
!
!
Configuration on router R2: vrf Test address-family ipv4 unicast import route-target
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BGP Routes on PE – Color Based Steering
!
1:150 export route-policy SET_COLOR_RED_HI_BW export route-target
!
1:150
!
!
interface TenGigE0/1/0/1 description cxr1 to exr1 ipv4 address 10.0.20.1 255.255.255.0
!
extcommunity-set opaque color129-red-igp
129 end-set
!
route-policy PASS pass end-policy
!
route-policy SET_COLOR_RED_HI_BW set extcommunity color color129-red-igp pass end-policy
!
router isis 1 is-type level-2-only net 49.0001.0000.0000.0004.00
log adjacency changes affinity-map RED bit-position 28 affinity-map BLUE bit-position 29 affinity-map GREEN bit-position 30 flex-algo 128 priority 228
!
flex-algo 129 priority 229
!
flex-algo 130 priority 230
!
address-family ipv4 unicast metric-style wide advertise link attributes router-id 4.4.4.4
segment-routing mpls
!
interface Loopback0 address-family ipv4 unicast prefix-sid index 4 prefix-sid algorithm 128 index 284 prefix-sid algorithm 129 index 294
!
prefix-sid algorithm 130 index 304
!
interface GigabitEthernet0/0/0/0 point-to-point address-family ipv4 unicast
!
!
interface TenGigE0/1/0/1 point-to-point address-family ipv4 unicast
!
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!
router bgp 65000 bgp router-id 4.4.4.4
address-family ipv4 unicast
!
address-family vpnv4 unicast
!
neighbor-group RR-services-group remote-as 65000 update-source Loopback0 address-family ipv4 unicast
!
address-family vpnv4 unicast
!
!
neighbor 1.1.1.1
use neighbor-group RR-services-group
!
neighbor 2.2.2.2
use neighbor-group RR-services-group
!
vrf Test rd auto address-family ipv4 unicast
!
redistribute connected neighbor 25.1.1.2
remote-as 4 address-family ipv4 unicast
!
!
route-policy PASS in route-policy PASS out
!
!
segment-routing
!
end
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C H A P T E R
11
Configure Segment Routing Path Computation
Element
The Segment Routing Path Computation Element (SR-PCE) provides stateful PCE functionality by extending the existing IOS-XR PCEP functionality with additional capabilities. SR-PCE is supported on the MPLS data plane and IPv4 control plane.
Note The Cisco IOS XRv 9000 is the recommended platform to act as the SR-PCE. Refer to the Cisco IOS XRv
9000 Router Installation and Configuration Guide for more information.
•
•
•
PCE-Initiated SR Policies, on page 204
•
SR-PCE Flexible Algorithm Multi-Domain Path Computation, on page 206
•
ACL Support for PCEP Connection, on page 210
•
Anycast SID-Aware Path Computation, on page 211
•
SR-PCE IPv4 Unnumbered Interface Support, on page 214
•
Inter-Domain Path Computation Using Redistributed SID, on page 216
•
PCE Support for MPLS-TE LSPs, on page 219
•
Configuring the North-Bound API on SR-PCE, on page 221
About SR-PCE
The path computation element protocol (PCEP) describes a set of procedures by which a path computation client (PCC) can report and delegate control of head-end label switched paths (LSPs) sourced from the PCC to a PCE peer. The PCE can request the PCC to update and modify parameters of LSPs it controls. The stateful model also enables a PCC to allow the PCE to initiate computations allowing the PCE to perform network-wide orchestration.
SR-PCE learns topology information by way of IGP (OSPF or IS-IS) or through BGP Link-State (BGP-LS).
SR-PCE is capable of computing paths using the following methods:
• TE metric—SR-PCE uses the TE metric in its path calculations to optimize cumulative TE metric.
• IGP metric—SR-PCE uses the IGP metric in its path calculations to optimize reachability.
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Configure SR-PCE
• LSP Disjointness—SR-PCE uses the path computation algorithms to compute a pair of disjoint LSPs.
The disjoint paths can originate from the same head-end or different head-ends. Disjoint level refers to the type of resources that should not be shared by the two computed paths. SR-PCE supports the following disjoint path computations:
• Link – Specifies that links are not shared on the computed paths.
• Node – Specifies that nodes are not shared on the computed paths.
• SRLG – Specifies that links with the same SRLG value are not shared on the computed paths.
• SRLG-node – Specifies that SRLG and nodes are not shared on the computed paths.
When the first request is received with a given disjoint-group ID, the first LSP is computed, encoding the shortest path from the first source to the first destination. When the second LSP request is received with the same disjoint-group ID, information received in both requests is used to compute two disjoint paths: one path from the first source to the first destination, and another path from the second source to the second destination. Both paths are computed at the same time.
TCP Authentication Option
TCP Message Digest 5 (MD5) authentication has been used for authenticating PCEP (TCP) sessions by using a clear text or encrypted password. This feature introduces support for TCP Authentication Option (TCP-AO), which replaces the TCP MD5 option.
TCP-AO uses Message Authentication Codes (MACs), which provides the following:
• Protection against replays for long-lived TCP connections
• More details on the security association with TCP connections than TCP MD5
• A larger set of MACs with minimal system and operational changes
TCP-AO is compatible with Master Key Tuple (MKT) configuration. TCP-AO also protects connections when using the same MKT across repeated instances of a connection. TCP-AO protects the connections by using traffic key that are derived from the MKT, and then coordinates changes between the endpoints.
Note TCP-AO and TCP MD5 are never permitted to be used simultaneously. TCP-AO supports IPv6, and is fully compatible with the proposed requirements for the replacement of TCP MD5.
Configure SR-PCE
This task explains how to configure SR-PCE.
Before you begin
The Cisco IOS XRv 9000 is the recommended platform to act as the SR-PCE.
SUMMARY STEPS
1.
configure
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Configure SR-PCE
2.
pce
3.
address ipv4 address
4.
state-sync ipv4 address
5.
tcp-buffer size size
6.
password { clear | encrypted } password
7.
tcp-ao key-chain [ include-tcp-options ] [ accept-ao-mismatch-connection ]
8.
segment-routing { strict-sid-only | te-latency }
9.
timers
10.
keepalive time
11.
minimum-peer-keepalive time
12.
reoptimization time
13.
exit
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure pce
Example:
RP/0/RP0/CPU0:router(config)# pce
Purpose
Enters global configuration mode.
Enables PCE and enters PCE configuration mode.
Step 3
Step 4
address ipv4 address
Example:
RP/0/RP0/CPU0:router(config-pce)# address ipv4
192.168.0.1
Configures a PCE IPv4 address.
state-sync ipv4 address
Example:
RP/0/RP0/CPU0:router(config-pce)# state-sync ipv4
192.168.0.3
Configures the remote peer for state synchronization.
Step 5 tcp-buffer size size
Example:
RP/0/RP0/CPU0:router(config-pce)# tcp-buffer size
1024000
Configures the transmit and receive TCP buffer size for each PCEP session, in bytes. The default buffer size is
256000. The valid range is from 204800 to 1024000.
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Configure SR-PCE
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Command or Action password { clear | encrypted } password
Example:
RP/0/RP0/CPU0:router(config-pce)# password encrypted pwd1
tcp-ao key-chain
[
Example:
[ include-tcp-options accept-ao-mismatch-connection ]
]
RP/0/RP0/CPU0:router(config-pce)# tcp-ao pce_tcp_ao include-tcp-options
Purpose
Enables TCP MD5 authentication for all PCEP peers. Any
TCP segment coming from the PCC that does not contain a MAC matching the configured password will be rejected.
Specify if the password is encrypted or clear text.
Note TCP-AO and TCP MD5 are never permitted to be used simultaneously.
Enables TCP Authentication Option (TCP-AO) authentication for all PCEP peers. Any TCP segment coming from the PCC that does not contain a MAC matching the configured key chain will be rejected.
• include-tcp-options —Includes other TCP options in the header for MAC calculation.
• accept-ao-mismatch-connection —Accepts connection even if there is a mismatch of AO options between peers.
Note TCP-AO and TCP MD5 are never permitted to be used simultaneously.
segment-routing { strict-sid-only | te-latency } Configures the segment routing algorithm to use strict SID or TE latency.
Example:
RP/0/RP0/CPU0:router(config-pce)# segment-routing strict-sid-only
Note This setting is global and applies to all LSPs that request a path from this controller.
Enters timer configuration mode.
timers
Example:
RP/0/RP0/CPU0:router(config-pce)# timers
keepalive time
Example:
RP/0/RP0/CPU0:router(config-pce-timers)# keepalive
60
Configures the timer value for locally generated keep-alive messages. The default time is 30 seconds.
minimum-peer-keepalive time
Example:
RP/0/RP0/CPU0:router(config-pce-timers)# minimum-peer-keepalive 30
Configures the minimum acceptable keep-alive timer that the remote peer may propose in the PCEP OPEN message during session establishment. The default time is 20 seconds.
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Configure the Disjoint Policy (Optional)
Step 12
Step 13
Command or Action
reoptimization time
Example:
RP/0/RP0/CPU0:router(config-pce-timers)# reoptimization 600
Purpose
Configures the re-optimization timer. The default timer is
1800 seconds.
exit
Example:
RP/0/RP0/CPU0:router(config-pce-timers)# exit
Exits timer configuration mode and returns to PCE configuration mode.
Configure the Disjoint Policy (Optional)
This task explains how to configure the SR-PCE to compute disjointness for a pair of LSPs signaled by PCCs that do not include the PCEP association group-ID object in their PCEP request. This can be beneficial for deployments where PCCs do not support this PCEP object or when the network operator prefers to manage the LSP disjoint configuration centrally.
SUMMARY STEPS
1.
disjoint-path
2.
group-id value type { link | node | srlg | srlg-node } [ sub-id value ]
3.
strict
4.
lsp { 1 | 2 } pcc ipv4 address lsp-name lsp_name [ shortest-path ]
DETAILED STEPS
Step 1
Command or Action disjoint-path
Example:
RP/0/RP0/CPU0:router(config-pce)# disjoint-path
Purpose
Enters disjoint configuration mode.
Step 2 group-id value type srlg-node
Example:
} [
{ link
sub-id value ]
| node | srlg |
RP/0/RP0/CPU0:router(config-pce-disjoint)# group-id
1 type node sub-id 1
Configures the disjoint group ID and defines the preferred level of disjointness (the type of resources that should not be shared by the two paths):
• link —Specifies that links are not shared on the computed paths.
• node —Specifies that nodes are not shared on the computed paths.
• srlg —Specifies that links with the same SRLG value are not shared on the computed paths.
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Step 3
Step 4
Command or Action Purpose
• srlg-node —Specifies that SRLG and nodes are not shared on the computed paths.
If a pair of paths that meet the requested disjointness level cannot be found, then the paths will automatically fallback to a lower level:
• If the requested disjointness level is SRLG or node, then link-disjoint paths will be computed.
• If the requested disjointness level was link, or if the first fallback from SRLG or node disjointness failed, then the lists of segments encoding two shortest paths, without any disjointness constraint, will be computed.
strict
Example:
RP/0/RP0/CPU0:router(config-pce-disjoint)# strict
(Optional) Prevents the automatic fallback behavior of the preferred level of disjointness. If a pair of paths that meet the requested disjointness level cannot be found, the disjoint calculation terminates and no new path is provided. The existing path is not modified.
lsp { 1 | 2 } pcc ipv4 address lsp-name lsp_name
[ shortest-path ]
Adds LSPs to the disjoint group.
Example:
RP/0/RP0/CPU0:router(config-pce-disjoint)# lsp 1 pcc ipv4 192.168.0.1 lsp-name rtrA_t1 shortest-path
RP/0/RP0/CPU0:router(config-pce-disjoint)# lsp 2 pcc ipv4 192.168.0.5 lsp-name rtrE_t2
The shortest-path keyword forces one of the disjoint paths to follow the shortest path from the source to the destination.
This option can only be applied to the the first LSP specified.
PCE-Initiated SR Policies
An SR-TE policy can be configured on the path computation element (PCE) to reduce link congestion or to minimize the number of network touch points.
Note The PCE-initiated SR-TE policies are entered in PCE configuration mode. For more information on configuring
SR-TE policies, see the
SR-TE Policy Overview, on page 103
.
To minimize the number of network touch points, an application, such as a Network Services Orchestrator
(NSO), can request the PCE to create an SR-TE policy. PCE deploys the SR-TE policy using PCC-PCE communication protocol (PCEP).
1.
PCE sends a PCInitiate message to the PCC.
2.
If the PCInitiate message is valid, the PCC sends a PCRpt message; otherwise, it sends PCErr message.
3.
If the PCInitiate message is accepted, the PCE updates the SR-TE policy by sending PCUpd message.
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PCE-Initiated SR Policies
You can achieve high-availability by configuring multiple PCEs with SR-TE policies. If the head-end (PCC) loses connectivity with one PCE, another PCE can assume control of the SR-TE policy.
Configuration Example: PCE-Initiated SR Policy with Explicit SID List
To configure a PCE-initiated SR-TE policy, you must complete the following configurations:
1.
Enter PCE configuration mode.
2.
Create the segment list.
Note When configuring an explicit path using IP addresses of intermediate links, the SR-TE process prefers the protected Adj-SID of the link, if one is available.
3.
Create the policy.
/* Enter PCE configuration mode and create the SR-TE segment lists */
Router# configure
Router(config)# pce
/* Create the SR-TE segment lists */
Router(config-pce)# segment-routing
Router(config-pce-sr)# traffic-eng
Router(config-pce-sr-te)# segment-list name addr2a
Router(config-pce-sr-te-sl)# index 10 address ipv4 1.1.1.2
Router(config-pce-sr-te-sl)# index 20 address ipv4 10.2.3.2
Router(config-pce-sr-te-sl)# index 30 address ipv4 1.1.1.4
Router(config-pce-sr-te-sl)# exit
/* Create the SR-TE policy */
Router(config-pce-sr-te)# peer ipv4 1.1.1.1
Router(config-pce-sr-te)# policy P1
Router(config-pce-sr-te-policy)# color 2 end-point ipv4 2.2.2.2
Router(config-pce-sr-te-policy)# candidate-paths
Router(config-pce-sr-te-policy-path)# preference 50
Router(config-pce-sr-te-policy-path-preference)# explicit segment-list addr2a
Router(config-pce-sr-te-pp-info)# commit
Router(config-pce-sr-te-pp-info)# end
Router(config)#
Running Config pce segment-routing traffic-eng segment-list name addr2a index 1 address ipv4 14.14.14.4
!
peer ipv4 1.1.1.1
policy P1 color 2 end-point ipv4 2.2.2.2
candidate-paths preference 50 explicit segment-list addr2a
!
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SR-PCE Flexible Algorithm Multi-Domain Path Computation
!
SR-PCE Flexible Algorithm Multi-Domain Path Computation
Flexible Algorithm provides a traffic engineered path automatically computed by the IGP to any destination reachable by the IGP. With the SR-PCE Flexible Algorithm Multi-Domain Path Computation feature, SR-PCE can use Flexible Algorithms to compute multi-domain paths. See the
Enabling Segment Routing Flexible
chapter for information about Segment Routing Flexible Algorithm.
The SR-PCE Flexible Algorithm Multi-Domain Path Computation feature incorporates the following functionality:
• BGP-LS has been augmented to allow selected nodes to advertise the Flexible Algorithm definition
(FAD) to the SR-PCE
• PCEP has been augmented (vendor-specific object) to allow a PCC to indicate SR policy constraint based on the Flexible Algorithm instance number
• SR-PCE algorithms have been augmented to compute paths based on a Flexible Algorithm constraint
The SR-PCE Flexible Algorithm multi-domain path computation requires the following:
• The same Flexible Algorithm instance ID is used across domains.
• The metric for those Flexible Algorithm instances must be the same across domains.
• The affinity constraints for those Flexible Algorithm instances may be different across domains.
• Multiple Flexible Algorithms can exist in a domain.
For example, considering a multi-domain topology (Domain 1 and Domain 2), the following scenarios meet the requirements listed above:
Scenario Domain 1 Domain 2
Scenario 1
Scenario 2
Scenario 3
Flexible Algorithm 128, metric delay
Flexible Algorithm 128, metric delay
Flexible Algorithm 128, metric delay
Flexible Algorithm 128, metric delay, exclude affinity blue
Flexible Algorithm 128, metric delay, exclude affinity yellow
Flexible Algorithm 128, metric delay, exclude affinity blue
Scenario 4 Flexible Algorithm 128, metric delay
Flexible Algorithm 129, metric IGP
Flexible Algorithm 128, metric delay
Flexible Algorithm 129, metric IGP
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Example: SR-PCE Flexible Algorithm Multi-Domain Path Computation Use Case
Note The use of a Flexible Algorithm constraint in a multi-domain SR topology does not preclude the use of an
SR policy that are optimized for a particular metric type. For example, a policy can request a PCE for a Multi
Domain policy based on metric delay. SR-PCE computes the path and encodes it with regular prefix SIDs and Adj-SIDs as required. Alternatively, a policy can request to have a constraint for a Flexible Algorithm instance X, which is defined in multiple domains and it minimizes based on metric delay. In this case, the
SR-PCE computes the multi-domain path and encodes it using only Flexible Algorithm prefix SIDs. This case benefits from the optimized label stack size that Flexible Algorithm provides (1 label per domain).
Example: SR-PCE Flexible Algorithm Multi-Domain Path Computation Use
Case
The following use case depicts a multi-domain topology with two IS-IS processes, each with a Flexible
Algorithm instance of 128 that minimizes metric delay. A multi-domain SR policy programmed at Node 1 leverages a Flexible Algorithm 128 path computed by the SR-PCE toward Node 8.
Figure 7: Multi-Domain Topology
Configuration on Node 8
IS-IS and Flexible Algorithm Configuration router isis 2 is-type level-2-only net 49.0002.0000.0000.0008.00
distribute link-state flex-algo 128 metric-type delay advertise-definition address-family ipv4 unicast metric-style wide mpls traffic-eng level-2-only mpls traffic-eng router-id Loopback0
!
router-id 1.1.1.8
segment-routing mpls
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Example: SR-PCE Flexible Algorithm Multi-Domain Path Computation Use Case interface Loopback0 passive address-family ipv4 unicast prefix-sid absolute 16008 prefix-sid algorithm 128 absolute 16808
!
Configuration on Node 4 (ABR/ASBR)
IS-IS and Flexible Algorithm Configuration router isis 1 is-type level-2-only net 49.0001.0000.0000.0004.00
distribute link-state instance-id 100 flex-algo 128 metric-type delay advertise-definition address-family ipv4 unicast metric-style wide mpls traffic-eng level-2-only mpls traffic-eng router-id Loopback0
!
router-id 1.1.1.4
segment-routing mpls interface Loopback0 passive address-family ipv4 unicast prefix-sid absolute 16004 prefix-sid algorithm 128 absolute 16804
!
router isis 2 is-type level-2-only net 49.0002.0000.0000.0004.00
distribute link-state instance-id 200 flex-algo 128 metric-type delay advertise-definition address-family ipv4 unicast metric-style wide mpls traffic-eng level-2-only mpls traffic-eng router-id Loopback0 router-id 1.1.1.4
!
segment-routing mpls interface Loopback0 passive address-family ipv4 unicast prefix-sid absolute 16004 prefix-sid algorithm 128 absolute 16804
!
BGP-LS Configuration router bgp 65000 bgp router-id 1.1.1.4
address-family link-state link-state
!
neighbor-group AS65000-LS-group remote-as 65000
Configure Segment Routing Path Computation Element
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Example: SR-PCE Flexible Algorithm Multi-Domain Path Computation Use Case update-source Loopback0 address-family link-state link-state
!
!
neighbor 1.1.1.10
use neighbor-group AS65000-LS-group
!
!
description *** To SR-PCE ***
!
Configuration on Node 1
IS-IS and Flexible Algorithm Configuration router isis 1 is-type level-2-only net 49.0001.0000.0000.0001.00
distribute link-state flex-algo 128 metric-type delay advertise-definition address-family ipv4 unicast metric-style wide mpls traffic-eng level-2-only mpls traffic-eng router-id Loopback0 router-id 1.1.1.1
segment-routing mpls
!
interface Loopback0 passive address-family ipv4 unicast prefix-sid absolute 16001 prefix-sid algorithm 128 absolute 16801
!
SR Policy Configuration segment-routing traffic-eng policy FOO color 100 end-point ipv4 1.1.1.8
candidate-paths preference 100 dynamic
!
!
!
!
!
pcep
!
constraints segments sid-algorithm 128
!
!
!
PCC Configuration
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ACL Support for PCEP Connection segment-routing traffic-eng pcc source-address ipv4 1.1.1.1
pce address ipv4 1.1.1.10
precedence 10
!
report-all
!
!
!
Configuration on PCE pce address ipv4 1.1.1.10
!
rest
!
router bgp 65000 bgp router-id 1.1.1.10
address-family link-state link-state
!
neighbor-group AS65000-LS-group remote-as 65000
!
!
update-source Loopback0 address-family link-state link-state neighbor 1.1.1.4
use neighbor-group AS65000-LS-group
!
description *** To Node-4 ***
!
neighbor 1.1.1.5
use neighbor-group AS65000-LS-group
!
description *** To Node-5 ***
!
!
ACL Support for PCEP Connection
PCE protocol (PCEP) (RFC5440) is a client-server model running over TCP/IP, where the server (PCE) opens a port and the clients (PCC) initiate connections. After the peers establish a TCP connection, they create a
PCE session on top of it.
The ACL Support for PCEP Connection feature provides a way to protect a PCE server using an Access
Control List (ACL) to restrict IPv4 PCC peers at the time the TCP connection is created based on the source address of a client. When a client initiates the TCP connection, the ACL is referenced, and the client source address is compared. The ACL can either permit or deny the address and the TCP connection will proceed or not.
Refer to the Implementing Access Lists and Prefix Lists chapter in the IP Addresses and Services Configuration
Guide for Cisco NCS 5500 Series Routers for detailed ACL configuration information.
To apply an ACL to the PCE, use the pce peer-filter ipv4 access-list acl_name command.
The following example shows how to configure an ACL and apply it to the PCE:
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Anycast SID-Aware Path Computation pce address ipv4 1.1.1.5
peer-filter ipv4 access-list sample-peer-filter
!
ipv4 access-list sample-peer-filter
10 permit ipv4 host 1.1.1.6 any
!
20 permit ipv4 host 1.1.1.7 any
30 deny ipv4 any any
Anycast SID-Aware Path Computation
This feature allows the SR-TE head-end or SR-PCE to compute a path that is encoded using Anycast prefix
SIDs of nodes along the path.
An Anycast SID is a type of prefix SID that identifies a set of nodes and is configured with n-flag clear. The set of nodes (Anycast group) is configured to advertise a shared prefix address and prefix SID. Anycast routing enables the steering of traffic toward multiple advertising nodes, providing load-balancing and redundancy.
Packets addressed to an Anycast address are forwarded to the topologically nearest nodes.
Note For information on configuring Anycast SID, see
Configuring a Prefix-SID on the IS-IS Enabled Loopback
and
Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface, on page 83
.
This example shows how Anycast SIDs are inserted into a computed SID list.
The following figure shows 3 isolated IGP domains without redistribution and without BGP 3107. Each Area
Border Router (ABR) 1 through 4 is configured with a node SID. ABRs 1 and 2 share Anycast SID 16012 and ABRs 3 and 4 share Anycast SID 16034.
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Anycast SID-Aware Path Computation
Consider the case where nodes A and Z are provider edge (PE) routers in the same VPN. Node A receives a
VPN route with BGP next-hop to node Z. Node A resolves the SR path to node Z based on ODN behaviors with delegation of path computation to SR-PCE.
Before considering Anycast SIDs, the head-end router or SR-PCE computes the SID list.
Assume that the computed path from node A to node Z traverses node 2 and node 4. This translates to SID list {16002, 16004, 1600Z} when node SIDs are leveraged to encode the path.
When an Anycast SID-aware path is requested, the path computation algorithm performs the following:
• Path Computation —Computes the path according to optimization objectives and constraints
• Path Encoding —Encodes the path in a SID list leveraging node-SIDs and adj-SIDs as applicable
• Anycast SID Replacement —Reiterates the original SID list by replacing node SIDs with Anycast SIDs present on the nodes along the computed path.
• Optimality Validation —The new paths are validated against the original optimization objectives and constraints (maintain same cumulative metric as original SID list and do not violate path constraints).
• Anycast SID Promotion —If the optimality validation is successful, then the Anycast-encoded SID list is signaled and instantiated in the forwarding.
The following figure depicts cumulative metrics between nodes in the network.
Under these conditions, the optimality check is met, and therefore, the Anycast-encoded SID list from node
A to node Z is {16012,16034,1600Z}.
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Anycast SID-Aware Path Computation
The Anycast SID aware path computation also provides resiliency. For example, if one of the ABRs (in this case, ABR 1) becomes unavailable or unreachable, the path from node A to node Z {16012,16034,1600Z} will still be valid and usable.
Configuration Examples
1.
Configure Prefix SIDs on the ABR nodes.
a.
Configure each node with a node SID.
b.
Configure each group of nodes with a shared Anycast SID.
See
Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface, on page 64
and
Prefix-SID on the OSPF-Enabled Loopback Interface, on page 83
.
2.
Configure SR policies to include Anycast SIDs for path computation using the anycast-sid-inclusion command.
This example shows how to configure a local SR policy to include Anycast SIDs for PCC-initiated path computation at the head-end router:
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy FOO
Router(config-sr-te-policy)# color 10 end-point ipv4 1.1.1.10
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# dynamic
Router(config-sr-te-pp-info)# anycast-sid-inclusion
Running Configuration
Use the anycast-sid-inclusion command to request Anycast SID-aware path computation for the following
SR policy types:
• Local SR policy with PCC-initiated path computation at the head-end router: segment-routing traffic-eng policy FOO color 10 end-point ipv4 1.1.1.10
candidate-paths
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SR-PCE IPv4 Unnumbered Interface Support preference 100 dynamic anycast-sid-inclusion
• Local SR policy with PCC-initiated/PCE-delegated path computation at the SR-PCE: segment-routing traffic-eng policy BAR color 20 end-point ipv4 1.1.1.20
candidate-paths preference 100 dynamic pcep anycast-sid-inclusion
• On-demand SR policies with a locally computed dynamic path at the head-end, or centrally computed dynamic path at the SR-PCE: segment-routing traffic-eng on-demand color 10 dynamic anycast-sid-inclusion
• On-demand SR policies with centrally computed dynamic path at the SR-PCE: segment-routing traffic-eng on-demand color 20 dynamic pcep anycast-sid-inclusion
SR-PCE IPv4 Unnumbered Interface Support
This feature allows IPv4 unnumbered interfaces to be part of an SR-PCE topology database.
An unnumbered IPv4 interface is not identified by its own unique IPv4 address. Instead, it is identified by the router ID of the node where this interfaces resides and the local SNMP index assigned for this interface.
This feature provides enhancements to the following components:
• IGPs (IS-IS and OSPF):
• Support the IPv4 unnumbered interfaces in the SR-TE context by flooding the necessary interface information in the topology
• SR-PCE:
Note SR-PCE and path computation clients (PCCs) need to be running Cisco IOS XR
7.0.2 or later.
• Compute and return paths from a topology containing IPv4 unnumbered interfaces.
• Process reported SR policies from a head-end router that contain hops with IPv4 unnumbered adjacencies.
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SR-PCE IPv4 Unnumbered Interface Support
PCEP extensions for IPv4 unnumbered interfaces adhere to IETF RFC8664 “PCEP Extensions for
Segment Routing” ( https://datatracker.ietf.org/doc/rfc8664/ ). The unnumbered hops use a Node or
Adjacency Identifier (NAI) of type 5. This indicates that the segment in the explicit routing object
(ERO) is an unnumbered adjacency with an IPv4 ID and an interface index.
• SR-TE process at the head-end router:
• Compute its own local path over a topology, including unnumbered interfaces.
• Process PCE-computed paths that contain hops with IPv4 unnumbered interfaces.
• Report a path that contains hops with IPv4 unnumbered interfaces to the PCE.
Configuration Example
The following example shows how to configure an IPv4 unnumbered interface:
RP/0/0/CPU0:rtrA(config)# interface GigabitEthernet0/0/0/0
RP/0/0/CPU0:rtrA(config-if)# ipv4 point-to-point
RP/0/0/CPU0:rtrA(config-if)# ipv4 unnumbered Loopback0
To bring up the IPv4 unnumbered adjacency under the IGP, configure the link as point-to-point under the
IGP configuration. The following example shows how to configure the link as point-to-point under the IGP configuration:
RP/0/0/CPU0:rtrA(config)# router ospf one
RP/0/0/CPU0:rtrA(config-ospf)# area 0
RP/0/0/CPU0:rtrA(config-ospf-ar)# interface GigabitEthernet0/0/0/0
RP/0/0/CPU0:rtrA(config-ospf-ar-if)# network point-to-point
Verification
Use the show ipv4 interface command to display information about the interface:
RP/0/0/CPU0:rtrA# show ipv4 interface GigabitEthernet0/0/0/0 brief
Tue Apr 2 12:59:53.140 EDT
Interface
GigabitEthernet0/0/0/0
IP-Address
192.168.0.1
Status
Up
Protocol
Up
This interface shows the IPv4 address of Loopback0.
Use the show snmp interface command to find the SNMP index for this interface:
RP/0/0/CPU0:rtrA# show snmp interface
Tue Apr 2 13:02:49.190 EDT ifName : Null0 ifName : Loopback0 ifIndex : 3 ifIndex : 10 ifName : GigabitEthernet0/0/0/0 ifIndex : 6
The interface is identified with the pair (IPv4:192.168.0.1, index:6).
Use the show ospf neighbor command to display the adjacency:
RP/0/0/CPU0:rtrA# show ospf neighbor gigabitEthernet 0/0/0/0 detail
…
Neighbor 192.168.0.4, interface address 192.168.0.4
In the area 0 via interface GigabitEthernet0/0/0/0
Neighbor priority is 1, State is FULL, 6 state changes
…
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Inter-Domain Path Computation Using Redistributed SID
Adjacency SIDs:
Label: 24001, Dynamic, Unprotected
Neighbor Interface ID: 4
The output of the show pce ipv4 topology command is enhanced to display the interface index instead of the
IP address for unnumbered interfaces:
RP/0/0/CPU0:sr-pce# show pce ipv4 topology
…
Link[2]: unnumbered local index 6, remote index 4
Local node:
OSPF router ID: 192.168.0.1 area ID: 0 ASN: 0
Remote node:
TE router ID: 192.168.0.4
OSPF router ID: 192.168.0.4 area ID: 0 ASN: 0
Metric: IGP 1, TE 1, Latency 1 microseconds
Bandwidth: Total 125000000 Bps, Reservable 0 Bps
Admin-groups: 0x00000000
Adj SID: 24001 (unprotected)
The output of show pce lsp detail command includes unnumbered hops:
RP/0/0/CPU0:sr-pce# show pce lsp detail
…
Reported path:
Metric type: TE, Accumulated Metric 3
SID[0]: Adj unnumbered, Label 24001, local 192.168.0.1(6), remote 192.168.0.4(4)
SID[1]: Adj unnumbered, Label 24002, local 192.168.0.4(7), remote 192.168.0.3(7)
SID[2]: Adj unnumbered, Label 24000, local 192.168.0.3(5), remote 192.168.0.2(5)
Computed path: (Local PCE)
Computed Time: Wed Apr 03 11:01:46 EDT 2019 (00:01:06 ago)
Metric type: TE, Accumulated Metric 3
SID[0]: Adj unnumbered, Label 24001, local 192.168.0.1(6), remote 192.168.0.4(4)
SID[1]: Adj unnumbered, Label 24002, local 192.168.0.4(7), remote 192.168.0.3(7)
SID[2]: Adj unnumbered, Label 24000, local 192.168.0.3(5), remote 192.168.0.2(5)
Inter-Domain Path Computation Using Redistributed SID
A Path Computation Element (PCE) computes SR-TE paths based on SR topology database that stores connectivity, state, and TE attributes of SR network nodes and links. BGP Labeled Unicast (BGP-LU) provides
MPLS transport across IGP boundaries by advertising loopbacks and label binding of impact edge and border routers across IGP boundaries.
This feature adds new functionality to the SR-PCE that enables it to compute a path for remote non-SR end-point device distributed by BGP-LU.
The remote end-point device in the BGP-LU domain is unknown to the SR-PCE. For the SR-PCE to know about the end-point device, the gateway ABR/ASBR learns the end-point prefix via BGP-LU. The prefix is then redistributed to SR-PCE topology database from the gateway ABR/ASBR. SR-PCE then can compute the best path from the head-end device to the selected gateway router.
The following topology shows an SR domain and a BGP-LU domain, with a gateway ABR/ASBR between the two domains.
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Inter-Domain Path Computation Using Redistributed SID
1.
The gateway ABR/ASBR is configured with BGP/IGP helper to learn the remote prefix through BGP-LU and redistribute the remote prefix to the IGP helper, then to SR-PCE.
2.
The SR-PCE selects the best gateway node to BGP-LU domain and computes the path to reach the remote prefix through the gateway node.
3.
The head-end device in the SR domain requests a path to the remote destination and signals the SR profile interworking with the BGP-LU domain.
The BGP-LU prefix advertisement to SR-PCE Traffic Engineer Database (TED) is done by creating an IGP helper on the ABR/ASBR to redistribute BGP-LU prefix information to IGP. IGP then sends the prefix information to the SR-PCE via BGP-LS.
If there are multiple ABR/ASBRs advertising the same remote BGP-LU prefix, the SR-PCE selects the best gateway node to the BGP-LU domain using the accumulative metric from the head-end device to the gateway and the advertised metric from the gateway to the destination.
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Example: Inter-Domain Path Computation Using Redistributed SID
Example: Inter-Domain Path Computation Using Redistributed SID
The following examples show the configurations for the IGP helper, BGP-LU, and proxy BGP-SR:
Configuration on the End-Point Device
Configure the end-point device to allocate a label for the BGP-LU prefix on the end-point device: router bgp 3107 bgp router-id 1.0.0.8
address-family ipv4 unicast network 1.0.0.8/32 route-policy bgplu-com allocate-label all route-policy bgplu-com set community (65002:999) end-policy
Configuration on the Gateway ABR/ASBR
1. Configure the remote prefix set and create the route policy for the BGP-LU domain: prefix-set bgplu
1.0.0.7/32,
1.0.0.8/32 ,
1.0.0.101/32,
1.0.0.102/32 end-set
!
route-policy bgp2isis if destination in bgplu then pass else drop endif end-policy
!
end
2. Configure the helper IGP instance on the Loopback interface: router isis 101 is-type level-2-only net 49.0001.0000.1010.1010.00
distribute link-state instance-id 9999 nsf cisco nsf lifetime 120 address-family ipv4 unicast metric-style wide mpls traffic-eng router-id Loopback10 mpls traffic-eng multicast-intact maximum-paths 64 router-id Loopback10 redistribute bgp 3107 metric 200 route-policy bgp2isis segment-routing mpls sr-prefer
!
interface Loopback10 >>> this loopback is for gateway SR-TE node-id passive address-family ipv4 unicast prefix-sid index 2001 explicit-null
3. Configure the gateway proxy BGP-SR and SR Mapping Server to allocate SR labels:
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PCE Support for MPLS-TE LSPs router bgp 3107 address-family ipv4 unicast segment-routing prefix-sid-map allocate-label all segment-routing global-block 16000 23999 mapping-server prefix-sid-map address-family ipv4
1.0.0.7/32 2007
1.0.0.8/32 2008
1.0.0.101/32 2101
1.0.0.102/32 2102
PCE Support for MPLS-TE LSPs
This feature allows Cisco's SR-PCE to act as a Path Computation Element (PCE) for MPLS Traffic Engineering
Label Switched Paths (MPLS-TE LSPs).
Note For more information about MPLS-TE, refer to the "Implementing MPLS Traffic Engineering" chapter in the
MPLS Configuration Guide for Cisco NCS 5500 Series Routers .
The supported functionality is summarized below:
• PCE type: Active Stateful PCE
• MPLS-TE LSP initiation methods:
• PCE Initiated—An active stateful PCE initiates an LSP and maintains the responsibility of updating the LSP.
• PCC Initiated—A PCC initiates the LSP and may delegate the control later to the Active stateful
PCE.
• MPLS-TE LSP metric—Metric optimized by the path computation algorithm:
• IGP metric
• TE metric
• Latency metric
• MPLS-TE LSP constraints—TE LSP attributes to be taken into account by the PCE during path computation:
• Resource Affinities
• Path Disjointness
• MPLS-TE LSP parameters:
• Setup priority—The priority of the TE LSP with respect to taking resources
• Hold priority—The priority of the TE LSP with respect to holding resources
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PCE Support for MPLS-TE LSPs
• FRR L flag—The "Local Protection Desired" bit. Can be set from an application instantiating an
MPLS-TE LSP via SR-PCE. SR-PCE passes this flag to the PCC, and the PCC will enable FRR for that LSP.
• Signaled Bandwidth—This value can be set from an application instantiating an MPLS-TE LSP via
SR-PCE. SR-PCE passes this value to the PCC.
• Binding SID—A segment identifier (SID) that a headend binds to an MPLS-TE LSP. When the headend receives a packet with active segment (top MPLS label) matching the BSID of a local
MPLS-TE LSP, the headend steers the packet into the associated MPLS-TE LSP.
Cisco Crosswork Optimization Engine is an application that leverages the SR-PCE in order to visualize and instantiate MPLS-TE LSPs. For more information, refer to the Visualize SR Policies and RSVP-TE Tunnels chapter in the Cisco Crosswork Optimization Engine 1.2.1 User Guide .
Note No extra configuration is required to enable MPLS-TE support at SR-PCE.
Example: Configuring a PCEP Session (Stateful Mode) on MPLS-TE PCC
The following example shows the configuration for an MPLS-TE PCC to establish a PCEP session with a
PCE (IPv4 address 1.1.1.100).
Note MPLS-TE PCC must operate in the stateful PCEP mode when connecting to SR-PCE.
The instantiation keyword enables the PCC to support MPLS-TE LSP instantiation by PCE (PCE-initiated).
The report keyword enables the PCC to report all the MPLS-TE LSPs configured on that node.
Note PCE-initiated LSPs are automatically reported to all configured PCEs.
The autoroute-announce keyword enables autoroute-announce globally for all PCE-initiated LSPs on the
PCC.
The redundancy pcc-centric keywords enable PCC-centric high-availability model for PCE-initiated LSPs.
The PCC-centric model changes the default PCC delegation behavior to the following:
• After LSP creation, LSP is automatically delegated to the PCE that computed it.
• If this PCE is disconnected, then the LSP is redelegated to another PCE.
• If the original PCE is reconnected, then the delegation fallback timer is started. When the timer expires, the LSP is redelegated back to the original PCE, even if it has worse preference than the current PCE.
mpls traffic-eng pce peer ipv4 1.1.1.100
!
stateful-client
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Configuring the North-Bound API on SR-PCE
!
!
!
end instantiation report autoroute-announce redundancy pcc-centric
Example: Configuring Multiple PCEP Sessions from a PCC Acting as MPLS-TE and SR-TE Headend Toward a Common PCE
The following example shows the configuration for a PCC (IPv4 addresses 1.1.1.1 and 1.1.1.2) to establish two PCEP sessions with a common PCE (IPv4 address 1.1.1.100). One session is configured under MPLS-TE, and the other under SR-TE.
Note The two PCEP sessions must use a different source address on the PCC when connecting to the same PCE.
For more information regarding PCEP configuration at SR-TE PCC, see the Configure the Head-End Router as PCEP PCC topic.
mpls traffic-eng pce peer source ipv4 1.1.1.1
peer ipv4 1.1.1.100
!
!
!
end segment-routing traffic-eng pcc source-address ipv4 1.1.1.2
!
!
!
end pce address ipv4 1.1.1.100
!
Configuring the North-Bound API on SR-PCE
The SR-PCE provides a north-bound HTTP-based API to allow communication between SR-PCE and external clients and applications.
Over this API, an external application can leverage the SR-PCE for topology discovery, SR policy discovery, and SR policy instantiation.
The Cisco Crosswork Optimization Engine is an application that leverages the SR-PCE. For more information, refer to the Cisco Crosswork Optimization Engine User Guides .
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Configuring the North-Bound API on SR-PCE
Use the following commands under PCE configuration mode to configure the API to allow communication between SR-PCE and external clients or applications.
Note The API server is enabled by default when SR-PCE is configured.
Command rest authentication basic
rest username password password
rest sibling ipv4 address
{ clear | encrypted }
Description
(Optional) Specify basic (plaintext) authentication.
By default, authentication is disabled.
Add credentials when connecting to API.
Note This command is used only if authentication is configured.
Opens a synchronization channel to another PCE in the same high availability (HA) pair.
Note For more information regarding SR-PCE
HA pairs, refer to the Multiple Cisco
SR-PCE HA Pairs chapter of the Cisco
Crosswork Optimization Engine 1.2.1 User
Guide .
Command api authentication { basic | digest }
Description
Specify the type of authentication:
• basic – Use HTTP Basic authentication
(plaintext)
• digest – Use HTTP Digest authentication (MD5)
Add credentials when connecting to API.
api username password { clear | encrypted } password
api sibling ipv4 address Opens a synchronization channel to another PCE in the same high availability (HA) pair.
Note For more information regarding SR-PCE
HA pairs, refer to the Multiple Cisco
SR-PCE HA Pairs chapter of the Cisco
Crosswork Optimization Engine 1.2.1 User
Guide .
Example: Configuring API on SR-PCE pce address ipv4 1.1.1.100
rest user admin password encrypted 1304131F0202
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!
authentication basic
!
sibling ipv4 1.1.1.200
!
end pce address ipv4 1.1.1.100
api user admin
!
password encrypted 1304131F0202
!
authentication digest sibling ipv4 1.1.1.200
!
end
The following example shows the current active connections:
RP/0/0/CPU0:pce1# show tcp brief | i 8080
Thu Aug 6 00:40:15.408 PDT
0xe9806fb8 0x60000000
0xe94023b8 0x60000000
0
0
0
0
:::8080
1.1.1.100:50487
0xeb20bb40 0x60000000
0xe98031a0 0x60000000
0
0
0 1.1.1.100:8080
0 0.0.0.0:8080
:::0
1.1.1.200:8080
1.1.1.200:44401
0.0.0.0:0
LISTEN
ESTAB
ESTAB
LISTEN
The first and fourth entries show the API server listening for IPv4 and IPv6 connections.
The second and third entries show the established sibling connection between PCE1 (1.1.1.100) and PCE2
(1.1.1.200).
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C H A P T E R
12
Configure Performance Measurement
Network performance metrics is a critical measure for traffic engineering (TE) in service provider networks.
Network performance metrics include the following:
• Packet loss
• Delay
• Delay variation
• Bandwidth utilization
These network performance metrics provide network operators information about the performance characteristics of their networks for performance evaluation and help to ensure compliance with service level agreements.
The service-level agreements (SLAs) of service providers depend on the ability to measure and monitor these network performance metrics. Network operators can use performance measurement (PM) feature to monitor the network metrics for links and end-to-end TE label switched paths (LSPs).
The following table explains the functionalities supported by performance measurement feature for measuring delay for links or SR policies.
Table 9: Performance Measurement Functionalities
Functionality Details
Profiles You can configure different profiles for different types of delay measurements.
Use the "interfaces" delay profile type for link-delay measurement. The "sr-policy" delay profile type is used for SR policy delay measurements. Delay profile allows you to schedule probe and configure metric advertisement parameters for delay measurement.
Protocols
Probe and burst scheduling
Two-Way Active Measurement Protocol (TWAMP) Light (using RFC 5357 with
IP/UDP encap).
Schedule probes and configure metric advertisement parameters for delay measurement.
Metric advertisements Advertise measured metrics periodically using configured thresholds. Also supports accelerated advertisements using configured thresholds.
Measurement history and counters
Maintain packet delay and loss measurement history, session counters, and packet advertisement counters.
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Measurement Modes
•
Measurement Modes, on page 226
•
Usage Guidelines and Limitations, on page 227
•
Link Delay Measurement, on page 228
•
SR Policy End-to-End Delay Measurement , on page 241
Measurement Modes
The following table compares the different hardware and timing requirements for the measurement modes supported in SR PM.
Table 10: Measurement Mode Requirements
Measurement Mode PTP Clock Synchronization between Sender and Reflector
One-way
Two-way
Sender:
PTP-Capable HW and HW
Timestamping
Required
Required
Reflector:
PTP-Capable HW and HW
Timestamping
Required
Required
Required
Not Required
One-Way
One-way measurement mode provides the most precise form of one-way delay measurement. PTP-capable hardware and hardware timestamping are required on both Sender and Reflector, with PTP Clock
Synchronization between Sender and Reflector.
Delay measurement in one-way mode is calculated as (T2 – T1).
Figure 8: One-Way
The PM query and response for one-way delay measurement can be described in the following steps:
1.
The local-end router sends PM query packets periodically to the remote side once the egress line card on the router applies timestamps on packets.
2.
The ingress line card on the remote-end router applies time-stamps on packets as soon as they are received.
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3.
The remote-end router sends the PM packets containing time-stamps back to the local-end router.
4.
One-way delay is measured using the time-stamp values in the PM packet.
Two-Way
Two-way meaurement mode provides two-way measurements. PTP-capable hardware and hardware timestamping are required on both Sender and Reflector, but PTP clock synchronization between Sender and
Reflector is not required.
Delay measurements in two-way mode are calculated as follows:
• Two-Way Delay = (T4 – T1) – (T3 – T2)
• One-Way Delay = Two-Way Delay/2
Figure 9: Two-Way
The PM query and response for two-way delay measurement can be described in the following steps:
1.
The local-end router sends PM query packets periodically to the remote side once the egress line card on the router applies timestamps on packets.
2.
Ingress line card on the remote-end router applies time-stamps on packets as soon as they are received.
3.
The remote-end router sends the PM packets containing time-stamps back to the local-end router. The remote-end router time-stamps the packet just before sending it for two-way measurement.
4.
The local-end router time-stamps the packet as soon as the packet is received for two-way measurement.
5.
One-way delay and optionally two-way delay is measured using the time-stamp values in the PM packet.
Usage Guidelines and Limitations
The following usage guidelines and limitations apply:
• SR PM is supported on hardware that supports Precision Time Protocol (PTP). This requirement applies to both one-way and two-way delay measurement.
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Link Delay Measurement
See the Configuring Precision Time Protocol chapter in the System Management Configuration Guide for Cisco NCS 5500 Series Routers for Restrictions for PTP and the Timing Hardware Support Matrix.
Link Delay Measurement
The PM for link delay uses the IP/UDP packet format defined in RFC 5357 (TWAMP-Light) for probes.
Two-Way Active Measurement Protocol (TWAMP) adds two-way or round-trip measurement capabilities.
TWAMP employs time stamps applied at the echo destination (reflector) to enable greater accuracy. In the case of TWAMP Light, the Session-Reflector doesn’t necessarily know about the session state. The
Session-Reflector simply copies the Sequence Number of the received packet to the Sequence Number field of the reflected packet. The controller receives the reflected test packets and collects two-way metrics. This architecture allows for collection of two-way metrics.
Usage Guidelines and Restrictions for PM for Link Delay
The following restrictions and guidelines apply for the PM for link delay feature for different links.
• For broadcast links, only point-to-point (P2P) links are supported. P2P configuration on IGP is required for flooding the value.
• For link bundles, the hashing function may select a member link for forwarding but the reply may come from the remote line card on a different member link of the bundle.
• For one-way delay measurement, clocks should be synchronized on two end-point nodes of the link using
PTP.
Configuration Example: PM for Link Delay
This example shows how to configure performance-measurement functionalities for link delay as a global default profile. The default values for the different parameters in the PM for link delay is given as follows:
• probe measurement mode : The default measurement mode for probe is two-way delay measurement.
If you are configuring one-way delay measurement, hardware clocks must be synchronized between the local-end and remote-end routers using precision time protocol (PTP). See
for more information.
• protocol : Interface delay measurement using RFC 5357 with IP/UDP encap (TWAMP-Light).
• burst interval : Interval for sending probe packet. The default value is 3000 milliseconds and the range is from 30 to 15000 milliseconds.
• computation interval : Interval for metric computation. Default is 30 seconds; range is 1 to 3600 seconds.
• periodic advertisement : Periodic advertisement is enabled by default.
• periodic-advertisement interval : The default value is 120 seconds and the interval range is from 30 to
3600 seconds.
• periodic-advertisement threshold : Checks the minimum-delay metric change for threshold crossing for periodic advertisement. The default value is 10 percent and the range is from 0 to 100 percent.
• periodic-advertisement minimum change : The default value is 1000 microseconds (usec) and the range is from 0 to 100000 microseconds.
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• accelerated advertisement : Accelerated advertisement is disabled by default.
• accelerated-advertisement threshold : Checks the minimum-delay metric change for threshold crossing for accelerated advertisement. The default value is 20 percent and the range is from 0 to 100 percent.
• accelerated-advertisement minimum change : The default value is 500 microseconds and the range is from 0 to 100000 microseconds.
RP/0/0/CPU0:router(config)# performance-measurement delay-profile interfaces
RP/0/0/CPU0:router(config-pm-dm-intf)# probe
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# measurement-mode one-way
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# burst-interval 60
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# computation-interval 60
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# exit
RP/0/0/CPU0:router(config-pm-dm-intf)# advertisement periodic
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# interval 120
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# threshold 20
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# minimum-change 1000
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# exit
RP/0/0/CPU0:router(config-pm-dm-intf)# advertisement accelerated
RP/0/0/CPU0:router(config-pm-dm-intf-adv-acc)# threshold 30
RP/0/0/CPU0:router(config-pm-dm-intf-adv-acc)# minimum-change 1000
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# exit
Configure the UDP Destination Port
Configuring the UDP port for TWAMP-Light protocol is optional. By default, PM uses port 862 as the
TWAMP-reserved UDP destination port for delay.
The UDP port is configured for each PM measurement probe type (delay, loss, protocol, authentication mode, etc.) on querier and responder nodes. If you configure a different UDP port, the UDP port for each PM measurement probe type must match on the querier and the responder nodes.
Note The same UDP destination port is used for delay measurement for links and SR Policy.
This example shows how to configure the UDP destination port for delay.
Router(config)# performance-measurement
Router(config-perf-meas)# protocol twamp-light
Router(config-pm-protocol)# measurement delay unauthenticated
Router(config-pm-proto-mode)# querier-dst-port 12000
Enable PM for Link Delay Over an Interface
This example shows how to enable PM for link delay over an interface.
RP/0/0/CPU0:router(config)# performance-measurement
RP/0/0/CPU0:router(config-perf-meas)# interface TenGigE0/0/0/0
RP/0/0/CPU0:router(config-pm-intf)# next-hop ipv4 10.10.10.2
// Optional IPv4 or IPv6 next-hop address
RP/0/0/CPU0:router(config-pm-intf)# delay-measurement
RP/0/0/CPU0:router(config-pm-dm-intf)# exit
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The source and destination IP addresses used in the OAM packet are determined by the IP address present on the interface where the delay-measurement operation is enabled and the setting of the optional next-hop address.
When the next-hop address is not specified, the following rules apply to determine the source and destination
IP addresses used in the OAM packet:
• If an IPv4 address is configured under the interface, then:
• OAM packet source IP address = Interface's IPv4 address
• OAM packet destination IP address = 127.0.0.0
• Else, if an IPv6 global address is configured under the interface, then:
• OAM packet source IP address = Interface's IPv6 global address
• OAM packet destination IP address = 0::ff:127.0.0.0
When the next-hop { ipv4 | ipv6 } address is configured, the following rules apply to determine the source and destination IP addresses used in the OAM packet:
• If a next-hop IPv4 address is configured, then:
• OAM packet source IP address = Interface's IPv4 address
• OAM packet destination IP address = Configured next-hop IPv4 address
Note If there is no IPv4 address configured under the interface, then the delay-measurement probe does not send OAM packets.
• If a next-hop IPv6 address is configured, then:
• OAM packet source IP address = Interface's IPv6 global address
• OAM packet destination IP address = Configured next-hop IPv6 address
Note If there is no IPv6 global address configured under the interface, then the delay-measurement probe does not send OAM packets.
This example shows how to enable PM for link delay over an interface with IPv4 address configured: interface TenGigE0/0/0/0 ipv4 address 10.10.10.1 255.255.255.0
performance-measurement interface TenGigE0/0/0/0 delay-measurement
This example shows how to enable PM for link delay over an interface IPv6 address configured:
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Link Delay Measurement interface TenGigE0/0/0/0 ipv6 address 10:10:10::1/64 performance-measurement interface TenGigE0/0/0/0 delay-measurement
This example shows how to enable PM for link delay over an interface with a specified next-hop IPv4 address: interface TenGigE0/0/0/0 ipv4 address 10.10.10.1 255.255.255.0
performance-measurement interface TenGigE0/0/0/0 next-hop ipv4 10.10.10.2
delay-measurement
This example shows how to enable PM for link delay over an interface with a specified next-hop IPv6 address: interface TenGigE0/0/0/0 ipv6 address 10:10:10::1/64 performance-measurement interface TenGigE0/0/0/0 next-hop ipv6 10:10:10::2 delay-measurement
Verification
RP/0/0/CPU0:router# show performance-measurement profile interface
Thu Dec 12 14:13:16.029 PST
-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
Interface Delay-Measurement:
Profile configuration:
Measurement Type
Probe computation interval
Type of services
Burst interval
Burst count
: Two-Way
: 30 (effective: 30) seconds
: Traffic Class: 6, DSCP: 48
: 3000 (effective: 3000) mSec
: 10 packets
Encap mode
Payload Type
Destination sweeping mode
Periodic advertisement
Interval
Threshold
Minimum-Change
Advertisement accelerated
Threshold crossing check
: UDP
: TWAMP-light
: Disabled
: Enabled
: 120 (effective: 120) sec
: 10%
: 500 uSec
: Disabled
: Minimum-delay
RP/0/0/CPU0:router# show performance-measurement summary detail location 0/2/CPU0
Thu Dec 12 14:09:59.162 PST
-------------------------------------------------------------------------------
0/2/CPU0
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-------------------------------------------------------------------------------
Total interfaces : 1
Total SR Policies
Total RSVP-TE tunnels
: 0
: 0
Total Maximum PPS
Total Interfaces PPS
Maximum Allowed Multi-hop PPS
: 2000 pkts/sec
: 0 pkts/sec
: 2000 pkts/sec
Multi Hop Requested PPS
Dampened Multi Hop Requested PPS
Inuse Burst Interval Adjustment Factor
: 0 pkts/sec (0% of max allowed)
: 0% of max allowed
: 100% of configuration
Interface Delay-Measurement:
Total active sessions
Counters:
Packets:
Total sent
Total received
Errors:
TX:
Reason interface down
Reason no MPLS caps
Reason no IP address
Reason other
RX:
Reason negative delay
Reason delay threshold exceeded
Reason missing TX timestamp
Reason missing RX timestamp
Reason probe full
Reason probe not started
Reason control code error
Reason control code notif
Probes:
Total started
Total completed
Total incomplete
Total advertisements
SR Policy Delay-Measurement:
Total active sessions
Counters:
Packets:
Total sent
Total received
Errors:
TX:
Reason interface down
Reason no MPLS caps
Reason no IP address
Reason other
RX:
Reason negative delay
Reason delay threshold exceeded
Reason missing TX timestamp
Reason missing RX timestamp
Reason probe full
Reason probe not started
Reason control code error
Reason control code notif
Probes:
Total started
Total completed
Total incomplete
: 1
: 26
: 26
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 3
: 2
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
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Total advertisements
RSVP-TE Delay-Measurement:
Total active sessions
Counters:
Packets:
Total sent
Total received
Errors:
TX:
Reason interface down
Reason no MPLS caps
Reason no IP address
Reason other
RX:
Reason negative delay
Reason delay threshold exceeded
Reason missing TX timestamp
Reason missing RX timestamp
Reason probe full
Reason probe not started
Reason control code error
Reason control code notif
Probes:
Total started
Total completed
Total incomplete
Total advertisements
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
: 0
Global Delay Counters:
Total packets sent
Total query packets received
Total invalid session id
Total missing session
: 26
: 26
: 0
: 0
RP/0/0/CPU0:router# show performance-measurement interfaces detail
Thu Dec 12 14:16:09.692 PST
-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
0/2/CPU0
-------------------------------------------------------------------------------
Interface Name: GigabitEthernet0/2/0/0 (ifh: 0x1004060)
Delay-Measurement
Loss-Measurement
: Enabled
: Disabled
Configured IPv4 Address
Configured IPv6 Address
Link Local IPv6 Address
Configured Next-hop Address
Local MAC Address
: 10.10.10.2
: 10:10:10::2
: fe80::3a:6fff:fec9:cd6b
: Unknown
: 023a.6fc9.cd6b
Next-hop MAC Address
Primary VLAN Tag
Secondary VLAN Tag
State
: 0291.e460.6707
: None
: None
: Up
Delay Measurement session:
Session ID : 1
Last advertisement:
Advertised at: Dec 12 2019 14:10:43.138 (326.782 seconds ago)
Advertised reason: First advertisement
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Advertised delays (uSec): avg: 839, min: 587, max: 8209, variance: 297
Next advertisement:
Threshold check scheduled in 1 more probe (roughly every 120 seconds)
Aggregated delays (uSec): avg: 751, min: 589, max: 905, variance: 112
Rolling average (uSec): 756
Current Probe:
Started at Dec 12 2019 14:15:43.154 (26.766 seconds ago)
Packets Sent: 9, received: 9
Measured delays (uSec): avg: 795, min: 631, max: 1199, variance: 164
Next probe scheduled at Dec 12 2019 14:16:13.132 (in 3.212 seconds)
Next burst packet will be sent in 0.212 seconds
Burst packet sent every 3.0 seconds
Probe samples:
Packet Rx Timestamp
Dec 12 2019 14:15:43.156
Dec 12 2019 14:15:46.156
Dec 12 2019 14:15:49.156
Dec 12 2019 14:15:52.157
Dec 12 2019 14:15:55.156
Dec 12 2019 14:15:58.156
Dec 12 2019 14:16:01.157
Dec 12 2019 14:16:04.157
Dec 12 2019 14:16:07.157
Measured Delay (nsec)
689223
876561
913548
1199620
794008
631437
656440
658267
736880
You can also use the following commands for verifying the PM for link delay on the local-end router.
Command show performance-measurement history probe interfaces [ interface ]
Description
Displays the PM link-delay probe history for interfaces.
show performance-measurement history aggregated interfaces [ interface ] show performance-measurement history advertisement interfaces [ interface ]
Displays the PM link-delay aggregated history for interfaces.
Displays the PM link-delay advertisement history for interfaces.
show performance-measurement counters [interface interface ] [location location-name ]
Displays the PM link-delay session counters.
You can also use the following commands for verifying the PM for link-delay configuration on the remote-end router.
Command Description show performance-measurement responder summary [ location location-name ] show performance-measurement responder interfaces [ interface ] show performance-measurement responder counters [ interface interface ] [ location location-name ]
Displays the PM for link-delay summary on the remote-end router (responder).
Displays PM for link-delay for interfaces on the remote-end router.
Displays the PM link-delay session counters on the remote-end router.
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SR Performance Measurement Named Profiles
You can create a named performance measurement profile for delay or liveness. Details:
Delay Profile
This example shows how to create a named SR performance measurement delay profile.
Router(config)# performance-measurement delay-profile sr-policy name profile2
Router(config-pm-dm-srpolicy)# probe
Router(config-pm-dm-srpolicy-probe)# burst-interval 60
Router(config-pm-dm-srpolicy-probe)# computation-interval 60
Router(config-pm-dm-srpolicy-probe)# protocol twamp-light
Router(config-pm-dm-srpolicy-probe)# tos dscp 63
Router(config-pm-dm-srpolicy)# advertisement
Router(config-pm-dm-srpolicy-adv)# periodic
Router(config-pm-dm-srpolicy-adv-per)# interval 60
Router(config-pm-dm-srpolicy-adv-per)# minimum-change 1000
Router(config-pm-dm-srpolicy-adv-per)# threshold 20
Router(config-pm-dm-srpolicy-adv-per)# commit
Apply the delay profile for an SR Policy.
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy TEST
Router(config-sr-te-policy)# color 4 end-point ipv4 10.10.10.10
Router(config-sr-te-policy)# performance-measurement
Router(config-sr-te-policy-perf-meas)# delay-measurement delay-profile name profile2
Router(config-sr-te-policy)#candidate-paths
Router(config-sr-te-policy-path)#preference 100
Router(config-sr-te-policy-path-pref)#explicit segment-list LIST1
Router(config-sr-te-pp-info)#weight 2
Router(config-sr-te-policy-path-pref)#explicit segment-list LIST2
Router(config-sr-te-pp-info)#weight 3
Running Configuration
Router# show run segment-routing traffic-eng policy TEST segment-routing traffic-eng policy TEST color 4 end-point ipv4 10.10.10.10
candidate-paths preference 100 explicit segment-list LIST1 weight 2
!
explicit segment-list LIST2 weight 3
!
!
!
performance-measurement delay-measurement delay-profile name profile2
Verification
Router# show performance-measurement profile named-profile delay sr-policy name profile2
----------------------------
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0/RSP0/CPU0
----------------------------
SR Policy Delay Measurement Profile Name: profile2
Profile configuration:
Measurement mode
Protocol type
Encap mode
Type of service:
PM-MPLS traffic class
: One-way
: TWAMP-light
: UDP
TWAMP-light DSCP
Probe computation interval
Burst interval
Packets per computation interval
Periodic advertisement
: 6
: 63
: 60 (effective: 60) seconds
: 60 (effective: 60) mSec
: 1000
: Enabled
Interval
Threshold
Minimum-change
Advertisement accelerated
Advertisement logging:
: 60 (effective: 60) sec
: 20%
: 1000 uSec
: Disabled
Delay exceeded
Threshold crossing check
Router alert
Destination sweeping mode
Liveness detection parameters:
Multiplier
Logging state change
: Disabled (default)
: Maximum-delay
: Disabled (default)
: Disabled
: 3
: Disabled
On-Demand SR Policy
Router(config-sr-te)# on-demand color 20
Router(config-sr-te-color)# performance-measurement delay-measurement
Router(config-sr-te-color-delay-meas)# delay-profile name profile2
Router(config-sr-te-color-delay-meas)# commit
Running Configuration
Router# show run segment-routing traffic-eng on-demand color 20 segment-routing traffic-eng on-demand color 20 performance-measurement delay-measurement delay-profile name profile2
Liveness Profile
This example shows how to create a named SR performance measurement liveness profile.
Router(config)# performance-measurement liveness-profile sr-policy name profile3
Router(config-pm-ld-srpolicy)# probe
Router(config-pm-ld-srpolicy-probe)# burst-interval 60
Router(config-pm-ld-srpolicy-probe)# measurement-mode loopback
Router(config-pm-ld-srpolicy-probe)# tos dscp 10
Router(config-pm-ld-srpolicy-probe)# liveness-detection
Router(config-pm-ld-srpolicy-probe)# multiplier 5
Router(config-pm-ld-srpolicy-probe)# commit
Apply the liveness profile for the SR policy
This example shows how to enable PM for SR policy liveness for a specific policy.
For the same policy, you cannot enable delay-measurement (delay-profile) and liveness-detection
(liveness-profile) at the same time. For example, if delay measurement is enabled, use the no
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Link Delay Measurement delay-measurement command to disable it, and then enable the following command for enabling liveness detection.
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy TRST2
Router(config-sr-te-policy)# color 40 end-point ipv4 20.20.20.20
Router(config-sr-te-policy)#candidate-paths
Router(config-sr-te-policy-path)#preference 50
Router(config-sr-te-policy-path-pref)#explicit segment-list LIST3
Router(config-sr-te-pp-info)#weight 2
Router(config-sr-te-policy-path-pref)#explicit segment-list LIST4
Router(config-sr-te-pp-info)#weight 3
Router(config-sr-te-policy)# performance-measurement
Router(config-sr-te-policy-perf-meas)# liveness-detection liveness-profile name profile3
Running Configuration
Router# show run segment-routing traffic-eng policy TRST2 segment-routing traffic-eng policy TRST2 color 40 end-point ipv4 20.20.20.20
candidate-paths preference 50 explicit segment-list LIST3 weight 2
!
explicit segment-list LIST4
!
!
weight 3
!
performance-measurement liveness-detection liveness-profile name profile3
!
Verification
Router# show performance-measurement profile named-profile delay sr-policy name profile3
-----------
0/RSP0/CPU0
-----------
SR Policy Liveness Detection Profile Name: profile1
Profile configuration:
Measurement mode
Protocol type
Type of service:
: Loopback
: TWAMP-light
TWAMP-light DSCP
Burst interval
Destination sweeping mode
Liveness detection parameters:
Multiplier
Logging state change
: 10
: 60 (effective: 60) mSec
: Disabled
: 3
: Disabled
SR Policy Liveness Detection Profile Name: profile3
Profile configuration:
Measurement mode : Loopback
Protocol type
Type of service:
: TWAMP-light
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Delay Normalization
TWAMP-light DSCP
Burst interval
Destination sweeping mode
Liveness detection parameters:
Multiplier
Logging state change
: 10
: 60 (effective: 60) mSec
: Disabled
: 3
: Disabled
On-Demand SR Policy
For the same policy, you cannot enable delay-measurement (delay-profile) and liveness-detection
(liveness-profile) at the same time. For example, to disable delay measurement, use the no delay-measurement command, and then enable the following command for enabling liveness detection.
Router(config-sr-te)#on-demand color 30
Router(config-sr-te-color)#performance-measurement
Router(config-sr-te-color-pm)# liveness-detection liveness-profile name profile1
Router(config-sr-te-color-delay-meas)# commit
Running Configuration
Router# show run segment-routing traffic-eng on-demand color 30 segment-routing traffic-eng on-demand color 30 performance-measurement liveness-detection
!
liveness-profile name profile3
Verification
Router# show performance-measurement profile named-profile liveness sr-policy name profile3
--------------------
0/RSP0/CPU0
--------------------
SR Policy Liveness Detection Profile Name: profile3
Profile configuration:
Measurement mode
Protocol type
Type of service:
: Loopback
: TWAMP-light
TWAMP-light DSCP
Burst interval
Destination sweeping mode
Liveness detection parameters:
Multiplier
Logging state change
: 10
: 60 (effective: 60) mSec
: Disabled
: 3
: Disabled
Delay Normalization
Performance measurement (PM) measures various link characteristics like packet loss and delay. Such characteristics can be used by IS-IS as a metric for Flexible Algorithm computation. Low latency routing using dynamic delay measurement is one of the primary use cases for Flexible Algorithm technology.
Delay is measured in microseconds. If delay values are taken as measured and used as link metrics during the
IS-IS topology computation, some valid ECMP paths might be unused because of the negligible difference in the link delay.
The Delay Normalization feature computes a normalized delay value and uses the normalized value instead.
This value is advertised and used as a metric during the Flexible Algorithm computation.
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Delay Normalization
The normalization is performed when the delay is received from the delay measurement component. When the next value is received, it is normalized and compared to the previous saved normalized value. If the values are different, then the LSP generation is triggered.
The following formula is used to calculate the normalized value:
• Dm – measured Delay
• Int – configured normalized Interval
• Off – configured normalized Offset (must be less than the normalized interval Int)
• Dn – normalized Delay
• a = Dm / Int (rounded down)
• b = a * Int + Off
If the measured delay (Dm) is less than or equal to b , then the normalized delay (Dn) is equal to b . Otherwise,
Dn is b + Int .
Example
The following example shows a low-latency service. The intent is to avoid high-latency links (1-6, 5-2). Links
1-2 and 5-6 are both low-latency links. The measured latency is not equal, but the difference is insignificant.
We can normalize the measured latency before it is advertised and used by IS-IS. Consider a scenario with the following:
• Interval = 10
• Offset = 3
The measured delays will be normalized as follows:
• Dm = 29 a = 29 / 10 = 2 (2.9, rounded down to 2) b = 2 * 10 + 3 = 23
In this case, Dm (29) is greater than b (23); so Dn is equal to b + I (23 + 10) = 33
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Delay Normalization
• Dm = 31 a = 31 / 10 = 3 (3.1, rounded down to 3) b = 3 * 10 + 3 = 33
In this case, Dm (31) is less than b (33); so Dn is b = 33
The link delay between 1-2 and 5-6 is normalized to 33.
Configuration
Delay normalization is disabled by default. To enable and configure delay normalization, use the delay
normalize interval interval [ offset offset ] command.
• interval – The value of the normalize interval in microseconds.
• offset – The value of the normalized offset in microseconds. This value must be smaller than the value of normalized interval.
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IS-IS Configuration router isis 1 interface GigEth 0/0/0/0 delay normalize interval 10 offset 3 address-family ipv4 unicast metric 77
SR Policy End-to-End Delay Measurement
The PM for SR Policy uses the IP/UDP packet format defined in RFC 5357 (TWAMP-Light) for probes.
Two-Way Active Measurement Protocol (TWAMP) adds two-way or round-trip measurement capabilities.
TWAMP employs time stamps applied at the echo destination (reflector) to enable greater accuracy. In the case of TWAMP Light, the Session-Reflector doesn’t necessarily know about the session state. The
Session-Reflector simply copies the Sequence Number of the received packet to the Sequence Number field of the reflected packet. The controller receives the reflected test packets and collects two-way metrics. This architecture allows for collection of two-way metrics.
The extended TE link delay metric (minimum-delay value) can be used to compute paths for SR policies as an optimization metric or as an accumulated delay bound.
There is a need to monitor the end-to-end delay experienced by the traffic sent over an SR policy to ensure that the delay does not exceed the requested “upper-bound” and violate SLAs. You can verify the end-to-end delay values before activating the candidate-path or the segment lists of the SR policy in forwarding table, or to deactivate the active candidate-path or the segment lists of the SR policy in forwarding table.
Note The end-to-end delay value of an SR policy will be different than the path computation result (for example, the sum of TE link delay metrics) due to several factors, such as queuing delay within the routers.
Restrictions and Usage Guidelines for PM for SR Policy Delay
Hardware clocks must be synchronized between the querier and the responder nodes of the link using PTP for one-way delay measurement.
Configuring Performance Measurement Parameters
This example shows how to configure performance-measurement parameters for SR policy delay as a global default profile. The default values for the different parameters in the PM for SR policy delay is given as follows:
• probe : The default mode for probe is one-way delay measurement. See
for more information.
• burst interval : Interval for sending probe packet. The default value is 3000 milliseconds and the range is from 30 to 15000 milliseconds.
• computation interval : Interval for metric computation. Default is 30 seconds; range is 1 to 3600 seconds.
• protocol :
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• twamp-light : SR Policy delay measurement using RFC 5357 with IP/UDP encap. This is the default protocol.
• tos : Type of Service
• dscp value : The default value is 48 and the range is from 0 to 63.
• traffic-class value : The default value is 6 and the range is from 0 to 7.
• advertisement threshold-check : minimum-delay/maximum-delay - The default value of periodic advertisement threshold-check is maximum-delay.
• periodic advertisement : Periodic advertisement is enabled by default.
• periodic-advertisement interval : The default value is 120 seconds and the interval range is from 30 to
3600 seconds.
• periodic-advertisement threshold : Checks the minimum-delay metric change for threshold crossing for periodic advertisement. The default value is 10 percent and the range is from 0 to 100 percent.
• periodic-advertisement minimum-change : The default value is 500 microseconds (usec) and the range is from 0 to 100000 microseconds.
• accelerated advertisement : Accelerated advertisement is disabled by default.
• accelerated-advertisement threshold : Checks the minimum-delay metric change for threshold crossing for accelerated advertisement. The default value is 20 percent and the range is from 0 to 100 percent.
• accelerated-advertisement minimum : The default value is 500 microseconds and the range is from 1 to 100000 microseconds.
Router(config)# performance-measurement delay-profile sr-policy
Router(config-pm-dm-srpolicy)# probe
Router(config-pm-dm-srpolicy-probe)# burst-interval 60
Router(config-pm-dm-srpolicy-probe)# computation-interval 60
Router(config-pm-dm-srpolicy-probe)# protocol twamp-light
Router(config-pm-dm-srpolicy-probe)# tos dscp 63
Router(config-pm-dm-srpolicy-probe)# exit
Router(config-pm-dm-srpolicy)# advertisement
Router(config-pm-dm-srpolicy-adv)# periodic
Router(config-pm-dm-srpolicy-adv-per)# interval 60
Router(config-pm-dm-srpolicy-adv-per)# minimum-change 1000
Router(config-pm-dm-srpolicy-adv-per)# threshold 20
Router(config-pm-dm-srpolicy-adv-per)# exit
Router(config-pm-dm-srpolicy-adv)# accelerated
Router(config-pm-dm-srpolicy-adv-acc)# minimum-change 1000
Router(config-pm-dm-srpolicy-adv-acc)# threshold 10
Router(config-pm-dm-srpolicy-adv-acc)# exit
Router(config-pm-dm-srpolicy-adv)# threshold-check minimum-delay
Router(config-pm-dm-srpolicy-adv)# exit
Router(config-pm-dm-srpolicy)#
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Configure the UDP Destination Port
Configuring the UDP port for TWAMP-Light protocol is optional. By default, PM uses port 862 as the
TWAMP-reserved UDP destination port for delay.
The UDP port is configured for each PM measurement probe type (delay, loss, protocol, authentication mode, etc.) on querier and responder nodes. If you configure a different UDP port, the UDP port for each PM measurement probe type must match on the querier and the responder nodes.
Note The same UDP destination port is used for delay measurement for links and SR Policy.
This example shows how to configure the UDP destination port for delay.
Router(config)# performance-measurement
Router(config-perf-meas)# protocol twamp-light
Router(config-pm-protocol)# measurement delay unauthenticated
Router(config-pm-proto-mode)# querier-dst-port 12000
Enable Performance Measurement for SR Policy
This example shows how to enable PM for SR policy delay for a specific policy.
Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy foo
Router(config-sr-te-policy)# performance-measurement
Router(config-sr-te-policy-perf-meas)# delay-measurement
SR Policy Probe IP/UDP ECMP Hashing Configuration
This example shows how to configure SR Policy ECMP IP-hashing mode.
• The destination IPv4 address 127.x.x.x – 127.y.y.y is used in the Probe messages to take advantages of
3-tuple IP hashing (source-address, destination-address, and local router ID) for ECMP paths of SR-MPLS
Policy.
Note The destination IPv4 address must be 127/8 range (loopback), otherwise it will be rejected.
• One PM session is always created for the actual endpoint address of the SR Policy.
• You can specify the number of IP addresses to sweep. The range is from 0 (default, no sweeping) to 128.
• Platforms may have a limitation for large label stack size to not check IP address for hashing.
Router(config)# performance-measurement delay-profile sr-policy
Router(config-pm-dm-srpolicy)# probe
Router(config-pm-dm-srpolicy-probe)# sweep
Router(config-pm-dm-srpolicy-probe-sweep)# destination ipv4 127.0.0.1 range 28
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Verification
Router# show performance-measurement sr-policy brief
Mon Jan 20 18:48:41.002 PST
-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
Policy Name LSP ID Tx/Rx Avg/Min/Max/Variance
----------------------------------------------------------------------------srte_c_10_ep_192.168.0.4
2 6/6 27012/26906/27203/106
Router# show performance-measurement sr-policy name srte_c_10_ep_192.168.0.4 detail verbose
Mon Jan 20 18:44:22.400 PST
-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
SR Policy name: srte_c_10_ep_192.168.0.4
Color : 10
Endpoint : 192.168.0.4
Number of candidate-paths : 1
Candidate-Path:
Instance
Preference
Protocol-origin
Discriminator
Source address
Reverse path label
: 2
: 100
: Configured
: 100
: 192.168.0.2
: Not configured
Number of segment-lists : 1
Last advertisement:
No advertisements have occured
Next advertisement:
Check scheduled at the end of the current probe (roughly every 30 seconds)
Aggregated delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
Rolling average (uSec): 45218
Last probe:
Packets Sent: 9, received: 9
Measured delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
Current Probe:
Started at Jan 20 2020 18:44:19.170 (3.453 seconds ago)
Packets Sent: 3, received: 3
Measured delays (uSec): avg: 26588, min: 26558, max: 26630, variance: 30
Next probe scheduled at Jan 20 2020 18:44:34.166 (in 11.543 seconds)
Next burst packet will be sent in 1.543 seconds
Burst packet sent every 5.0 seconds
Liveness Detection: Disabled
Segment-List : R4
16004
Number of atomic paths : 3
Last advertisement:
No advertisements have occured
Next advertisement:
Aggregated delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
Rolling average (uSec): 45218
Last probe:
Packets Sent: 9, received: 9
Measured delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
Current probe:
Packets Sent: 3, received: 3
Measured delays (uSec): avg: 26588, min: 26558, max: 26630, variance: 30
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Liveness Detection: Disabled
Atomic path:
Hops : 127.0.0.0
Session ID
Last advertisement:
: 33554434
No advertisements have occured
Next advertisement:
Aggregated delays (uSec): avg: 45407, min: 26629, max: 82600, variance: 18778
Rolling average (uSec): 45407
Last Probe:
Packets Sent: 3, received: 3
Measured delays (uSec): avg: 45407, min: 26629, max: 82600, variance: 18778
Current Probe:
Packets Sent: 1, received: 1
Measured delays (uSec): avg: 26630, min: 26630, max: 26630, variance: 0
Probe samples:
Packet Rx Timestamp
Jan 20 2020 18:44:19.198
Liveness Detection: Disabled
Measured Delay (nsec)
26630730
Atomic path:
Hops
Session ID
: 127.0.0.1
: 33554435
Last advertisement:
No advertisements have occured
Next advertisement:
Aggregated delays (uSec): avg: 45128, min: 26521, max: 81961, variance: 18607
Rolling average (uSec): 45128
Last Probe:
Packets Sent: 3, received: 3
Measured delays (uSec): avg: 45128, min: 26521, max: 81961, variance: 18607
Current Probe:
Packets Sent: 1, received: 1
Measured delays (uSec): avg: 26576, min: 26576, max: 26576, variance: 0
Probe samples:
Packet Rx Timestamp Measured Delay (nsec)
Jan 20 2020 18:44:19.198
Liveness Detection: Disabled
26576938
Atomic path:
Hops
Session ID
Last advertisement:
: 192.168.0.4
: 33554433
No advertisements have occured
Next advertisement:
Aggregated delays (uSec): avg: 45119, min: 26512, max: 81956, variance: 18607
Rolling average (uSec): 45119
Last Probe:
Packets Sent: 3, received: 3
Measured delays (uSec): avg: 45119, min: 26512, max: 81956, variance: 18607
Current Probe:
Packets Sent: 1, received: 1
Measured delays (uSec): avg: 26558, min: 26558, max: 26558, variance: 0
Probe samples:
Packet Rx Timestamp
Jan 20 2020 18:44:19.198
Liveness Detection: Disabled
Measured Delay (nsec)
26558375
Router# show performance-measurement history probe sr-policy
Mon Jan 20 18:46:55.445 PST
-------------------------------------------------------------------------------
0/0/CPU0
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-------------------------------------------------------------------------------
SR Policy name: srte_c_10_ep_192.168.0.4
Color : 10
Endpoint : 192.168.0.4
Candidate-Path:
Preference
Protocol-origin
: 100
: Configured
Discriminator : 100
Delay-Measurement history (uSec):
Probe Start Timestamp Pkt(TX/RX) Average
Jan 20 2020 18:46:34.174
Jan 20 2020 18:46:19.174
9/9
9/9
26880
26899
Jan 20 2020 18:46:04.173
Jan 20 2020 18:45:49.172
Jan 20 2020 18:45:34.172
Jan 20 2020 18:45:19.171
Jan 20 2020 18:45:04.171
9/9
9/9
9/9
9/9
9/9
26813
26985
26744
26740
27115
Jan 20 2020 18:44:49.171
Jan 20 2020 18:44:34.171
Jan 20 2020 18:44:19.170
Jan 20 2020 18:44:06.543
9/9
9/9
9/9
9/9
26878
26824
26944
45218
Segment-List
16004
: R4
Delay-Measurement history (uSec):
Probe Start Timestamp
Jan 20 2020 18:46:34.174
Pkt(TX/RX) Average
9/9 26880
Jan 20 2020 18:46:19.174
Jan 20 2020 18:46:04.173
Jan 20 2020 18:45:49.172
Jan 20 2020 18:45:34.172
Jan 20 2020 18:45:19.171
9/9
9/9
9/9
9/9
9/9
26899
26813
26985
26744
26740
Jan 20 2020 18:45:04.171
Jan 20 2020 18:44:49.171
Jan 20 2020 18:44:34.171
Jan 20 2020 18:44:19.170
Jan 20 2020 18:44:06.543
9/9
9/9
9/9
9/9
9/9
27115
26878
26824
26944
45218
Min
26684
26822
26571
26713
26557
26435
26938
26539
26562
26558
26512
Min
26684
26822
26571
26713
26557
26435
26938
26539
26562
26558
26512
Max
27070
27004
27164
27293
27005
27093
27591
27143
27265
27422
82600
Max
27070
27004
27164
27293
27005
27093
27591
27143
27265
27422
82600
Atomic path:
Hops : 127.0.0.0
Delay-Measurement history (uSec):
Probe Start Timestamp Pkt(TX/RX) Average
Jan 20 2020 18:46:34.174
Jan 20 2020 18:46:19.174
Jan 20 2020 18:46:04.173
Jan 20 2020 18:45:49.172
Jan 20 2020 18:45:34.172
3/3
3/3
3/3
3/3
3/3
26927
26982
26895
27054
26801
Jan 20 2020 18:45:19.171
Jan 20 2020 18:45:04.171
Jan 20 2020 18:44:49.171
Jan 20 2020 18:44:34.171
Jan 20 2020 18:44:19.170
Jan 20 2020 18:44:06.543
3/3
3/3
3/3
3/3
3/3
3/3
26807
27226
26976
26880
26994
45407
Atomic path:
Hops : 127.0.0.1
Delay-Measurement history (uSec):
Probe Start Timestamp
Jan 20 2020 18:46:34.174
Jan 20 2020 18:46:19.174
Jan 20 2020 18:46:04.173
Jan 20 2020 18:45:49.172
Pkt(TX/RX)
3/3
3/3
3/3
3/3
Average
26865
26846
26787
26954
Min
26747
26970
26647
26764
26694
26524
26938
26644
26679
26630
26629
Min
26705
26822
26581
26728
Max
27070
27004
27164
27293
27005
27093
27591
27143
27265
27422
82600
Max
26988
26881
26939
27180
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Jan 20 2020 18:45:34.172
Jan 20 2020 18:45:19.171
Jan 20 2020 18:45:04.171
Jan 20 2020 18:44:49.171
Jan 20 2020 18:44:34.171
Jan 20 2020 18:44:19.170
Jan 20 2020 18:44:06.543
3/3
3/3
3/3
3/3
3/3
3/3
3/3
26724
26705
27043
26848
26800
26927
45128
Atomic path:
Hops : 192.168.0.4
Delay-Measurement history (uSec):
Probe Start Timestamp Pkt(TX/RX) Average
Jan 20 2020 18:46:34.174
Jan 20 2020 18:46:19.174
3/3
3/3
26848
26871
Jan 20 2020 18:46:04.173
Jan 20 2020 18:45:49.172
Jan 20 2020 18:45:34.172
Jan 20 2020 18:45:19.171
Jan 20 2020 18:45:04.171
3/3
3/3
3/3
3/3
3/3
26759
26947
26708
26708
27078
Jan 20 2020 18:44:49.171
Jan 20 2020 18:44:34.171
Jan 20 2020 18:44:19.170
Jan 20 2020 18:44:06.543
3/3
3/3
3/3
3/3
26812
26793
26911
45119
26577
26452
26972
26550
26562
26576
26521
Min
26684
26833
26571
26713
26557
26435
27016
26539
26582
26558
26512
26957
27032
27124
27062
27204
27327
81961
Max
26967
26913
26876
27163
26939
27075
27138
27043
27181
27308
81956
Router# show performance-measurement counters sr-policy name srte_c_10_ep_192.168.0.4
Mon Jan 20 18:47:55.499 PST
-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
SR Policy name: srte_c_10_ep_192.168.0.4
Candidate-Path:
Instance : 2
Preference
Protocol-origin
Discriminator
Packets:
Total sent
: 100
: Configured
: 100
: 141
: 141 Total received
Errors:
Total sent errors
Total received errors
Probes:
: 0
: 0
Total started
Total completed
Total incomplete
Total advertisements
Segment-List
16004
Packets:
Total sent
Total received
Errors:
: R4
: 16
: 15
: 0
: 2
: 141
: 141
Total sent errors
Total received errors
Probes:
Total started
Total completed
Total incomplete
Total advertisements
: 0
: 0
: 16
: 15
: 0
: 2
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C H A P T E R
13
Configure Topology-Independent Loop-Free
Alternate (TI-LFA)
Topology-Independent Loop-Free Alternate (TI-LFA) uses segment routing to provide link, node, and Shared
Risk Link Groups (SRLG) protection in topologies where other fast reroute techniques cannot provide protection.
• Classic Loop-Free Alternate (LFA) is topology dependent, and therefore cannot protect all destinations in all networks. A limitation of LFA is that, even if one or more LFAs exist, the optimal LFA may not always be provided.
• Remote LFA (RLFA) extends the coverage to 90-95% of the destinations, but it also does not always provide the most desired repair path. RLFA also adds more operational complexity by requiring a targeted
LDP session to the RLFAs to protect LDP traffic.
TI-LFA provides a solution to these limitations while maintaining the simplicity of the IPFRR solution.
The goal of TI-LFA is to reduce the packet loss that results while routers converge after a topology change due to a link or node failure. Rapid failure repair (< 50 msec) is achieved through the use of pre-calculated backup paths that are loop-free and safe to use until the distributed network convergence process is completed.
The optimal repair path is the path that the traffic will eventually follow after the IGP has converged. This is called the post-convergence path. This path is preferred for the following reasons:
• Optimal for capacity planning — During the capacity-planning phase of the network, the capacity of a link is provisioned while taking into consideration that such link with be used when other links fail.
• Simple to operate — There is no need to perform a case-by-case adjustments to select the best LFA among multiple candidate LFAs.
• Fewer traffic transitions — Since the repair path is equal to the post-convergence path, the traffic switches paths only once.
The following topology illustrates the optimal and automatic selection of the TI-LFA repair path.
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Figure 10: TI-LFA Repair Path
Configure Topology-Independent Loop-Free Alternate (TI-LFA)
Node 2 protects traffic to destination Node 5.
With classic LFA, traffic would be steered to Node 4 after a failure of the protected link. This path is not optimal, since traffic is routed over edge node Node 4 that is connected to lower capacity links.
TI-LFA calculates a post-convergence path and derives the segment list required to steer packets along the post-convergence path without looping back.
In this example, if the protected link fails, the shortest path from Node2 to Node5 would be:
Node2
→
Node6
→
Node7
→
Node3
→
Node5
Node7 is the PQ-node for destination Node5. TI-LFA encodes a single segment (prefix SID of Node7) in the header of the packets on the repair path.
TI-LFA Protection Types
TI-LFA supports the following protection:
• Link protection — The link is excluded during the post-convergence backup path calculation.
• Node protection — The neighbor node is excluded during the post convergence backup path calculation.
• Shared Risk Link Groups (SRLG) protection — SRLG refer to situations in which links in a network share a common fiber (or a common physical attribute). These links have a shared risk: when one link fails, other links in the group might also fail. TI-LFA SRLG protection attempts to find the post-convergence backup path that excludes the SRLG of the protected link. All local links that share any SRLG with the protecting link are excluded.
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Usage Guidelines and Limitations
When you enable link protection, you can also enable node protection, SRLG protection, or both, and specify a tiebreaker priority in case there are multiple LFAs.
The following example illustrates the link, node, and SRLG protection types. In this topology, Node2 applies different protection models to protect traffic to Node7.
Figure 11: TI-LFA Protection Types
•
Usage Guidelines and Limitations, on page 251
•
Configuring TI-LFA for IS-IS, on page 252
•
Configuring TI-LFA for OSPF, on page 254
•
TI-LFA Node and SRLG Protection: Examples, on page 256
•
Configuring Global Weighted SRLG Protection, on page 257
•
SR-MPLS over GRE as TI-LFA Backup Path, on page 260
Usage Guidelines and Limitations
The TI-LFA guidelines and limitations are listed below:
TI-LFA Functionality IS-IS
Protected Traffic Types
Protection for SR labeled traffic
Protection of IPv4 unlabeled traffic
Supported
Protection of IPv6 unlabeled traffic
Supported
(IS-ISv4)
Unsupported
Protection Types
OSPFv2
Supported
Supported
N/A
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TI-LFA Functionality
Link Protection
Node Protection
Local SRLG Protection
Weighted Remote SRLG Protection
Line Card Disjoint Protection
IS-IS
Supported
Supported
Supported
Supported
Supported
Interface Types
Ethernet Interfaces
Ethernet Bundle Interfaces
Supported
Supported
TI-LFA over GRE Tunnel as Protecting Interface Supported
Additional Functionality
BFD-triggered
BFDv6-triggered
Prefer backup path with lowest total metric
Supported
Supported
Supported
Prefer backup path from ECMP set
Prefer backup path from non-ECMP set
Supported
Supported
Load share prefixes across multiple backups paths Supported
Limit backup computation up to the prefix priority Supported
1
Unless specified, IS-IS support is IS-ISv4 and IS-ISv6
OSPFv2
Supported
Supported
Supported
Supported
Unsupported
Supported
Supported
Supported
Supported
N/A
Supported
Supported
Supported
Supported
Supported
Configuring TI-LFA for IS-IS
This task describes how to enable per-prefix Topology Independent Loop-Free Alternate (TI-LFA) computation to converge traffic flows around link, node, and SRLG failures.
Before you begin
Ensure that the following topology requirements are met:
• Router interfaces are configured as per the topology.
• Routers are configured with IS-IS.
• Segment routing for IS-IS is configured. See
Enabling Segment Routing for IS-IS Protocol, on page 61 .
• Enter the following commands in global configuration mode:
Router(config)# ipv4 unnumbered mpls traffic-eng Loopback0
Router(config)# mpls traffic-eng
Router(config-mpls-te)# exit
Router(config)#
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SUMMARY STEPS
Step 3
1.
configure
2.
router isis instance-id
3.
interface type interface-path-id
4.
address-family ipv4 [ unicast ]
5.
fast-reroute per-prefix
6.
fast-reroute per-prefix ti-lfa
7.
fast-reroute per-prefix tiebreaker { node-protecting | srlg-disjoint } index priority
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
RP/0/RP0/CPU0:router(config)# router isis 1
Purpose
Enters global configuration mode.
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
Note You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Enters interface configuration mode.
interface type interface-path-id
Example:
RP/0/RP0/CPU0:router(config-isis)# interface
GigabitEthernet0/0/2/1
Step 4 address-family ipv4 [ unicast ]
Example:
RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast
Specifies the IPv4 address family, and enters router address family configuration mode.
Enables per-prefix fast reroute.
Step 5
Step 6 fast-reroute per-prefix
Example:
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix fast-reroute per-prefix ti-lfa
Example:
RP/0/RP0/CPU0:router(config-isis-if-af)#
Enables per-prefix TI-LFA fast reroute link protection.
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Step 7
Command or Action fast-reroute per-prefix ti-lfa
Purpose fast-reroute per-prefix tiebreaker srlg-disjoint
Example:
} index priority
{ node-protecting | Enables TI-LFA node or SRLG protection and specifies the tiebreaker priority. Valid priority values are from 1 to 255.
The lower the priority value, the higher the priority of the rule. Link protection always has a lower priority than node or SRLG protection.
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix tie-breaker srlg-disjoint index 100
Note The same attribute cannot be configured more than once on an interface.
Note For IS-IS, TI-LFA node protection and SRLG protection can be configured on the interface or the instance.
TI-LFA has been successfully configured for segment routing.
Configuring TI-LFA for OSPF
This task describes how to enable per-prefix Topology Independent Loop-Free Alternate (TI-LFA) computation to converge traffic flows around link, node, and SRLG failures.
Note TI-LFA can be configured on the instance, area, or interface. When configured on the instance or area, all interfaces in the instance or area inherit the configuration.
Before you begin
Ensure that the following topology requirements are met:
• Router interfaces are configured as per the topology.
• Routers are configured with OSPF.
• Segment routing for OSPF is configured. See
Enabling Segment Routing for OSPF Protocol, on page
.
• Enter the following commands in global configuration mode:
Router(config)# ipv4 unnumbered mpls traffic-eng Loopback0
Router(config)# mpls traffic-eng
Router(config-mpls-te)# exit
Router(config)#
SUMMARY STEPS
1.
configure
2.
router ospf process-name
3.
area area-id
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4.
interface type interface-path-id
5.
fast-reroute per-prefix
6.
fast-reroute per-prefix ti-lfa
7.
fast-reroute per-prefix tiebreaker { node-protecting | srlg-disjoint } index priority
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router ospf process-name
Example:
Step 3
Step 4
Step 5
RP/0/RP0/CPU0:router(config)# router ospf 1
area area-id
Example:
RP/0/RP0/CPU0:router(config-ospf)# area 1
interface type interface-path-id
Example:
Purpose
Enters global configuration mode.
Enables OSPF routing for the specified routing process, and places the router in router configuration mode.
Enters area configuration mode.
Enters interface configuration mode.
RP/0/RP0/CPU0:router(config-ospf-ar)# interface
GigabitEthernet0/0/2/1 fast-reroute per-prefix
Example:
Enables per-prefix fast reroute.
Step 6
Step 7
RP/0/RP0/CPU0:router(config-ospf-ar-if)# fast-reroute per-prefix fast-reroute per-prefix ti-lfa
Example:
Enables per-prefix TI-LFA fast reroute link protection.
RP/0/RP0/CPU0:router(config-ospf-ar-if)# fast-reroute per-prefix ti-lfa fast-reroute per-prefix tiebreaker srlg-disjoint
Example:
} index priority
{ node-protecting | Enables TI-LFA node or SRLG protection and specifies the tiebreaker priority. Valid priority values are from 1 to 255.
The lower the priority value, the higher the priority of the rule. Link protection always has a lower priority than node or SRLG protection.
RP/0/RP0/CPU0:router(config-ospf-ar-if)# fast-reroute per-prefix tie-breaker srlg-disjoint index 100
Note The same attribute cannot be configured more than once on an interface.
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TI-LFA Node and SRLG Protection: Examples
TI-LFA has been successfully configured for segment routing.
TI-LFA Node and SRLG Protection: Examples
The following examples show the configuration of the tiebreaker priority for TI-LFA node and SRLG protection, and the behavior of post-convergence backup-path. These examples use OSPF, but the same configuration and behavior applies to IS-IS.
Example: Enable link-protecting and node-protecting TI-LFA router ospf 1 area 1 interface GigabitEthernet0/0/2/1 fast-reroute per-prefix fast-reroute per-prefix ti-lfa fast-reroute per-prefix tiebreaker node-protecting index 100
Both link-protecting and node-protecting TI-LFA backup paths will be computed. If the priority associated with the node-protecting tiebreaker is higher than any other tiebreakers, then node-protecting post-convergence backup paths will be selected, if it is available.
Example: Enable link-protecting and SRLG-protecting TI-LFA router ospf 1 area 1 interface GigabitEthernet0/0/2/1 fast-reroute per-prefix fast-reroute per-prefix ti-lfa fast-reroute per-prefix tiebreaker srlg-disjoint index 100
Both link-protecting and SRLG-protecting TI-LFA backup paths will be computed. If the priority associated with the SRLG-protecting tiebreaker is higher than any other tiebreakers, then SRLG-protecting post-convergence backup paths will be selected, if it is available.
Example: Enable link-protecting, node-protecting and SRLG-protecting TI-LFA router ospf 1 area 1 interface GigabitEthernet0/0/2/1 fast-reroute per-prefix fast-reroute per-prefix ti-lfa fast-reroute per-prefix tiebreaker node-protecting index 100 fast-reroute per-prefix tiebreaker srlg-disjoint index 200
Link-protecting, node-protecting, and SRLG-protecting TI-LFA backup paths will be computed. If the priority associated with the node-protecting tiebreaker is highest from all tiebreakers, then node-protecting post-convergence backup paths will be selected, if it is available. If the node-protecting backup path is not available, SRLG-protecting post-convergence backup path will be used, if it is available.
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Configuring Global Weighted SRLG Protection
A shared risk link group (SRLG) is a set of links sharing a common resource and thus shares the same risk of failure. The existing loop-free alternate (LFA) implementations in interior gateway protocols (IGPs) support
SRLG protection. However, the existing implementation considers only the directly connected links while computing the backup path. Hence, SRLG protection may fail if a link that is not directly connected but shares the same SRLG is included while computing the backup path. Global weighted SRLG protection feature provides better path selection for the SRLG by associating a weight with the SRLG value and using the weights of the SRLG values while computing the backup path.
To support global weighted SRLG protection, you need information about SRLGs on all links in the area topology. For IS-IS, you can flood SRLGs for remote links or manually configuring SRLGs on remote links.
For OSPF, the SRLG values are advertised in the Extended Link LSA when SRLG is configured for that interface and Segment Routing is enabled.
The administrative weight (cost) of the SRLG can be configured using the admin-weight command. This command can be applied for all SRLG (global), or for a specific (named) SRLG. The default (global) admin-weight value is 1 for IS-IS, and 1000 for OSPF.
Configuration Examples: Global Weighted SRLG Protection for IS-IS
There are three types of configurations that are supported for the global weighted SRLG protection feature for IS-IS:
• Local SRLG with global weighted SRLG protection
• Remote SRLG flooding
• Remote SRLG static provisioning
This example shows how to configure the local SRLG with global weighted SRLG protection feature.
RP/0/RP0/CPU0:router(config)# srlg
RP/0/RP0/CPU0:router(config-srlg)# interface TenGigE0/0/0/0
RP/0/RP0/CPU0:router(config-srlg-if)# name group1
RP/0/RP0/CPU0:router(config-srlg-if)# exit
RP/0/RP0/CPU0:router(config-srlg)# interface TenGigE0/0/0/1
RP/0/RP0/CPU0:router(config-srlg-if)# name group1
RP/0/RP0/CPU0:router(config-srlg)# exit
RP/0/RP0/CPU0:router(config-srlg)# name group1 value 100
RP/0/RP0/CPU0:router(config-srlg)# exit
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-af)# fast-reroute per-prefix srlg-protection weighted-global
RP/0/RP0/CPU0:router(config-isis-af)# fast-reroute per-prefix tiebreaker srlg-disjoint index
1
RP/0/RP0/CPU0:router(config-isis-af)# exit
RP/0/RP0/CPU0:router(config-isis)# interface TenGigE0/0/0/0
RP/0/RP0/CPU0:router(config-isis-if)# point-to-point
RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix ti-lfa
RP/0/RP0/CPU0:router(config-isis-if-af)# exit
RP/0/RP0/CPU0:router(config-isis-if)# exit
RP/0/RP0/CPU0:router(config-isis)# srlg
RP/0/RP0/CPU0:router(config-isis-srlg)# name group1
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RP/0/RP0/CPU0:router(config-isis-srlg-name)# admin-weight 5000
This example shows how to configure the global weighted SRLG protection feature with remote SRLG flooding. The configuration includes local and remote router configuration. On the local router, the global weighted SRLG protection is enabled by using the fast-reroute per-prefix srlg-protection weighted-global command. In the remote router configuration, you can control the SRLG value flooding by using the advertise application lfa link-attributes srlg command. You should also globally configure SRLG on the remote router.
The local router configuration for global weighted SRLG protection with remote SRLG flooding is as follows:
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-af)# fast-reroute per-prefix srlg-protection weighted-global
RP/0/RP0/CPU0:router(config-isis-af)# fast-reroute per-prefix tiebreaker srlg-disjoint index
1
RP/0/RP0/CPU0:router(config-isis-af)# exit
RP/0/RP0/CPU0:router(config-isis)# interface TenGigE0/0/0/0
RP/0/RP0/CPU0:router(config-isis-if)# point-to-point
RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix ti-lfa
RP/0/RP0/CPU0:router(config-isis-if-af)# exit
RP/0/RP0/CPU0:router(config-isis-if)# exit
RP/0/RP0/CPU0:router(config-isis)# srlg
RP/0/RP0/CPU0:router(config-isis-srlg)# name group1
RP/0/RP0/CPU0:router(config-isis-srlg-name)# admin-weight 5000
The remote router configuration for global weighted SRLG protection with remote SRLG flooding is as follows:
RP/0/RP0/CPU0:router(config)# srlg
RP/0/RP0/CPU0:router(config-srlg)# interface TenGigE0/0/0/0
RP/0/RP0/CPU0:router(config-srlg-if)# name group1
RP/0/RP0/CPU0:router(config-srlg-if)# exit
RP/0/RP0/CPU0:router(config-srlg)# interface TenGigE0/0/0/1
RP/0/RP0/CPU0:router(config-srlg-if)# name group1
RP/0/RP0/CPU0:router(config-srlg-if)# exit
RP/0/RP0/CPU0:router(config-srlg)# name group1 value 100
RP/0/RP0/CPU0:router(config-srlg)# exit
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-af)# advertise application lfa link-attributes srlg
This example shows configuring the global weighted SRLG protection feature with static provisioning of
SRLG values for remote links. You should perform these configurations on the local router.
RP/0/RP0/CPU0:router(config)# srlg
RP/0/RP0/CPU0:router(config-srlg)# interface TenGigE0/0/0/0
RP/0/RP0/CPU0:router(config-srlg-if)# name group1
RP/0/RP0/CPU0:router(config-srlg-if)# exit
RP/0/RP0/CPU0:router(config-srlg)# interface TenGigE0/0/0/1
RP/0/RP0/CPU0:router(config-srlg-if)# name group1
RP/0/RP0/CPU0:router(config-srlg-if)# exit
RP/0/RP0/CPU0:router(config-srlg)# name group1 value 100
RP/0/RP0/CPU0:router(config-srlg)# exit
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-af)# fast-reroute per-prefix srlg-protection weighted-global
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RP/0/RP0/CPU0:router(config-isis-af)# fast-reroute per-prefix tiebreaker srlg-disjoint index
1
RP/0/RP0/CPU0:router(config-isis-af)# exit
RP/0/RP0/CPU0:router(config-isis)# interface TenGigE0/0/0/0
RP/0/RP0/CPU0:router(config-isis-if)# point-to-point
RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix
RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix ti-lfa
RP/0/RP0/CPU0:router(config-isis-if-af)# exit
RP/0/RP0/CPU0:router(config-isis-if)# exit
RP/0/RP0/CPU0:router(config-isis)# srlg
RP/0/RP0/CPU0:router(config-isis-srlg)# name group1
RP/0/RP0/CPU0:router(config-isis-srlg-name)# admin-weight 5000
RP/0/RP0/CPU0:router(config-isis-srlg-name)# static ipv4 address 10.0.4.1 next-hop ipv4 address 10.0.4.2
RP/0/RP0/CPU0:router(config-isis-srlg-name)# static ipv4 address 10.0.4.2 next-hop ipv4 address 10.0.4.1
Configuration Examples: Global Weighted SRLG Protection for OSPF
There are two types of configurations that are supported for the global weighted SRLG protection feature for
OSPF:
• Local SRLG with global weighted SRLG protection
• Remote SRLG static provisioning
Note There is no specific configuration to enable SRLG flooding in OSPF. The SRLG values are advertised in the
Extended Link LSA if SRLG is configured for that interface and Segment Routing is enabled.
This example shows how to configure the local SRLG with global weighted SRLG protection feature.
Router(config)# srlg
Router(config-srlg)# interface hundredGigE 0/0/0/0
Router(config-srlg-if)# name group1
Router(config-srlg-if)# exit
Router(config-srlg)# interface hundredGigE 0/0/0/1
Router(config-srlg-if)# name group1
Router(config-srlg-if)# exit
Router(config-srlg)# name group1 value 100
Router(config-srlg)# exit
Router(config)# router ospf 1
Router(config-ospf)# fast-reroute per-prefix srlg-protection weighted-global
Router(config-ospf)# fast-reroute per-prefix tiebreaker srlg-disjoint index 1
Router(config-ospf-ar)# interface hundredGigE 0/0/0/0
Router(config-ospf-ar-if)# fast-reroute per-prefix
Router(config-ospf-ar-if)# fast-reroute per-prefix ti-lfa
Router(config-ospf-ar-if)# exit
Router(config-ospf-ar)# exit
Router(config-ospf)# srlg
Router(config-ospf-srlg)# admin-weight 3000
Router(config-ospf-srlg)# name group1
Router(config-ospf-srlg-name)# admin-weight 5000
This example shows configuring the global weighted SRLG protection feature with static provisioning of
SRLG values for remote links. You should perform these configurations on the remote router.
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Router(config)# srlg
Router(config-srlg)# interface hundredGigE 0/0/0/0
Router(config-srlg-if)# name group1
Router(config-srlg-if)# exit
Router(config-srlg)# interface hundredGigE 0/0/0/1
Router(config-srlg-if)# name group1
Router(config-srlg-if)# exit
Router(config-srlg)# name group1 value 100
Router(config-srlg)# exit
Router(config)# router ospf 1
Router(config-ospf)# area 1
Router(config-ospf-ar)# interface hundredGigE 0/0/0/0
Router(config-ospf-ar-if)# exit
Router(config-ospf-ar)# exit
SR-MPLS over GRE as TI-LFA Backup Path
This feature allows the router (as ABR) to program a Generic Routing Encapsulation (GRE) tunnel as an outgoing interface for TI-LFA backup paths computed by the IGP in a Segment Routing network.
Single-segment TI-LFA scenario is supported. In this scenario, the router pushes one extra label when programming the backup path.
Note GRE is a tunneling protocol that provides a simple generic approach to transport packets of one protocol over another protocol by means of encapsulation. See the Configuring GRE Tunnels chapter in the Interface and
Hardware Component Configuration Guide for Cisco NCS 5500 Series Routers .
Multi-Level Network Topology
The following example shows a multi-level network topology with interconnecting links between ABRs.
Note This could also be a multi-instance network topology.
Two links between ABR 2 and ABR 3 are required, one in each IS-IS level. These links provide protection in each direction and ensure that there is always an alternate path inside the IGP domain.
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Note Alternatively, a single link with two logical sub-interfaces could be used between the ABRs.
TI-LFA performs the backup path calculation inside the domain (process, level, or area) of the failed link.
For example, if the link between nodes 2 and 5 failed, the link between ABR 2 and 3 would create a TI-LFA path in L1 IS-IS level. If the link between nodes 1 and 2 failed, the link between ABR 2 and 3 would create a TI-LFA path in L2 IS-IS level.
However, if the interconnecting link between ABRs are in the same Shared Risk Link Groups (SRLG) as other links inside the domain (for example, the link between Nodes 2 and 3 are in the same SRLG as link between Nodes 2 and 5), TI-LFA with local SRLG protection would not find an alternate path.
In cases where it is not feasible to provide interconnecting links between ABRs (for example, the ABR nodes might be in different locations with no connectivity options), TI-LFA will not be able to compute backup paths for all of the prefixes.
To address these issues, you can create a GRE tunnel in each domain, between the ABRs, which can be used as TI-LFA backup paths.
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Configure Topology-Independent Loop-Free Alternate (TI-LFA)
Now, if a link failure occurs in either IS-IS level (for example, between nodes 1 and 2 or between nodes 2 and 5), the path is protected by the GRE tunnel.
Backup Path for Link Failure Between Nodes 2 and 5
Traffic from node 1 is rerouted over the GRE tunnel TI-LFA backup path between ABR nodes 2 and 3.
Traffic flowing in the opposite direction, from node 5 to node 1, is simply routed over nodes 6-3-4 to node
1.
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Limitations
Limitations
The following behaviors and limitations apply to the router when a GRE tunnel is programmed as backup interface for TI-LFA:
• The MPLS label of a protected prefix must be the same in the primary and backup paths (SWAP scenario)
• Single-segment TI-LFA is supported. In this scenario, the router pushes one extra label when programming the backup path. The total label stack is 2, including the primary label and backup label.
• Double-segment (or more) TI-LFA is not supported. In this scenario, the router pushes two or more extra labels when programming the backup path.
• GRE tunnel as a primary or backup path for an SR policy with TI-LFA protection is not supported.
Example: SR-MPLS over GRE as TI-LFA Backup Path
The examples in this section use the following network topology:
Configurations Without Interconnecting ABR Links
The following sample configurations show OSPF configurations for nodes 2, 3 and 5. Nodes 2 and 3 are ABRs between Area 0 and Area 100. There is no connection between the ABRs.
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Configuration on ABR 2 for Area 0 and Area 100 router ospf 100 router-id 2.2.2.2
segment-routing mpls segment-routing forwarding mpls fast-reroute per-prefix fast-reroute per-prefix ti-lfa enable segment-routing sr-prefer area 0 interface Loopback0
!
prefix-sid index 2
!
interface TenGigE0/0/1/10 network point-to-point
!
!
area 100 interface TenGigE0/0/1/11 network point-to-point
RP/0/RSP0/CPU0:ABR2# show ospf neighbor area-sorted
Fri Jul 19 09:43:59.328 UTC
Neighbors for OSPF 100
Area 0
Neighbor ID
1.1.1.1
Pri State Dead Time Address
1 FULL/ - 00:00:35 10.1.2.1
Total neighbor count: 1
Area 100
Neighbor ID
5.5.5.5
Pri State Dead Time Address
1 FULL/ - 00:00:33 10.2.5.5
Total neighbor count: 1
Configuration on ABR 3 for Area 0 and Area 100 router ospf 100 router-id 3.3.3.3
segment-routing mpls segment-routing forwarding mpls fast-reroute per-prefix fast-reroute per-prefix ti-lfa enable segment-routing sr-prefer area 0 interface Loopback0 prefix-sid index 3
!
interface TenGigE0/0/0/9 network point-to-point
!
!
area 100 interface TenGigE0/0/0/3
!
network point-to-point
RP/0/RSP0/CPU0:ABR3# show ospf neighbor area-sorted
Fri Jul 19 09:33:35.816 UTC
Up Time Interface
1d20h Te0/0/1/10
Up Time Interface
1d20h Te0/0/1/11
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Neighbors for OSPF 100
Area 0
Neighbor ID
4.4.4.4
Pri State Dead Time Address
1 FULL/ - 00:00:36 10.3.4.4
Total neighbor count: 1
Area 100
Neighbor ID
6.6.6.6
Pri State Dead Time Address
1 FULL/ - 00:00:36 10.3.6.6
Total neighbor count: 1
Configuration on Node 5 segment-routing mpls
!
set-attributes address-family ipv4 sr-label-preferred
!
connected-prefix-sid-map address-family ipv4
5.5.5.5/32 index 5 range 1
!
interface TenGigabitEthernet0/0/26 description *** Connected to ABR 2 ip address 10.2.5.5 255.255.255.0
ip ospf network point-to-point cdp enable
!
interface TenGigabitEthernet0/0/27 description *** Connected to Node 6 ip address 10.5.6.5 255.255.255.0
ip ospf network point-to-point cdp enable router ospf 100 router-id 5.5.5.5
segment-routing area 100 mpls segment-routing mpls fast-reroute per-prefix enable prefix-priority low fast-reroute per-prefix ti-lfa fast-reroute per-prefix ti-lfa area 100 passive-interface default no passive-interface TenGigabitEthernet0/0/26 no passive-interface TenGigabitEthernet0/0/27 network 10.2.5.0 0.0.0.255 area 100 network 10.5.5.0 0.0.0.255 area 100 network 10.5.6.0 0.0.0.255 area 100 network 5.5.5.5 0.0.0.0 area 100
Up Time Interface
2d17h Te0/0/0/9
Up Time Interface
2d19h Te0/0/0/3
RP/0/RSP0/CPU0:Node5# show ip ospf neighbor
Load for five secs: 4%/1%; one minute: 4%; five minutes: 4%
Time source is NTP, 09:50:51.417 UTC Fri Jul 19 2019
Neighbor ID Pri State
6.6.6.6
2.2.2.2
0
0
FULL/
FULL/
-
-
Dead Time
00:00:32
00:00:36
Address
10.5.6.6
10.5.2.5
Interface
TenGigabitEthernet0/0/27
TenGigabitEthernet0/0/26
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TI-LFA Fast Reroute Coverage on Node 5
The following output shows that this configuration provides only 52% TI-LFA fast reroute coverage on Node
5:
RP/0/RSP0/CPU0:Node5# show ip ospf fast-reroute prefix-summary
Load for five secs: 4%/1%; one minute: 4%; five minutes: 4%
Time source is NTP, 10:32:20.236 UTC Fri Jul 19 2019
OSPF Router with ID (5.5.5.5) (Process ID 100)
Base Topology (MTID 0)
Area 100:
Interface Protected
Lo0
Te0/0/27
Te0/0/26
Yes
Yes
Yes
Primary paths Protected paths Percent protected
All High Low All High Low All High Low
0
7
10
0
4
5
0
3
5
0
1
8
0
1
4
0
0
4
0%
14%
80%
0%
25%
80%
0%
0%
80%
Area total: 17 9 8 9 5 4 52% 55% 50%
Process total: 17 9 8 9 5 4 52% 55% 50%
GRE Tunnel Configuration
The following examples show how to configure GRE tunnels between the ABRs in each area to provide
TI-LFA backup paths for the Segment Routing network.
GRE BLU is configured in Area 0 using Loopback50 (on ABR2) and Loopback 60 (on ABR 3). These loopbacks are advertised in Area 100:
Figure 12: GRE BLU
GRE RED is configured in Area 100 using Loopback55 (on ABR2) and Loopback 66 (on ABR3). These loopbacks are advertised in Area 0:
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Figure 13: GRE RED
Example: SR-MPLS over GRE as TI-LFA Backup Path
Configuration on ABR 2 interface Loopback0 ipv4 address 2.2.2.2 255.255.255.255
!
interface Loopback50 description Lo for GRE BLU ipv4 address 50.0.0.50
255.255.255.0
!
interface Loopback55 description Lo for GRE RED ipv4 address 55.55.55.55
255.255.255.255
!
interface tunnel-ip5060 description GRE virtual link for Area 0 BLU ipv4 address 66.3.2.2 255.255.255.0
tunnel source Loopback50 tunnel destination 60.0.0.60
!
interface tunnel-ip5566 description GRE virtual link for Area 100 RED ipv4 address 100.3.2.2 255.255.255.0
tunnel source Loopback55 tunnel destination 66.66.66.66
router ospf 100 router-id 2.2.2.2
segment-routing mpls segment-routing forwarding mpls fast-reroute per-prefix fast-reroute per-prefix ti-lfa enable segment-routing sr-prefer area 0 interface Loopback0
!
prefix-sid index 2 interface Loopback55 passive enable
!
interface tunnel-ip5060 cost 1000
!
interface TenGigE0/0/1/10
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!
network point-to-point
!
area 100 interface Loopback50
!
passive enable interface tunnel-ip5566 cost 1000
!
interface TenGigE0/0/1/11 network point-to-point
Note In the above configuration, GRE tunnel-ip5060 belongs to area 0, but its source and destination addresses are advertised in area 100. This ensures disjointness between the GRE tunnel and the links in area 0 that it protects.
The same applies to GRE tunnel-ip5566 which belongs to area 100 and its source and destination addresses are advertised in area 0.
A high cost is applied to the GRE tunnel interfaces so that they are used only as a backup path.
Configuration on ABR 3 interface Loopback0 ipv4 address 3.3.3.3 255.255.255.255
!
interface Loopback60 description Lo for GRE BLU ipv4 address 60.0.0.60
255.255.255.0
!
interface Loopback66 description Lo for GRE RED ipv4 address 66.66.66.66
255.255.255.255
!
interface tunnel-ip5060 description GRE virtual link for Area 0 BLU ipv4 address 66.3.2.3 255.255.255.0
tunnel source Loopback60
!
tunnel destination 50.0.0.50
interface tunnel-ip5566 description GRE virtual link for Area 100 RED ipv4 address 100.3.2.3 255.255.255.0
tunnel source Loopback66 tunnel destination 55.55.55.55
router ospf 100 router-id 3.3.3.3
segment-routing mpls segment-routing forwarding mpls fast-reroute per-prefix fast-reroute per-prefix ti-lfa enable segment-routing sr-prefer area 0 interface Loopback0
!
prefix-sid index 3 interface TenGigE0/0/0/9 network point-to-point
!
interface Loopback66
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!
passive enable interface tunnel-ip5060 cost 1000
!
area 100 interface TenGigE0/0/0/3 network point-to-point
!
interface Loopback60
!
passive enable interface tunnel-ip5566 cost 1000
Note In the above configuration, GRE tunnel-ip5060 belongs to area 0, but its source and destination addresses are advertised in area 100. This ensures disjointness between the GRE tunnel and the links in area 0 that it protects.
The same applies to GRE tunnel-ip5566 which belongs to area 100 and its source and destination addresses are advertised in area 0.
A high cost is applied to the GRE tunnel interfaces so that they are used only as a backup path.
TI-LFA Fast Reroute Coverage on Node 5 After GRE Tunnel Configuration
The following output shows that this configuration provides 100% TI-LFA fast reroute coverage on Node 5:
RP/0/RSP0/CPU0:Node5# show ip ospf fast-reroute prefix-summary
Load for five secs: 5%/1%; one minute: 4%; five minutes: 4%
Time source is NTP, 11:20:31.743 UTC Fri Jul 19 2019
OSPF Router with ID (5.5.5.5) (Process ID 100)
Base Topology (MTID 0)
Area 100:
Interface Protected Primary paths Protected paths Percent protected
Lo0
Te0/0/27
Te0/0/26
Yes
Yes
Yes
All High Low All High Low
0 0 0 0 0 0
9
11
6
6
3
5
9
11
6
6
3
5
All High
0% 0%
Low
0%
100% 100% 100%
100% 100% 100%
Area total:
Process total:
20
20
12
12
8
8
20
20
12
12
8 100% 100% 100%
8 100% 100% 100%
Traffic Flow with GRE Tunnel as TI-LFA Backup
With a link failure between Node 1 and ABR 2, traffic flowing from Node 1 to Node 5 is simply routed through
Nodes 4-3-6 to Node 5.
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Configure Topology-Independent Loop-Free Alternate (TI-LFA)
With GRE tunnel as TI-LFA backup, traffic flowing from Node 5 to Node 1 will be encapsulated at ABR2 and routing over the GRE tunnel.
With a link failure between Node 5 and ABR 2, traffic flowing from Node 5 to Node 1 is simply routed through
Nodes 6-3-4 to Node 1.
With GRE tunnel as TI-LFA backup, traffic flowing from Node 1 to Node 5 will be encapsulated at ABR2 and routing over the GRE tunnel.
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Configure Segment Routing Microloop Avoidance
The Segment Routing Microloop Avoidance feature enables link-state routing protocols, such as IS-IS and
OSPF, to prevent or avoid microloops during network convergence after a topology change.
•
About Segment Routing Microloop Avoidance, on page 273
•
Configure Segment Routing Microloop Avoidance for IS-IS, on page 273
•
Configure Segment Routing Microloop Avoidance for OSPF, on page 274
About Segment Routing Microloop Avoidance
Microloops are brief packet loops that occur in the network following a topology change (link down, link up, or metric change events). Microloops are caused by the non-simultaneous convergence of different nodes in the network. If nodes converge and send traffic to a neighbor node that has not converged yet, traffic may be looped between these two nodes, resulting in packet loss, jitter, and out-of-order packets.
The Segment Routing Microloop Avoidance feature detects if microloops are possible following a topology change. If a node computes that a microloop could occur on the new topology, the node creates a loop-free
SR-TE policy path to the destination using a list of segments. After the RIB update delay timer expires, the
SR-TE policy is replaced with regular forwarding paths.
Configure Segment Routing Microloop Avoidance for IS-IS
This task describes how to enable Segment Routing Microloop Avoidance and set the Routing Information
Base (RIB) update delay value for IS-IS.
Before you begin
Ensure that the following topology requirements are met:
• Router interfaces are configured as per the topology.
• Routers are configured with IS-IS.
• Segment routing for IS-IS is configured. See
Enabling Segment Routing for IS-IS Protocol, on page 61
.
• Enter the following commands in global configuration mode:
Router(config)# ipv4 unnumbered mpls traffic-eng Loopback0
Router(config)# mpls traffic-eng
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Router(config-mpls-te)# exit
Router(config)#
SUMMARY STEPS
1.
configure
2.
router isis instance-id
3.
address-family ipv4 [ unicast ]
4.
microloop avoidance segment-routing
5.
microloop avoidance rib-update-delay delay-time
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
Step 3
Step 4
Step 5
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
RP/0/RP0/CPU0:router(config)# router isis 1
Purpose
Enters global configuration mode.
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Specifies the IPv4 address family and enters router address family configuration mode.
address-family ipv4 [ unicast ]
Example:
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast microloop avoidance segment-routing
Example:
Enables Segment Routing Microloop Avoidance.
RP/0/RP0/CPU0:router(config-isis-af)# microloop avoidance segment-routing
microloop avoidance rib-update-delay delay-time
Example:
RP/0/RP0/CPU0:router(config-isis-af)# microloop avoidance rib-update-delay 3000
Specifies the amount of time the node uses the microloop avoidance policy before updating its forwarding table. The delay-time is in milliseconds. The range is from 1-60000.
The default value is 5000.
Configure Segment Routing Microloop Avoidance for OSPF
This task describes how to enable Segment Routing Microloop Avoidance and set the Routing Information
Base (RIB) update delay value for OSPF.
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Configure Segment Routing Microloop Avoidance for OSPF
Before you begin
Ensure that the following topology requirements are met:
• Router interfaces are configured as per the topology.
• Routers are configured with OSPF.
• Segment routing for OSPF is configured. See
Enabling Segment Routing for OSPF Protocol, on page
• Enter the following commands in global configuration mode:
Router(config)# ipv4 unnumbered mpls traffic-eng Loopback0
Router(config)# mpls traffic-eng
Router(config-mpls-te)# exit
Router(config)#
SUMMARY STEPS
1.
configure
2.
router ospf process-name
3.
microloop avoidance segment-routing
4.
microloop avoidance rib-update-delay delay-time
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure
router ospf process-name
Example:
Step 3
RP/0/RP0/CPU0:router(config)# router ospf 1 microloop avoidance segment-routing
Example:
Step 4
RP/0/RP0/CPU0:router(config-ospf)# microloop avoidance segment-routing
microloop avoidance rib-update-delay delay-time
Example:
RP/0/RP0/CPU0:router(config-ospf)# microloop avoidance rib-update-delay 3000
Purpose
Enters global configuration mode.
Enables OSPF routing for the specified routing process, and places the router in router configuration mode.
Enables Segment Routing Microloop Avoidance.
Specifies the amount of time the node uses the microloop avoidance policy before updating its forwarding table. The delay-time is in milliseconds. The range is from 1-60000.
The default value is 5000.
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Configure Segment Routing Mapping Server
The mapping server is a key component of the interworking between LDP and segment routing. It enables
SR-capable nodes to interwork with LDP nodes. The mapping server advertises Prefix-to-SID mappings in
IGP on behalf of other non-SR-capable nodes.
•
Segment Routing Mapping Server, on page 277
•
Segment Routing and LDP Interoperability, on page 278
•
Configuring Mapping Server, on page 280
•
Enable Mapping Advertisement, on page 282
•
Enable Mapping Client, on page 284
Segment Routing Mapping Server
The mapping server functionality in Cisco IOS XR segment routing centrally assigns prefix-SIDs for some or all of the known prefixes. A router must be able to act as a mapping server, a mapping client, or both.
• A router that acts as a mapping server allows the user to configure SID mapping entries to specify the prefix-SIDs for some or all prefixes. This creates the local SID-mapping policy. The local SID-mapping policy contains non-overlapping SID-mapping entries. The mapping server advertises the local
SID-mapping policy to the mapping clients.
• A router that acts as a mapping client receives and parses remotely received SIDs from the mapping server to create remote SID-mapping entries.
• A router that acts as a mapping server and mapping client uses the remotely learnt and locally configured mapping entries to construct the non-overlapping consistent active mapping policy. IGP instance uses the active mapping policy to calculate the prefix-SIDs of some or all prefixes.
The mapping server automatically manages the insertions and deletions of mapping entries to always yield an active mapping policy that contains non-overlapping consistent SID-mapping entries.
• Locally configured mapping entries must not overlap each other.
• The mapping server takes the locally configured mapping policy, as well as remotely learned mapping entries from a particular IGP instance, as input, and selects a single mapping entry among overlapping mapping entries according to the preference rules for that IGP instance. The result is an active mapping policy that consists of non-overlapping consistent mapping entries.
• At steady state, all routers, at least in the same area or level, must have identical active mapping policies.
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Usage Guidelines and Restrictions
Usage Guidelines and Restrictions
• The position of the mapping server in the network is not important. However, since the mapping advertisements are distributed in IGP using the regular IGP advertisement mechanism, the mapping server needs an IGP adjacency to the network.
• The role of the mapping server is crucial. For redundancy purposes, you should configure multiple mapping servers in the networks.
• The mapping server functionality does not support a scenario where SID-mapping entries learned through one IS-IS instance are used by another IS-IS instance to determine the prefix-SID of a prefix. For example, mapping entries learnt from remote routers by 'router isis 1' cannot be used to calculate prefix-SIDs for prefixes learnt, advertised, or downloaded to FIB by 'router isis 2'. A mapping server is required for each
IS-IS instance.
• Segment Routing Mapping Server does not support Virtual Routing and Forwarding (VRF) currently.
Segment Routing and LDP Interoperability
IGP provides mechanisms through which segment routing (SR) interoperate with label distribution protocol
(LDP). The control plane of segment routing co-exists with LDP.
The Segment Routing Mapping Server (SRMS) functionality in SR is used to advertise SIDs for destinations, in the LDP part of the network, that do not support SR. SRMS maintains and advertises segment identifier
(SID) mapping entries for such destinations. IGP propagates the SRMS mapping entries and interacts with
SRMS to determine the SID value when programming the forwarding plane. IGP installs prefixes and corresponding labels, into routing information base (RIB), that are used to program the forwarding information base (FIB).
Example: Segment Routing LDP Interoperability
Consider a network with a mix of segment routing (SR) and label distribution protocol (LDP). A continuous multiprotocol label switching (MPLS) LSP (Labeled Switched Path) can be established by facilitating interoperability. One or more nodes in the SR domain act as segment routing mapping server (SRMS). SRMS advertises SID mappings on behalf of non-SR capable nodes. Each SR-capable node learns about SID assigned to non-SR capable nodes without explicitly configuring individual nodes.
Consider a network as shown in the following image. This network is a mix of both LDP and SR-capable nodes.
In this mixed network:
• Nodes P6, P7, P8, PE4 and PE3 are LDP-capable
• Nodes PE1, PE2, P5 and P6 are SR-capable
• Nodes PE1, PE2, P5 and P6 are configured with segment routing global block (SRGB) of (100, 200)
• Nodes PE1, PE2, P5 and P6 are configured with node segments of 101, 102, 105 and 106 respectively
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Example: Segment Routing LDP Interoperability
A service flow must be established from PE1 to PE3 over a continuous MPLS tunnel. This requires SR and
LDP to interoperate.
LDP to SR
The traffic flow from LDP to SR (right to left) involves:
1.
PE3 learns a service route whose nhop is PE1. PE3 has an LDP label binding from the nhop P8 for the
FEC PE1. PE3 forwards the packet P8.
2.
P8 has an LDP label binding from its nhop P7 for the FEC PE1. P8 forwards the packet to P7.
3.
P7 has an LDP label binding from its nhop P6 for the FEC PE1. P7 forwards the packet to P6.
4.
P6 does not have an LDP binding from its nhop P5 for the FEC PE1. But P6 has an SR node segment to the IGP route PE1. P6 forwards the packet to P5 and swaps its local LDP label for FEC PE1 by the equivalent node segment 101. This process is called label merging.
5.
P5 pops 101, assuming PE1 has advertised its node segment 101 with the penultimate-pop flag set and forwards to PE1.
6.
PE1 receives the tunneled packet and processes the service label.
The end-to-end MPLS tunnel is established from an LDP LSP from PE3 to P6 and the related node segment from P6 to PE1.
SR to LDP
Suppose that the operator configures P5 as a Segment Routing Mapping Server (SRMS) and advertises the mappings (P7, 107), (P8, 108), (PE3, 103) and (PE4, 104). If PE3 was SR-capable, the operator may have configured PE3 with node segment 103. Because PE3 is non-SR capable, the operator configures that policy at the SRMS; the SRMS advertises the mapping on behalf of the non-SR capable nodes. Multiple SRMS servers can be provisioned in a network for redundancy. The mapping server advertisements are only understood by the SR-capable nodes. The SR capable routers install the related node segments in the MPLS data plane in exactly the same manner if node segments were advertised by the nodes themselves.
The traffic flow from SR to LDP (left to right) involves:
1.
PE1 installs the node segment 103 with nhop P5 in exactly the same manner if PE3 had advertised node segment 103.
2.
P5 swaps 103 for 103 and forwards to P6.
3.
The nhop for P6 for the IGP route PE3 is non-SR capable. (P7 does not advertise the SR capability.)
However, P6 has an LDP label binding from that nhop for the same FEC. (For example, LDP label 103.)
P6 swaps 103 for 103 and forwards to P7. We refer to this process as label merging.
4.
P7 swaps this label with the LDP label received from P8 and forwards to P8.
5.
P8 pops the LDP label and forwards to PE3.
6.
PE3 receives the packet and processes as required.
The end-to-end MPLS LSP is established from an SR node segment from PE1 to P6 and an LDP LSP from
P6 to PE3.
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Configuring Mapping Server
Configuring Mapping Server
Perform these tasks to configure the mapping server and to add prefix-SID mapping entries in the active local mapping policy.
SUMMARY STEPS
1.
configure
2.
segment-routing
3.
mapping-server
4.
prefix-sid-map
5.
address-family ipv4 | ipv6
6.
ip-address / prefix-length first-SID-value range range
7.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
RP/0/RP0/CPU0:router# configure segment-routing
Example:
RP/0/RP0/CPU0:router(config)# segment-routing
Purpose
Enters global configuration mode.
Enables segment routing.
Step 3
Step 4
Step 5 mapping-server
Example:
Enables mapping server configuration mode.
RP/0/RP0/CPU0:router(config-sr)# mapping-server prefix-sid-map
Example:
RP/0/RP0/CPU0:router(config-sr-ms)# prefix-sid-map
Enables prefix-SID mapping configuration mode.
Note Two-way prefix SID can be enabled directly under IS-IS or through a mapping server.
Configures address-family for IS-IS.
address-family ipv4 | ipv6
Example:
This example shows the address-family for ipv4:
RP/0/RP0/CPU0:router(config-sr-ms-map)# address-family ipv4
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Configuring Mapping Server
Step 6
Step 7
Command or Action
This example shows the address-family for ipv6:
Purpose
RP/0/RP0/CPU0:router(config-sr-ms-map)# address-family ipv6 ip-address / prefix-length first-SID-value range range
Example:
RP/0/RP0/CPU0:router(config-sr-ms-map-af)#
10.1.1.1/32 10 range 200
RP/0/RP0/CPU0:router(config-sr-ms-map-af)#
20.1.0.0/16 400 range 300
Adds SID-mapping entries in the active local mapping policy. In the configured example:
• Prefix 10.1.1.1/32 is assigned prefix-SID 10, prefix
10.1.1.2/32 is assigned prefix-SID 11,…, prefix
10.1.1.199/32 is assigned prefix-SID 200
• Prefix 20.1.0.0/16 is assigned prefix-SID 400, prefix
20.2.0.0/16 is assigned prefix-SID 401,…, and so on.
Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Verify information about the locally configured prefix-to-SID mappings.
Note Specify the address family for IS-IS.
RP/0/RP0/CPU0:router# show segment-routing mapping-server prefix-sid-map ipv4
Prefix SID Index Range Flags
20.1.1.0/24
10.1.1.1/32
400
10
300
200
Number of mapping entries: 2
RP/0/RP0/CPU0:router# show segment-routing mapping-server prefix-sid-map ipv4 detail
Prefix
20.1.1.0/24
SID Index:
Range:
400
300
Last Prefix: 20.2.44.0/24
Last SID Index: 699
Flags:
10.1.1.1/32
SID Index:
Range:
Last Prefix:
10
200
10.1.1.200/32
Last SID Index: 209
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Enable Mapping Advertisement
Flags:
Number of mapping entries: 2
What to do next
Enable the advertisement of the local SID-mapping policy in the IGP.
Enable Mapping Advertisement
In addition to configuring the static mapping policy, you must enable the advertisement of the mappings in the IGP.
Perform these steps to enable the IGP to advertise the locally configured prefix-SID mapping.
Configure Mapping Advertisement for IS-IS
SUMMARY STEPS
1.
router isis instance-id
2.
address-family { ipv4 | ipv6 } [ unicast ]
3.
segment-routing prefix-sid-map advertise-local
4.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action
router isis instance-id
Example:
RP/0/RP0/CPU0:router(config)# router isis 1
Purpose
Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.
• You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.
Step 2 address-family { ipv4 | ipv6 } [ unicast ]
Example:
The following is an example for ipv4 address family:
Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.
Step 3
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast segment-routing prefix-sid-map advertise-local
Example:
Configures IS-IS to advertise locally configured prefix-SID mappings.
RP/0/RP0/CPU0:router(config-isis-af)# segment-routing prefix-sid-map advertise-local
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Configure Mapping Advertisement for OSPF
Step 4
Command or Action
Use the commit or end command.
Purpose commit —Saves the configuration changes and remains within the configuration session.
end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Verify IS-IS prefix-SID mapping advertisement and TLV.
RP/0/RP0/CPU0:router# show isis database verbose
<...removed...>
SID Binding: 10.1.1.1/32 F:0 M:0 S:0 D:0 A:0 Weight:0 Range:200
SID: Start:10 , Algorithm:0, R:0 N:0 P:0 E:0 V:0 L:0
SID Binding: 20.1.1.0/24 F:0 M:0 S:0 D:0 A:0 Weight:0 Range:300
SID: Start:400 , Algorithm:0, R:0 N:0 P:0 E:0 V:0 L:0
Configure Mapping Advertisement for OSPF
SUMMARY STEPS
1.
router ospf process-name
2.
segment-routing prefix-sid-map advertise-local
3.
Use the commit or end command.
DETAILED STEPS
Step 1
Command or Action
router ospf process-name
Example:
Step 2
Step 3
RP/0/RP0/CPU0:router(config)# router ospf 1 segment-routing prefix-sid-map advertise-local
Example:
Purpose
Enables OSPF routing for the specified routing instance, and places the router in router configuration mode.
Configures OSPF to advertise locally configured prefix-SID mappings.
RP/0/RP0/CPU0:router(config-ospf)# segment-routing prefix-sid-map advertise-local
Use the commit or end command.
commit —Saves the configuration changes and remains within the configuration session.
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Enable Mapping Client
Command or Action Purpose end —Prompts user to take one of these actions:
• Yes — Saves configuration changes and exits the configuration session.
• No —Exits the configuration session without committing the configuration changes.
• Cancel —Remains in the configuration session, without committing the configuration changes.
Verify OSP prefix-SID mapping advertisement and TLV.
RP/0/RP0/CPU0:router# show ospf database opaque-area
<...removed...>
Extended Prefix Range TLV: Length: 24
AF : 0
Prefix : 10.1.1.1/32
Range Size: 200
Flags : 0x0
SID sub-TLV: Length: 8
Flags
MTID
: 0x60
: 0
Algo : 0
SID Index : 10
Enable Mapping Client
By default, mapping client functionality is enabled.
You can disable the mapping client functionality by using the segment-routing prefix-sid-map receive disable command.
You can re-enable the mapping client functionality by using the segment-routing prefix-sid-map receive command.
The following example shows how to enable the mapping client for IS-IS:
RP/0/RP0/CPU0:router(config)# router isis 1
RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast
RP/0/RP0/CPU0:router(config-isis-af)# segment-routing prefix-sid-map receive
The following example shows how to enable the mapping client for OSPF:
RP/0/RP0/CPU0:router(config)# router ospf 1
RP/0/RP0/CPU0:router(config-ospf)# segment-routing prefix-sid-map receive
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C H A P T E R
16
Using Segment Routing OAM
Segment Routing Operations, Administration, and Maintenance (OAM) helps service providers to monitor label-switched paths (LSPs) and quickly isolate forwarding problems to assist with fault detection and troubleshooting in the network. The Segment Routing OAM feature provides support for BGP prefix SIDs,
IGP prefix and Flexible Algorithm SIDs, and Nil-FEC (forwarding equivalence classes) LSP Ping and
Traceroute functionality.
•
MPLS Ping and Traceroute for BGP and IGP Prefix-SID, on page 285
•
Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID, on page 286
•
MPLS LSP Ping and Traceroute Nil FEC Target, on page 288
•
Examples: LSP Ping and Traceroute for Nil_FEC Target , on page 288
•
Segment Routing Ping and Traceroute, on page 290
•
Segment Routing Ping and Traceroute for Flexible Algorithm, on page 294
•
Segment Routing over IPv6 OAM, on page 295
MPLS Ping and Traceroute for BGP and IGP Prefix-SID
MPLS Ping and Traceroute operations for Prefix SID are supported for various BGP and IGP scenarios, for example:
• Within an IS-IS level or OSPF area
• Across IS-IS levels or OSPF areas
• Route redistribution from IS-IS to OSPF and from OSPF to IS-IS
• Anycast Prefix SID
• Combinations of BGP and LDP signaled LSPs
The MPLS LSP Ping feature is used to check the connectivity between ingress Label Switch Routers (LSRs) and egress LSRs along an LSP. MPLS LSP ping uses MPLS echo request and reply messages, similar to
Internet Control Message Protocol (ICMP) echo request and reply messages, to validate an LSP. The destination
IP address of the MPLS echo request packet is different from the address used to select the label stack. The destination IP address is defined as a 127.x.y.z/8 address and it prevents the IP packet from being IP switched to its destination, if the LSP is broken.
The MPLS LSP Traceroute feature is used to isolate the failure point of an LSP. It is used for hop-by-hop fault localization and path tracing. The MPLS LSP Traceroute feature relies on the expiration of the Time to
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Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID
Live (TTL) value of the packet that carries the echo request. When the MPLS echo request message hits a transit node, it checks the TTL value and if it is expired, the packet is passed to the control plane, else the message is forwarded. If the echo message is passed to the control plane, a reply message is generated based on the contents of the request message.
The MPLS LSP Tree Trace (traceroute multipath) operation is also supported for BGP and IGP Prefix SID.
MPLS LSP Tree Trace provides the means to discover all possible equal-cost multipath (ECMP) routing paths of an LSP to reach a destination Prefix SID. It uses multipath data encoded in echo request packets to query for the load-balancing information that may allow the originator to exercise each ECMP. When the packet
TTL expires at the responding node, the node returns the list of downstream paths, as well as the multipath information that can lead the operator to exercise each path in the MPLS echo reply. This operation is performed repeatedly for each hop of each path with increasing TTL values until all ECMP are discovered and validated.
MPLS echo request packets carry Target FEC Stack sub-TLVs. The Target FEC sub-TLVs are used by the responder for FEC validation. The BGP and IGP IPv4 prefix sub-TLV has been added to the Target FEC
Stack sub-TLV. The IGP IPv4 prefix sub-TLV contains the prefix SID, the prefix length, and the protocol
(IS-IS or OSPF). The BGP IPv4 prefix sub-TLV contains the prefix SID and the prefix length.
Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID
These examples use the following topology:
MPLS Ping for Prefix-SID
RP/0/RP0/CPU0:router-arizona# ping mpls ipv4 1.1.1.4/32
Thu Dec 17 01:01:42.301 PST
Sending 5, 100-byte MPLS Echos to 1.1.1.4, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
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MPLS Traceroute for Prefix-SID
RP/0/RP0/CPU0:router-arizona# traceroute mpls ipv4 1.1.1.4/32
Thu Dec 17 14:45:05.563 PST
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 12.12.12.1 MRU 4470 [Labels: 16004 Exp: 0]
L 1 12.12.12.2 MRU 4470 [Labels: 16004 Exp: 0] 3 ms
L 2 23.23.23.3 MRU 4470 [Labels: implicit-null Exp: 0] 3 ms
! 3 34.34.34.4 11 ms
MPLS Tree Trace for Prefix-SID
RP/0/RP0/CPU0:router-arizona# traceroute mpls multipath ipv4 1.1.1.4/32
Thu Dec 17 14:55:46.549 PST
Starting LSP Path Discovery for 1.1.1.4/32
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
LL!
Path 0 found, output interface TenGigE0/0/0/0 nexthop 12.12.12.2
source 12.12.12.1 destination 127.0.0.0
L!
Path 1 found, output interface TenGigE0/0/0/0 nexthop 12.12.12.2
source 12.12.12.1 destination 127.0.0.2
LL!
Path 2 found, output interface TenGigE0/0/0/1 nexthop 15.15.15.5
source 15.15.15.1 destination 127.0.0.1
L!
Path 3 found, output interface TenGigE0/0/0/1 nexthop 15.15.15.5
source 15.15.15.1 destination 127.0.0.0
Paths (found/broken/unexplored) (4/0/0)
Echo Request (sent/fail) (10/0)
Echo Reply (received/timeout) (10/0)
Total Time Elapsed 53 ms
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MPLS LSP Ping and Traceroute Nil FEC Target
MPLS LSP Ping and Traceroute Nil FEC Target
The Nil-FEC LSP ping and traceroute operations are extensions of regular MPLS ping and traceroute.
Nil-FEC LSP Ping/Traceroute functionality supports segment routing and MPLS Static. It also acts as an additional diagnostic tool for all other LSP types. This feature allows operators to provide the ability to freely test any label stack by allowing them to specify the following:
• label stack
• outgoing interface
• nexthop address
In the case of segment routing, each segment nodal label and adjacency label along the routing path is put into the label stack of an echo request message from the initiator Label Switch Router (LSR); MPLS data plane forwards this packet to the label stack target, and the label stack target sends the echo message back.
The following table shows the syntax for the ping and traceroute commands.
Table 11: LSP Ping and Traceroute Nil FEC Commands
Command Syntax ping mpls nil-fec labels { label [ ,label ]} [ output { interface tx-interface } [ nexthop nexthop-ip-addr ]] traceroute mpls nil-fec labels { label [ ,label ]} [ output { interface tx-interface } [ nexthop nexthop-ip-addr ]]
Examples: LSP Ping and Traceroute for Nil_FEC Target
These examples use the following topology:
Node loopback IP address: 172.18.1.3
172.18.1.4
172.18.1.5
172.18.1.7
Node label: 16004 16005 16007
Nodes: Arizona ---- Utah ------- Wyoming ---- Texas
Interface:
Interface IP address:
GigabitEthernet0/2/0/1 GigabitEthernet0/2/0/1
10.1.1.3
10.1.1.4
RP/0/RP0/CPU0:router-utah# show mpls forwarding
Tue Jul 5 13:44:31.999 EDT
Local Outgoing
Label Label
Prefix or ID
Outgoing
Interface
Next Hop Bytes
Switched
------ ----------- ------------------ ------------ --------------- ------------
16004 Pop
Pop
No ID
No ID
Gi0/2/0/1
Gi0/2/0/2
10.1.1.4
10.1.2.2
1392
0
16005 16005
16005
16007 16007
16007
24000 Pop
24001 Pop
No ID
No ID
No ID
No ID
SR Adj (idx 0)
SR Adj (idx 2)
Gi0/2/0/0
Gi0/2/0/1
Gi0/2/0/0
Gi0/2/0/1
Gi0/2/0/0
Gi0/2/0/0
10.1.1.4
10.1.2.2
10.1.1.4
10.1.2.2
10.1.1.4
10.1.1.4
0
0
4752
0
0
0
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24002 Pop
24003 Pop
24004 Pop
24005 Pop
24006 Pop
24007 Pop
24008 Pop
SR Adj (idx 0)
SR Adj (idx 2)
No ID
No ID
No ID
No ID
No ID
Gi0/2/0/1
Gi0/2/0/1 tt10 tt11 tt12 tt13 tt30
10.1.2.2
10.1.2.2
point2point point2point point2point point2point point2point
0
0
0
0
0
0
0
Ping Nil FEC Target
RP/0/RP0/CPU0:router-arizona# ping mpls nil-fec labels 16005,16007 output interface
GigabitEthernet 0/2/0/1 nexthop 10.1.1.4 repeat 1
Sending 1, 72-byte MPLS Echos with Nil FEC labels 16005,16007, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'd' - see DDMAP for return code,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 1/1/1 ms
Total Time Elapsed 0 ms
Traceroute Nil FEC Target
RP/0/RP0/CPU0:router-arizona# traceroute mpls nil-fec labels 16005,16007 output interface
GigabitEthernet 0/2/0/1 nexthop 10.1.1.4
Tracing MPLS Label Switched Path with Nil FEC labels 16005,16007, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'd' - see DDMAP for return code,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.1.1.3 MRU 1500 [Labels: 16005/16007/explicit-null Exp: 0/0/0]
L 1 10.1.1.4 MRU 1500 [Labels: implicit-null/16007/explicit-null Exp: 0/0/0] 1 ms
L 2 10.1.1.5 MRU 1500 [Labels: implicit-null/explicit-null Exp: 0/0] 1 ms
! 3 10.1.1.7 1 ms
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Segment Routing Ping and Traceroute
Segment Routing Ping and Traceroute
Segment Routing Ping
The MPLS LSP ping feature is used to check the connectivity between ingress and egress of LSP. MPLS LSP ping uses MPLS echo request and reply messages, similar to Internet Control Message Protocol (ICMP) echo request and reply messages, to validate an LSP. Segment routing ping is an extension of the MPLS LSP ping to perform the connectivity verification on the segment routing control plane.
Note Segment routing ping can only be used when the originating device is running segment routing.
You can initiate the segment routing ping operation only when Segment Routing control plane is available at the originator, even if it is not preferred. This allows you to validate the SR path before directing traffic over the path. Segment Routing ping can use either generic FEC type or SR control-plane FEC type (SR-OSPF,
SR-ISIS). In mixed networks, where some devices are running MPLS control plane (for example, LDP) or do not understand SR FEC, generic FEC type allows the device to successfully process and respond to the echo request. By default, generic FEC type is used in the target FEC stack of segment routing ping echo request. Generic FEC is not coupled to a particular control plane; it allows path verification when the advertising protocol is unknown or might change during the path of the echo request. If you need to specify the target
FEC, you can select the FEC type as OSPF, IS-IS, or BGP. This ensures that only devices that are running segment routing control plane, and can therefore understand the segment routing IGP FEC, respond to the echo request.
Configuration Examples
These examples show how to use segment routing ping to test the connectivity of a segment routing control plane. In the first example, FEC type is not specified. You can also specify the FEC type as shown in the other examples.
RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/5 ms
RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type generic
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
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Segment Routing Ping
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type igp ospf
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type igp isis
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type bgp
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
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Segment Routing Traceroute
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
Segment Routing Traceroute
The MPLS LSP traceroute is used to isolate the failure point of an LSP. It is used for hop-by-hop fault localization and path tracing. The MPLS LSP traceroute feature relies on the expiration of the Time to Live
(TTL) value of the packet that carries the echo request. When the MPLS echo request message hits a transit node, it checks the TTL value and if it is expired, the packet is passed to the control plane, else the message is forwarded. If the echo message is passed to the control plane, a reply message is generated based on the contents of the request message. Segment routing traceroute feature extends the MPLS LSP traceroute functionality to segment routing networks.
Similar to segment routing ping, you can initiate the segment routing traceroute operation only when Segment
Routing control plane is available at the originator, even if it is not preferred. Segment Routing traceroute can use either generic FEC type or SR control-plane FEC type (SR-OSPF, SR-ISIS). By default, generic FEC type is used in the target FEC stack of segment routing traceroute echo request. If you need to specify the target FEC, you can select the FEC type as OSPF, IS-IS, or BGP. This ensures that only devices that are running segment routing control plane, and can therefore understand the segment routing IGP FEC, respond to the echo request.
The existence of load balancing at routers in an MPLS network provides alternate paths for carrying MPLS traffic to a target router. The multipath segment routing traceroute feature provides a means to discover all possible paths of an LSP between the ingress and egress routers.
Configuration Examples
These examples show how to use segment routing traceroute to trace the LSP for a specified IPv4 prefix SID address. In the first example, FEC type is not specified. You can also specify the FEC type as shown in the other examples.
RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.12.12.2 3 ms
RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type generic
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
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Segment Routing Traceroute
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.12.12.2 2 ms
RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type igp ospf
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.12.12.2 2 ms
RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type igp isis
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.12.12.2 2 ms
RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type bgp
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null/implicit-null Exp: 0/0]
! 1 10.12.12.2 2 ms
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Segment Routing Ping and Traceroute for Flexible Algorithm
This example shows how to use multipath traceroute to discover all the possible paths for a IPv4 prefix SID.
RP/0/RP0/CPU0:router# traceroute sr-mpls multipath 10.1.1.2/32
Starting LSP Path Discovery for 10.1.1.2/32
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
Path 0 found, output interface GigabitEthernet0/0/0/2 nexthop 10.13.13.2
source 10.13.13.1 destination 127.0.0.0
!
Path 1 found, output interface Bundle-Ether1 nexthop 10.12.12.2
source 10.12.12.1 destination 127.0.0.0
Paths (found/broken/unexplored) (2/0/0)
Echo Request (sent/fail) (2/0)
Echo Reply (received/timeout) (2/0)
Total Time Elapsed 14 ms
Segment Routing Ping and Traceroute for Flexible Algorithm
Flexible Algorithm validation method is based on segment identifier (SID) label and label switched path (LSP) destination, instead of being based on IP address. The assigner is validated against the topology prefix information provided by SR-PCE database. If the assigner is valid, then the label given is also validated against the SR-PCE database. On the egress side, the destination label is contained in a new SR Label sub-TLV. This label is verified against a SID list provided by SR-PCE.
Note Observe the following guidelines and restrictions:
• All routers within an area must share the same Flexible Algorithm definition for a Flexible Algorithm to be valid.
• All routers within the domain must be configured with the same SRGB range of values.
• BGP-LS must be enabled.
• Only prefix SIDs and Flexible Algorithm SIDs are supported.
• Only single label stack is supported.
Segment Routing Ping for Flexible Algorithm
Router# ping sr-mpls labels 16131 lsp-end-point 1.1.1.5
Fri Dec 13 19:26:29.517 IST
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Sending 5, 100-byte MPLS Echos with SR Label FEC with lsp end point 1.1.1.5, SID Label(s)
[16131], timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/6 ms
Segment Routing Traceroute for Flexible Algorithm
Router# traceroute sr-mpls labels 16130 lsp-end-point 1.1.1.5
Fri Dec 13 19:26:59.368 IST
Tracing MPLS Label Switched Path to SR Label FEC with lsp end point 1.1.1.5, SID Label(s)
[16130], timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 13.13.13.1 MRU 1500 [Labels: 16130 Exp: 0]
L 1 13.13.13.3 MRU 1500 [Labels: 16130 Exp: 0] 5 ms
L 2 16.16.16.4 MRU 1500 [Labels: implicit-null Exp: 0] 4 ms
! 3 18.18.18.5 4 ms
Segment Routing over IPv6 OAM
Segment Routing over IPv6 data plane (SRv6) implementation adds a new type of routing extension header.
Hence, the existing ICMPv6 mechanisms including ping and traceroute can be used in the SRv6 network.
There is no change in the way ping and traceroute operations work for IPv6- or SRv6-capable nodes in an
SRv6 network.
Restrictions and Usage Guidelines
The following restriction applies for SRv6 OAM:
• Ping to an SRv6 SID is not supported.
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Examples: SRv6 OAM
The following example shows using ping in an SRv6 network.
RP/0/RP0/CPU0:Router# ping ipv6 2001::33:33:33:33
Mon Sep 17 20:04:10.068 UTC
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001::33:33:33:33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/4 ms
The following example shows using traceroute in an SRv6 network.
RP/0/RP0/CPU0:Router# traceroute ipv6 2001::33:33:33:33 probe 1 timeout 0 srv6
Fri Sep 14 15:59:25.170 UTC
Type escape sequence to abort.
Tracing the route to 2001::33:33:33:33
1 2001::22:22:22:22[IP tunnel: DA=cafe:0:0:a4:1:::: SRH =(2001::33:33:33:33 ,SL=1)] 2 msec
2 2001::2:2:2:2[IP tunnel: DA=cafe:0:0:a4:1:::: SRH =(2001::33:33:33:33 ,SL=1)] 2 msec
3 2001::44:44:44:44 2 msec
4 2001::33:33:33:33 3 msec
The following example shows using traceroute in an SRv6 network without an SRH.
RP/0/RSP1/CPU0:Router# traceroute ipv6 2001::44:44:44:44 srv6
Wed Jan 16 14:35:27.511 UTC
Type escape sequence to abort.
Tracing the route to 2001::44:44:44:44
1 2001::2:2:2:2 3 msec 2 msec 2 msec
2 2001::44:44:44:44 3 msec 3 msec 3 msec
The following example shows using ping for a specified IP address in the VRF.
RP/0/RP0/CPU0:Router# ping 10.15.15.1 vrf red
Mon Sep 17 20:07:10.085 UTC
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.15.15.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
The following example shows using traceroute for a specified IP address in the VRF.
RP/0/RP0/CPU0:Router# traceroute 10.15.15.1 vrf red
Mon Sep 17 20:07:18.478 UTC
Type escape sequence to abort.
Tracing the route to 10.15.15.1
1 10.15.15.1 3 msec 2 msec 2 msec
The following example shows using traceroute for CE1 (4.4.4.5) to CE2 (5.5.5.5) in the VRF:
RP/0/RP0/CPU0:Router# traceroute 5.5.5.5 vrf a
Wed Jan 16 15:08:46.264 UTC
Type escape sequence to abort.
Tracing the route to 5.5.5.5
1 14.14.14.1 5 msec 1 msec 1 msec
2 15.15.15.1 3 msec 2 msec 2 msec
3 15.15.15.2 2 msec * 3 msec
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