NetFlow Configuration Guide, Cisco IOS Release 15.0S

NetFlow Configuration Guide
Cisco IOS Release 15.0S
Americas Headquarters
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
http://www.cisco.com
Tel: 408 526-4000
800 553-NETS (6387)
Fax: 408 527-0883
THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL
STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT
WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS.
THE SOFTWARE LICENSE AND LIMITED WARRANTY FOR THE ACCOMPANYING PRODUCT ARE SET FORTH IN THE INFORMATION PACKET THAT
SHIPPED WITH THE PRODUCT AND ARE INCORPORATED HEREIN BY THIS REFERENCE. IF YOU ARE UNABLE TO LOCATE THE SOFTWARE LICENSE
OR LIMITED WARRANTY, CONTACT YOUR CISCO REPRESENTATIVE FOR A COPY.
The Cisco implementation of TCP header compression is an adaptation of a program developed by the University of California, Berkeley (UCB) as part of UCB’s public
domain version of the UNIX operating system. All rights reserved. Copyright © 1981, Regents of the University of California.
NOTWITHSTANDING ANY OTHER WARRANTY HEREIN, ALL DOCUMENT FILES AND SOFTWARE OF THESE SUPPLIERS ARE PROVIDED “AS IS” WITH
ALL FAULTS. CISCO AND THE ABOVE-NAMED SUPPLIERS DISCLAIM ALL WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING, WITHOUT
LIMITATION, THOSE OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OR ARISING FROM A COURSE OF
DEALING, USAGE, OR TRADE PRACTICE.
IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT, SPECIAL, CONSEQUENTIAL, OR INCIDENTAL DAMAGES, INCLUDING,
WITHOUT LIMITATION, LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL, EVEN IF CISCO
OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at
www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership
relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display
output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in
illustrative content is unintentional and coincidental.
NetFlow Configuration Guide
© 2010 Cisco Systems, Inc. All rights reserved.
Cisco IOS NetFlow Overview
First Published: June 19, 2006
Last Updated: June 19, 2006
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology. This module provides an overview
of the NetFlow application and advanced NetFlow features and services.
Contents
•
Information About Cisco IOS NetFlow, page 1
•
How to Configure Cisco IOS NetFlow, page 8
•
Configuration Examples for Cisco IOS NetFlow, page 8
•
Where to Go Next, page 8
•
Additional References, page 8
•
Glossary, page 10
Information About Cisco IOS NetFlow
This section contains information about the NetFlow application and available advanced NetFlow
features and services.
•
The NetFlow Application, page 2
•
NetFlow Benefits: Monitoring, Analysis and Planning, Security, and Accounting and Billing, page 2
•
NetFlow Cisco IOS Packaging Information, page 3
•
NetFlow Flows, page 4
•
NetFlow Main Cache Operation, page 4
•
NetFlow Data Capture, page 4
•
NetFlow Export Formats, page 5
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Cisco IOS NetFlow Overview
Information About Cisco IOS NetFlow
•
NetFlow Operation: Processing Order of NetFlow Features, page 5
•
NetFlow Preprocessing Features: Filtering and Sampling, page 6
•
NetFlow Advanced Features and Services: BGP Next Hop, Multicast, MPLS, NetFlow Layer 2 and
Security Monitoring Exports, and IPv6, page 6
•
NetFlow Postprocessing Features: Aggregation Schemes and Export to Multiple Destinations,
page 7
•
NetFlow MIBs, page 7
The NetFlow Application
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the routing
devices in the network. It is emerging as a primary network accounting and security technology.
NetFlow identifies packet flows for both ingress and egress IP packets. It does not involve any
connection-setup protocol, either between routers or to any other networking device or end station.
NetFlow does not require any change externally—either to the packets themselves or to any networking
device. NetFlow is completely transparent to the existing network, including end stations and application
software and network devices like LAN switches. Also, NetFlow capture and export are performed
independently on each internetworking device; NetFlow need not be operational on each router in the
network.
NetFlow is supported on IP and IP encapsulated traffic over most interface types and encapsulations.
However, NetFlow does not support ATM LAN emulation (LANE) and does not support an Inter-Switch
Link (ISL)/virtual LAN (VLAN), ATM, or Frame Relay interfaces when more than one input access
control list (ACL) is used on the interface. Cisco 12000 IP Service Engine ATM line cards do not have
this restriction when more than one input ACL is used on the interface.
You can display and clear NetFlow statistics. NetFlow statistics consist of IP packet size distribution
data, IP flow switching cache information, and flow information. See the “NetFlow Flows” section on
page 4.
NetFlow Benefits: Monitoring, Analysis and Planning, Security, and
Accounting and Billing
NetFlow captures a rich set of traffic statistics. These traffic statistics include user, protocol, port, and
type of service (ToS) information that can be used for a wide variety of purposes such as network
application and user monitoring, network analysis and planning, security analysis, accounting and
billing, traffic engineering, and NetFlow data warehousing and data mining.
Network Application and User Monitoring
NetFlow data enables you to view detailed, time- and application-based usage of a network. This
information allows you to plan and allocate network and application resources, and provides for
extensive near real-time network monitoring capabilities. It can be used to display traffic patterns and
application-based views. NetFlow provides proactive problem detection and efficient troubleshooting,
and it facilitates rapid problem resolution. You can use NetFlow information to efficiently allocate
network resources and to detect and resolve potential security and policy violations.
2
Cisco IOS NetFlow Overview
Information About Cisco IOS NetFlow
Network Planning
NetFlow can capture data over a long period of time, which enables you to track and anticipate network
growth and plan upgrades. NetFlow service data can be used to optimize network planning, which
includes peering, backbone upgrade planning, and routing policy planning. It also enables you to
minimize the total cost of network operations while maximizing network performance, capacity, and
reliability. NetFlow detects unwanted WAN traffic, validates bandwidth and quality of service (QoS)
usage, and enables the analysis of new network applications. NetFlow offers valuable information that
you can use to reduce the cost of operating the network.
Denial of Service and Security Analysis
You can use NetFlow data to identify and classify denial of service (DoS) attacks, viruses, and worms
in real-time. Changes in network behavior indicate anomalies that are clearly reflected in NetFlow data.
The data is also a valuable forensic tool that you can use to understand and replay the history of security
incidents.
Accounting and Billing
NetFlow data provides fine-grained metering for highly flexible and detailed resource utilization
accounting. For example, flow data includes details such as IP addresses, packet and byte counts,
timestamps, type-of-service, and application ports. Service providers might utilize the information for
billing based on time-of-day, bandwidth usage, application usage, or quality of service. Enterprise
customers might utilize the information for departmental chargeback or cost allocation for resource
utilization.
Traffic Engineering
NetFlow provides autonomous system (AS) traffic engineering details. You can use NetFlow-captured
traffic data to understand source-to-destination traffic trends. This data can be used for load-balancing
traffic across alternate paths or for forwarding traffic to a preferred route. NetFlow can measure the
amount of traffic crossing peering or transit points to help you determine if a peering arrangement with
other service providers is fair and equitable.
NetFlow Data Storage and Data Mining
NetFlow data (or derived information) can be stored for later retrieval and analysis in support of
marketing and customer service programs. For example, the data can be used to find out which
applications and services are being used by internal and external users and to target those users for
improved service and advertising. In addition, NetFlow data gives market researchers access to the who,
what, where, and how long information relevant to enterprises and service providers.
NetFlow Cisco IOS Packaging Information
Cisco 7200/7500/7400/MGX/AS5800
Although NetFlow functionality is included in all software images for these platforms, you must
purchase a separate NetFlow feature license. NetFlow licenses are sold on a per-node basis.
Other Routers
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
3
Cisco IOS NetFlow Overview
Information About Cisco IOS NetFlow
NetFlow Flows
A NetFlow network flow is defined as a unidirectional stream of packets between a given source and
destination. The source and destination are each defined by a network-layer IP address and
transport-layer source and destination port numbers. Specifically, a flow is defined by the combination
of the following seven key fields:
•
Source IP address
•
Destination IP address
•
Source port number
•
Destination port number
•
Layer 3 protocol type
•
Type of service (ToS)
•
Input logical interface
These seven key fields define a unique flow. If a packet has one key field different from another packet,
it is considered to belong to another flow. A flow might also contain other accounting fields (such as the
AS number in the NetFlow export Version 5 flow format), depending on the export record version that
you configure. Flows are stored in the NetFlow cache.
NetFlow Main Cache Operation
The key components of NetFlow are the NetFlow cache that stores IP flow information, and the NetFlow
export or transport mechanism that sends NetFlow data to a network management collector, such as the
NetFlow Collection Engine. NetFlow operates by creating a NetFlow cache entry (a flow record) for
each active flow. NetFlow maintains a flow record within the cache for each active flow. Each flow
record in the NetFlow cache contains fields that can later be exported to a collection device, such as the
NetFlow Collection Engine.
NetFlow Data Capture
NetFlow captures data from ingress (incoming) and egress (outgoing) packets. NetFlow gathers data for
the following ingress IP packets:
•
IP-to-IP packets
•
IP-to-Multiprotocol Label Switching (MPLS) packets
•
Frame Relay-terminated packets
•
ATM-terminated packets
NetFlow captures data for all egress (outgoing) packets through the use of the following features:
4
•
Egress NetFlow Accounting—NetFlow gathers data for all egress packets for IP traffic only.
•
NetFlow MPLS Egress—NetFlow gathers data for all egress MPLS-to-IP packets.
Cisco IOS NetFlow Overview
Information About Cisco IOS NetFlow
NetFlow Export Formats
NetFlow exports data in UDP datagrams in one of five formats: Version 9, Version 8, Version 7,
Version 5, or Version 1. Version 9 export format, the latest version, is the most flexible and extensive
format. Version 1 was the initial NetFlow export format; Version 7 is supported only on certain
platforms, and Version 8 only supports export from aggregation cache. (Versions 2 through 4 and Version
6 were either not released or are not supported.)
•
Version 9—A flexible and extensible format, which provides the versatility needed for support of
new fields and record types. This format accommodates new NetFlow-supported technologies such
as multicast, Multiprotocol Label Switching (MPLS), and Border Gateway Protocol (BGP) next
hop. The distinguishing feature of the NetFlow Version 9 format is that it is template based.
Templates provide a means of extending the record format, a feature that should allow future
enhancements to NetFlow services without requiring concurrent changes to the basic flow-record
format. Internet Protocol Information Export (IPFIX) was based on the Version 9 export format.
•
Version 8—A format added to support data export from aggregation caches. Version 8 allows export
datagrams to contain a subset of the usual Version 5 export data, if that data is valid for a particular
aggregation cache scheme.
•
Version 7—A version supported on Catalyst 6000 series switches with a Multilayer Switch Feature
Card (MSFC) on CatOS Release 5.5(7) and later.
On Catalyst 6000 series switches with an MSFC, you can export using either the Version 7 or
Version 8 format.
Information about and instructions for configuring NetFlow on Catalyst 6000 series switches is
available in the Catalyst 6500 Series Switches documentation.
•
Version 5—A version that adds BGP autonomous system (AS) information and flow sequence
numbers.
•
Version 1, the initially released export format, is rarely used today. Do not use the Version 1 export
format unless the legacy collection system you are using requires it. Use either the Version 9 export
format or the Version 5 export format for data export from the main cache.
For more information on a specific NetFlow data export format, see the “Configuring NetFlow and
NetFlow Data Export” module.
NetFlow Operation: Processing Order of NetFlow Features
The NetFlow application supports features that you can set up to further analyze network traffic data.
NetFlow divides these features and services into the following three categories for processing:
•
Preprocessing features that allow you to collect subsets of your network traffic data for analysis.
•
Advanced features and services based on the flexible NetFlow Version 9 export format that allow
you to collect data on types of traffic in addition to IP traffic.
•
Postprocessing features that allow you to define fields that control how traffic data is exported.
You need to decide if you want to further analyze your network traffic. If you do want to do further
analysis, you need to make choices in two areas:
•
Do you want to customize or fine-tune the way that you collect NetFlow data? For example, you
might want to configure packet sampling, or packet filtering, or an aggregation scheme.
•
Do you want to collect and analyze data about the use of other Cisco IOS applications? For example,
you might want to configure NetFlow support for BGP next hop, multicast, MPLS, or IPv6.
5
Cisco IOS NetFlow Overview
Information About Cisco IOS NetFlow
Before you configure or enable an additional NetFlow feature or service, you need to understand the
prerequisites, restrictions, and key concepts that apply to each feature or service. Refer to the following
sections for information about and links to the NetFlow features and services:
•
NetFlow Preprocessing Features: Filtering and Sampling, page 6
•
NetFlow Advanced Features and Services: BGP Next Hop, Multicast, MPLS, NetFlow Layer 2 and
Security Monitoring Exports, and IPv6, page 6
•
NetFlow Postprocessing Features: Aggregation Schemes and Export to Multiple Destinations,
page 7
NetFlow Preprocessing Features: Filtering and Sampling
Table 1 briefly describes preprocessing features and indicates where you can find concept and task
information about each. You set up these features to select the subset of traffic of interest to you before
NetFlow processing begins.
Table 1
NetFlow Preprocessing Features
Preprocessing Feature
Brief Description
Source for Concept and Task
Information
Packet sampling
Sets up statistical sampling of
network traffic for traffic
engineering or capacity planning
See the “Using NetFlow Filtering or
Sampling to Select the Network
Traffic to Track” module.
Filtering
Sets up a specific subset of network See the “Using NetFlow Filtering or
traffic for class-based traffic analysis Sampling to Select the Network
Traffic to Track” module.
and monitoring on-network or
off-network traffic
NetFlow Advanced Features and Services: BGP Next Hop, Multicast, MPLS,
NetFlow Layer 2 and Security Monitoring Exports, and IPv6
Table 2 briefly describes advanced features and services supported by NetFlow and indicates where you
can find concept and task information about each. Configure these features and services to collect and
analyze NetFlow traffic statistics about them (features such as BGP Next Hop, multicast, and MPLS).
Table 2
6
NetFlow Advanced Features and Services
Source for Concept and Task
Information
Feature or Service
Brief Description
BGP next hop support
Sets up the export of BGP next hop
information for the purpose of
measuring network traffic on a per
BGP next hop basis
See the “Configuring NetFlow
BGP Next Hop Support for
Accounting and Analysis” module.
Multicast support
Sets up the capture of multicastspecific data that allows you to get a
complete multicast traffic billing
solution
See the “Configuring NetFlow
Multicast Accounting” module.
Cisco IOS NetFlow Overview
Information About Cisco IOS NetFlow
Table 2
NetFlow Advanced Features and Services (continued)
Source for Concept and Task
Information
Feature or Service
Brief Description
MPLS support
Sets up the capture of MPLS traffic
containing both IP and non-IP
packets for use in MPLS network
management, network planning, and
enterprise accounting
See the “Configuring MPLS-aware
NetFlow” module.
NetFlow Layer 2 and
Security Monitoring
Exports
Sets up the capture of Layer 2 and
Layer 3 fields for use in security
monitoring, network management,
network planning, and enterprise
accounting
See the “NetFlow Layer 2 and
Security Monitoring Exports”
module.
NetFlow Postprocessing Features: Aggregation Schemes and Export to
Multiple Destinations
Table 3 briefly describes postprocessing features and indicates where you can find concept and task
information about each. You configure these features to set up the export of NetFlow data.
Table 3
NetFlow Postprocessing Features
Source for Concept and Task
Information
Postprocessing Features
Brief Description
Aggregation schemes
Sets up extra aggregation caches with “Configuring NetFlow
different combinations of fields that Aggregation Caches”
determine which traditional flows are
grouped together and collected when
a flow expires from the main cache
Export to multiple
destinations
Sets up identical streams of NetFlow “Configuring NetFlow and
data to be sent to multiple hosts
NetFlow Data Export”
NetFlow MIBs
The NetFlow MIB and the NetFlow MIB and Top Talkers features provide real time access to NetFlow
cache information. These feature do not require a collector to obtain NetFlow data. This allows smaller
enterprises to collect NetFlow data.
With the NetFlow MIB feature, you can access in real time the system information that is stored in the
NetFlow cache by utilizing a MIB implementation based on the Simple Network Management Protocol
(SNMP). This information is accessed by get and set commands entered on the network management
system (NMS) workstation for which SNMP has been implemented. The NetFlow MIB feature provides
MIB objects that allow you to monitor cache flow information, the current NetFlow configuration, and
statistics. For details about the NetFlow MIB, see the “Configuring SNMP and using the NetFlow MIB
to Monitor NetFlow Data” module.
The NetFlow MIB and Top Talkers feature uses NetFlow functionality to obtain information regarding
heaviest traffic patterns and most-used applications in the network. You can use this feature for security
monitoring or accounting purposes for top talkers, and matching and identifying addresses for key users
7
Cisco IOS NetFlow Overview
How to Configure Cisco IOS NetFlow
of the network. You configure the criteria by which flows from the NetFlow cache are sorted and placed
in a special cache. The flows that are displayed by this feature are known as “top talkers.” For details
about the NetFlow MIB and Top Talkers, see the “Configuring NetFlow Top Talkers using Cisco IOS
CLI Commands or SNMP Commands” module.
How to Configure Cisco IOS NetFlow
There are no tasks for the “Cisco IOS NetFlow Overview” module.
See the “Related Documents” section on page 9 for links to configuration information for NetFlow
features and services.
Configuration Examples for Cisco IOS NetFlow
There are no configuration examples for the “Cisco IOS NetFlow Overview” module.
See the “Related Documents” section on page 9 for links to configuration information for NetFlow
features and services.
Where to Go Next
To configure basic NetFlow, refer to the “Configuring NetFlow and NetFlow Data Export” module. See
the “Related Documents” section on page 9 for links to configuration information about additional
NetFlow features and services.
Additional References
The following sections provide references related to configuring NetFlow.
8
Cisco IOS NetFlow Overview
Additional References
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
“Cisco IOS NetFlow Overview”
List of the features documented in the Book Title
configuration guide
“Cisco IOS NetFlow Features Roadmap”
The minimum information about and tasks required for “Getting Started with Configuring NetFlow and NetFlow Data
configuring NetFlow and NetFlow Data Export
Export”
Tasks for configuring NetFlow to capture and export
network traffic data
“Configuring NetFlow and NetFlow Data Export”
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring Random Sampled NetFlow
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring NetFlow aggregation caches
“Configuring NetFlow Aggregation Caches”
Tasks for configuring NetFlow BGP next hop support
“Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis”
Tasks for configuring NetFlow multicast support
“Configuring NetFlow Multicast Accounting”
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
“NetFlow Layer 2 and Security Monitoring Exports”
Tasks for configuring the SNMP NetFlow MIB
“Configuring SNMP and using the NetFlow MIB to Monitor
NetFlow Data”
Tasks for configuring the NetFlow MIB and Top
Talkers feature
“Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands”
Information for installing, starting, and configuring the “Cisco CNS NetFlow Collection Engine Documentation”
CNS NetFlow Collection Engine
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
9
Cisco IOS NetFlow Overview
Glossary
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
•
RFC 2460
Internet Protocol, Version 6 (IPv6) Specification
•
RFC 3954
Cisco Systems NetFlow Services Export Version 9
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
Glossary
AS—autonomous system. A collection of networks under a common administration sharing a common
routing strategy. Autonomous systems are subdivided into areas. An autonomous system must be
assigned a unique 16-bit number by the Internet Assigned Numbers Authority (IANA).
BGP—Border Gateway Protocol. An interdomain routing protocol that replaces Exterior Gateway
Protocol (EGP). A BGP system exchanges reachability information with other BGP systems. BGP is
defined by RFC 1163.
BGP next hop—IP address of the next hop to be used to reach a certain destination.
flow—(NetFlow) A set of packets with the same source IP address, destination IP address, protocol,
source/destination ports, and type-of-service, and the same interface on which the flow is monitored.
Ingress flows are associated with the input interface, and egress flows are associated with the output
interface.
IPv6—IP Version 6. Replacement for the current version of IP (Version 4). IPv6 includes support for
flow ID in the packet header, which can be used to identify flows. Formerly called IPng (next
generation).
ISL—Inter-Switch Link. Cisco-proprietary protocol that maintains VLAN information as traffic flows
between switches and routers.
MPLS—Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets
along normally routed paths (sometimes called MPLS hop-by-hop forwarding).
10
Cisco IOS NetFlow Overview
Glossary
multicast—When single packets are copied by the network and sent to a specific subset of network
addresses, they are said to be multicast. These addresses are specified in the Destination Address field.
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the routing
devices in the network. It is emerging as a primary network accounting and security technology.
NetFlow aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router or switch that is running NetFlow and decodes, aggregates, and stores them. You can
generate reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow V9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
QoS—quality of service. A measure of performance for a transmission system that reflects the system’s
transmission quality and service availability.
traffic engineering—Techniques and processes that cause routed traffic to travel through the network
on a path other than the one that would have been chosen if standard routing methods were used.
VLAN—virtual LAN. Group of devices on one or more LANs that are configured (by management
software) so that they can communicate as if they were attached to the same wire, when in fact they are
located on a number of different LAN segments. Because VLANs are based on logical instead of
physical connections, they are extremely flexible.
CCDE, CCENT, CCSI, Cisco Eos, Cisco Explorer, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Nurse Connect, Cisco Pulse,
Cisco SensorBase, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco TrustSec, Cisco Unified Computing System, Cisco WebEx,
DCE, Flip Channels, Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to
the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed
(Stylized), Cisco Store, Flip Gift Card, and One Million Acts of Green are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS,
Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert
logo, Cisco IOS, Cisco Lumin, Cisco Nexus, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity,
Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center, Explorer, Follow Me Browsing, GainMaker, iLYNX, IOS,
iPhone, IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking
Academy, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect, ROSA, SenderBase, SMARTnet,
Spectrum Expert, StackWise, WebEx, and the WebEx logo are registered trademarks of Cisco and/or its affiliates in the United States and certain
other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (1002R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2008 Cisco Systems, Inc. All rights reserved.
11
Cisco IOS NetFlow Overview
Glossary
12
Cisco IOS NetFlow Features Roadmap
First Published: June 19, 2006
Last Updated: March 31, 2010
This roadmap lists the features documented in the Cisco IOS NetFlow Configuration Guide. This
roadmap is organized by software releases and features available in that release. For any feature, click
the link in the “Where Documented” column to view the document that contains information about the
feature.
Many legacy features have been incorporated into the configuration files, and these features may not
have entries in this roadmap. In addition, information in this roadmap supports other software releases
or platforms. For the latest feature information and caveats, see the release notes for your platform and
software release.
Feature and Release Support
Table 1 lists Cisco IOS NetFlow feature support for the following Cisco IOS software release trains:
•
Cisco IOS Software Release 12.0S
•
Cisco IOS Software Release 12.2S
•
Cisco IOS Software Release 12.2SB
•
Cisco IOS Software Release 12.2SR
•
Cisco IOS Software Release 12.2SX
•
Cisco IOS Software Releases 12.2T, 12.3, 12.3T, 12.4, 12.4T and 15.0M
•
Cisco IOS XE Software Release
•
Cisco IOS Software Release 12.2ZY
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco
Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a
specific software release, feature set, or platform. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Cisco IOS NetFlow Features Roadmap
Table 1 lists the most recent release of each software train first and the features in alphabetical order
within the release.
Table 1
Supported Cisco IOS NetFlow Features
Release
Feature Name
Feature Description
Where Documented
Cisco IOS Software Release 12.0S
12.0(26)S
12.0(25)S
12.0(24)S
MPLS-aware NetFlow
Configuring
Multiprotocol Label Switching (MPLS)-aware
NetFlow is an extension of the NetFlow accounting MPLS-aware NetFlow
feature that provides highly granular traffic statistics
for Cisco routers. MPLS-aware NetFlow collects
statistics on a per-flow basis just as NetFlow does.
MPLS-aware NetFlow uses the NetFlow Version 9
export format.
12.0(26)S
NetFlow BGP Next Hop
Support
The NetFlow Border Gateway Protocol (BGP) Next
Hop Support feature lets you measure network traffic
on a per BGP next hop basis. Without the NetFlow
BGP Next Hop Support feature, NetFlow exports
only IP next hop information (which provides data
on only the next router); this feature adds BGP next
hop information to the data export.
12.0(11)S
Configuring NetFlow
NetFlow Minimum Prefix The NetFlow Minimum Prefix Mask for
Mask for Router-Based
Router-Based Aggregation feature allows you to set Aggregation Caches
a minimum mask size for prefix aggregation,
Aggregation
destination-prefix aggregation, and source-prefix
aggregation schemes.
12.0(19)S
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
12.0(22)S
NetFlow Subinterface
Support
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
12.0(15)S
NetFlow ToS-Based
Router Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
12.0(24)S
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
2
Configuring NetFlow
BGP Next Hop Support
for Accounting and
Analysis
Configuring NetFlow and
NetFlow Data Export
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.0(26)S
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
Where Documented
Cisco IOS Software Release 12.2S
Configuring NetFlow
BGP Next Hop Support
for Accounting and
Analysis
12.2(18)S
NetFlow BGP Next Hop
Support
The NetFlow Border Gateway Protocol (BGP) Next
Hop Support feature lets you measure network traffic
on a per BGP next hop basis. Without the NetFlow
BGP Next Hop Support feature, NetFlow exports
only IP next hop information (which provides data
on only the next router); this feature adds BGP next
hop information to the data export.
12.2(25)S
NetFlow Input Filters
The NetFlow Input Filters feature provides NetFlow Using NetFlow Filtering
or Sampling to Select the
data for a specific subset of traffic by letting you
create filters to select flows for NetFlow processing. Network Traffic to Track
For example, you can select flows from a specific
group of hosts. This feature also lets you select
various sampling rates for selected flows. The
NetFlow Input Filters feature is used, for example,
for class-based traffic analysis and monitoring
on-network or off-network traffic.
12.2(25)S
NetFlow MIB
The NetFlow MIB feature provides MIB objects to
allow you to monitor flow cache information, the
current NetFlow configuration, and statistics.
Configuring SNMP and
the NetFlow MIB to
Monitor NetFlow Data
12.2(25)S
NetFlow MIB and Top
Talkers
The NetFlow MIB and Top Talkers feature uses
NetFlow functionality to obtain information
regarding heaviest traffic patterns and most-used
applications in the network.
Configuring NetFlow Top
Talkers using Cisco IOS
CLI Commands or SNMP
Commands
12.2(18)S
NetFlow Multicast
Support
Configuring NetFlow
The NetFlow Multicast Support feature lets you
Multicast Accounting
capture multicast-specific data (both packets and
bytes) for multicast flows. For example, you can
capture the packet-replication factor for a specific
flow as well as for each outgoing stream. This feature
provides complete end-to-end usage information
about network traffic for a complete multicast traffic
billing solution.
3
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
12.2(14)S
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
12.2(14)S
NetFlow Subinterface
Support
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
12.2(14)S
NetFlow ToS-Based
Router Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
12.2(18)S
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
12.2(18)S
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
Feature Description
Where Documented
Configuring NetFlow and
NetFlow Data Export
Cisco IOS Software Release 12.2SB
12.2(28)SBB
4
Egress NetFlow
Accounting
Configuring NetFlow and
The Egress NetFlow Accounting feature allows
NetFlow Data Export
NetFlow statistics to be gathered on egress traffic
(traffic that is exiting the router). Previous versions
of NetFlow allowed statistics to be gathered only on
ingress traffic (traffic that is entering the router).
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
Where Documented
12.2(27)SBC
NetFlow BGP Next Hop
Support
The NetFlow Border Gateway Protocol (BGP) Next
Hop Support feature lets you measure network traffic
on a per BGP next hop basis. Without the NetFlow
BGP Next Hop Support feature, NetFlow exports
only IP next hop information (which provides data
on only the next router); this feature adds BGP next
hop information to the data export.
Configuring NetFlow
BGP Next Hop Support
for Accounting and
Analysis
12.2(31)SB2
NetFlow MIB
The NetFlow MIB feature provides MIB objects to
allow you to monitor flow cache information, the
current NetFlow configuration, and statistics.
Configuring SNMP and
the NetFlow MIB to
Monitor NetFlow Data
12.2(27)SBC
Configuring NetFlow
NetFlow Minimum Prefix The NetFlow Minimum Prefix Mask for
Mask for Router-Based
Router-Based Aggregation feature allows you to set Aggregation Caches
Aggregation
a minimum mask size for prefix aggregation,
destination-prefix aggregation, and source-prefix
aggregation schemes.
12.2(27)SBC
NetFlow Multicast
Support
12.2(27)SBC
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
12.2(27)SBC
NetFlow Subinterface
Support
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
12.2(27)SBB
NetFlow ToS-Based
Router Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
12.2(27)SBC
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
Configuring NetFlow
The NetFlow Multicast Support feature lets you
Multicast Accounting
capture multicast-specific data (both packets and
bytes) for multicast flows. For example, you can
capture the packet-replication factor for a specific
flow as well as for each outgoing stream. This feature
provides complete end-to-end usage information
about network traffic for a complete multicast traffic
billing solution.
Configuring NetFlow and
NetFlow Data Export
5
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.2(28)SB
MPLS-aware NetFlow
Configuring
Multiprotocol Label Switching (MPLS)-aware
NetFlow is an extension of the NetFlow accounting MPLS-aware NetFlow
feature that provides highly granular traffic statistics
for Cisco routers. MPLS-aware NetFlow collects
statistics on a per-flow basis just as NetFlow does.
MPLS-aware NetFlow uses the NetFlow Version 9
export format.
12.2(27)SBC
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
Where Documented
Cisco IOS Software Release 12.2SR
12.2(33)SRA
Egress NetFlow
Accounting
Configuring NetFlow and
The Egress NetFlow Accounting feature allows
NetFlow Data Export
NetFlow statistics to be gathered on egress traffic
(traffic that is exiting the router). Previous versions
of NetFlow allowed statistics to be gathered only on
ingress traffic (traffic that is entering the router).
12.2(33)SRA
MPLS Egress NetFlow
Accounting
Configuring MPLS
The MPLS Egress NetFlow Accounting feature
allows you to capture IP flow information for packets Egress NetFlow
undergoing MPLS label disposition; that is, packets Accounting and Analysis
that arrive on a router as MPLS packets and are
transmitted as IP packets.
12.2(33)SRB
NDE for VRF Interfaces
The NetFlow data export (NDE) for VRF Interfaces NDE for VRF Interfaces
feature enables the creation and export of hardware
NetFlow cache entries for traffic entering a router on
the last multiprotocol label switching (MPLS) hop of
an IPv4 MPLS virtual private network (VPN).
12.2(33)SRA
NetFlow BGP Next Hop
Support
The NetFlow Border Gateway Protocol (BGP) Next
Hop Support feature lets you measure network traffic
on a per BGP next hop basis. Without the NetFlow
BGP Next Hop Support feature, NetFlow exports
only IP next hop information (which provides data
on only the next router); this feature adds BGP next
hop information to the data export.
6
Configuring NetFlow
BGP Next Hop Support
for Accounting and
Analysis
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.2(33)SRA
NetFlow Input Filters
The NetFlow Input Filters feature provides NetFlow Using NetFlow Filtering
or Sampling to Select the
data for a specific subset of traffic by letting you
create filters to select flows for NetFlow processing. Network Traffic to Track
For example, you can select flows from a specific
group of hosts. This feature also lets you select
various sampling rates for selected flows. The
NetFlow Input Filters feature is used, for example,
for class-based traffic analysis and monitoring
on-network or off-network traffic.
12.2(33)SRD
NetFlow MIB
The NetFlow MIB feature provides MIB objects to
allow you to monitor flow cache information, the
current NetFlow configuration, and statistics.
12.2(33)SRA
Configuring NetFlow
NetFlow Minimum Prefix The NetFlow Minimum Prefix Mask for
Mask for Router-Based
Router-Based Aggregation feature allows you to set Aggregation Caches
Aggregation
a minimum mask size for prefix aggregation,
destination-prefix aggregation, and source-prefix
aggregation schemes.
12.2(33)SRA
NetFlow Multicast
Support
12.2(33)SRA
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
12.2(33)SRA
NetFlow Subinterface
Support
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
12.2(33)SRA
NetFlow ToS-Based
Router Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
Where Documented
Configuring SNMP and
the NetFlow MIB to
Monitor NetFlow Data
Configuring NetFlow
The NetFlow Multicast Support feature lets you
Multicast Accounting
capture multicast-specific data (both packets and
bytes) for multicast flows. For example, you can
capture the packet-replication factor for a specific
flow as well as for each outgoing stream. This feature
provides complete end-to-end usage information
about network traffic for a complete multicast traffic
billing solution.
Configuring NetFlow and
NetFlow Data Export
7
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.2(33)SRA
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
12.2(33)SRB
NetFlow v9 For IPv6
The NetFlow v9 For IPv6 feature adds version 9
export support for IPv6.
12.2(33)SRA
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
Where Documented
NetFlow v9 For IPv6
Cisco IOS Software Release 12.2SX
12.2(18)SXF
Egress NetFlow
Accounting
Configuring NetFlow and
The Egress NetFlow Accounting feature allows
NetFlow Data Export
NetFlow statistics to be gathered on egress traffic
(traffic that is exiting the router). Previous versions
of NetFlow allowed statistics to be gathered only on
ingress traffic (traffic that is entering the router).
12.2(18)SXE
MPLS Egress NetFlow
Accounting
Configuring MPLS
The MPLS Egress NetFlow Accounting feature
allows you to capture IP flow information for packets Egress NetFlow
undergoing MPLS label disposition; that is, packets Accounting and Analysis
that arrive on a router as MPLS packets and are
transmitted as IP packets.
12.2(33)SXI
NetFlow Accounting for
Unicast and Multicast on
GRE tunnel interface
GRE is a tunneling protocol developed by Cisco that
can encapsulate a wide variety of protocol packet
types inside IP tunnels, creating a virtual
point-to-point link to Cisco routers at remote points
over an IP internetwork. This feature provides
netflow accounting for IP v4 unicast and multicast
flows over GRE tunnels. It provides accounting for
packets entering as well as exiting a tunnel interface.
8
Configuring Netflow
Accounting for Unicast
and Multicast on GRE
Tunnel Interfaces
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
Where Documented
12.2(18)SXF
NetFlow BGP Next Hop
Support
The NetFlow Border Gateway Protocol (BGP) Next
Hop Support feature lets you measure network traffic
on a per BGP next hop basis. Without the NetFlow
BGP Next Hop Support feature, NetFlow exports
only IP next hop information (which provides data
on only the next router); this feature adds BGP next
hop information to the data export.
Configuring NetFlow
BGP Next Hop Support
for Accounting and
Analysis
12.2SX1
NetFlow Input Filters
The NetFlow Input Filters feature provides NetFlow Using NetFlow Filtering
or Sampling to Select the
data for a specific subset of traffic by letting you
create filters to select flows for NetFlow processing. Network Traffic to Track
For example, you can select flows from a specific
group of hosts. This feature also lets you select
various sampling rates for selected flows. The
NetFlow Input Filters feature is used, for example,
for class-based traffic analysis and monitoring
on-network or off-network traffic.
12.2SX1
NetFlow MIB and Top
Talkers
The NetFlow MIB and Top Talkers feature uses
NetFlow functionality to obtain information
regarding heaviest traffic patterns and most-used
applications in the network.
12.2(18)SXF
Configuring NetFlow
NetFlow Minimum Prefix The NetFlow Minimum Prefix Mask for
Mask for Router-Based
Router-Based Aggregation feature allows you to set Aggregation Caches
Aggregation
a minimum mask size for prefix aggregation,
destination-prefix aggregation, and source-prefix
aggregation schemes.
12.2(18)SXF
NetFlow Multicast
Support
12.2(18)SXE
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
12.2(33)SXH
NetFlow Subinterface
Support
Configuring NetFlow Top
Talkers using Cisco IOS
CLI Commands or SNMP
Commands
Configuring NetFlow
The NetFlow Multicast Support feature lets you
Multicast Accounting
capture multicast-specific data (both packets and
bytes) for multicast flows. For example, you can
capture the packet-replication factor for a specific
flow as well as for each outgoing stream. This feature
provides complete end-to-end usage information
about network traffic for a complete multicast traffic
billing solution.
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
Configuring NetFlow and
NetFlow Data Export
9
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.2(18)SXF
NetFlow ToS-Based
Router Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
12.2(18)SXF
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
12.2(33)SXH
NetFlow v9 For IPv6
The NetFlow v9 For IPv6 feature adds version 9
export support for IPv6.
12.2(18)SXF
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
Where Documented
NetFlow v9 For IPv6
Cisco IOS Software Releases 12.2T, 12.3, 12.3T, 12.4, 12.4T and 15.0M
12.3(11)T
Egress NetFlow
Accounting
Configuring NetFlow and
The Egress NetFlow Accounting feature allows
NetFlow Data Export
NetFlow statistics to be gathered on egress traffic
(traffic that is exiting the router). Previous versions
of NetFlow allowed statistics to be gathered only on
ingress traffic (traffic that is entering the router).
12.3(8)T
MPLS-aware NetFlow
Configuring
Multiprotocol Label Switching (MPLS)-aware
NetFlow is an extension of the NetFlow accounting MPLS-aware NetFlow
feature that provides highly granular traffic statistics
for Cisco routers. MPLS-aware NetFlow collects
statistics on a per-flow basis just as NetFlow does.
MPLS-aware NetFlow uses the NetFlow Version 9
export format.
10
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.3(11)T
MPLS Egress NetFlow
Accounting
Configuring MPLS
The MPLS Egress NetFlow Accounting feature
allows you to capture IP flow information for packets Egress NetFlow
undergoing MPLS label disposition; that is, packets Accounting and Analysis
that arrive on a router as MPLS packets and are
transmitted as IP packets.
12.3(1)
NetFlow BGP Next Hop
Support
The NetFlow Border Gateway Protocol (BGP) Next
Hop Support feature lets you measure network traffic
on a per BGP next hop basis. Without the NetFlow
BGP Next Hop Support feature, NetFlow exports
only IP next hop information (which provides data
on only the next router); this feature adds BGP next
hop information to the data export.
12.4(4)T
NetFlow Dynamic Top
Talkers CLI
The NetFlow Dynamic Top Talkers CLI feature gives Detecting and Analyzing
you an overview of the highest volume traffic in your Network Threats With
NetFlow
network by aggregating flows on a common field.
For example, you can aggregate all of the flows for a
destination network by aggregating them on the
destination prefix.
12.3(4)T
NetFlow Input Filters
The NetFlow Input Filters feature provides NetFlow Using NetFlow Filtering
or Sampling to Select the
data for a specific subset of traffic by letting you
create filters to select flows for NetFlow processing. Network Traffic to Track
For example, you can select flows from a specific
group of hosts. This feature also lets you select
various sampling rates for selected flows. The
NetFlow Input Filters feature is used, for example,
for class-based traffic analysis and monitoring
on-network or off-network traffic.
12.3(14)T
NetFlow Layer 2 and
Security Monitoring
Exports
NetFlow Layer 2 and
The NetFlow Layer 2 and Security Monitoring
Security Monitoring
Exports feature adds the ability for NetFlow to
capture the values from several fields in Layer 3 IP Exports
traffic and Layer 2 LAN traffic to obtain information
that can be used to classify and identify network
traffic. This information can be used to help identify
network attacks and their origin.
12.3(7)T
NetFlow MIB
The NetFlow MIB feature provides MIB objects to
allow you to monitor flow cache information, the
current NetFlow configuration, and statistics.
Configuring SNMP and
using the NetFlow MIB to
Monitor NetFlow Data
12.3(11)T
NetFlow MIB and Top
Talkers
The NetFlow MIB and Top Talkers feature uses
NetFlow functionality to obtain information
regarding heaviest traffic patterns and most-used
applications in the network.
Configuring NetFlow Top
Talkers using Cisco IOS
CLI Commands or SNMP
Commands
12.1(2)T
Configuring NetFlow
NetFlow Minimum Prefix The NetFlow Minimum Prefix Mask for
Mask for Router-Based
Router-Based Aggregation feature allows you to set Aggregation Caches
Aggregation
a minimum mask size for prefix aggregation,
destination-prefix aggregation, and source-prefix
aggregation schemes.
Where Documented
Configuring NetFlow
BGP Next Hop Support
for Accounting and
Analysis
11
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.3(1)
NetFlow Multicast
Support
Configuring NetFlow
The NetFlow Multicast Support feature lets you
Multicast Accounting
capture multicast-specific data (both packets and
bytes) for multicast flows. For example, you can
capture the packet-replication factor for a specific
flow as well as for each outgoing stream. This feature
provides complete end-to-end usage information
about network traffic for a complete multicast traffic
billing solution.
12.2(2)T
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
12.4(4)T
NetFlow Reliable Export
with SCTP
The NetFlow Reliable Export With SCTP feature
provides a more robust and flexible method for
exporting NetFlow data to collectors than UDP,
which was the only transport option prior to the
introduction of this feature.
NetFlow Reliable Export
with SCTP
12.2(15)T
NetFlow Subinterface
Support
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
Configuring NetFlow and
NetFlow Data Export
12.2(4)T
NetFlow ToS-Based
Router Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
12.3(1)
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
12
Where Documented
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
12.3(2)T
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
12.4(2)T
Support for capturing the
value from the fragment
offset field of IP headers
added to NetFlow Layer 2
and Security Monitoring
Exports2
The NetFlow Layer 2 and Security Monitoring
Exports feature enables the capture of values from
fields in Layer 3 and Layer 2 of IP traffic for
accounting and security analysis.
Where Documented
Detecting and Analyzing
Network Threats With
NetFlow
Cisco IOS XE Software Release
2.1
Egress NetFlow
Accounting
Configuring NetFlow and
The Egress NetFlow Accounting feature allows
NetFlow Data Export
NetFlow statistics to be gathered on egress traffic
(traffic that is exiting the router). Previous versions
of NetFlow allowed statistics to be gathered only on
ingress traffic (traffic that is entering the router).
2.1
NetFlow Aggregation
The NetFlow ToS-Based Router Aggregation feature Configuring NetFlow
Aggregation Caches
enables you to limit router-based type of service
(ToS) aggregation of NetFlow export data. The
aggregation of export data provides a summarized
NetFlow export data that can be exported to a
collection device. The result is lower bandwidth
requirements for NetFlow export data and reduced
platform requirements for NetFlow data collection
devices.
2.1
Configuring NetFlow
NetFlow Minimum Prefix The NetFlow Minimum Prefix Mask for
Mask for Router-Based
Router-Based Aggregation feature allows you to set Aggregation Caches
Aggregation
a minimum mask size for prefix aggregation,
destination-prefix aggregation, and source-prefix
aggregation schemes.
2.1
NetFlow Multiple Export The NetFlow Multiple Export Destinations feature Configuring NetFlow and
Destinations
enables configuration of multiple destinations of the NetFlow Data Export
NetFlow data.
2.1
NetFlow Subinterface
Support
The NetFlow Subinterface Support feature provides
the ability to enable NetFlow on a per-subinterface
basis.
Configuring NetFlow and
NetFlow Data Export
13
Cisco IOS NetFlow Features Roadmap
Table 1
Supported Cisco IOS NetFlow Features (continued)
Release
Feature Name
Feature Description
2.1
NetFlow v9 Export
Format
NetFlow Version 9 is a flexible and extensible format Configuring NetFlow and
NetFlow Data Export
that provides the versatility needed to support new
fields and record types. This format accommodates
new NetFlow-supported technologies such as
Multicast, Multiprotocol Label Switching (MPLS),
and Border Gateway Protocol (BGP) next hop. The
distinguishing feature of the NetFlow Version 9
format is that it is template based.
2.1
Random Sampled
NetFlow
Using NetFlow Filtering
Random Sampled NetFlow provides NetFlow data
for a subset of traffic in a Cisco router by processing or Sampling to Select the
Network Traffic to Track
only one randomly selected packet out of n
sequential packets (n is a user-configurable
parameter). Packets are sampled as they arrive
(before any NetFlow cache entries are made for those
packets). Statistical traffic sampling substantially
reduces consumption of router resources (especially
CPU resources) while providing valuable NetFlow
data. The main uses of Random Sampled NetFlow
are traffic engineering, capacity planning, and
applications where full NetFlow is not needed for an
accurate view of network traffic.
Where Documented
Cisco IOS Software Release 12.2ZY
12.2(18)ZYA2 Application-aware
NetFlow
Application-aware NetFlow enables the capture of
application information collected by PISA NBAR
and exports using NetFlow Version 9.
NetFlow Layer 2 and
Security Monitoring
Exports
1. This feature is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform,
and platform hardware.
2. This is a minor enhancement. Minor enhancements are not typically listed in Feature Navigator.
CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect,
Cisco Pulse, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco Unified Computing System, Cisco WebEx, DCE, Flip Channels,
Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to the Human Network
are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed (Stylized), Cisco Store,
and Flip Gift Card are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP,
CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems,
Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center,
Explorer, Fast Step, Follow Me Browsing, FormShare, GainMaker, GigaDrive, HomeLink, iLYNX, Internet Quotient, IOS, iPhone, iQuick Study,
IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers,
Networking Academy, Network Registrar, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect,
ROSA, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx,
and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (0908R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2009 Cisco Systems, Inc. All rights reserved.
14
Getting Started with Configuring Cisco IOS
NetFlow and NetFlow Data Export
First Published: June 19, 2006
Last Updated: August 09, 2010
This module contains the minimum amount of information about and instructions necessary for
configuring NetFlow to capture and export network traffic data. This module is intended to help you get
started using NetFlow and NetFlow Data Export as quickly as possible. If you want more detailed
information about and instructions for configuring NetFlow and NetFlow Data Export please refer to
Configuring NetFlow and NetFlow Data Export.
NetFlow capture and export are performed independently on each internetworking device on which
NetFlow is enabled. NetFlow need not be operational on each router in the network.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router.
NetFlow is emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring NetFlow and NetFlow Data Export” section on
page 13.
Use Cisco Feature Navigator to find information about platform support and Cisco software image
support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on
Cisco.com is not required.
Contents
•
Prerequisites for Configuring NetFlow and NetFlow Data Export, page 2
•
Restrictions for Configuring NetFlow and NetFlow Data Export, page 2
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Prerequisites for Configuring NetFlow and NetFlow Data Export
•
Information About Configuring NetFlow and NetFlow Data Export, page 3
•
How to Configure NetFlow and NetFlow Data Export, page 4
•
Configuration Examples for Configuring NetFlow and NetFlow Data Export, page 9
•
Additional References, page 11
•
Feature Information for Configuring NetFlow and NetFlow Data Export, page 13
•
Glossary, page 16
Prerequisites for Configuring NetFlow and NetFlow Data Export
Before you enable NetFlow:
•
Configure the router for IP routing
•
Ensure that one of the following is enabled on your router, and on the interfaces that you want to
configure NetFlow on: Cisco Express Forwarding (CEF), distributed CEF, or fast switching
•
Understand the resources required on your router because NetFlow consumes additional memory
and CPU resources
Restrictions for Configuring NetFlow and NetFlow Data Export
NetFlow Data Capture
NetFlow consumes additional memory. If you have memory constraints, you might want to preset the
size of the NetFlow cache so that it contains a smaller number of entries. The default cache size depends
on the platform. For example, the default cache size for the Cisco 7500 router is 65536 (64K) entries.
Memory Impact
During times of heavy traffic, the additional flows can fill up the global flow hash table. If you need to
increase the size of the global flow hash table, increase the memory of the router.
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
Egress NetFlow Accounting in Cisco IOS 12.3T Releases, 12.3(11)T or Later
The Egress NetFlow Accounting feature captures NetFlow statistics for IP traffic only. MPLS statistics
are not captured. The MPLS Egress NetFlow Accounting feature can be used on a provider edge (PE)
router to capture IP traffic flow information for egress IP packets that arrived at the router as MPLS
packets and underwent label disposition.
Egress NetFlow accounting might adversely affect network performance because of the additional
accounting-related computation that occurs in the traffic-forwarding path of the router.
Locally generated traffic (traffic that is generated by the router on which the Egress NetFlow Accounting
feature is configured) is not counted as flow traffic for the Egress NetFlow Accounting feature.
2
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Note
In Cisco IOS 12.2S releases, egress NetFlow captures either IPv4 or MPLS packets as they leave the
router.
NetFlow Data Export
Restrictions for NetFlow Version 9 Data Export
•
Backward compatibility—Version 9 is not backward-compatible with Version 5 or Version 8. If you
need Version 5 or Version 8, you must configure it.
•
Export bandwidth—Export bandwidth use increases for Version 9 (because of template flowsets)
versus Version 5. The increase in bandwidth usage versus Version 5 varies with the frequency with
which template flowsets are sent. The default is to resend templates every 20 packets, which has a
bandwidth cost of about 4 percent. If necessary, you can lower the resend rate with the ip
flow-export template refresh-rate packets command.
•
Performance impact—Version 9 slightly decreases overall performance, because generating and
maintaining valid template flowsets require additional processing.
Information About Configuring NetFlow and NetFlow Data
Export
This section contains information that you should understand before you configure NetFlow to analyze
network traffic.
•
NetFlow Data Capture, page 3
•
NetFlow Flows: Key Fields, page 4
•
NetFlow Data Export Using the Version 9 Export Format, page 4
NetFlow Data Capture
NetFlow captures data from ingress (incoming) and egress (outgoing) packets. NetFlow gathers statistics
for the following ingress IP packets:
•
IP-to-IP packets
•
IP-to-Multiprotocol Label Switching (MPLS) packets
•
Frame Relay-terminated packets
•
ATM-terminated packets
NetFlow captures data for all egress (outgoing) packets through the use of the following features:
•
Egress NetFlow Accounting—NetFlow gathers statistics for all egress packets for IP traffic only.
•
NetFlow MPLS Egress—NetFlow gathers statistics for all egress MPLS-to-IP packets.
3
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
NetFlow Flows: Key Fields
A network flow is identified as a unidirectional stream of packets between a given source and
destination—both are defined by a network-layer IP address and by transport-layer source and
destination port numbers. Specifically, a flow is identified as the combination of the following key fields:
•
Source IP address
•
Destination IP address
•
Source port number
•
Destination port number
•
Layer 3 protocol type
•
Type of service (ToS)
•
Input logical interface
These seven key fields define a unique flow. If a packet has one key field different from another packet,
it is considered to belong to another flow. A flow might contain other accounting fields (such as the AS
number in the NetFlow export Version 5 flow format) that depend on the export record version that you
configure. Flows are stored in the NetFlow cache.
NetFlow Data Export Using the Version 9 Export Format
NetFlow Data Export format Version 9 is a flexible and extensible format, which provides the versatility
needed for support of new fields and record types. This format accommodates new NetFlow-supported
technologies such as Multicast, Multiprotocol Label Switching (MPLS), and Border Gateway Protocol
(BGP) next hop. Version 9 export format enables you to use the same version for main and aggregation
caches, and the format is extendable, so you can use the same export format with future features.
How to Configure NetFlow and NetFlow Data Export
This section contains instructions for configuring NetFlow to capture and export network traffic data.
Perform the following tasks to configure NetFlow to capture and export network traffic data:
•
Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format, page 4 (required)
•
Verify that NetFlow is Operational and View NetFlow Statistics, page 6 (optional)
•
Verifying that NetFlow Data Export is Operational, page 9 (optional)
Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format
Perform the steps in this required task to configure NetFlow and NetFlow Data Export Using the Version
9 Export Format.
SUMMARY STEPS
4
1.
enable
2.
configure terminal
3.
ip flow-export destination {{ip-address | hostname} udp-port}
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
4.
Repeat Step 3 once to configure an additional export destination
5.
ip flow-export version 9
6.
interface interface-type interface-number
7.
ip flow {ingress | egress}
8.
exit
9.
Repeat Steps 6 through 8 to enable NetFlow on other interfaces
10. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-export destination {{ip-address |
hostname} udp-port}
Example:
(Optional) IP address or hostname of the workstation to
which you want to send the NetFlow information and the
number of the UDP port on which the workstation is
listening for this input.
Router(config)# ip flow-export destination
172.16.10.2 99
Note
Step 4
Repeat Step 3 once to configure a second
NetFlow export destination.
(Optional) You can configure a maximum of two export
destinations for NetFlow.
Step 5
ip flow-export version 9
(Optional) Enables the export of information in NetFlow
cache entries.
Example:
Router(config)# ip flow-export version 9
•
The workstation is running an application such as
NetFlow Collection Engine (NFC) that is used to
analyze the exported data.
The version 9 keyword specifies that the export packet
uses the Version 9 format.
Caution
Entering this command on a Cisco 12000 Series
Internet Router causes packet forwarding to stop
for a few seconds while NetFlow reloads the
route processor and line card CEF tables. To
avoid interruption of service to a live network,
apply this command during a change window, or
include it in the startup-config file to be executed
during a router reboot.
5
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
Step 6
Command or Action
Purpose
interface interface-type interface-number
(Required) Specifies the interface that you want to enable
NetFlow on and enters interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
Step 7
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—captures traffic that is being received by the
interface
•
egress—captures traffic that is being transmitted by the
interface.
Example:
Router(config-if)# ip flow ingress
or
Example:
Router(config-if)# ip flow egress
Step 8
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
Router(config-if)# exit
You only need to use this command if you want to
enable NetFlow on another interface.
Step 9
Repeat Steps 6 through 8 to enable NetFlow on other
interfaces
(Optional) —
Step 10
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
Verify that NetFlow is Operational and View NetFlow Statistics
To verify that NetFlow is working properly perform the steps in this optional task.
SUMMARY STEPS
1.
show ip flow interface
2.
show ip cache flow
3.
show ip cache verbose flow
DETAILED STEPS
Step 1
show ip flow interface
Use this command to display the NetFlow configuration for an interface. The following is sample output
from this command:
Router# show ip flow interface
Ethernet0/0
ip flow ingress
Router#
Step 2
6
show ip cache flow
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
Use this command to verify that NetFlow is operational, and to display a summary of the NetFlow
statistics. The following is sample output from this command:
Router# show ip cache flow
IP packet size distribution (1103746 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.249 .694 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .027 .000 .027 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
35 active, 4061 inactive, 980 added
2921778 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 21640 bytes
0 active, 1024 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-FTP
108
0.0
1133
40
2.4
1799.6
0.9
TCP-FTPD
108
0.0
1133
40
2.4
1799.6
0.9
TCP-WWW
54
0.0
1133
40
1.2
1799.6
0.8
TCP-SMTP
54
0.0
1133
40
1.2
1799.6
0.8
TCP-BGP
27
0.0
1133
40
0.6
1799.6
0.7
TCP-NNTP
27
0.0
1133
40
0.6
1799.6
0.7
TCP-other
297
0.0
1133
40
6.8
1799.7
0.8
UDP-TFTP
27
0.0
1133
28
0.6
1799.6
1.0
UDP-other
108
0.0
1417
28
3.1
1799.6
0.9
ICMP
135
0.0
1133
427
3.1
1799.6
0.8
Total:
945
0.0
1166
91
22.4
1799.6
0.8
SrcIf
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
.
.
.
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Router#
Step 3
SrcIPaddress
192.168.67.6
10.10.18.1
10.10.18.1
10.234.53.1
10.10.19.1
10.10.19.1
192.168.87.200
192.168.87.200
DstIf
Et1/0.1
Null
Null
Et1/0.1
Null
Null
Et1/0.1
Et1/0.1
DstIPaddress
172.16.10.200
172.16.11.5
172.16.11.5
172.16.10.2
172.16.11.6
172.16.11.6
172.16.10.2
172.16.10.2
Pr
01
11
11
01
11
11
06
06
SrcP
0000
0043
0045
0000
0044
00A2
0014
0015
DstP
0C01
0043
0045
0800
0044
00A2
0014
0015
Pkts
51
51
51
51
51
51
50
52
172.16.1.84
172.16.1.84
172.16.1.85
172.16.1.85
10.251.10.1
10.162.37.71
Et1/0.1
Et1/0.1
Et1/0.1
Et1/0.1
Et1/0.1
Null
172.16.10.19
172.16.10.19
172.16.10.20
172.16.10.20
172.16.10.2
172.16.11.3
06
06
06
06
01
06
0087
0050
0089
0050
0000
027C
0087
0050
0089
0050
0800
027C
50
51
49
50
51
49
show ip cache verbose flow
Use this command to verify that NetFlow is operational and to display a detailed summary of the
NetFlow statistics. The following is sample output from this command:
Router# show ip cache verbose flow
IP packet size distribution (1130681 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.249 .694 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
7
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .027 .000 .027 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
35 active, 4061 inactive, 980 added
2992518 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 21640 bytes
0 active, 1024 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-FTP
108
0.0
1133
40
2.4
1799.6
0.9
TCP-FTPD
108
0.0
1133
40
2.4
1799.6
0.9
TCP-WWW
54
0.0
1133
40
1.2
1799.6
0.8
TCP-SMTP
54
0.0
1133
40
1.2
1799.6
0.8
TCP-BGP
27
0.0
1133
40
0.6
1799.6
0.7
TCP-NNTP
27
0.0
1133
40
0.6
1799.6
0.7
TCP-other
297
0.0
1133
40
6.6
1799.7
0.8
UDP-TFTP
27
0.0
1133
28
0.6
1799.6
1.0
UDP-other
108
0.0
1417
28
3.0
1799.6
0.9
ICMP
135
0.0
1133
427
3.0
1799.6
0.8
Total:
945
0.0
1166
91
21.9
1799.6
0.8
SrcIf
Port Msk
Et0/0
0000 /0
Et0/0
0043 /0
Et0/0
0045 /0
Et0/0
0000 /0
Et0/0
0044 /0
.
.
.
Et0/0
0087 /0
Et0/0
0050 /0
Et0/0
0089 /0
Et0/0
0050 /0
Et0/0
0000 /0
Et0/0
027C /0
Router#
8
SrcIPaddress
AS
192.168.67.6
0
10.10.18.1
0
10.10.18.1
0
10.234.53.1
0
10.10.19.1
0
172.16.1.84
0
172.16.1.84
0
172.16.1.85
0
172.16.1.85
0
10.251.10.1
0
10.162.37.71
0
DstIf
Port Msk
Et1/0.1
0C01 /0
Null
0043 /0
Null
0045 /0
Et1/0.1
0800 /0
Null
0044 /0
Et1/0.1
0087 /0
Et1/0.1
0050 /0
Et1/0.1
0089 /0
Et1/0.1
0050 /0
Et1/0.1
0800 /0
Null
027C /0
AS
0
0
0
0
0
0
0
0
0
0
0
DstIPaddress
NextHop
172.16.10.200
0.0.0.0
172.16.11.5
0.0.0.0
172.16.11.5
0.0.0.0
172.16.10.2
0.0.0.0
172.16.11.6
0.0.0.0
Pr TOS Flgs Pkts
B/Pk Active
01 00 10
799
28 1258.1
11 00 10
799
28 1258.0
11 00 10
799
28 1258.0
01 00 10
799
28 1258.1
11 00 10
799
28 1258.1
172.16.10.19
0.0.0.0
172.16.10.19
0.0.0.0
172.16.10.20
0.0.0.0
172.16.10.20
0.0.0.0
172.16.10.2
0.0.0.0
172.16.11.3
0.0.0.0
06 00
06
06
06
01
06
00
40
00 00
40
00 00
40
00 00
40
00 10
1500
00 00
40
799
1258.1
799
1258.0
798
1256.5
799
1258.0
799
1258.1
798
1256.4
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Configuration Examples for Configuring NetFlow and NetFlow Data Export
Verifying that NetFlow Data Export is Operational
To verify that NetFlow data export is operational and to view the statistics for NetFlow data export
perform the step in this optional task.
SUMMARY STEPS
1.
show ip flow export
DETAILED STEPS
Step 1
show ip flow export
Use this command to display the statistics for the NetFlow data export, including statistics for the main
cache and for all other enabled caches. The following is sample output from this command:
Router# show ip flow export
Flow export v9 is enabled for main cache
Exporting flows to 172.16.10.2 (99)
Exporting using source interface Ethernet0/0
Version 9 flow records
0 flows exported in 0 udp datagrams
0 flows failed due to lack of export packet
0 export packets were sent up to process level
0 export packets were dropped due to no fib
0 export packets were dropped due to adjacency issues
0 export packets were dropped due to fragmentation failures
0 export packets were dropped due to encapsulation fixup failures
Router#
Configuration Examples for Configuring NetFlow and NetFlow
Data Export
This section contains basic NetFlow configuration examples:
•
Configuring Egress NetFlow Accounting: Example, page 9
•
Configuring NetFlow Subinterface Support: Example, page 10
•
Configuring NetFlow Multiple Export Destinations: Example, page 10
•
Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format, page 10
•
Configure NetFlow for Analyzing PPPoE Session Traffic, page 11
Configuring Egress NetFlow Accounting: Example
The following example shows how to configure Egress NetFlow Accounting:
configure terminal
!
interface ethernet 0/0
ip flow egress
!
9
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Configuration Examples for Configuring NetFlow and NetFlow Data Export
Configuring NetFlow Subinterface Support: Example
The following examples show how to configure NetFlow Subinterface Support:
•
NetFlow Subinterface Support for ingress (received) traffic on a subinterface, page 10
•
NetFlow SubInterface Support for egress (transmitted) traffic on a subinterface, page 10
NetFlow Subinterface Support for ingress (received) traffic on a subinterface
configure terminal
!
interface ethernet 0/0.1
ip flow ingress
!
NetFlow SubInterface Support for egress (transmitted) traffic on a subinterface
configure terminal
!
interface ethernet 1/0.1
ip flow egress
!
Note
NetFlow performs additional checks for the status of each subinterface that requires more CPU
processing time and bandwidth. If you have several subinterfaces configured and you want to configure
NetFlow data capture on all of them, we recommend that you configure NetFlow on the main interface
instead of on the individual subinterfaces.
Configuring NetFlow Multiple Export Destinations: Example
The following example shows how to configure NetFlow Multiple Export Destinations:
configure terminal
!
ip flow-export destination 10.10.10.10 9991
ip flow-export destination 172.16.10.2 9991
!
Note
You can configure a maximum of two export destinations for the main cache and for each aggregation
cache.
Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format
The following example shows how to configure NetFlow and NetFlow data export using the Version 9
export format:
configure terminal
!
ip flow-export destination 10.10.10.10 9991
ip flow-export version 9
!
10
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Additional References
Configure NetFlow for Analyzing PPPoE Session Traffic
If you want to obtain accurate NetFlow traffic statistics for PPPoE sessions, you must configure NetFlow
on the virtual-template interface, not the physical interface that is configured with VLAN encapsulation.
For example, if you configure NetFlow on the physical interface which is configured for VLAN
encapsulation as shown in the following configuration, the NetFlow traffic statistics will not be an
accurate representation of the traffic on the PPPoE sessions.
!
interface GigabitEthernet2/0/0.10
encapsulation dot1Q 10
ip flow egress
pppoe enable
The following example shows how to configure egress NetFlow on a virtual template interface so that
you can accurately analyze the packet size distribution statistics of the traffic that the router is sending
to the end user over the PPoE session:
configure terminal
Router(config)# interface Virtual-Template 1
Router(config-if)# ip unnumbered ethernet 0
Router(config-if)# encapsulation ppp
Router(config-if)# ip flow egress
The following display output from the show ip cache flow command shows that this PPPoE session
traffic is comprised primarily of 1536 byte packets.
Router# show ip cache flow
IP packet size distribution (11014160 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .999 .000 .000 .000 .000 .000 .000
Additional References
The following sections provide references related to the configuring of NetFlow to capture and export
netflow traffic data.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
11
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Additional References
Related Topic
Document Title
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
12
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Feature Information for Configuring NetFlow and NetFlow Data Export
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
Feature Information for Configuring NetFlow and NetFlow Data
Export
Table 1 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
13
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Feature Information for Configuring NetFlow and NetFlow Data Export
Table 1
Feature Information for Configuring NetFlow and NetFlow Data Export
Feature Name
Releases
Feature Configuration Information
Egress NetFlow Accounting
12.3(11)T
15.0(1)S
The Egress NetFlow Accounting feature allows
NetFlow statistics to be gathered on egress traffic that is
exiting the router. Previous versions of NetFlow allow
statistics to be gathered only on ingress traffic that is
entering the router.
The following section provides information for
configuring this feature:
•
Configuring Egress NetFlow Accounting: Example
If you want more detailed information about this feature
please refer to the Configuring NetFlow and NetFlow
Data Export.
The following commands were introduced by this
feature: ip flow egress and ip flow-egress
input-interface.
The following commands were modified by this
feature: flow-sampler, match, show ip cache flow,
show ip cache verbose flow, and
show ip flow interface.
NetFlow Subinterface Support
12.2(14)S,
12.0(22)S
12.2(15)T
The NetFlow Subinterface Support feature provides the
ability to enable NetFlow on a per-subinterface basis.
The following section provides information for
configuring this feature:
•
Configuring NetFlow Subinterface Support:
Example
If you want more detailed information about this feature
please refer to the Configuring NetFlow and NetFlow
Data Export.
The following command was introduced by this feature:
ip flow ingress.
The following command was modified by this feature:
show ip interface.
14
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Feature Information for Configuring NetFlow and NetFlow Data Export
Table 1
Feature Information for Configuring NetFlow and NetFlow Data Export (continued)
Feature Name
Releases
Feature Configuration Information
NetFlow Multiple Export
Destinations:
12.0(19)S
12.2(2)T
12.2(14)S
15.0(1)S
The NetFlow Multiple Export Destinations feature
enables configuration of multiple destinations of the
NetFlow data.
The following section provides information for
configuring this feature:
•
Configuring NetFlow Multiple Export
Destinations: Example
If you want more detailed information about this feature
please refer to the Configuring NetFlow and NetFlow
Data Export.
The following commands were modified by this
feature: ip flow-aggregation cache, ip flow-export
destination, and show ip flow export.
NetFlow v9 Export Format
12.0(24)S
12.3(1)
12.2(18)S
12.2(27)SBC
12.2(18)SXF
15.0(1)S
The NetFlow v9 Export Format is flexible and
extensible, which provides the versatility needed to
support new fields and record types. This format
accommodates new NetFlow-supported technologies
such as Multicast, MPLS, NAT, and BGP next hop.
The following section provides information for
configuring this feature:
•
Configure NetFlow and NetFlow Data Export
Using the Version 9 Export Format
If you want more detailed information about this feature
please refer to the Configuring NetFlow and NetFlow
Data Export.
The following commands were modified by this
feature: debug ip flow export, export, ip flow-export,
and show ip flow export.
15
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Glossary
Glossary
AS—autonomous system. A collection of networks under a common administration sharing a common
routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned
a unique 16-bit number by the Internet Assigned Numbers Authority (IANA).
CEF—Cisco Express Forwarding. Layer 3 IP switching technology that optimizes network performance
and scalability for networks with large and dynamic traffic patterns.
BGP—Border Gateway Protocol. An interdomain routing protocol that replaces Exterior Gateway
Protocol (EGP). A BGP system exchanges reachability information with other BGP systems. BGP is
defined by RFC 1163.
BGP next hop—IP address of the next hop to be used by a router to reach a certain destination.
dCEF—distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
export packet—Type of packet built by a device (for example, a router) with NetFlow services enabled
that is addressed to another device (for example, the NetFlow Collection Engine). The packet contains
NetFlow statistics. The other device processes the packet (parses, aggregates, and stores information on
IP flows).
fast switching—Cisco feature in which a route cache is used to expedite packet switching through a
router.
flow—A set of packets with the same source IP address, destination IP address, protocol,
source/destination ports, and type-of-service, and the same interface on which the flow is monitored.
Ingress flows are associated with the input interface, and egress flows are associated with the output
interface.
MPLS—Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets
along a normally routed path (sometimes called MPLS hop-by-hop forwarding).
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
RP—Route Processor. A processor module in the Cisco 7000 series routers that contains the CPU,
system software, and most of the memory components that are used in the router. Sometimes called a
Supervisory Processor.
16
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Glossary
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2009 Cisco Systems, Inc. All rights reserved.
17
Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export
Glossary
18
Cisco IOS NetFlow Basic Configuration
Configuring NetFlow and NetFlow Data Export
First Published: June 19, 2006
Last Updated: August 09, 2010
This module contains information about and instructions for configuring NetFlow to capture and export
network traffic data. NetFlow capture and export are performed independently on each internetworking
device on which NetFlow is enabled. NetFlow need not be operational on each router in the network.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router.
NetFlow is emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring NetFlow and NetFlow Data Export” section on
page 36.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Configuring NetFlow and NetFlow Data Export, page 2
•
Restrictions for Configuring NetFlow and NetFlow Data Export, page 2
•
Information About Configuring NetFlow and NetFlow Data Export, page 3
•
How to Configure NetFlow and NetFlow Data Export, page 19
•
Configuration Examples for Configuring NetFlow and NetFlow Data Export, page 31
•
Additional References, page 33
•
Feature Information for Configuring NetFlow and NetFlow Data Export, page 36
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring NetFlow and NetFlow Data Export
Prerequisites for Configuring NetFlow and NetFlow Data Export
•
Glossary, page 38
Prerequisites for Configuring NetFlow and NetFlow Data Export
Before you enable NetFlow you must:
•
Configure the router for IP routing
•
Ensure that one of the following is enabled on your router, and on the interfaces that you want to
configure NetFlow on: Cisco Express Forwarding (CEF), distributed CEF, or fast switching
•
Understand the resources required on your router because NetFlow consumes additional memory
and CPU resources
Restrictions for Configuring NetFlow and NetFlow Data Export
NetFlow Data Capture
NetFlow consumes additional memory. If you have memory constraints, you might want to preset the
size of the NetFlow cache so that it contains a smaller number of entries. The default cache size depends
on the platform. For example, the default cache size for the Cisco 7500 router is 65536 (64K) entries.
Memory Impact
During times of heavy traffic, the additional flows can fill up the global flow hash table. If you need to
increase the size of the global flow hash table, increase the memory of the router.
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
Egress NetFlow Accounting in Cisco IOS 12.3T Releases, 12.3(11)T or Later
The Egress NetFlow Accounting feature captures NetFlow statistics for IP traffic only. MPLS statistics
are not captured. The MPLS Egress NetFlow Accounting feature can be used on a provider edge (PE)
router to capture IP traffic flow information for egress IP packets that arrived at the router as MPLS
packets and underwent label disposition.
Egress NetFlow accounting might adversely affect network performance because of the additional
accounting-related computation that occurs in the traffic-forwarding path of the router.
Locally generated traffic (traffic that is generated by the router on which the Egress NetFlow Accounting
feature is configured) is not counted as flow traffic for the Egress NetFlow Accounting feature.
Note
2
In Cisco IOS 12.2S releases, egress NetFlow captures either IPv4 or MPLS packets as they leave the
router.
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
NetFlow Data Export
Restrictions for NetFlow Version 9 Data Export
•
Backward compatibility—Version 9 is not backward-compatible with Version 5 or Version 8. If you
need Version 5 or Version 8, you must configure it.
•
Export bandwidth—Export bandwidth use increases for Version 9 (because of template flowsets)
versus Version 5. The increase in bandwidth usage versus Version 5 varies with the frequency with
which template flowsets are sent. The default is to resend templates every 20 packets, which has a
bandwidth cost of about 4 percent. If necessary, you can lower the resend rate with the ip
flow-export template refresh-rate packets command.
•
Performance impact—Version 9 slightly decreases overall performance, because generating and
maintaining valid template flowsets require additional processing.
Restrictions for NetFlow Version 8 Export Format
Version 8 export format is available only for aggregation caches, and it cannot be expanded to support
new features.
Restrictions for NetFlow Version 5 Export Format
Version 5 export format is suitable only for the main cache, and it cannot be expanded to support new
features.
Restrictions for NetFlow Version 1 Export Format
The Version 1 format was the initially released version. Do not use Version 1 format unless you are using
a legacy collection system that requires it. Use Version 9 or Version 5 export format.
Information About Configuring NetFlow and NetFlow Data
Export
This section contains information that you should understand before you configure NetFlow to analyze
network traffic.
•
NetFlow Data Capture, page 3
•
NetFlow Cache Management and Data Export, page 4
•
NetFlow Cache Management and Data Export, page 4
•
NetFlow Export Format Versions 9, 8, 5, and 1, page 5
•
Egress NetFlow Accounting Benefits: NetFlow Accounting Simplified, page 17
•
NetFlow Subinterface Support Benefits: Fine-Tuning Your Data Collection, page 19
•
NetFlow Multiple Export Destinations: Benefits, page 19
•
NetFlow on a Distributed VIP Interface, page 19
NetFlow Data Capture
NetFlow captures data from ingress (incoming) and egress (outgoing) packets. NetFlow gathers statistics
for the following ingress IP packets:
3
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
•
IP-to-IP packets
•
IP-to-Multiprotocol Label Switching (MPLS) packets
•
Frame Relay-terminated packets
•
ATM-terminated packets
NetFlow captures data for all egress (outgoing) packets through the use of the following features:
•
Egress NetFlow Accounting—NetFlow gathers statistics for all egress packets for IP traffic only.
•
NetFlow MPLS Egress—NetFlow gathers statistics for all egress MPLS-to-IP packets.
NetFlow Flows: Key Fields
A network flow is identified as a unidirectional stream of packets between a given source and
destination—both are defined by a network-layer IP address and by transport-layer source and
destination port numbers. Specifically, a flow is identified as the combination of the following key fields:
•
Source IP address
•
Destination IP address
•
Source port number
•
Destination port number
•
Layer 3 protocol type
•
Type of service (ToS)
•
Input logical interface
These seven key fields define a unique flow. If a packet has one key field different from another packet,
it is considered to belong to another flow. A flow might contain other accounting fields (such as the AS
number in the NetFlow export Version 5 flow format) that depend on the export record version that you
configure. Flows are stored in the NetFlow cache.
NetFlow Cache Management and Data Export
The key components of NetFlow are the NetFlow cache or data source that stores IP flow information,
and the NetFlow export or transport mechanism that sends NetFlow data to a network management
collector, such as the NetFlow Collection Engine. NetFlow operates by creating a NetFlow cache entry
(a flow record) for each active flow. A flow record is maintained within the NetFlow cache for each
active flows. Each flow record in the NetFlow cache contains fields that can later be exported to a
collection device, such as the NetFlow Collection Engine.
NetFlow is very efficient, the amount of export data being about 1.5 percent of the switched traffic in the
router. NetFlow accounts for every packet (non-sampled mode) and provides a highly condensed and
detailed view of all network traffic that entered the router or switch.
The key to NetFlow-enabled switching scalability and performance is highly intelligent flow cache
management, especially for densely populated and busy edge routers handling large numbers of
concurrent, short duration flows. The NetFlow cache management software contains a highly
sophisticated set of algorithms for efficiently determining if a packet is part of an existing flow or should
generate a new flow cache entry. The algorithms are also capable of dynamically updating per-flow
accounting measurements residing in the NetFlow cache, and cache aging/flow expiration
determination.
4
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Rules for expiring NetFlow cache entries include:
•
Flows which have been idle for a specified time are expired and removed from the cache.
•
Long lived flows are expired and removed from the cache. (Flows are not allowed to live more than
30 minutes by default; the underlying packet conversation remains undisturbed.)
•
As the cache becomes full a number of heuristics are applied to aggressively age groups of flows
simultaneously.
•
TCP connections which have reached the end of byte stream (FIN) or which have been reset (RST)
are expired.
Expired flows are grouped together into “NetFlow export” datagrams for export from the NetFlowenabled device. NetFlow export datagrams can consist of up to 30 flow records for Version 5 or Version 9
flow export. NetFlow functionality is configured on a per-interface basis. To configure NetFlow export
capabilities, you need to specify the IP address and application port number of the Cisco NetFlow or
third-party flow collector. The flow collector is a device that provides NetFlow export data filtering and
aggregation capabilities. Figure 1 shows an example of NetFlow data export from the main and
aggregation caches to a collector.
Figure 1
NetFlow Data Export from the Main and Aggregation Caches
Direction of traffic
CE1
NetFlow
enabled
on ingress
interface
PE
Core network
UDP export of aggregated flows
from aggregation caches on the
PE router to collector
Uses export Versions 8 and 9
CE2
NetFlow
collector
Workstation
135047
User Data Protocol (UDP)
export of nonaggregated flows
from the main cache of the
PE router to collector
Uses export Version 5 and 9
NetFlow Export Format Versions 9, 8, 5, and 1
Overview
NetFlow exports data in User Datagram Protocol (UDP) datagrams in one of the following formats:
Version 9, Version 8, Version 7, Version 5, or Version 1.
5
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
•
Version 9—A flexible and extensible format, which provides the versatility needed for support of
new fields and record types. This format accommodates new NetFlow-supported technologies such
as Multicast, Multiprotocol Label Switching (MPLS), and Border Gateway Protocol (BGP)
next hop. Version 9 export format enables you to use the same version for main and aggregation
caches, and the format is extendable, so you can use the same export format with future features.
•
Version 8—A format added to support data export from aggregation caches. Export datagrams
contain a subset of the usual Version 5 export data, which is valid for the particular aggregation
cache scheme.
•
Version 5—A later enhanced version that adds BGP autonomous system (AS) information and flow
sequence numbers. (Versions 2 through 4 were not released.) This is the most commonly used
format.
•
Version 1, the initially released export format, is rarely used today. Do not use the Version 1 export
format unless the legacy collection system you are using requires it. Use either the Version 9 export
format or the Version 5 export format.
Details
The following sections provide more detailed information on NetFlow Data Export Formats:
•
NetFlow Export Version Formats, page 6
•
NetFlow Export Packet Header Format, page 7
•
NetFlow Flow Record and Export Format Content Information, page 9
•
NetFlow Data Export Format Selection, page 11
•
NetFlow Version 9 Data Export Format, page 12
•
NetFlow Version 8 Data Export Format, page 13
•
NetFlow Version 5 Data Export Format, page 15
•
NetFlow Version 1 Data Export Format, page 16
NetFlow Export Version Formats
For all export versions, the NetFlow export datagram consists of a header and a sequence of flow records.
The header contains information such as sequence number, record count, and system uptime. The flow
record contains flow information, for example IP addresses, ports, and routing information.
NetFlow Version 9 export format is the newest NetFlow export format. The distinguishing feature of the
NetFlow Version 9 export format is that it is template based. Templates make the record format
extensible. This feature allows future enhancements to NetFlow without requiring concurrent changes
to the basic flow-record format.
The use of templates with the NetFlow Version 9 export format provides several other key benefits:
6
•
You can export almost any information from a router or switch including Layer 2 through 7
information, routing information, IP Version 6 (IPv6), IP Version 4 (IPv4), multicast, and
Multiprotocol Label Switching (MPLS) information. This new information allows new applications
for export data and new views of network behavior.
•
Third-party business partners who produce applications that provide collector or display services for
NetFlow are not required to recompile their applications each time a new NetFlow export field is
added. Instead, they might be able to use an external data file that documents the known template
formats.
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
•
New features can be added to NetFlow more quickly, without breaking current implementations.
•
NetFlow is “future-proofed” against new or developing protocols, because the Version 9 export
format can be adapted to provide support for them and for other non-NetFlow-based approaches to
data collection.
The work of the Internet Engineering Task Force (IETF) IP Information Export (IPFIX) Working Group
(WG) and the IETF Pack Sampling (PSAMP) WG are based on the NetFlow Version 9 export format.
The Version 1 export format was the original format supported in the initial Cisco IOS software releases
containing NetFlow functionality and is rarely used today. The Version 5 export format is a later
enhancement that adds Border Gateway Protocol (BGP) autonomous system information and flow
sequence numbers. Versions 2 through 4 and Version 6 export formats were either not released or are not
supported. Version 8 export format is the NetFlow export format to use when you enable router-based
NetFlow aggregation on Cisco IOS router platforms.
Figure 2 shows a typical datagram used for NetFlow fixed format export Versions 1, 5, 7, and 8.
Figure 2
Typical Datagram for NetFlow Fixed Format Export Versions 1, 5, 7, 8
IP header
UDP header
NetFlow header
Flow record
Flow record
Flow record
121902
...
NetFlow Export Packet Header Format
In all five export versions, the datagram consists of a header and one or more flow records. The first field
of the header contains the version number of the export datagram. Typically, a receiving application that
accepts any of the format versions allocates a buffer large enough for the largest possible datagram from
any of the format versions and then uses the header to determine how to interpret the datagram. The
second field in the header contains the number of records in the datagram (indicating the number of
expired flows represented by this datagram). Datagram headers for NetFlow Export Versions 5, 8, and 9
also include a “sequence number” field used by NetFlow collectors to check for lost datagrams.
7
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
The NetFlow Version 9 export packet header format is shown in Figure 3.
Figure 3
NetFlow Version 9 Export Packet Header Format
Version 9
1 2 3 4 5 6 7 8 9
1
0
1
1
1
2
Version
1
3
1
4
1
5
1
6
1
7
1
8
1
9
2
0
2
1
2
2
2
3
2
4
2
5
2
6
2
7
2
8
2
9
3
0
31
bits
Count
System Uptime
UNIX Seconds
Package Sequence
121897
Source ID
Table 1 lists the NetFlow Version 9 export packet header field names and descriptions.
Table 1
NetFlow Version 9 Export Packet Header Field Names and Descriptions
Field Name
Description
Version
The version of NetFlow records exported in this packet; for Version 9, this value
is 0x0009.
Count
Number of FlowSet records (both template and data) contained within this packet.
System Uptime
Time in milliseconds since this device was first booted.
UNIX Seconds
Seconds since 0000 Coordinated Universal Time (UTC) 1970.
Package Sequence Incremental sequence counter of all export packets sent by this export device; this
value is cumulative, and it can be used to find out whether any export packets have
been missed.
This is a change from the NetFlow Version 5 and Version 8 headers, where this
number represented “total flows.”
Source ID
8
The Source ID field is a 32-bit value that is used to guarantee uniqueness for each
flow exported from a particular device. (The Source ID field is the equivalent of
the engine type and engine ID fields found in the NetFlow Version 5 and Version 8
headers.) The format of this field is vendor specific. In Cisco’s implementation,
the first two bytes are reserved for future expansion, and are always zero. Byte 3
provides uniqueness with respect to the routing engine on the exporting device.
Byte 4 provides uniqueness with respect to the particular line card or Versatile
Interface Processor on the exporting device. Collector devices should use the
combination of the source IP address and the Source ID field to associate an
incoming NetFlow export packet with a unique instance of NetFlow on a
particular device.
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
NetFlow Flow Record and Export Format Content Information
This section gives details about the Cisco export format flow record. Table 2 indicates which flow record
format fields are available for Version 5, and 9. (Y indicates that the field is available. N indicates that
the field is not available.)
Table 2
NetFlow Flow Record Format Fields for Format Versions 5, and 9
Field
Version 5
Version 9
source IP address
Y
Y
destination IP address
Y
Y
source TCP/UDP application port
Y
Y
destination TCP/UDP application port
Y
Y
next hop router IP address
Y
Y
input physical interface index
Y
Y
output physical interface index
Y
Y
packet count for this flow
Y
Y
byte count for this flow
Y
Y
start of flow timestamp
Y
Y
end of flow timestamp
Y
Y
IP Protocol (for example, TCP=6; UDP=17)
Y
Y
Type of Service (ToS) byte
Y
Y
TCP Flags (cumulative OR of TCP flags)
Y
Y
source AS number
Y
Y
destination AS number
Y
Y
source subnet mask
Y
Y
destination subnet mask
Y
Y
flags (indicates, among other things, which flows are invalid)
Y
Y
N
Y
Other flow fields
1
1. For a list of other flow fields available in Version 9 export format, see Figure 5.
9
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Figure 4 is an example of the NetFlow Version 5 export record format, including the contents and
description of byte locations. The terms in bold indicate values that were added for the Version 5 format.
Figure 4
Time
Port
utilization
QoS
• Packet count
• Byte count
• Source IP address
• Destination IP address
From/To
• Start sysUpTime
• End sysUpTime
• Source TCP/UDP port
• Destination TCP/UDP port
Application
• Input ifIndex
• Output ifIndex
• Next hop address
• Source AS number
• Dest. AS number
• Source prefix mask
• Dest. prefix mask
• Type of Service
• TCP flags
• Protocol
Routing
and
peering
60682
Usage
NetFlow Version 5 Export Record Format
Table 3 shows the field names and descriptions for the NetFlow Version 5 export record format.
Table 3
10
NetFlow Version 5 Export Record Format Field Names and Descriptions
Content
Bytes
Descriptions
srcaddr
0–3
Source IP address
dstaddr
4–7
Destination IP address
nexthop
8–11
Next hop router's IP address
input
12–13
Ingress interface SNMP ifIndex
output
14–15
Egress interface SNMP ifIndex
dPkts
16–19
Packets in the flow
dOctets
20–23
Octets (bytes) in the flow
first
24–27
SysUptime at start of the flow
last
28–31
SysUptime at the time the last packet of the flow was received
srcport
32–33
Layer 4 source port number or equivalent
dstport
34–35
Layer 4 destination port number or equivalent
pad1
36
Unused (zero) byte
tcp_flags
37
Cumulative OR of TCP flags
prot
38
Layer 4 protocol (for example, 6=TCP, 17=UDP)
tos
39
IP type-of-service byte
src_as
40–41
Autonomous system number of the source, either origin or peer
dst_as
42–43
Autonomous system number of the destination, either origin or peer
src_mask
44
Source address prefix mask bits
dst_mask
45
Destination address prefix mask bits
pad2
46–47
PAD 2 is unused (zero) bytes
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Figure 5 shows a typical flow record for the Version 9 export format. The NetFlow Version 9 export
record format is different from the traditional NetFlow fixed format export record. In NetFlow Version 9,
a template describes the NetFlow data and the flow set contains the actual data. This allows for flexible
export. Detailed information about the fields currently in Version 9 and export format architecture are
available in the NetFlow Version 9 Flow-Record Format document.
NetFlow Version 9 Export Packet Example
Header
First Template FlowSet
Template Record
First Record FlowSet
(Template ID 256)
First data Record
Second Data Record
Second Template Flow Set
Template Record
Template Record
Second Record FlowSet
(Template ID 257)
Data Record
Data Record
Data Record
Data Record
NetFlow Version 9 Header: 32 bits
Version 9
Count = 4 (FlowSets)
System Uptime
UNIX Seconds
Package Sequence
Source ID
Template FlowSet 16 bits
FlowSet ID = 0
Length = 28 bytes
Template ID = 256
Field Count = 5
IPv4_SRCADDR (0x0008)
Length = 4
IPv4_DSTADDR (0x000C)
Length = 4
IPv4_NEXT_HOP (0x000E)
Length = 4
PKTS_32 (0x0002)
Length = 4
BYTES_32 (0x0001)
Length = 4
Data FlowSet: 32 bits
FlowSet
Length =
ID = 256
64 bytes
192.168.1.12
10.5.12.254
192.168.1.1
5009
5344365
192.168.1.27
10.5.12.23
192.168.1.1
748
388934
192.168.1.56
10.5.12.65
192.168.1.1
5
6534
121979
Figure 5
For all export versions, you specify a destination where NetFlow data export packets are sent, such as
the workstation running NetFlow Collection Engine, either when the number of recently expired flows
reaches a predetermined maximum, or every second—whichever occurs first. For a Version 1 datagram,
up to 24 flows can be sent in a single UDP datagram of approximately 1200 bytes; for a Version 5
datagram, up to 30 flows can be sent in a single UDP datagram of approximately 1500 bytes.
For detailed information on the flow record formats, data types, and export data fields for Versions 1, 7,
and 9 and platform-specific information when applicable, see Appendix 2 in the NetFlow Solutions
Service Guide.
NetFlow Data Export Format Selection
NetFlow exports data in UDP datagrams in export format Version 9, 8, 5, or 1. Table 4 describes
situations when you might select a particular NetFlow export format.
11
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Table 4
When to Select a Particular NetFlow Export Format
Export Format
Select When…
Version 9
You need to export data from various technologies, such as Multicast, DoS, IPv6,
BGP next hop, and so on. This format accommodates new NetFlow-supported
technologies such as Multicast, MPLS, and BGP next hop.
The Version 9 export format supports export from the main cache and from
aggregation caches.
Version 8
You need to export data from aggregation caches. Version 8 export format is available
only for export from aggregation caches.
Version 5
You need to export data from the NetFlow main cache, and you are not planning to
support new features.
Version 5 export format does not support export from aggregation caches.
Version 1
You need to export data to a legacy collection system that requires Version 1 export
format. Otherwise, do not use Version 1 export format. Use Version 9 or Version 5
export format.
NetFlow Version 9 Data Export Format
The NetFlow Version 9 Export Format feature was introduced in Cisco IOS Release 12.0(24)S and was
integrated into Cisco IOS Release 12.3(1) and Cisco IOS Release 12.2(18)S.
NetFlow Version 9 data export supports CEF switching, dCEF switching, and fast switching.
NetFlow Version 9 is a flexible and extensible means for transferring NetFlow records from a network
node to a collector. NetFlow Version 9 has definable record types and is self-describing for easier
NetFlow Collection Engine configuration.
Using Version 9 export, you define new formats on the router that you can send to the NetFlow
Collection Engine (formerly called NetFlow FlowCollector) at set intervals. You enable the features that
you want, and the field values corresponding to those features are sent to the NetFlow Collection Engine.
Third-party business partners who produce applications that provide NetFlow Collection Engine or
display services for NetFlow do not need to recompile their applications each time a new NetFlow
technology is added. Instead, with the NetFlow v9 Export Format feature, they can use an external data
file that documents the known template formats and field types.
In NetFlow Version 9
•
Record formats are defined by templates.
•
Template descriptions are communicated from the router to the NetFlow Collection Engine.
•
Flow records are sent from the router to the NetFlow Collection Engine with minimal template
information so that the NetFlow Collection Engine can relate the records to the appropriate template.
•
Version 9 is independent of the underlying transport (UDP, TCP, SCTP, and so on).
NetFlow Version 9 Template-Based Flow Record Format
The main feature of NetFlow Version 9 export format is that it is template based. A template describes
a NetFlow record format and attributes of the fields (such as type and length) within the record. The
router assigns each template an ID, which is communicated to the NetFlow Collection Engine along with
the template description. The template ID is used for all further communication from the router to the
NetFlow Collection Engine.
12
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
NetFlow Version 9 Export Flow Records
The basic output of NetFlow is a flow record. In NetFlow Version 9 export format, a flow record follows
the same sequence of fields as found in the template definition. The template to which NetFlow flow
records belong is determined by the prefixing of the template ID to the group of NetFlow flow records
that belong to a template. For a complete discussion of existing NetFlow flow-record formats, see the
NetFlow Services Solutions Guide.
NetFlow Version 9 Export Packet
In NetFlow Version 9, an export packet consists of the packet header and flowsets. The packet header
identifies the new version and provides other information. See Figure 3 on page 8 for Version 9 export
packet header details. Flowsets are of two types: template flowsets and data flowsets. The template
flowset describes the fields that will be in the data flowsets (or flow records). Each data flowset contains
the values or statistics of one or more flows with the same template ID. When the NetFlow Collection
Engine receives a template flowset, it stores the flowset and export source address so that subsequent
data flowsets that match the flowset ID and source combination are parsed according to the field
definitions in the template flowset. Version 9 supports NetFlow Collection Engine Version 4.0. For an
example of a Version 9 export packet, see Figure 5 on page 11.
NetFlow Export Templates
NetFlow implements a variety of templates, each exporting a different set of fields for a specific purpose.
For example, the MPLS templates are different from the OER templates and the various option
templates.
Table 5 lists the export templates and the specific set of fields the export pertains to.
Table 5
NetFlow Export Templates
Number of Export Templates
Exports Fields Pertaining to...
1
IPv4 main cache
8
MPLS labels 0-3
21
Aggregation caches with or without BGP
subflows
3
BGP, BGP NH and multicast
4
OER
2
MAC and auxiliary information
11
Random sampler information, interface names,
sampling option and exporter status options
NetFlow Version 8 Data Export Format
The Version 8 data export format is the NetFlow export format used when the router-based NetFlow
aggregation feature is enabled on Cisco IOS router platforms. The Version 8 format allows for export
datagrams to contain a subset of the Version 5 export data that is based on the configured aggregation
cache scheme. For example, a certain subset of the Version 5 export data is exported for the destination
prefix aggregation scheme, and a different subset is exported for the source-prefix aggregation scheme.
13
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
The Version 8 export format was introduced in Cisco IOS 12.0(3)T for the Cisco IOS NetFlow
Aggregation feature. An additional six aggregation schemes that also use Version 8 format were defined for
the NetFlow ToS-Based Router Aggregation feature introduced in Cisco IOS 12.0(15)S and integrated
into Cisco IOS Releases 12.2(4)T and 12.2(14)S. Refer to the “Configuring NetFlow Aggregation
Caches” module for information on configuring Version 8 data export for aggregation caches.
The Version 8 datagram consists of a header with the version number (which is 8) and time stamp
information, followed by one or more records corresponding to individual entries in the NetFlow cache.
Figure 6 displays the NetFlow Version 8 export packet header format.
Figure 6
NetFlow Version 8 Export Packet Header Format
Version 8
1 2 3 4 5 6 7 8 9
31
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 bits
Version
Count
System Uptime
UNIX Seconds
UNIX NanoSeconds
Flow Sequence Number
Engine ID
Sampling Interval
Aggregation
Agg Version
Reserved
Table 6 lists the NetFlow Version 8 export packet header field names and definitions.
Table 6
14
NetFlow Version 8 Export Packet Header Field Names and Descriptions
Field Name
Description
Version
Flow export format version number. In this case 8.
Count
Number of export records in the datagram.
System Uptime
Number of milliseconds since the router last booted.
UNIX Seconds
Number of seconds since 0000 UTC 1970.
UNIX NanoSeconds
Number of residual nanoseconds since 0000 UTC 1970.
Flow Sequence Number
Sequence counter of total flows sent for this export stream.
Engine Type
The type of switching engine. RP = 0 and LC = 1.
Engine ID
Slot number of the NetFlow engine.
Aggregation
Type of aggregation scheme being used.
Agg Version
Aggregation subformat version number. The current value is “2.”
Sampling Interval
Interval value used if Sampled NetFlow is configured.
Reserved
Zero field.
121898
Engine Type
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
NetFlow Version 5 Data Export Format
The Version 5 data export format adds support for Border Gateway Protocol (BGP) autonomous system
information and flow sequence numbers.
Because NetFlow uses UDP to send export datagrams, datagrams can be lost. The Version 5 header
format contains a flow sequence number to find out whether flow export information has been lost. The
sequence number is equal to the sequence number of the previous datagram plus the number of flows in
the previous datagram. After receiving a new datagram, the receiving application can subtract the
expected sequence number from the sequence number in the header to get the number of missed flows.
All fields in Version 5 export format are in network byte order. Figure 7 shows the NetFlow Version 5
export packet header format.
Figure 7
NetFlow Version 5 Export Packet Header Format
Version 5
1 2 3 4 5 6 7 8 9
31
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 bits
Version
Count
System Uptime
UNIX Seconds
UNIX NanoSeconds
Flow Sequence Number
Engine Type
121900
Reserved
Engine ID
Table 7 lists the NetFlow Version 5 export packet header field names and descriptions.
Table 7
NetFlow Version 5 Export Packet Header Field Names and Descriptions
Field
Description
Version
Version of NetFlow records exported in this packet.
Count
Number of FlowSet records (both template and data) contained within
this packet.
System Uptime
Time in milliseconds since this device was first booted.
UNIX Seconds
Seconds since 0000 UTC 1970.
UNIX NanoSeconds
Residual nanoseconds since 0000 UTC 1970.
Flow Sequence Number
Sequence number of total flows seen.
Reserved
Zero field.
Engine Type
Type of flow switching engine: 0 for RP, 1 for VIP/LC.
Engine ID
VIP or LC slot number of the flow switching engine.
15
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Table 8 describes the Version 5 export format header network byte order.
Table 8
NetFlow Version 5 Export Format Header Network Byte Order
Bytes
Content
Description
0 to 3
Version and count
NetFlow export format version number and number of flows
exported in this packet (1 to 30)
4 to 7
SysUptime
Current time (in milliseconds) since the router booted
8 to 11
unix_secs
Seconds since 0000 UTC 1970
12 to 15
unix_nsecs
Residual nanoseconds since 0000 UTC 1970
16 to 19
flow_sequence
Sequence counter of total flows seen
20 to 23
Reserved
Unused (zero) bytes
Table 9 lists the byte definitions for the Version 5 flow record format.
Table 9
Version 5 Flow Record Format
Bytes
Content
Description
0 to 3
srcaddr
Source IP address.
4 to 7
dstaddr
Destination IP address.
8 to 11
nexthop
IP address of the next hop router.
12 to 15
input and output
SNMP index of the input and output interfaces.
16 to 19
dPkts
Packets in the flow.
20 to 23
dOctets
Total number of Layer 3 bytes in the flow’s packets.
24 to 27
First
SysUptime at start of flow.
28 to 31
Last
SysUptime at the time the last packet of flow was received.
32 to 35
srcport and dstport
TCP/UDP source and destination port number or equivalent.
36 to 39
pad1, tcp_flags, prot, Unused (zero) byte, cumulative OR of TCP flags, IP protocol
and tos
(for example, 6 = TCP, 17 = UDP), and IP ToS.
40 to 43
src_as and dst_as
Autonomous system of the source and destination, either
origin or peer.
44 to 47
src_mask, dst_mask,
and pad2
Source and destination address prefix mask bits. Pad 2 is
unused (zero) bytes.
NetFlow Version 1 Data Export Format
The NetFlow Version 1 data export format was the format supported in the initial Cisco IOS software
releases containing NetFlow functionality. It is rarely used today. Do not use the Version 1 export format
unless the legacy collection system you are using requires it. Use either the Version 9 export format or
the Version 5 export format.
16
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
Figure 8 shows the NetFlow Version 1 export packet header format.
Figure 8
Version 1 Export Packet Header Format
Version 1
1 2 3 4 5 6 7 8 9
31
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 bits
Version
Count
System Uptime
UNIX Seconds
121901
UNIX NanoSeconds
Table 10 lists the NetFlow Version 1 export packet header field names and descriptions.
Table 10
NetFlow Version 1 Packet Header Field Names and Descriptions
Field Name
Description
Version
Version of NetFlow records exported in this packet.
Count
Number of FlowSet records (both template and data) contained within this
packet.
System Uptime
Time in milliseconds since this device was first booted.
UNIX Seconds
Seconds since 0000 UTC 1970.
UNIX NanoSeconds
Residual nanoseconds since 0000 UTC 1970.
Egress NetFlow Accounting Benefits: NetFlow Accounting Simplified
The Egress NetFlow Accounting feature can simplify NetFlow configuration. The following example
shows how.
In Figure 9 and Figure 10 both incoming and outgoing (ingress and egress) flow statistics are required
for the server. The server is attached to Router B. The “cloud” in the figure represents the core of the
network and includes Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs).
All traffic denoted by the arrows must be accounted for. The solid arrows represent IP traffic and the
dotted arrows represent MPLS VPNs.
Figure 9 shows how the flow traffic was tracked before the introduction of the Egress NetFlow
Accounting feature. Figure 10 shows how the flow traffic is tracked after the introduction of the Egress
NetFlow Accounting feature. The Egress NetFlow Accounting feature simplifies configuration tasks and
makes it easier for you to collect and track incoming and outgoing flow statistics for the server in this
example.
Since only ingress flows could be tracked before the Egress NetFlow Accounting feature was introduced,
the following NetFlow configurations had to be implemented for the tracking of ingress and egress flows
from Router B:
•
Enable NetFlow on an interface on Router B to track ingress IP traffic from Router A to Router B.
•
Enable NetFlow on an interface on Router D to track ingress IP traffic from Router B to Router D.
17
Configuring NetFlow and NetFlow Data Export
Information About Configuring NetFlow and NetFlow Data Export
•
Enable NetFlow on an interface on Router A to track ingress traffic from the MPLS VPN from
Router B to Router A.
•
Enable NetFlow on an interface on Router B to track ingress traffic from the MPLS VPN from
Router D to Router B.
Figure 9
Ingress-Only NetFlow Example
A
D
C
B
Server
121274
Flows are
counted here
A configuration such as the one used in Figure 9 requires that NetFlow statistics from three separate
routers be added together to obtain the flow statistics for the server.
In comparison, the example in Figure 10 shows NetFlow, the Egress NetFlow Accounting feature, and
the MPLS Egress NetFlow Accounting feature being used to capture ingress and egress flow statistics
for Router B, thus obtaining the required flow statistics for the server.
In Figure 10, the following NetFlow configurations are applied to Router B:
•
Enable NetFlow on an interface on Router B to track ingress IP traffic from Router A to Router B.
•
Enable the Egress NetFlow Accounting feature on an interface on Router B to track egress IP traffic
from Router B to Router D.
•
Enable NetFlow an interface on Router B to track ingress traffic from the MPLS VPN from Router B
to Router D.
•
Enable NetFlow on an interface on Router B to track ingress traffic from the MPLS VPN from
Router B to Router A.
After NetFlow is configured on Router B, you can display all NetFlow statistics for the server by entering
the show ip cache flow command or the show ip cache verbose flow command for Router B.
Figure 10
Egress NetFlow Accounting Example
.
A
D
C
18
B
Server
121275
Flows are
counted here
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
NetFlow Subinterface Support Benefits: Fine-Tuning Your Data Collection
You can configure NetFlow on a per-subinterface basis. If your network contains thousands of
subinterfaces and you want to collect export records from only a few subinterfaces, you can do that. The
result is lower bandwidth requirements for NetFlow data export and reduced platform requirements for
NetFlow data-collection devices.
The configuration of NetFlow on selected subinterfaces provides the following benefits:
•
Reduced bandwidth requirement between routing devices and NetFlow management workstations.
•
Reduced NetFlow workstation requirements; the number of flows sent to the workstation for
processing is reduced.
NetFlow Multiple Export Destinations: Benefits
The NetFlow Multiple Export Destinations feature enables configuration of multiple destinations for the
NetFlow data. With this feature enabled, two identical streams of NetFlow data are sent to the destination
host. Currently, the maximum number of export destinations allowed is two.
The NetFlow Multiple Export Destinations feature improves the chances of receiving complete NetFlow
data because it provides redundant streams of data. Because the same export data is sent to more than
one NetFlow collector, fewer packets are lost.
NetFlow on a Distributed VIP Interface
On a Cisco 7500 series router with an Route Switch Processor (RSP) and with VIP controllers, the VIP
hardware can be configured to switch packets received by the VIP interfaces with no per-packet
intervention on the part of the RSP. This process is called distributed switching. When VIP distributed
switching is enabled, the input VIP interface switches IP packets instead of forwarding them to the RSP
for switching. Distributed switching decreases the demand on the RSP. VIP interfaces with distributed
switching enabled can be configured for NetFlow.
How to Configure NetFlow and NetFlow Data Export
This section contains instructions for configuring NetFlow to capture and export network traffic data.
Perform the following tasks to configure NetFlow to capture and export network traffic data:
•
Configuring NetFlow, page 20 (required)
•
Verifying that NetFlow Is Operational and View NetFlow Statistics, page 21 (optional)
•
Configuring NetFlow Data Export Using the Version 9 Export Format, page 23 (optional)
•
Verifying that NetFlow Data Export Is Operational, page 26 (optional)
•
Clearing NetFlow Statistics on the Router, page 27 (optional)
•
Customizing the NetFlow Main Cache Parameters, page 28 (optional)
19
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
Configuring NetFlow
Perform the steps in this required task to enable NetFlow.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface interface-type interface-number
4.
ip flow {ingress | egress}
5.
exit
6.
Repeat Steps 3 through 5 to enable NetFlow on other interfaces.
7.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface interface-type interface-number
(Required) Specifies the interface that you want to enable
NetFlow on and enters interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
Step 4
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—captures traffic that is being received by the
interface
•
egress—captures traffic that is being transmitted by the
interface
Example:
Router(config-if)# ip flow ingress
or
This is the Egress NetFlow Accounting feature that is
described in the “Egress NetFlow Accounting Benefits:
NetFlow Accounting Simplified” section on page 17.
Example:
Router(config-if)# ip flow egress
Step 5
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
Router(config-if)# exit
20
You only need to use this command if you want to
enable NetFlow on another interface.
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
Command or Action
Purpose
Step 6
Repeat Steps 3 through 5 to enable NetFlow on other
interfaces.
(Optional) —
Step 7
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
Verifying that NetFlow Is Operational and View NetFlow Statistics
Perform the steps in this optional task to verify that NetFlow is operational and to view the NetFlow
statistics.
SUMMARY STEPS
1.
show ip flow interface
2.
show ip cache flow
3.
show ip cache verbose flow
DETAILED STEPS
Step 1
show ip flow interface
Use this command to display the NetFlow configuration for an interface. The following is sample output
from this command:
Router# show ip flow interface
Ethernet0/0
ip flow ingress
Router#
Step 2
show ip cache flow
Use this command to verify that NetFlow is operational, and to display a summary of the NetFlow
statistics. The following is sample output from this command:
Router# show ip cache flow
IP packet size distribution (1103746 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.249 .694 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .027 .000 .027 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
35 active, 4061 inactive, 980 added
2921778 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 21640 bytes
0 active, 1024 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
21
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
-------TCP-FTP
TCP-FTPD
TCP-WWW
TCP-SMTP
TCP-BGP
TCP-NNTP
TCP-other
UDP-TFTP
UDP-other
ICMP
Total:
SrcIf
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
.
.
.
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Et0/0
Router#
Step 3
Flows
108
108
54
54
27
27
297
27
108
135
945
/Sec
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
/Flow
1133
1133
1133
1133
1133
1133
1133
1133
1417
1133
1166
/Pkt
40
40
40
40
40
40
40
28
28
427
91
/Sec
2.4
2.4
1.2
1.2
0.6
0.6
6.8
0.6
3.1
3.1
22.4
/Flow
1799.6
1799.6
1799.6
1799.6
1799.6
1799.6
1799.7
1799.6
1799.6
1799.6
1799.6
/Flow
0.9
0.9
0.8
0.8
0.7
0.7
0.8
1.0
0.9
0.8
0.8
SrcIPaddress
192.168.67.6
10.10.18.1
10.10.18.1
10.234.53.1
10.10.19.1
10.10.19.1
192.168.87.200
192.168.87.200
DstIf
Et1/0.1
Null
Null
Et1/0.1
Null
Null
Et1/0.1
Et1/0.1
DstIPaddress
172.16.10.200
172.16.11.5
172.16.11.5
172.16.10.2
172.16.11.6
172.16.11.6
172.16.10.2
172.16.10.2
Pr
01
11
11
01
11
11
06
06
SrcP
0000
0043
0045
0000
0044
00A2
0014
0015
DstP
0C01
0043
0045
0800
0044
00A2
0014
0015
Pkts
51
51
51
51
51
51
50
52
172.16.1.84
172.16.1.84
172.16.1.85
172.16.1.85
10.251.10.1
10.162.37.71
Et1/0.1
Et1/0.1
Et1/0.1
Et1/0.1
Et1/0.1
Null
172.16.10.19
172.16.10.19
172.16.10.20
172.16.10.20
172.16.10.2
172.16.11.3
06
06
06
06
01
06
0087
0050
0089
0050
0000
027C
0087
0050
0089
0050
0800
027C
50
51
49
50
51
49
show ip cache verbose flow
Use this command to verify that NetFlow is operational and to display a detailed summary of the
NetFlow statistics. The following is sample output from this command:
Router# show ip cache verbose flow
IP packet size distribution (1130681 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.249 .694 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .027 .000 .027 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
35 active, 4061 inactive, 980 added
2992518 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 21640 bytes
0 active, 1024 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-FTP
108
0.0
1133
40
2.4
1799.6
0.9
TCP-FTPD
108
0.0
1133
40
2.4
1799.6
0.9
TCP-WWW
54
0.0
1133
40
1.2
1799.6
0.8
TCP-SMTP
54
0.0
1133
40
1.2
1799.6
0.8
TCP-BGP
27
0.0
1133
40
0.6
1799.6
0.7
TCP-NNTP
27
0.0
1133
40
0.6
1799.6
0.7
22
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
TCP-other
UDP-TFTP
UDP-other
ICMP
Total:
SrcIf
Port Msk
Et0/0
0000 /0
Et0/0
0043 /0
Et0/0
0045 /0
Et0/0
0000 /0
Et0/0
0044 /0
.
.
.
Et0/0
0087 /0
Et0/0
0050 /0
Et0/0
0089 /0
Et0/0
0050 /0
Et0/0
0000 /0
Et0/0
027C /0
Router#
297
27
108
135
945
SrcIPaddress
AS
192.168.67.6
0
10.10.18.1
0
10.10.18.1
0
10.234.53.1
0
10.10.19.1
0
172.16.1.84
0
172.16.1.84
0
172.16.1.85
0
172.16.1.85
0
10.251.10.1
0
10.162.37.71
0
0.0
0.0
0.0
0.0
0.0
1133
1133
1417
1133
1166
DstIf
Port Msk
Et1/0.1
0C01 /0
Null
0043 /0
Null
0045 /0
Et1/0.1
0800 /0
Null
0044 /0
Et1/0.1
0087 /0
Et1/0.1
0050 /0
Et1/0.1
0089 /0
Et1/0.1
0050 /0
Et1/0.1
0800 /0
Null
027C /0
AS
0
0
0
0
0
0
0
0
0
0
0
40
28
28
427
91
6.6
0.6
3.0
3.0
21.9
1799.7
1799.6
1799.6
1799.6
1799.6
0.8
1.0
0.9
0.8
0.8
DstIPaddress
NextHop
172.16.10.200
0.0.0.0
172.16.11.5
0.0.0.0
172.16.11.5
0.0.0.0
172.16.10.2
0.0.0.0
172.16.11.6
0.0.0.0
Pr TOS Flgs Pkts
B/Pk Active
01 00 10
799
28 1258.1
11 00 10
799
28 1258.0
11 00 10
799
28 1258.0
01 00 10
799
28 1258.1
11 00 10
799
28 1258.1
172.16.10.19
0.0.0.0
172.16.10.19
0.0.0.0
172.16.10.20
0.0.0.0
172.16.10.20
0.0.0.0
172.16.10.2
0.0.0.0
172.16.11.3
0.0.0.0
06 00
06
06
06
01
06
00
40
00 00
40
00 00
40
00 00
40
00 10
1500
00 00
40
799
1258.1
799
1258.0
798
1256.5
799
1258.0
799
1258.1
798
1256.4
Configuring NetFlow Data Export Using the Version 9 Export Format
Perform the steps in this optional task to configure NetFlow Data Export using the Version 9 export
format.
Note
This task does not include instructions for configuring Reliable NetFlow Data Export using SCTP. Refer
to the NetFlow Reliable Export with SCTP module for information about, and instructions for
configuring Reliable NetFlow Data Export using SCTP.
Prerequisites
This task does not include the steps for configuring NetFlow. You must configure NetFlow by enabling
it on at least one interface in the router in order to export traffic data with NetFlow Data Export. Refer
to the “Configuring NetFlow” section on page 20 for information about configuring NetFlow.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination {{ip-address | hostname} udp-port}
23
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
4.
Repeat Step 3 once to configure an additional export destination.
5.
ip flow export source interface-type interface-number
6.
ip flow-export version 9 [origin-as | peer-as] [bgp-nexthop]
7.
ip flow-export interface-names
8.
ip flow-export template refresh-rate packets
9.
ip flow-export template timeout-rate minutes
10. ip flow-export template options export-stats
11. ip flow-export template options refresh-rate packets
12. ip flow-export template options timeout-rate minutes
13. end
DETAILED STEPS
Step 1
Command
Purpose
enable
(Required) Enters privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-export destination {{ip-address
| hostname} udp-port}
(Required) Specifies the IP address, or hostname of the NetFlow
collector, and the UDP port the NetFlow collector is listening on.
Example:
Router(config)# ip flow-export
destination 172.16.10.2 99
Step 4
Repeat Step 3 once to configure a second
NetFlow export destination.
(Optional) You can configure a maximum of two export destinations
for NetFlow.
This is the NetFlow Multiple Export Destinations feature that is
described in the “NetFlow Multiple Export Destinations: Benefits”
section on page 19.
Step 5
ip flow-export source interface-type
interface-number
Example:
Router(config)# ip flow-export source
ethernet 0/0
24
(Optional) The IP address from the interface specified is used as the
source IP address for the UDP datagrams that are sent by NetFlow
data export to the destination host.
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
Step 6
Command
Purpose
ip flow-export version 9 [origin-as |
peer-as] [bgp-nexthop]
(Optional) Enables the export of information in NetFlow cache
entries.
•
The version 9 keyword specifies that the export packet uses the
Version 9 format.
•
The origin-as keyword specifies that export statistics include
the originating AS for the source and destination.
•
The peer-as keyword specifies that export statistics include the
peer AS for the source and destination.
•
The bgp-nexthop keyword specifies that export statistics
include BGP next hop-related information.
Example:
Router(config)# ip flow-export version 9
Caution
Step 7
ip flow-export interface-names
Example:
Entering this command on a Cisco 12000 series Internet
router causes packet forwarding to stop for a few seconds
while NetFlow reloads the route processor and line card
Cisco Express Forwarding tables. To avoid interruption
of service to a live network, apply this command during a
change window, or include it in the startup-config file to
be executed during a router reboot.
Configures NetFlow data export to include the interface names from
the flows when it exports the NetFlow cache entry to a destination
system.
Router(config)# ip flow-export
interface-names
Step 8
ip flow-export template refresh-rate
packets
(Optional) Enables the export of information in NetFlow cache
entries.
•
The template keyword specifies template-specific
configurations.
•
The refresh-rate packets keyword-argument pair specifies the
number of packets exported before the templates are resent. You
can specify from 1 to 600 packets. The default is 20 packets.
Example:
Router(config)# ip flow-export template
refresh-rate 15
Step 9
ip flow-export template timeout-rate
minutes
(Optional) Enables the export of information in NetFlow cache
entries.
•
The template keyword specifies that the timeout-rate keyword
applies to the template.
•
The timeout-rate minutes keyword-argument pair specifies the
time elapsed before the templates are resent. You can specify
from 1 to 3600 minutes. The default is 30 minutes.
Example:
Router(config)# ip flow-export template
timeout-rate 90
25
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
Step 10
Command
Purpose
ip flow-export template options
export-stats
(Optional) Enables the export of information in NetFlow cache
entries.
•
The template keyword specifies template-specific
configurations.
•
The options keyword specifies template options.
•
The export-stats keyword specifies that the export statistics
include the total number of flows exported and the total number
of packets exported.
Example:
Router(config)# ip flow-export template
options export-stats
Step 11
ip flow-export template options
refresh-rate packets
(Optional) Enables the export of information in NetFlow cache
entries.
•
The template keyword specifies template-specific
configurations.
•
The options keyword specifies template options.
•
The refresh-rate packets keyword-argument pair specifies the
number of packets exported before the templates are resent. You
can specify from 1 to 600 packets. The default is 20 packets.
Example:
Router(config)# ip flow-export template
options refresh-rate 25
Step 12
ip flow-export template options
timeout-rate minutes
(Optional) Enables the export of information in NetFlow cache
entries.
•
The template keyword specifies template-specific
configurations.
•
The options keyword specifies template options.
•
The timeout-rate minutes keyword-argument pair specifies the
time elapsed before the templates are resent. You can specify
from 1 to 3600 minutes. The default is 30 minutes.
Example:
Router(config)# ip flow-export template
options timeout-rate 120
Step 13
(Required) Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config)# end
Verifying that NetFlow Data Export Is Operational
Perform the steps in this optional task to verify that NetFlow data export is operational and how to view
the statistics for NetFlow data export.
SUMMARY STEPS
26
1.
show ip flow export
2.
show ip flow export template
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
DETAILED STEPS
Step 1
show ip flow export
Use this command to display the statistics for the NetFlow data export, including statistics for the main
cache and for all other enabled caches. The following is sample output from this command:
Router# show ip flow export
Flow export v9 is enabled for main cache
Exporting flows to 172.16.10.2 (99)
Exporting using source interface Ethernet0/0
Version 9 flow records
0 flows exported in 0 udp datagrams
0 flows failed due to lack of export packet
0 export packets were sent up to process level
0 export packets were dropped due to no fib
0 export packets were dropped due to adjacency issues
0 export packets were dropped due to fragmentation failures
0 export packets were dropped due to encapsulation fixup failures
Router#
Step 2
show ip flow export template
Use this command to display the statistics for the NetFlow data export (such as the template timeout rate
and the refresh rate) for the template-specific configurations. The following is sample output from this
command:
Router# show ip flow export template
Template Options Flag = 1
Total number of Templates added = 1
Total active Templates = 1
Flow Templates active = 0
Flow Templates added = 0
Option Templates active = 1
Option Templates added = 1
Template ager polls = 0
Option Template ager polls = 140
Main cache version 9 export is enabled
Template export information
Template timeout = 90
Template refresh rate = 15
Option export information
Option timeout = 120
Option refresh rate = 25
Router#
Clearing NetFlow Statistics on the Router
Perform the steps in this optional task to clear NetFlow statistics on the router.
SUMMARY STEPS
1.
enable
2.
clear ip flow stats
27
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
DETAILED STEPS
Step 1
enable
Use this enter privileged EXEC mode on the router:
Router> enable
Router#
Step 2
clear ip flow stats
Use this command to clear the NetFlow statistics on the router. For example:
Router# clear ip flow stats
Customizing the NetFlow Main Cache Parameters
NetFlow operates by creating a NetFlow cache entry (a flow record) for each active flow. A flow record
is maintained within the NetFlow cache for all active flows. Each flow record in the NetFlow cache
contains fields that can later be exported to a collection device, such as the NetFlow Collection Engine.
NetFlow enables the accumulation of data on flows. Each flow is identified by unique characteristics
such as IP address, interface, application, and type of service (ToS).
To customize the parameters for the main NetFlow cache, perform the steps this optional task.
NetFlow Cache Entry Management on a Routing Device
The routing device checks the NetFlow cache once per second and causes the flow to expire in the
following instances:
•
Flow transport is completed (TCP connections that have reached the end of the byte stream [FIN] or
which have been reset [RST] are expired).
•
The flow cache has become full.
•
A flow becomes inactive. By default, a flow unaltered in the last 15 seconds is classified as inactive.
•
An active flow has been monitored for a specified number of minutes. By default, active flows are
flushed from the cache when they have been monitored for 30 minutes.
Routing device default timer settings are 15 seconds for the inactive timer and 30 minutes for the active
timer. You can configure your own time interval for the inactive timer between 10 and 600 seconds. You
can configure the time interval for the active timer between 1 and 60 minutes.
NetFlow Cache Size
After you enable NetFlow on an interface, NetFlow reserves memory to accommodate a number of
entries in the NetFlow cache. Normally the size of the NetFlow cache meets the needs of your NetFlow
traffic rates. The cache default size is 64K flow cache entries. Each cache entry requires 64 bytes of
storage. About 4 MB of DRAM are required for a cache with the default number of entries. You can
increase or decrease the number of entries maintained in the cache, if required. For environments with a
large amount of flow traffic (such as an internet core router), we recommend a larger value such as
131072 (128K). To obtain information on your flow traffic, use the show ip cache flow.
28
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
A NetFlow cache can be resized depending on the platform and the amount of DRAM on a line card. For
example, the NetFlow cache size is configurable for software-based platforms such as Cisco 75xx and
72xx series routers. The amount of memory on a Cisco 12000 line card determines how many flows are
possible in the cache.
Using the ip flow-cache entries command, you can configure the size of your NetFlow cache between
1024 entries and 524,288 entries. Using the cache entries command (after you configure NetFlow
aggregation), you can configure the size of the NetFlow aggregation cache from 1024 entries to 524,288
entries.
Caution
We recommend that you not change the values for NetFlow cache entries. Improper use of this feature
could cause network problems. To return to the default value for NetFlow cache entries, use the
no ip flow-cache entries global configuration command.
Restrictions
If you modify any parameters for the NetFlow main cache after you enable NetFlow the changes will not
take effect until you reboot the router or disable NetFlow on every interface it is enabled on, and then
re-enable NetFlow on the interfaces.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface interface-type interface-number
4.
no ip flow {ingress | egress}
5.
exit
6.
Repeat Steps 3 through 5 for every interface that has NetFlow enabled on it.
7.
ip flow-cache entries number
8.
ip flow-cache timeout active minutes
9.
ip flow-cache timeout inactive seconds
10. interface interface-type interface-number
11. ip flow {ingress | egress}
12. exit
13. Repeat Steps 10 through 12 for every interface that previously had NetFlow enabled on it.
14. end
29
Configuring NetFlow and NetFlow Data Export
How to Configure NetFlow and NetFlow Data Export
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface interface-type interface-number
Example:
(Required if NetFlow is already enabled on the interface)
Specifies the interface that you want to disable NetFlow on
and enters interface configuration mode.
Router(config)# interface ethernet 0/0
Step 4
no ip flow {ingress | egress}
Example:
(Required if NetFlow is enabled on the interface) Disables
NetFlow on the interface.
•
ingress—captures traffic that is being received by the
interface
•
egress—captures traffic that is being transmitted by the
interface
Router(config-if)# no ip flow ingress
or
Example:
Router(config-if)# no ip flow egress
Step 5
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
Router(config-if)# exit
You only need to use this command if you need to
disable NetFlow on another interface.
Step 6
Repeat Steps 3 through 5 for the remaining interfaces (Required if NetFlow is enabled on any other interfaces) —
that have NetFlow enabled on them.
Step 7
ip flow-cache entries number
Example:
(Optional) Changes the number of entries maintained in the
NetFlow cache.
•
Router(config)# ip flow-cache entries 131072
Step 8
ip flow-cache timeout active minutes
Example:
Router(config)# ip flow-cache timeout active 20
Step 9
ip flow-cache timeout inactive seconds
(Optional) Specifies flow cache timeout parameters.
•
The active keyword specifies the active flow timeout.
•
The minutes argument specifies the number of minutes
that an active flow remains in the cache before the flow
times out. The range is from 1 to 60. The default is 30.
(Optional) Specifies flow cache timeout parameters.
•
The inactive keyword specifies the inactive flow
timeout.
•
The seconds argument specifies the number of seconds
that an inactive flow remains in the cache before it
times out. The range is from 10 to 600. The default is 15
Example:
Router(config)# ip flow-cache timeout inactive
130
30
The number argument is the number of entries to be
maintained. The valid range is from 1024 to 524288
entries. The default is 65536 (64K).
Configuring NetFlow and NetFlow Data Export
Configuration Examples for Configuring NetFlow and NetFlow Data Export
Step 10
Command or Action
Purpose
interface interface-type interface-number
(Required) Specifies the interface that you want to enable
NetFlow on and enters interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
Step 11
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—captures traffic that is being received by the
interface
•
egress—captures traffic that is being transmitted by the
interface
Example:
Router(config-if)# ip flow ingress
or
Example:
Router(config-if)# ip flow egress
Step 12
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
Router(config-if)# exit
You only need to use this command if you need to
enable NetFlow on another interface.
Step 13
Repeat Steps 10 through 12 for the remaining
interfaces that you disabled NetFlow on in Steps 3
through 5.
(Required for any other interfaces that you need to enable
NetFlow on.) —
Step 14
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
Configuration Examples for Configuring NetFlow and NetFlow
Data Export
This section contains basic NetFlow configuration examples:
•
Configuring Egress NetFlow Accounting: Example, page 31
•
Configuring NetFlow Subinterface Support: Example, page 32
•
Configuring NetFlow Multiple Export Destinations: Example, page 32
•
Configuring NetFlow Version 5 Data Export: Example, page 33
•
Configuring NetFlow Version 1 Data Export: Example, page 33
Configuring Egress NetFlow Accounting: Example
The following example shows how to configure Egress NetFlow Accounting as described in the “Egress
NetFlow Accounting Benefits: NetFlow Accounting Simplified” section on page 17:
configure terminal
!
interface ethernet 0/0
ip flow egress
31
Configuring NetFlow and NetFlow Data Export
Configuration Examples for Configuring NetFlow and NetFlow Data Export
!
Configuring NetFlow Subinterface Support: Example
The following examples show how to configure NetFlow Subinterface Support as described in the
“NetFlow Subinterface Support Benefits: Fine-Tuning Your Data Collection” section on page 19:
•
NetFlow Subinterface Support for ingress (received) traffic on a subinterface, page 32
•
NetFlow SubInterface Support for egress (transmitted) traffic on a subinterface, page 32
NetFlow Subinterface Support for ingress (received) traffic on a subinterface
configure terminal
!
interface ethernet 0/0.1
ip flow ingress
!
NetFlow SubInterface Support for egress (transmitted) traffic on a subinterface
configure terminal
!
interface ethernet 1/0.1
ip flow egress
!
Note
NetFlow performs additional checks for the status of each subinterface that requires more CPU
processing time and bandwidth. If you have several subinterfaces configured and you want to configure
NetFlow data capture on all of them, we recommend that you configure NetFlow on the main interface
instead of on the individual subinterfaces.
Configuring NetFlow Multiple Export Destinations: Example
The following example shows how to configure NetFlow Multiple Export Destinations as described in
the “NetFlow Multiple Export Destinations: Benefits” section on page 19:
configure terminal
!
ip flow-export destination 10.10.10.10 9991
ip flow-export destination 172.16.10.2 9991
!
Note
32
You can configure a maximum of two export destinations for the main cache and for each aggregation
cache.
Configuring NetFlow and NetFlow Data Export
Additional References
Configuring NetFlow Version 5 Data Export: Example
The following example shows how to configure the NetFlow data export using the Version 5 export
format with the peer AS information.
configure terminal
!
ip flow-export version 5 peer-as
ip flow-export destination 172.16.10.2 99
exit
Router# show ip flow export
Flow export v5 is enabled for main cache
Exporting flows to 172.16.10.2 (99)
Exporting using source IP address 172.16.6.1
Version 5 flow records, peer-as
0 flows exported in 0 udp datagrams
0 flows failed due to lack of export packet
0 export packets were sent up to process level
0 export packets were dropped due to no fib
0 export packets were dropped due to adjacency issues
0 export packets were dropped due to fragmentation failures
0 export packets were dropped due to encapsulation fixup failures
Router#
Configuring NetFlow Version 1 Data Export: Example
The following example shows how to configure the NetFlow data export using the Version 5 export
format with the peer AS information.
configure terminal
!
ip flow-export destination 172.16.10.2 99
exit
Router# show ip flow export
Flow export v1 is enabled for main cache
Exporting flows to 172.16.10.2 (99)
Exporting using source IP address 172.16.6.1
Version 1 flow records
0 flows exported in 0 udp datagrams
0 flows failed due to lack of export packet
0 export packets were sent up to process level
0 export packets were dropped due to no fib
0 export packets were dropped due to adjacency issues
0 export packets were dropped due to fragmentation failures
0 export packets were dropped due to encapsulation fixup failures
Router#
Note
No AS number or BGP next-hop information is exported with the Version 1 export format.
Additional References
The following sections provide references related to the configuring of NetFlow to capture and export
NetFlow traffic data.
33
Configuring NetFlow and NetFlow Data Export
Additional References
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats with NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export with
SCTP
NetFlow Reliable Export with SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
34
Configuring NetFlow and NetFlow Data Export
Additional References
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
The Cisco Support website provides extensive online
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies.
http://www.cisco.com/cisco/web/support/index.html
To receive security and technical information about
your products, you can subscribe to various services,
such as the Product Alert Tool (accessed from Field
Notices), the Cisco Technical Services Newsletter, and
Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website
requires a Cisco.com user ID and password.
35
Configuring NetFlow and NetFlow Data Export
Feature Information for Configuring NetFlow and NetFlow Data Export
Feature Information for Configuring NetFlow and NetFlow Data
Export
Table 11 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 11
Table 11 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for Configuring NetFlow and NetFlow Data Export
Feature Name
Releases
Feature Configuration Information
Egress NetFlow Accounting
12.3(11)T
15.0(1)S
The Egress NetFlow Accounting feature allows
NetFlow statistics to be gathered on egress traffic that is
exiting the router. Previous versions of NetFlow allow
statistics to be gathered only on ingress traffic that is
entering the router.
The following sections provide information about this
feature:
•
Egress NetFlow Accounting Benefits: NetFlow
Accounting Simplified
•
Configuring Egress NetFlow Accounting: Example
The following commands were introduced by this
feature: ip flow egress and ip flow-egress
input-interface.
The following commands were modified by this
feature: flow-sampler, match, show ip cache flow,
show ip cache verbose flow, and
show ip flow interface.
36
Configuring NetFlow and NetFlow Data Export
Feature Information for Configuring NetFlow and NetFlow Data Export
Table 11
Feature Information for Configuring NetFlow and NetFlow Data Export (continued)
Feature Name
Releases
Feature Configuration Information
NetFlow Subinterface Support
12.2(14)S,
12.0(22)S,
12.2(15)T
12.2(33)SB
The NetFlow Subinterface Support feature provides the
ability to enable NetFlow on a per-subinterface basis.
The following sections provide information about this
feature:
•
NetFlow Subinterface Support Benefits:
Fine-Tuning Your Data Collection
•
Configuring NetFlow Subinterface Support:
Example
The following command was introduced by this feature:
ip flow ingress.
The following command was modified by this feature:
show ip interface.
NetFlow Multiple Export
Destinations:
12.0(19)S,
12.2(2)T,
12.2(14)S
15.0(1)S
The NetFlow Multiple Export Destinations feature
enables configuration of multiple destinations of the
NetFlow data.
The following sections provide information about this
feature:
•
NetFlow Multiple Export Destinations: Benefits
•
Configuring NetFlow Multiple Export
Destinations: Example
The following commands were modified by this
feature: ip flow-aggregation cache, ip flow-export
destination, and show ip flow export.
NetFlow v9 Export Format
12.0(24)S, 12.3(1),
12.2(18)S,
12.2(27)SBC,
12.2(18)SXF
15.0(1)S
The NetFlow v9 Export Format is flexible and
extensible, which provides the versatility needed to
support new fields and record types. This format
accommodates new NetFlow-supported technologies
such as Multicast, MPLS, NAT, and BGP next hop.
The following sections provide information about this
feature:
•
NetFlow Export Format Versions 9, 8, 5, and 1
•
Configuring NetFlow Data Export Using the
Version 9 Export Format
The following commands were modified by this
feature: debug ip flow export, export, ip flow-export,
and show ip flow export.
Support for interface names added to 12.4(2)T
NetFlow data export1
The interface-names keyword for the ip flow-export
command configures NetFlow data export to include
the interface names from the flows when it exports the
NetFlow cache entry to a destination system.
1. This is a minor enhancement. Minor enhancements are not typically listed in Feature Navigator.
37
Configuring NetFlow and NetFlow Data Export
Glossary
Glossary
AS—autonomous system. A collection of networks under a common administration sharing a common
routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned
a unique 16-bit number by the Internet Assigned Numbers Authority (IANA).
CEF—Cisco Express Forwarding. Layer 3 IP switching technology that optimizes network performance
and scalability for networks with large and dynamic traffic patterns.
BGP—Border Gateway Protocol. An interdomain routing protocol that replaces Exterior Gateway
Protocol (EGP). A BGP system exchanges reachability information with other BGP systems. BGP is
defined by RFC 1163.
BGP next hop—IP address of the next hop to be used by a router to reach a certain destination.
dCEF—distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
export packet—Type of packet built by a device (for example, a router) with NetFlow services enabled
that is addressed to another device (for example, the NetFlow Collection Engine). The packet contains
NetFlow statistics. The other device processes the packet (parses, aggregates, and stores information on
IP flows).
fast switching—Cisco feature in which a route cache is used to expedite packet switching through a
router.
flow—A set of packets with the same source IP address, destination IP address, protocol,
source/destination ports, and type-of-service, and the same interface on which the flow is monitored.
Ingress flows are associated with the input interface, and egress flows are associated with the output
interface.
MPLS—Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets
along a normally routed path (sometimes called MPLS hop-by-hop forwarding).
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
RP—Route Processor. A processor module in the Cisco 7000 series routers that contains the CPU,
system software, and most of the memory components that are used in the router. Sometimes called a
Supervisory Processor.
38
Configuring NetFlow and NetFlow Data Export
Glossary
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2010 Cisco Systems, Inc. All rights reserved.
39
Configuring NetFlow and NetFlow Data Export
Glossary
40
Cisco IOS NetFlow Advanced
Configuration
Configuring NetFlow BGP Next Hop Support for
Accounting and Analysis
First Published: June 19, 2006
Last Updated: August 09, 2010
This document provides information about and instructions for configuring NetFlow Border Gateway
Protocol (BGP) next hop support. This feature lets you measure network traffic on a per BGP next hop
basis.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting
and Analysis” section on page 11.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
This document includes the following sections:
•
Prerequisites for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis, page 2
•
Restrictions for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis, page 2
•
Information About Configuring NetFlow BGP Next Hop Support for Accounting and Analysis,
page 3
•
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis, page 3
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Prerequisites for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
•
Configuration Examples for NetFlow BGP Next Hop Support for Accounting and Analysis, page 8
•
Additional References, page 9
•
Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis,
page 11
•
Glossary, page 12
Prerequisites for Configuring NetFlow BGP Next Hop Support
for Accounting and Analysis
Before you can configure the NetFlow BGP Next Hop Support feature, you must:
•
Configure the router for IP routing
•
Configure Cisco Express Forwarding (CEF) switching or distributed CEF (dCEF) switching on the
router and on the interfaces that you want to enable NetFlow on (fast switching is not supported)
•
Configure NetFlow v9 (Version 9) data export (if only Version 5 is configured, then BGP next hop
data is visible in the caches, but is not exported)
•
Configure BGP
Restrictions for Configuring NetFlow BGP Next Hop Support for
Accounting and Analysis
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
Recursive Load Sharing
The NetFlow cache does not capture the BGP next hop when the route to that BGP next hop is recursively
load-shared via several IGP links. Instead, the NetFlow cache captures (as the BGP next hop) the
effective simple next hop from among a random selection of the load-shared routes to which the BGP
route recurses.
Memory Impact
For BGP-controlled routes, the NetFlow BGP Next Hop Support feature adds 16 bytes to each NetFlow
flow record. This increases memory requirements by 16 bytes times the number of flow cache entries
that have BGP-controlled prefixes.
Performance Impact
Because the BGP next hop is fetched from the CEF path only once per flow, the performance impact of
the NetFlow BGP Next Hop Support feature is minimal.
2
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Information About Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Information About Configuring NetFlow BGP Next Hop Support
for Accounting and Analysis
To configure the NetFlow BGP Next Hop Support feature, you must understand the following concepts:
•
NetFlow BGP Next Hop Support Benefits, page 3
•
NetFlow BGP Next Hop Support and NetFlow Aggregation, page 3
NetFlow BGP Next Hop Support Benefits
Without the NetFlow BGP Next Hop Support feature, NetFlow exports only IP next hop information
(which provides information for only the next router). This feature adds BGP next hop information to
the data export.
The NetFlow BGP Next Hop Support feature lets you find out through which service provider the traffic
is going. This functionality is useful if you have arrangements with several other service providers for
fault-protected delivery of traffic. The feature lets you charge customers more per packet when traffic
has a more costly destination—you can pass on some of the cost associated with expensive trans-oceanic
links or charge more when traffic is sent to another ISP with which you have an expensive charge
agreement.
This feature requires the NetFlow Version 9 export format for its data export.
NetFlow BGP Next Hop Support and NetFlow Aggregation
The Cisco IOS NetFlow Aggregation feature summarizes NetFlow export data on a router before the data
is exported to the NetFlow Collection Engine (formerly called the NetFlow FlowCollector). The
NetFlow BGP Next Hop Support feature provides the BGP next hop and its related aggregation scheme
and provides BGP next hop information within each NetFlow record.
How to Configure NetFlow BGP Next Hop Support for
Accounting and Analysis
See the following sections for configuration tasks for the NetFlow BGP Next Hop Support feature. Each
task in the list is identified as either required or optional.
•
Configuring NetFlow BGP Next Hop Accounting, page 3 (required)
•
Verifying the Configuration, page 6 (optional)
Configuring NetFlow BGP Next Hop Accounting
Perform the steps in this required task to configure NetFlow BGP next hop accounting.
This section shows how to configure NetFlow BGP next hop accounting for the main cache and
aggregation caches. You can enable the export of origin AS information or peer AS information, but not
both.
3
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export version 9 [origin-as | peer-as] bgp-nexthop
4.
ip flow-aggregation cache bgp-nexthop-tos
5.
enabled
6.
exit
7.
interface interface-type interface-number
8.
ip flow {ingress | egress}
9.
exit
10. Repeat Steps 7 through 9 to enable NetFlow on other interfaces
11. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Example:
Router# configure terminal
4
(Required) Enters global configuration mode.
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis
Step 3
Command or Action
Purpose
ip flow-export version 9 [origin-as | peer-as]
bgp-nexthop
(Required) Enables the export of information in
NetFlow cache entries.
•
The version 9 keyword specifies that the export
packet uses the Version 9 format.
•
The origin-as keyword specifies that export
statistics include the origin autonomous system
(AS) for the source and destination.
•
The peer-as keyword specifies that export statistics
include the peer AS for the source and destination.
•
The bgp-nexthop keyword specifies that export
statistics include BGP next hop related information.
Example:
Router(config)# ip flow-export version 9 origin-as
bgp-nexthop
This command enables the export of origin AS
information as well as BGP next hop information from
the NetFlow main cache.
Caution
Step 4
ip flow-aggregation cache bgp-nexthop-tos
Example:
Router(config)# ip flow-aggregation cache
bgp-nexthop-tos
Step 5
enabled
Entering this command on a Cisco 12000
Series Internet Router causes packet
forwarding to stop for a few seconds while
NetFlow reloads the route processor and line
card CEF tables. To avoid interruption of
service to a live network, apply this command
during a change window, or include it in the
startup-config file to be executed during a
router reboot.
(Optional) Enables NetFlow aggregation cache schemes
and enters aggregation cache configuration mode.
•
The bgp-nexthop-tos keyword configures the BGP
next hop ToS aggregation cache scheme.
This command specifies the BGP next hop ToS
aggregation cache scheme.
(Required) Enables the aggregation cache.
Example:
Router(config-flow-cache)# enabled
Step 6
exit
(Required) Exits aggregation cache configuration mode
and returns to global configuration mode.
Example:
Note
Router(config-if)# exit
Step 7
interface interface-type interface-number
Example:
You only need to use this command if you want
to enable NetFlow on another interface.
(Required) Specifies the interface that you want to
enable NetFlow on and enters interface configuration
mode.
Router(config)# interface ethernet 0/0
5
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis
Step 8
Command or Action
Purpose
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—captures traffic that is being received by
the interface
•
egress—captures traffic that is being transmitted by
the interface
Example:
Router(config-if)# ip flow ingress
or
Example:
Router(config-if)# ip flow egress
Step 9
exit
(Optional) Exits interface configuration mode and
returns to global configuration mode.
Example:
Note
Router(config-if)# exit
Step 10 Repeat Steps 7 through 9 to enable NetFlow on other
You only need to use this command if you want
to enable NetFlow on another interface.
(Optional) —
interfaces
Step 11 end
(Required) Exits the current configuration mode and
returns to privileged EXEC mode.
Example:
Router(config-if)# end
Troubleshooting Tips
If there are no BGP-specific flow records in the NetFlow cache, make sure that CEF or dCEF switching
is enabled and that the destination for NetFlow data export is configured. Also check the routing table
for BGP routes.
Verifying the Configuration
Perform the steps in this optional task to verify successful configuration of NetFlow BGP next hop
accounting.
SUMMARY STEPS
1.
enable
2.
show ip cache verbose flow
3.
show ip cache flow aggregation bgp-nexthop-tos
4.
exit
DETAILED STEPS
Step 1
enable
Use this command to enable privileged EXEC mode. Enter your password if required. For example:
Router> enable
Router#
Step 2
6
show ip cache verbose flow
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
How to Configure NetFlow BGP Next Hop Support for Accounting and Analysis
Use this command to verify successful configuration of NetFlow BGP next hop accounting. For
example:
Router# show ip cache verbose flow
IP packet size distribution (120 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .000 .000 1.00 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 17826816 bytes
8 active, 262136 inactive, 8 added
26 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 1081480 bytes
8 active, 65528 inactive, 8 added, 8 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
SrcIf
SrcIPaddress
DstIf
Port Msk AS
Port Msk
MUL:M_Opaks M_Obytes BGP:BGP_NextHop
Et0/0/2
12.0.0.2
Et0/0/4
0000 /8 0
0800 /8
BGP:26.0.0.6
Et0/0/2
12.0.0.2
Et0/0/4
0000 /8 0
0800 /8
BGP:26.0.0.6
Et0/0/2
12.0.0.2
Et0/0/4
0000 /8 0
0000 /8
BGP:26.0.0.6
AS
DstIPaddress
NextHop
Pr TOS Flgs Pkts
B/Pk
Active
13.0.0.5
11.0.0.6
01 00
0
10
100
20
0.0
15.0.0.7
11.0.0.6
01 00
0
10
100
20
0.0
15.0.0.7
11.0.0.6
01 00
0
10
100
20
0.0
This command displays a detailed summary of NetFlow statistics (including additional NetFlow fields
in the header when NetFlow Version 9 data export is configured).
Step 3
show ip cache flow aggregation bgp-nexthop-tos
Use this command to verify the configuration of a BGP next hop type of service (ToS) aggregation cache.
For example:
Router# show ip cache flow aggregation bgp-nexthop-tos
IP Flow Switching Cache, 278544 bytes
1 active, 4095 inactive, 1 added
8 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 17224 bytes
1 active, 1023 inactive, 1 added, 1 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
Src If
Active
BGP NextHop
Et0/0/2
8.2
BGP:26.0.0.6
Src AS
Dst If
0
Et0/0/4
Dst AS
0
TOS Flows
00
9
Pkts
36
B/Pk
40
7
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Configuration Examples for NetFlow BGP Next Hop Support for Accounting and Analysis
Step 4
exit
Use this command to exit to user EXEC mode. For example:
Router# exit
Router>
Configuration Examples for NetFlow BGP Next Hop Support for
Accounting and Analysis
This section provides the following configuration example: Configuring NetFlow BGP Next Hop
Accounting: Examples, page 8
Configuring NetFlow BGP Next Hop Accounting: Examples
The following example shows how to configure NetFlow BGP next hop accounting with origin AS and
BGP next hop statistics for the main cache:
configure terminal
!
ip flow-export version 9 origin-as bgp-nexthop
ip flow-export destination 172.16.10.2 991
!
interface ethernet 0/0
ip flow ingress
!
end
The following example shows how to configure a NetFlow BGP next hop ToS aggregation cache scheme:
configure terminal
!
ip flow-aggregation cache bgp-nexthop-tos
export destination 172.16.10.2 991
enabled
!
interface ethernet 0/0
ip flow ingress
!
end
8
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Additional References
Additional References
For additional information related to NetFlow BGP next hop support for accounting and analysis, see
the following references.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
9
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Additional References
Standards
Standards
Title
None
—
MIBs
MIBs
MIBs Link
None
—
RFCs
RFCs
Title
None
—
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
10
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Feature Information for Configuring NetFlow BGP Next Hop
Support for Accounting and Analysis
Table 1 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the “Cisco IOS NetFlow
Features Roadmap” module.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 1
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Feature Name
Software
Feature Configuration Information
NetFlow BGP Next Hop Support
12.3(1)
12.2(18)S
12.0(26)S
12.2(27)SBC
15.0(1)S
The NetFlow Border Gateway Protocol (BGP) Next Hop
Support feature lets you measure network traffic on a per
BGP next hop basis. Without the NetFlow BGP Next Hop
Support feature, NetFlow exports only IP next hop
information (which provides only the address of the next
router); this feature adds BGP next hop information to the
data export.
The following sections provide information about this
feature:
•
NetFlow BGP Next Hop Support Benefits, page 3
•
NetFlow BGP Next Hop Support and NetFlow
Aggregation, page 3
•
Configuring NetFlow BGP Next Hop Accounting,
page 3
•
Verifying the Configuration, page 6
The following commands were modified by this feature:
ip flow-aggregation cache, ip flow-export, show ip
cache flow aggregation, and show ip cache verbose flow.
11
Configuring NetFlow BGP Next Hop Support for Accounting and Analysis
Glossary
Glossary
BGP—Border Gateway Protocol. Interdomain routing protocol that replaces Exterior Gateway Protocol
(EGP). BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163.
BGP next hop—IP address of the next hop to be used to reach a specific destination.
CEF—Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network
performance and scalability for networks with large and dynamic traffic patterns.
dCEF—distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
fast switching—Cisco feature in which a route cache expedites packet switching through a router.
FIB—forwarding information base. A table containing the information needed to forward IP datagrams.
At a minimum, this table contains the interface identifier and next hop information for each reachable
destination network prefix. The FIB is distinct from the routing table (also called the routing information
base), which holds all routing information received from routing peers.
flow—(NetFlow) A set of packets with the same source IP address, destination IP address, source and
destination ports, and type of service, and the same interface on which flow is monitored. Ingress flows
are associated with the input interface, and egress flows are associated with the output interface.
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
ToS—type of service byte. Second byte in the IP header that indicates the desired quality of service for
a particular datagram.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2008–2010 Cisco Systems, Inc. All rights reserved.
12
Configuring MPLS Egress NetFlow Accounting
and Analysis
First Published: June 19, 2006
Last Updated: June 10, 2010
This module contains information about and instructions for configuring the MPLS Egress NetFlow
Accounting feature. The MPLS Egress NetFlow Accounting feature allows you to capture IP flow
information for packets that are undergoing MPLS label disposition; that is, packets that arrive on a
router as MPLS packets and that are transmitted as IP packets.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring MPLS Egress NetFlow Accounting” section on
page 11.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Configuring MPLS Egress NetFlow Accounting, page 2
•
Restrictions for Configuring MPLS Egress NetFlow Accounting, page 2
•
Information About Configuring MPLS Egress NetFlow Accounting, page 3
•
How to Configure MPLS Egress NetFlow Accounting, page 4
•
Configuration Examples for Configuring MPLS Egress NetFlow Accounting, page 7
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring MPLS Egress NetFlow Accounting and Analysis
Prerequisites for Configuring MPLS Egress NetFlow Accounting
•
Additional References, page 9
•
Feature Information for Configuring MPLS Egress NetFlow Accounting, page 11
•
Glossary, page 12
Prerequisites for Configuring MPLS Egress NetFlow Accounting
The network must support the following Cisco IOS features before you enable the MPLS Egress
NetFlow Accounting feature:
•
Multiprotocol label switching (MPLS)
Before you can configure the MPLS Egress NetFlow Accounting feature, you must:
•
Configure the router for IP routing
•
Configure Cisco Express Forwarding (CEF) switching or distributed CEF (dCEF) switching on the
router and on the interfaces that you want to enable MPLS Egress NetFlow Accounting on (fast
switching is not supported)
Restrictions for Configuring MPLS Egress NetFlow Accounting
The MPLS Egress NetFlow Accounting feature is not supported in Cisco IOS Release 12.2(25)S and
later. Use the Egress NetFlow Accounting feature, which captures either IP or MPLS packets as they
leave the router.
Capturing Flows from Sites that Connect to the Same PE Router
The captured egress flows must originate from different sites of the same Virtual Private Network (VPN),
and they cannot connect to the same provider edge (PE) router. If both source and destination VPN sites
are connected to the PE router, the MPLS egress NetFlow accounting feature does not capture these
egress flows. You can capture these flows by enabling ingress NetFlow on the incoming customer edge
(CE)-PE link of the PE router. For example, in Figure 1, traffic from site 3 (VPN1 destined for site 2) is
captured by an ingress NetFlow enabled on the PE2-CE3 link of PE2.
Memory Impact
During times of heavy traffic, the additional flows can fill up the global flow hash table. If you need to
increase the size of the global flow hash table, increase the memory of the router.
Performance Impact
MPLS egress NetFlow accounting might adversely affect network performance because of the additional
accounting-related computations that occur in the traffic-forwarding path of the router.
2
Configuring MPLS Egress NetFlow Accounting and Analysis
Information About Configuring MPLS Egress NetFlow Accounting
Information About Configuring MPLS Egress NetFlow
Accounting
The following sections provide information that you should understand before you configure MPLS
egress NetFlow accounting:
•
MPLS Egress NetFlow Accounting Benefits: Enhanced Network Monitoring and More Accurate
Accounting Statistics, page 3
•
MPLS VPN Flow Capture with MPLS Egress NetFlow Accounting, page 3
MPLS Egress NetFlow Accounting Benefits: Enhanced Network Monitoring
and More Accurate Accounting Statistics
Enhanced Network Monitoring for Complete Billing Solution
You can now capture flows on the egress and ingress router interfaces and obtain complete end-to-end
usage information on network traffic. The accounting server uses the collected data for various levels of
aggregation for accounting reports and application programming interface (API) accounting
information, thus providing a complete billing solution.
More Accurate Accounting Statistics
NetFlow data statistics provided by the MPLS Egress NetFlow Accounting feature can account for all
packets that are dropped in the core of the service provider network, thus providing more accurate traffic
statistics and patterns.
MPLS VPN Flow Capture with MPLS Egress NetFlow Accounting
The MPLS Egress NetFlow Accounting feature allows you to capture IP flow information for packets
that arrive on a router as MPLS packets and are transmitted as IP packets.
This feature allows you to capture the MPLS Virtual Private Network (VPN) IP flows that are traveling
through the service provider backbone from one site of a VPN to another site of the same VPN.
Formerly, you could capture flows only for IP packets on the ingress interface of a router. You could not
capture flows for MPLS encapsulated frames, which were switched through CEF from the input port.
Therefore, in an MPLS VPN environment, you captured flow information when packets were received
from a customer edge (CE) router and forwarded to the backbone. However, you could not capture flow
information when packets were transmitted to a CE router because those packets were received as MPLS
frames.
The MPLS Egress NetFlow Accounting feature lets you capture the flows on the outgoing interfaces.
Figure 1 shows a sample MPLS VPN network topology that includes four VPN 1 sites and two VPN 2
sites. If MPLS egress NetFlow is enabled on an outgoing PE interface, you can capture IP flow
information for packets that arrive at the PE as MPLS packets (from an MPLS VPN) and that are
transmitted as IP packets. For example,
•
To capture the flow of traffic going to site 2 of VPN 1 from any remote VPN 1 sites, you enable
MPLS egress NetFlow on link PE2-CE5 of provider edge router PE2.
•
To capture the flow of traffic going to site 1 of VPN 2 from any remote VPN 2 site, you enable MPLS
egress NetFlow on link PE3-CE4 of the provider edge router PE3.
3
Configuring MPLS Egress NetFlow Accounting and Analysis
How to Configure MPLS Egress NetFlow Accounting
The flows are stored in a global flow cache maintained by the router. You can use the show ip cache flow
command or other aggregation flow commands to view the egress flow data.
Sample MPLS VPN Network Topology with MPLS Egress NetFlow Accounting
Site 2
VPN 1
C
VPN-SC
Backbone
Site 1
VPN 1
CE5
Collector 2
P
CE1
PE1
Site 2
VPN 2
CE2
P
PE2
Collector 1
PE3
Site 3
VPN 1
PE4
Site 1
VPN 2
Site 4
VPN 1
CE4
CE6
CE3
42949
Figure 1
The PE routers export the captured flows to the configured collector devices in the provider network.
Applications such as the Network Data Analyzer or the VPN Solution Center (VPN-SC) can gather
information from the captured flows and compute and display site-to-site VPN traffic statistics.
How to Configure MPLS Egress NetFlow Accounting
Perform the following tasks to configure and verify MPLS egress NetFlow accounting:
•
Configuring MPLS Egress NetFlow Accounting, page 4 (required)
•
Verifying MPLS Egress NetFlow Accounting Configuration, page 5 (optional)
Configuring MPLS Egress NetFlow Accounting
Perform the steps in this required task to configure MPLS egress NetFlow accounting.
SUMMARY STEPS
4
1.
enable
2.
configure terminal
3.
interface interface-type interface-number
4.
mpls netflow egress
5.
end
Configuring MPLS Egress NetFlow Accounting and Analysis
How to Configure MPLS Egress NetFlow Accounting
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface interface-type interface-number
(Required) Specifies the interface and enters interface
configuration mode.
Example:
Router(config)# interface ethernet 1/4
Step 4
mpls netflow egress
(Required) Enables the MPLS Egress NetFlow Accounting
feature on the egress router interface.
Example:
Router(config-if)# mpls netflow egress
Step 5
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
To display debug messages for MPLS egress NetFlow accounting, use the debug mpls netflow
command.
Verifying MPLS Egress NetFlow Accounting Configuration
Perform the steps in this optional task to verify that the MPLS Egress NetFlow Accounting configuration
is as you expect.
SUMMARY STEPS
1.
show ip cache flow
2.
show mpls forwarding-table detail
3.
show mpls interfaces internal
DETAILED STEPS
Step 1
show ip cache flow
Use this command to verify that the MPLS Egress NetFlow Accounting configuration is as you expect.
For example:
5
Configuring MPLS Egress NetFlow Accounting and Analysis
How to Configure MPLS Egress NetFlow Accounting
Router# show ip cache flow
IP packet size distribution (10 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .000 .000 1.00 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 4456704 bytes
1 active, 65535 inactive, 2 added
26 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
last clearing of statistics never
Protocol
-------ICMP
Total :
SrcIf
Et1/1
Step 2
Total
Flows
1
1
Flows
/Sec
0.0
0.0
Packets Bytes
/Flow /Pkt
5
100
5
100
SrcIPaddress
DstIf
209.165.200.225 Et1/4
Packets Active(Sec) Idle(Sec)
/Sec
/Flow
/Flow
0.0
0.0
15.7
0.0
0.0
15.7
DstIPaddress Pr SrcP DstP Pkts
209.165.201.2 01 0000 0800
5
show mpls forwarding-table detail
Use this command to verify the configuration of MPLS egress NetFlow accounting. Check that the quick
flag is set for prefixes, which indicates capture by MPLS egress NetFlow accounting. For example:
Router# show mpls forwarding-table detail
Local
tag
16
Outgoing
Prefix
Bytes tag
tag or VC
or Tunnel Id
switched
Aggregate
34.0.0.0/8[V]
0
MAC/Encaps=0/0, MTU=0, Tag Stack{}
VPN route: vpn1
Feature Quick flag set
Outgoing
interface
Next Hop
Note
As shown above, the quick flag is set for the first two prefixes; therefore, traffic destined for
those prefixes is captured by MPLS egress NetFlow accounting.
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
17
Untagged
2.0.0.0/8[V]
0
Et0/0/2
34.0.0.1
MAC/Encaps=0/0, MTU=1500, Tag Stack{}
VPN route: vpn1
Feature Quick flag set
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
18
Untagged
42.42.42.42/32[V] 4185
Et0/0/2
34.0.0.1
MAC/Encaps=0/0, MTU=1500, Tag Stack{}
VPN route: vpn1
Feature Quick flag set
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
19
2/33
41.41.41.41/32
0
AT1/0/0.1 point2point
MAC/Encaps=4/8, MTU=4470, Tag Stack{2/33(vcd=2)}
00028847 00002000
No output feature configured
Note
6
As shown above, the feature is not configured because MPLS egress NetFlow accounting is not
enabled on the outgoing interface for this prefix.
Configuring MPLS Egress NetFlow Accounting and Analysis
Configuration Examples for Configuring MPLS Egress NetFlow Accounting
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7
20
Aggregate
39.39.39.39/32[V] 0
Local Outgoing
Prefix
Bytes tag
tag
tag or VC
or Tunnel Id
switched
MAC/Encaps=0/0, MTU=0, Tag Stack{}
VPN route: vpn1
No output feature configured
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7
Router#
Step 3
8 9 10 11 12 13 14 15
Outgoing
interface
Next Hop
8 9 10 11 12 13 14 15
show mpls interfaces internal
Use this command to show whether or not MPLS egress NetFlow accounting is enabled on the interface.
For example:
Router# show mpls interfaces internal
Interface Ethernet0/0/1:
IP tagging enabled (tdp)
TSP Tunnel tagging not enabled
Tag Frame Relay Transport tagging not enabled
Tagging operational
IP to Tag Fast Feature Switching Vector
Tag Switching Turbo Feature Vector
MTU = 1500, status=0x100043, appcount=1
Output_feature_state=0x0
Note
The “Output_feature_state=0x0” entry indicates that MPLS egress NetFlow accounting is
disabled on interface Ethernet 0/0/1.
Tag VPI = 1, Control VC = 0/32
Interface Ethernet0/0/2:
IP tagging enabled (tdp)
TSP Tunnel tagging not enabled
Tag Frame Relay Transport tagging not enabled
Tagging operational
IP to Tag Fast Feature Switching Vector
Tag Switching Turbo Feature Vector
MTU = 1500, status=0x100043, appcount=1
Output_feature_state=0x1
Note
The “Output_feature_state=0x1” entry indicates that MPLS egress NetFlow accounting is
enabled on interface Ethernet 0/0/2.
Tag VPI = 1, Control VC = 0/32
Interface ATM1/0/0.1:
IP tagging enabled (tdp)
Configuration Examples for Configuring MPLS Egress NetFlow
Accounting
This section contains the following configuration example for MPLS egress NetFlow accounting:
•
Enabling MPLS Egress NetFlow Accounting: Example, page 8
7
Configuring MPLS Egress NetFlow Accounting and Analysis
Configuration Examples for Configuring MPLS Egress NetFlow Accounting
Enabling MPLS Egress NetFlow Accounting: Example
This section contains a sample configuration for the MPLS Egress NetFlow Accounting feature.
The show ip vrf command lists the Virtual Private Network (VPN) routing and forwarding instances
(VRFs) configured in the router:
Router# show ip vrf
Name
vpn1
vpn3
Default RD
100:1
300:1
Interfaces
Ethernet1/4
Loopback1
Ethernet1/2
Loopback2
In the following example, MPLS Egress NetFlow Accounting is enabled on interface Ethernet 1/4:
configure terminal
!
interface ethernet 1/4
ip address 172.17.24.2 255.255.255.0
mpls netflow egress
exit
Enter the show running-config command to view the current configuration in the router:
Router# show running-config
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
ip cef
no ip domain-lookup
!
This section of the output shows the VRF being defined and shows that the MPLS Egress NetFlow
Accounting feature is enabled:
ip vrf vpn1
rd 100:1
route-target export 100:1
route-target import 100:1
!
interface Loopback0
ip address 10.41.41.41 255.255.255.255
no ip directed-broadcast
no ip mroute-cache
!
interface Ethernet1/4
ip vrf forwarding vpn1
ip address 172.17.24.2 255.255.255.0
no ip directed-broadcast
mpls netflow egress
!
8
Configuring MPLS Egress NetFlow Accounting and Analysis
Additional References
Additional References
The following sections provide references related to configuring the MPLS Egress NetFlow Accounting
feature.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Cisco IOS
NetFlow Configuration Guide configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
9
Configuring MPLS Egress NetFlow Accounting and Analysis
Additional References
Standards
Standard
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIB
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFC
Title
RFC 1163
Border Gateway Protocol (BGP)
RFC 1340
Assigned Numbers
RFC 1918
Address Allocation For Private Internets
RFC 2547
BGP/MPLS VPNs
Technical Assistance
Description
Link
The Cisco Support website provides extensive online
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies.
http://www.cisco.com/cisco/web/support/index.html
To receive security and technical information about
your products, you can subscribe to various services,
such as the Product Alert Tool (accessed from Field
Notices), the Cisco Technical Services Newsletter, and
Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website
requires a Cisco.com user ID and password.
10
Configuring MPLS Egress NetFlow Accounting and Analysis
Feature Information for Configuring MPLS Egress NetFlow Accounting
Feature Information for Configuring MPLS Egress NetFlow
Accounting
Table 1 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.1(5)T or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 1
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for Configuring MPLS Egress NetFlow Accounting
Feature Name
Releases
Feature Configuration Information
MPLS Egress NetFlow Accounting
12.1(5)T
12.0(20)S
The MPLS Egress NetFlow Accounting feature allows you
to capture IP flow information for packets that are
undergoing MPLS label disposition; that is, packets that
arrive on a router as MPLS packets and that are transmitted
as IP packets.
The following sections provide information about this
feature:
•
MPLS Egress NetFlow Accounting Benefits:
Enhanced Network Monitoring and More Accurate
Accounting Statistics, page 3
•
MPLS VPN Flow Capture with MPLS Egress NetFlow
Accounting, page 3
•
Configuring MPLS Egress NetFlow Accounting,
page 4
•
Verifying MPLS Egress NetFlow Accounting
Configuration, page 5
•
Enabling MPLS Egress NetFlow Accounting:
Example, page 8
The following commands were introduced or modified by
this feature: debug mpls netflow, mpls netflow egress,
show mpls forwarding-table, and show mpls interface.
11
Configuring MPLS Egress NetFlow Accounting and Analysis
Glossary
Glossary
BGP—Border Gateway Protocol. An interdomain routing protocol that replaces Exterior Gateway
Protocol (EGP). A BGP system exchanges reachability information with other BGP systems. BGP is
defined by RFC 1163.
BGP/MPLS/VPN—A Virtual Private Network (VPN) solution that uses Multiprotocol Label Switching
(MPLS) and Border Gateway Protocol (BGP) to allow multiple remote customer sites to be connected
over an IP backbone. Refer to RFC 2547 for details.
CE router—A customer edge router. A router that is part of a customer network and interfaces to a
provider edge (PE) router.
customer network—A network that is under the control of an end customer. A customer network can
use private addresses as defined in RFC 1918. Customer networks are logically isolated from each other
and from the provider network. A customer network is also known as a C network.
egress PE—The provider edge router through which traffic moves from the backbone to the destination
Virtual Private Network (VPN) site.
flow—A set of packets with the same source IP address, destination IP address, source/destination ports,
and type-of-service, and the same interface on which flow is monitored. Ingress flows are associated
with the input interface, and egress flows are associated with the output interface.
ingress PE—The provider edge router through which traffic enters the backbone (provider network)
from a Virtual Private Network (VPN) site.
label—A short, fixed length identifier that tells switching nodes how the data (packets or cells) should
be forwarded.
MPLS—Multiprotocol Label Switching. An emerging industry standard for the forwarding of packets
along normally routed paths (sometimes called MPLS hop-by-hop forwarding).
PE router—A provider edge router. A router at the edge of a provider network that interfaces to
customer edge (CE) routers.
provider network—A backbone network that is under the control of a service provider and provides
transport among customer sites. A provider network is also known as the P network.
VPN—Virtual Private Network. The result of a router configuration that enables IP traffic to use
tunneling to travel securely over a public TCP/IP network.
VRF—Virtual Private Network (VPN) routing/forwarding instance. The VRF is a key element in the
MPLS VPN technology. VRFs exist on PEs only. A VRF is populated with VPN routes and allows one
PE to have multiple routing tables. One VRF is required per VPN on each PE in the VPN.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2010 Cisco Systems, Inc. All rights reserved.
12
Configuring SNMP and using the NetFlow MIB to
Monitor NetFlow Data
First Published: May 2, 2005
Last Updated: October 02, 2009
NetFlow is a technology that provides highly granular per-flow statistics on traffic in a Cisco router. The
NetFlow MIB feature provides MIB objects to allow users to configure NetFlow and to monitor flow
cache information, the current NetFlow configuration, and statistics.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring SNMP and using the NetFlow MIB to Monitor
NetFlow Data” section on page 22.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Configuring SNMP and the NetFlow MIB to Monitor NetFlow Data, page 2
•
Restrictions for Configuring SNMP and the NetFlow MIB to Monitor NetFlow Data, page 2
•
Information About Configuring SNMP and the NetFlow MIB to Monitor NetFlow Data, page 2
•
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data, page 5
•
Configuration Examples using SNMP and the NetFlow MIB to Monitor NetFlow Data, page 19
•
Additional References, page 20
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Prerequisites for Configuring SNMP and the NetFlow MIB to Monitor NetFlow Data
•
Feature Information for Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data,
page 22
•
Glossary, page 23
Prerequisites for Configuring SNMP and the NetFlow MIB to
Monitor NetFlow Data
Before you enable NetFlow you must:
•
Configure the router for IP routing
•
Ensure that one of the following is enabled on your router, and on the interfaces that you want to
configure NetFlow on: Cisco Express Forwarding (CEF), distributed CEF, or fast switching
•
Understand the resources required on your router because NetFlow consumes additional memory
and CPU resources
•
Configure SNMP on the router on which the NetFlow MIB feature is to be used. Refer to the
Configuring the Router to use SNMP for more information. For more information on configuring an
SNMP server, refer to the Configuring SNMP Support in the Cisco IOS Network Management
Configuration Guide.
Restrictions for Configuring SNMP and the NetFlow MIB to
Monitor NetFlow Data
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
Information About Configuring SNMP and the NetFlow MIB to
Monitor NetFlow Data
To configure SNMP and the NetFlow MIB to monitor NetFlow data, you should understand the
following concepts:
2
•
NetFlow MIB Feature Benefits, page 3
•
NetFlow MIB Overview, page 3
•
Using SNMP and MIBs to Extract NetFlow Information, page 4
•
Objects That are Used by the NetFlow MIB, page 5
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Information About Configuring SNMP and the NetFlow MIB to Monitor NetFlow Data
NetFlow MIB Feature Benefits
NetFlow is a technology that collects traffic flow statistics on routing devices. NetFlow has been used
for a variety of applications, including traffic engineering, usage-based billing, and denial of service
(DoS) attack monitoring.
The NetFlow MIB feature is useful for obtaining IP flow information from a Cisco router when a
NetFlow export operation is not possible. NetFlow exporting does not have to be enabled for the NetFlow
MIB feature to be used. The NetFlow MIB feature can be implemented instantaneously at any point in
the network to obtain flow information.
With the NetFlow MIB feature, system information that is stored in the flow cache can be accessed in
real time by utilizing a MIB implementation based on SNMP. This information is accessed using get and
set commands entered on the network management system (NMS) workstation for which SNMP has
been implemented. The NMS workstation is also known as the SNMP manager.
NetFlow MIB Overview
The Netflow MIB provides a simple and easy method to configure NetFlow, NetFlow aggregation
caches, and NetFlow Data Export. You use the snmpget and snmpwalk tools to get NetFlow cache
information and current NetFlow configuration information. The NetFlow MIB feature enables medium
to small size enterprises to take advantage of NetFlow technology over SNMP at a reduced infrastructure
cost. The MIB is created to provide Netflow information in these areas:
•
Cache information and configuration.
•
Export information and configuration.
•
Export Statistics.
•
Protocol Statistics.
•
Version 9 Export Template information.
•
Top Flows information.
Terminology Used
Flow
A flow is defined as an unidirectional sequence of packets between a given source and destination
endpoints. Network flows are highly granular; flow endpoints are identified both by IP address as well
as by transport layer application port numbers. NetFlow also utilizes the IP Protocol type, Type of
Service (ToS) and the input interface identifier to uniquely identify flows.
Exporter
A device (for example, a router) with NetFlow services enabled. The exporter monitors packets entering
an observation point and creates flows out of these packets. The information from these flows are
exported in the form of Flow Records to the collector. You can configure NetFlow data export using the
NetFlow MIB.
Flow Record
A Flow Record provides information about an IP Flow that exists on the Exporter. The Flow Records are
commonly referred to as NetFlow Services data or NetFlow data.
3
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Information About Configuring SNMP and the NetFlow MIB to Monitor NetFlow Data
Collector
The NetFlow Collector receives Flow Records from one or more Exporters. It processes the received
export packet, i.e. parses, stores the Flow Record information. The flow records may be optionally
aggregated before storing into the hard disk.
Template
NetFlow Version 9 Export format is template based. Version 9 record format consists of a packet header
followed by at least one or more template or data FlowSets. A template FlowSet (collection of one or
more template) provides a description of the fields that will be present in future data FlowSets.
Templates provide an extensible design to the record format, a feature that should allow future
enhancements to NetFlow services without requiring concurrent changes to the basic flow-record
format.
One additional record type is also a part of Version 9 specification: an options template. Rather than
supplying information about IP flows, options are used to supply meta-data about the NetFlow process
itself.
Top Flows
This feature provides a mechanism which allows the top N flows in the netflow cache to be viewed in
real time.
Criteria can be set to limit the feature to particular flows of interest, which can aid in DoS detection.
Only the number of flows (TopN) and the sort criteria (SortBy) need be set.
Top Flows is not intended as a mechanism for exporting the entire netflow cache.
For more information on the Top Flows and the NetFlow MIB refer to the Configuring NetFlow Top
Talkers using Cisco IOS CLI Commands or SNMP Commands.
Egress flows
This feature analyzes traffic that is being forwarded by the router. This feature is often referred to as
Egress NetFlow.
Using SNMP and MIBs to Extract NetFlow Information
SNMP has historically been used to collect network information. SNMP permits retrieval of critical
information from network elements such as routers, switches, and workstations. The NetFlow MIB
feature uses SNMP to configure NetFlow and to gather NetFlow statistics.
The NetFlow MIB feature allows NetFlow statistics and other NetFlow data for the managed devices on
your system to be retrieved by SNMP. You can specify retrieval of NetFlow information from a managed
device (for example, a router) either by entering commands on that managed device or by entering SNMP
commands from the NMS workstation to configure the router via the MIB. If the NetFlow information
is configured from the NMS workstation, no access to the router is required and all configuration can be
performed via SNMP. The NetFlow MIB request for information is sent from an NMS workstation via
SNMP to the router and is retrieved from the router. This information can then be stored or viewed, thus
allowing NetFlow information to be easily accessed and transported across a multivendor programming
environment.
4
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Objects That are Used by the NetFlow MIB
The NetFlow MIB feature defines managed objects that enable a network administrator to remotely
monitor the following NetFlow information:
•
Flow cache configuration information
•
NetFlow export information
•
General NetFlow statistics
How to Configure SNMP and use the NetFlow MIB to Monitor
NetFlow Data
Note
Some of the tasks in this section include examples of the SNMP CLI syntax used to set configuration
parameters on the router, and to read values from MIB objects on the router. These SNMP CLI syntax
examples are taken from a Linux workstation using public domain SNMP tools. The SNMP CLI syntax
for your workstation might be different. Refer to the documentation that was provided with your SNMP
tools for the correct syntax for your network management workstation.
This section contains the following procedures:
•
Configuring the Router to use SNMP, page 5 (required)
•
Configuring Options for the Main Cache, page 6 (optional)
•
Identifying the Interface Number to use for Enabling NetFlow with SNMP, page 9 (required)
•
Configuring NetFlow on an Interface, page 10 (required)
•
Configuring the Destination-Prefix Aggregation Cache, page 11 (optional)
Configuring the Router to use SNMP
Before the NetFlow MIB feature can be used, the router must be configured support SNMP. To enable
SNMP on the router perform the steps in this required task.
Note
The SNMP community read-only (RO) string for the examples is public. The SNMP community
read-write (RW) string for the examples is private. You should use more complex strings for these
values in your configurations.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
snmp-server community string1 ro
4.
snmp-server community string2 rw
5.
end
5
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
snmp-server community string ro
Example:
(Required) Sets up the community access string to permit
access to SNMP.
•
The string argument is a community string that consists
of from 1 to 32 alphanumeric characters and functions
much like a password, permitting access to the SNMP
protocol. Blank spaces are not permitted in the
community string.
•
The ro keyword specifies read-only access. SNMP
management stations using this string can retrieve MIB
objects.
Router(config)# snmp-server community public ro
Step 4
snmp-server community string rw
Example:
(Required) Sets up the community access string to permit
access to SNMP.
•
The string argument is a community string that consists
of from 1 to 32 alphanumeric characters and functions
much like a password, permitting access to the SNMP
protocol. Blank spaces are not permitted in the
community string.
•
The rw keyword specifies read-write access. SNMP
management stations using this string can retrieve and
modify MIB objects.
Note
The string argument must be different from the
read-only string argument specified in the
preceding step (Step 3).
Router(config)# snmp-server community private
rw
Step 5
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
end
Example:
Router(config)# end
Configuring Options for the Main Cache
This optional task describes the procedure for modifying the parameters for the NetFlow main cache.
Perform the steps in this optional task using either the router CLI commands or the SNMP commands to
modify the parameters for the NetFlow main cache.
6
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
ip flow-cache entries number
4.
ip flow-cache timeout active minutes
5.
ip flow-cache timeout inactive seconds
6.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCICacheEntries.type unsigned number
2.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCIActiveTimeOut.type unsigned
number
3.
snmpset -c private -m all -v2c [ip-address | hostname] ccnfCIInactiveTimeOut.type unsigned
number
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-cache entries number
(Optional) Specifies the maximum number of entries to be
captured for the main flow cache.
Example:
Note
Router(config)# ip flow-cache entries 4000
Step 4
ip flow-cache timeout active minutes
Example:
The valid range for the number argument is from
1024 to 524288 entries.
(Optional) Configures operational parameters for the main
cache.
•
The timeout keyword dissolves the session in the
cache.
•
The active minutes keyword-argument pair is the
number of minutes that an entry is active. The range is
from 1 to 60 minutes. The default is 30 minutes.
Router(config)# ip flow-cache timeout active 30
7
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Step 5
Command or Action
Purpose
ip flow-cache timeout inactive seconds
(Optional) Configures operational parameters for the main
cache.
Example:
•
The timeout keyword dissolves the session in the main
cache.
•
The inactive seconds keyword-argument pair is the
number of seconds that an inactive entry will stay in the
main cache before it times out. The range is from
10 to 600 seconds. The default is 15 seconds.
Router(config)# ip flow-cache timeout inactive
100
Step 6
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config)# end
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCICacheEntries.type unsigned
number
(Optional) Defines the maximum number of entries to be
captured for the main flow cache.
•
The value for the type argument in
cnfCICacheEntries.type unsigned number is 0 for the
main cache.
•
The value for the number argument in
cnfCICacheEntries.type number is the maximum
number of cache entries.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCICacheEntries.0 unsigned 4000
Note
8
The valid range for the number argument is from
1024 to 524288 entries.
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Step 2
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCIActiveTimeOut.type unsigned
number
(Optional) Specifies the number of seconds that an active
flow remains in the main cache before it times out.
•
The value for the type argument in
cnfCIActiveTimeout.type unsigned number is 0 for
the main cache.
•
The value for the number argument in
cnfCIActiveTimeout.type unsigned number is the
number of seconds that an active flow remains in the
cache before it times out.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCIActiveTimeOut.0 unsigned 60
The range for the number argument is from 1 to 60
minutes. The default is 30 minutes.
Note
Step 3
snmpset -c private -m all -v2c [ip-address |
hostname] ccnfCIInactiveTimeOut.type unsigned
number
(Optional) Specifies the number of seconds that an inactive
flow remains in the main cache before it times out.
•
The value for the type argument in
cnfCIInactiveTimeout.type unsigned number is 0 for
the main cache.
•
The value for the number argument in
cnfCIInactiveTimeout.type unsigned number is the
number of seconds that an inactive flow remains in the
main cache before it times out.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCIInactiveTimeOut.0 unsigned 30
Note
The range for the number argument is from
10 to 600 seconds. The default is 15 seconds.
Identifying the Interface Number to use for Enabling NetFlow with SNMP
Before you can use SNMP to enable NetFlow on an interface you must identify the correct SNMP
interface number on the router. To identify the interface number for the interface that you want to enable
NetFlow on perform the steps in this required task.
SUMMARY STEPS
1.
enable
2.
show snmp mib ifmib ifindex type number
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode. Enter the password if prompted.
Router> enable
Step 2
show snmp mib ifmib ifindex type number
Displays the SNMP interface number for the interface specified.
Router# show snmp mib ifmib ifindex fastethernet 0/0
Ethernet0/0: Ifindex = 1
9
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Configuring NetFlow on an Interface
Perform the steps in this required task using either the router CLI commands or the SNMP commands
to enable NetFlow on the router.
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
interface type number
4.
ip flow {ingress | egress}
5.
exit
6.
Repeat Steps 3 through 5 to enable NetFlow on other interfaces
7.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCINetflowEnable.interface-number
integer [0 | 1 | 2 | 3]
2.
Repeat Step 1 to enable NetFlow on other interfaces.
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
(Required) Specifies the interface that you want to enable
NetFlow on and enters interface configuration mode.
Example:
Router(config)# interface fastethernet0/0
Step 4
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—captures traffic that is being received by the
interface
•
egress—captures traffic that is being transmitted by the
interface.
Example:
Router(config-if)# ip flow ingress
and/or
Example:
Router(config-if)# ip flow egress
10
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Step 5
Command or Action
Purpose
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
Router(config-if)# exit
You only need to use this command if you want to
enable NetFlow on another interface.
Step 6
Repeat Steps 3 through 5 to enable NetFlow on other
interfaces.
(Optional) —
Step 7
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCINetflowEnable.interface-number
integer [0 | 1 | 2 | 3]
(Required) Configures NetFlow for an interface.
Note
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCINetflowEnable.1 integer 1
Step 2
Repeat Step 1 to enable NetFlow on other interfaces
The value for the interface-number argument is
found by entering the router CLI command show
snmp mib ifmib ifindex on the router in privileged
EXEC mode.
The values for the direction argument are:
•
0—Disable NetFlow
•
1—Enable Ingress NetFlow
•
2—Enable Egress NetFlow
•
3—Enable Ingress and Egress NetFlow
(Optional) —
Configuring the Destination-Prefix Aggregation Cache
This task describes the procedure for modifying the parameters for aggregation caches. The
destination-prefix is used in this task. With the exception of specifying the aggregation cache that you
want to modify, the steps are the same for modifying these parameters for the other aggregation caches.
Perform the steps in this optional task using either the router CLI commands or the SNMP commands to
modify configuration parameters for an aggregation cache.
Prerequisites
You must enable NetFlow on at least one interface before configuring a NetFlow aggregation cache.
SUMMARY STEPS
Router CLI Commands
1.
enable
11
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
2.
configure terminal
3.
ip flow-aggregation cache destination-prefix
4.
cache entries number
5.
cache timeout active minutes
6.
cache timeout inactive seconds
7.
enable
8.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCICacheEnable.type integer
truth-value
2.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCICacheEntries.type unsigned number
3.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCIActiveTimeOut.type unsigned
number
4.
snmpset -c private -m all -v2c [ip-address | hostname] ccnfCIInactiveTimeOut.type unsigned
number
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-aggregation cache destination-prefix
Example:
(Required) Enters aggregation cache configuration mode
for the destination-prefix aggregation cache.
•
Router(config)# ip flow-aggregation cache
destination-prefix
Note
Step 4
cache entries number
The destination-prefix keyword is equivalent to the
type argument of 4 in Step 2 of the SNMP commands.
For information on other keywords for this
command, see the Cisco IOS NetFlow Command
Reference.
(Optional) Defines the number of entries that are allowed in
the aggregation flow cache.
Example:
Router(config-flow-cache)# cache entries 4000
Step 5
cache timeout active minutes
(Optional) Specifies the number of minutes that an active
flow remains in the cache before it times out.
Example:
Note
Router(config)# cache timeout active 30
12
The range is from 1 to 60 minutes. The default is 30
minutes.
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Step 6
Command or Action
Purpose
cache timeout inactive seconds
(Optional) Specifies the number of seconds that an inactive
flow remains in the cache before it times out.
Example:
Note
Router(config-flow-cache)# cache timeout
inactive 100
Step 7
enable
The range is from 10 to 600 seconds. The default is
15 seconds.
(Required) Activates the destination-prefix aggregation
cache.
Example:
Router(config-flow-cache)# enable
Step 8
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
13
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCICacheEnable.type integer
truth-value
(Required) Enables the aggregation cache.
•
Values for the type argument are:
– Main—0
Example:
– AS—1
workstation% snmpset -c private -m all -v2c
10.4.9.14 cnfCICacheEnable.4 integer 1
– Protocol Port—2
– Source Prefix—3
– Destination Prefix—4
– prefix—5
– Destination Only—6
– Source Destination—7
– Full Flow—8
– AS ToS—9
– Protocol Port ToS—10
– Source Prefix ToS—11
– Destination Prefix Tos—12
– Prefix Tos—13
– Prefix Port—14
– BGP Nexthop Tos—15
•
Values for truth-value in cnfCICacheEnable.type
integer truth-value are:
– 1—enable the aggregation cache
– 2—disable the aggregation cache
Step 2
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCICacheEntries.type unsigned
number
(Optional) Defines the maximum number of entries to be
captured for the aggregation flow cache.
•
The value for the type argument in
cnfCICacheEntries.type unsigned number is 4 for the
destination-prefix cache.
•
The value for the number argument in
cnfCICacheEntries.type unsigned number is the
maximum number of cache entries.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCICacheEntries.4 unsigned 4000
Note
14
The valid range for the number argument is from
1024 to 524288 entries.
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Step 3
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCIActiveTimeOut.type unsigned
number
(Optional) Specifies the number of seconds that an active
flow remains in the cache before it times out.
•
The value for the type argument in
cnfCIActiveTimeout.type unsigned number is 4 for
the destination-prefix cache.
•
The value for the number argument in
cnfCIActiveTimeout.type unsigned number is the
number of seconds that an active flow remains in the
cache before it times out.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.14 cnfCIActiveTimeOut.4 unsigned 60
Note
Step 4
snmpset -c private -m all -v2c [ip-address |
hostname] ccnfCIInactiveTimeOut.type unsigned
number
(Optional) Specifies the number of seconds that an inactive
flow remains in the cache before it times out.
•
The value for the type argument in
cnfCIInactiveTimeout.type unsigned number is 4 for
the destination-prefix cache.
•
The value for the number argument in
cnfCIInactiveTimeout.type unsigned number is the
number of seconds that an inactive flow remains in the
cache before it times out.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.14 cnfCIInactiveTimeOut.4 unsigned 30
The range for the number argument is from 1 to 60
minutes. The default is 30 minutes.
Note
The range for the number argument is from
10 to 600 seconds. The default is 15 seconds.
Configuring NetFlow Export from the Main NetFlow Cache using the Version 9
Export Format
The following example configures the router to export statistics from the NetFlow main cache (0),
including peer autonomous system and BGP-related information using export Version 9.
Perform the steps in this optional task using either the router CLI commands or the SNMP commands to
configure the router to export statistics from the main cache using the Version 9.
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
ip flow-export version 9 [origin-as | peer-as] [bgp-nexthop]
4.
ip flow-export {destination {ip-address | hostname} udp-port}
5.
Repeat Step 4 to add a second NetFlow collector
6.
end
15
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfEIExportVersion.type unsigned version
cnfEIPeerAS.type integer version cnfEIBgpNextHop.type integer truth-value
2.
snmpset -c private -m all -v2c [ip-address | hostname]
cnfEICollectorStatus.type.address-type.ip-version.ip-address.port integer [4 | 6]
3.
Repeat Step 2 to add a second NetFlow collector
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-export version 9 [origin-as | peer-as]
[bgp-nexthop]
(Required) Enables the export of information in NetFlow
cache entries.
•
The version 9 keyword specifies that the export packet
uses the Version 9 format.
•
The origin-as keyword specifies that export statistics
include the originating AS for the source and
destination.
•
The peer-as keyword specifies that export statistics
include the peer AS for the source and destination.
•
The bgp-nexthop keyword specifies that export
statistics include BGP next hop-related information.
Example:
Router(config)# ip flow-export version 9
peer-as bgp-nexthop
Caution
Step 4
ip flow-export destination {ip-address |
hostname} udp-port}
Example:
Router(config)# ip flow-export destination
10.0.19.2 999
16
Entering this command on a Cisco 12000 Series
Internet Router causes packet forwarding to stop
for a few seconds while NetFlow reloads the
route processor and line card CEF tables. To
avoid interruption of service to a live network,
apply this command during a change window, or
include it in the startup-config file to be executed
during a router reboot.
(Required) Specifies the IP address, or hostname of the
NetFlow collector, and the UDP port the NetFlow collector
is listening on.
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Command or Action
Purpose
Step 5
Repeat Step 4 to add a second NetFlow collector
(Optional) —
Step 6
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config)# end
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfEIExportVersion.type unsigned
version cnfEIPeerAS.type integer truth-value
cnfEIBgpNextHop.type integer truth-value
(Required) Specifies the export format and that the export
statistics include peer autonomous system and BGP-related
information.
•
The values for the type argument are:
Example:
– Main—0
workstation% snmpset -c private -m all -v2c
10.4.9.14 cnfEIExportVersion.0 unsigned 9
cnfEIPeerAS.0 integer 1 cnfEIBgpNextHop.0
integer 1
– AS—1
– Protocol Port—2
– Source Prefix—3
– Destination Prefix—4
– prefix—5
– Destination Only—6
– Source Destination—7
– Full Flow—8
– AS ToS—9
– Protocol Port ToS—10
– Source Prefix ToS—11
– Destination Prefix Tos—12
– Prefix Tos—13
– Prefix Port—14
– BGP Nexthop Tos—15
•
The values for the version argument are:
– 5—Version 5 export format. The number of records
stored in the datagram is a variable between 1 and
30 for the Version 5 export format.
– 9—Version 9 export format.
•
The values for the truth-value argument are:
– 1—enable the keyword
– 2—disable the keyword
17
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
How to Configure SNMP and use the NetFlow MIB to Monitor NetFlow Data
Step 2
snmpset -c private -m all -v2c [ip-address |
hostname]
cnfEICollectorStatus.type.address-type.ip-versi
on.ip-address.port integer [4 | 6]
(Required) Enables the exporting of information in NetFlow
cache entries.
•
Values the type argument are:
– Main—0
Example:
– AS—1
workstation% snmpset -c private -m all -v2c
10.4.9.14
cnfEICollectorStatus.0.1.4.10.0.19.2.3 integer
4
– Protocol Port—2
– Source Prefix—3
– Destination Prefix—4
– prefix—5
– Destination Only—6
– Source Destination—7
– Full Flow—8
– AS ToS—9
– Protocol Port ToS—10
– Source Prefix ToS—11
– Destination Prefix Tos—12
– Prefix Tos—13
– Prefix Port—14
– BGP Nexthop Tos—15
•
The address-type, and ip-version arguments specify the
type of IP address.
– The address-type argument is 1.
– The ip-version argument is the length in bytes of
the address. Currently IPv4 is the only type that is
supported, so the ip-version value should be 4 (four
bytes in an IPv4 IP address).
•
The ip-address variable specifies the IPv4 IP address of
the collector.
•
The port argument is the UDP port the collector is
listening on for NetFlow data.
•
The [4 | 6] keywords create and remove the NetFlow
collector.
– The 4 keyword creates the collector in the router’s
configuration, and activates the collector.
– The 6 keyword removes the collector from router’s
configuration.
Step 3
18
Repeat Step 2 to add another collector
(Optional) —
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Configuration Examples using SNMP and the NetFlow MIB to Monitor NetFlow Data
Configuration Examples using SNMP and the NetFlow MIB to
Monitor NetFlow Data
This section provides the following configuration examples:
•
Configuring the Minimum Mask for a Source Prefix Aggregation Scheme using SNMP: Example,
page 19
•
Configuring NetFlow Data Export for the Source Prefix Aggregation Scheme using SNMP:
Example, page 19
•
Configuring a NetFlow Minimum Mask for a Prefix Aggregation Cache using SNMP: Example,
page 19
•
Using SNMP to Gather Flow Information From the Router: Example, page 20
Configuring the Minimum Mask for a Source Prefix Aggregation Scheme using
SNMP: Example
The following example enables a Source-Prefix aggregation cache and sets the source prefix mask to 16
bits.
workstation% snmpset -c private -m all -v2c 10.4.9.14 cnfCICacheEnable.3 integer 1
CISCO-NETFLOW-MIB::cnfCICacheEnable.sourcePrefix = INTEGER: true(1)
workstation% snmpset -c private -m all -v2c 10.4.9.14 cnfCIMinSourceMask.3 unsigned 16
CISCO-NETFLOW-MIB::cnfCIMinSourceMask.sourcePrefix = Gauge32: 16
Configuring NetFlow Data Export for the Source Prefix Aggregation Scheme
using SNMP: Example
The following example enables a Source-Prefix aggregation cache and configures NetFlow Data Export
for the aggregation cache.
workstation% snmpset -c private -m all -v2c 10.4.9.14 cnfCICacheEnable.3 integer 1
CISCO-NETFLOW-MIB::cnfCICacheEnable.sourcePrefix = INTEGER: true(1)
workstation% snmpset -c private -m all -v2c 10.4.9.14
cnfEICollectorStatus.3.1.4.10.0.19.2.3 integer 4
CISCO-NETFLOW-MIB::cnfEICollectorStatus.sourcePrefix.ipv4."....".3 = INTEGER:
createAndGo(4)
Configuring a NetFlow Minimum Mask for a Prefix Aggregation Cache using
SNMP: Example
The following example enables a Prefix aggregation cache and sets the prefix mask to 16 bits.
workstation% snmpset -c private -m all -v2c 10.4.9.14 cnfCICacheEnable.5 integer 1
19
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Additional References
CISCO-NETFLOW-MIB::cnfCICacheEnable.prefix = INTEGER: true(1)
workstation% snmpset -c private -m all -v2c 10.4.9.14 cnfCIMinSourceMask.5 unsigned 16
CISCO-NETFLOW-MIB::cnfCIMinSourceMask.prefix = Gauge32: 16
Using SNMP to Gather Flow Information From the Router: Example
The following examples show how to retrieve NetFlow status and statistics using SNMP.
•
Retrieving Netflow Statistics using SNMP
•
View the NetFlow Main Cache Timeout Values using SNMP
Retrieving Netflow Statistics using SNMP
This command will retrieve the Netflow Statistics from the main cache using the MIB.
workstation% snmpget -c public -v2c 10.4.9.14 cnfPSPacketSizeDistribution.0
cnfPSPacketSizeDistribution.0 =
00 00 00 00
03 e8 00 00
00 00
00 00 00 00
00 00 00 00
00 00
00 00 00 00
00 00 00 00
00 00
00 00 00 00
00 00
00 00
00 00
00 00
00 00
00 00
00 00
00 00
00 00
The IP packet size distribution values are in the same order as shown in the CLI, with each pair of bytes
representing a value of 1000 times the respective value in the CLI.
For example, for the packet range 65-96, the byte pair is 0x03e8 which is 1000 times 1. So to obtain the
same values as the CLI, divide the value by 1000.
View the NetFlow Main Cache Timeout Values using SNMP
This command will retrieve the cache timeout values from the main cache using the MIB.
workstation% snmpget -c public -v2c 10.4.9.14 cnfCIActiveFlows.0 cnfCIInactiveFlows.0
cnfCIActiveTimeOut.0 cnfCIInactiveTimeOut.0
CISCO-NETFLOW-MIB::cnfCIActiveFlows.main = Gauge32: 1
CISCO-NETFLOW-MIB::cnfCIInactiveFlows.main = Gauge32: 3999
CISCO-NETFLOW-MIB::cnfCIActiveTimeOut.main = Gauge32: 60 minutes
CISCO-NETFLOW-MIB::cnfCIInactiveTimeOut.main = Gauge32: 30 seconds
Additional References
The following sections provide references related to configuring SNMP and the NetFlow MIB to monitor
NetFlow data.
20
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Additional References
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
“Cisco IOS NetFlow Overview”
List of the features documented in the Book Title
configuration guide
“Cisco IOS NetFlow Features Roadmap”
The minimum information about and tasks required for “Getting Started with Configuring NetFlow and NetFlow Data
configuring NetFlow and NetFlow Data Export
Export”
Tasks for configuring NetFlow to capture and export
network traffic data
“Configuring NetFlow and NetFlow Data Export”
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring Random Sampled NetFlow
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring NetFlow aggregation caches
“Configuring NetFlow Aggregation Caches”
Tasks for configuring NetFlow BGP next hop support
“Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis”
Tasks for configuring NetFlow multicast support
“Configuring NetFlow Multicast Accounting”
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
“NetFlow Layer 2 and Security Monitoring Exports”
Tasks for configuring the NetFlow MIB and Top
Talkers feature
“Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands”
Information for installing, starting, and configuring the “Cisco CNS NetFlow Collection Engine Documentation”
CNS NetFlow Collection Engine
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
21
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Feature Information for Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
MIBs
MIBs
•
MIBs Link
CISCO-NETFLOW-MIB.my
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL (requires CCO login account):
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
Feature Information for Configuring SNMP and using the
NetFlow MIB to Monitor NetFlow Data
Table 1 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Releases 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
22
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Glossary
Note
Table 1
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for Configuring the NetFlow Top Talkers Feature using the Cisco IOS CLI or SNMP
Commands
Feature Name
Releases
Feature Configuration Information
NetFlow MIB
12.3(7)T,
12.2(25)S
12.2(27)SBC
12.2(33)SRD
The NetFlow MIB feature provides MIB objects to allow
users to monitor NetFlow cache information, the current
NetFlow configuration, and statistics.
The following sections provide information about this
feature:
•
Information About Configuring SNMP and the
NetFlow MIB to Monitor NetFlow Data, page 2
•
How to Configure SNMP and use the NetFlow MIB to
Monitor NetFlow Data, page 5
The following command was introduced by this feature: ip
flow-cache timeout.
Glossary
AS—autonomous system. A collection of networks under a common administration sharing a common
routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned
a unique 16-bit number by the Internet Assigned Numbers Authority (IANA).
BGP—Border Gateway Protocol. Interdomain routing protocol that replaces Exterior Gateway Protocol
(EGP). A BGP system exchanges reachability information with other BGP systems. BGP is defined by
RFC 1163.
BGP next hop—IP address of the next hop to be used to reach a specific destination.
CEF—Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network
performance and scalability for networks with large and dynamic traffic patterns.
dCEF—distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
MIB—Management Information Base. Database of network management information that is used and
maintained by a network management protocol, such as Simple Network Management System (SNMP)
or the Common Management Information Protocol (CMIP). The value of a MIB object can be changed
or retrieved using SNMP or CMIP commands, usually through a GUI network management system. MIB
objects are organized in a tree structure that includes public (standard) and private (proprietary)
branches.
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
23
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data
Glossary
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—A Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
NMS—network management system. A system responsible for managing at least part of a network. An
NMS is generally a reasonably powerful and well-equipped computer, such as an engineering
workstation. NMSs communicate with agents to help keep track of network statistics and resources.
SNMP—Simple Network Management Protocol. A network management protocol used almost
exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and
to manage configurations, statistics collection, performance, and security.
SNMP communities—An authentication scheme that enables an intelligent network device to validate
SNMP requests.
ToS byte—type of service. Second byte in the IP header that indicates the desired quality of service for
a particular datagram.
CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect,
Cisco Pulse, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco Unified Computing System, Cisco WebEx, DCE, Flip Channels,
Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to the Human Network
are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed (Stylized), Cisco Store,
and Flip Gift Card are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP,
CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems,
Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center,
Explorer, Fast Step, Follow Me Browsing, FormShare, GainMaker, GigaDrive, HomeLink, iLYNX, Internet Quotient, IOS, iPhone, iQuick Study,
IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers,
Networking Academy, Network Registrar, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect,
ROSA, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx,
and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (0908R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2005–2009 Cisco Systems, Inc. All rights reserved.
24
NetFlow Reliable Export With SCTP
First Published: June 19, 2006
Last Updated: June 19, 2006
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology. This document describes the
NetFlow application and the new NetFlow Reliable Export With Stream Control Transmission Protocol
(SCTP) feature.
The NetFlow Reliable Export with SCTP feature adds the ability for NetFlow to use the reliable and
congestion-aware SCTP when exporting statistics to a network management system that supports the
NetFlow data export formats, such as a system running CNS NetFlow Collection Engine (NFC).
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for NetFlow Reliable Transport Using SCTP” section on page 29.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for NetFlow Reliable Export With SCTP, page 2
•
Restrictions for NetFlow Reliable Export With SCTP, page 2
•
Information About NetFlow Reliable Export With SCTP, page 2
•
How to Configure NetFlow Reliable Export with SCTP, page 9
•
Verifying NetFlow Reliable Export With SCTP, page 22
•
Configuration Examples for NetFlow Reliable Export With SCTP, page 25
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
NetFlow Reliable Export With SCTP
Prerequisites for NetFlow Reliable Export With SCTP
•
Additional References, page 27
•
Feature Information for NetFlow Reliable Transport Using SCTP, page 29
•
Glossary, page 30
Prerequisites for NetFlow Reliable Export With SCTP
NetFlow and Cisco Express Forwarding (CEF), distributed CEF (dCEF), or fast switching must be
configured on your system.
Restrictions for NetFlow Reliable Export With SCTP
The NetFlow SCTP collector must support SCTP.
Information About NetFlow Reliable Export With SCTP
To configure the NetFlow feature, you should understand the following concepts:
•
NetFlow Data Capture, page 2
•
NetFlow Benefits, page 3
•
NetFlow Cisco IOS Packaging Information, page 4
•
Elements of a NetFlow Network Flow, page 4
•
NetFlow Main Cache Operation, page 4
•
NetFlow Data Capture, page 5
•
NetFlow Export Formats, page 5
•
NetFlow Reliable Export With SCTP, page 5
NetFlow Data Capture
NetFlow identifies packet flows for both ingress and egress IP packets. It does not involve any
connection-setup protocol. NetFlow is completely transparent to the existing network, including end
stations and application software and network devices like LAN switches. Also, NetFlow capture and
export are performed independently on each internetworking device; NetFlow need not be operational
on each router in the network.
NetFlow is supported on IP and IP encapsulated traffic over most interface types and Layer 2
encapsulations.
You can display and clear NetFlow statistics. NetFlow statistics consist of IP packet size distribution, IP
flow switching cache information, and flow information.
2
NetFlow Reliable Export With SCTP
Information About NetFlow Reliable Export With SCTP
NetFlow Benefits
NetFlow captures a rich set of traffic statistics. These traffic statistics include user, protocol, port, and
type of service (ToS) information that can be used for a wide variety of purposes such as network
application and user monitoring (user monitoring is performed by monitoring the IP addresses of the
devices that users are running applications on), network analysis and planning, denial of service (DoS)
and security analysis, accounting and billing, traffic engineering, and data mining.
NetFlow can capture a rich set of traffic statistics. These traffic statistics include user, protocol, port, and
type of service (ToS) information that can be used for a wide variety of purposes, including network
traffic analysis and capacity planning, security, enterprise accounting and departmental chargebacks,
Internet Service Provider (ISP) billing, data warehousing, and data mining for marketing purposes.
Network Application and User Monitoring
NetFlow data enables you to view detailed, time and application based usage of a network. This
information allows you to plan and allocate network and application resources, and provides for
extensive near real-time network monitoring capabilities. It can be used to display traffic patterns and
application-based views. NetFlow provides proactive problem detection and efficient troubleshooting,
and it facilitates rapid problem resolution. You can use NetFlow information to efficiently allocate
network resources and to detect and resolve potential security and policy violations.
Network Analysis and Planning
You can use NetFlow to capture data for extended periods of time, which enables you to track network
utilization and anticipate network growth and plan upgrades. NetFlow service data can be used to
optimize network planning, which includes peering, backbone upgrades, and routing policy planning. It
also enables you to minimize the total cost of network operations while maximizing network
performance, capacity, and reliability. NetFlow detects unwanted WAN traffic, validates bandwidth and
quality of service (QoS) behavior, and enables the analysis of new network applications. NetFlow offers
valuable information that you can use to reduce the cost of operating the network.
Denial of Service and Security Analysis
You can use NetFlow data to identify and classify in real time denial of service (DoS) attacks, viruses,
and worms. Changes in network behavior indicate anomalies that are clearly reflected in NetFlow data.
The data is also a valuable forensic tool that you can use to understand and replay the history of security
incidents.
Accounting and Billing
NetFlow data provides fine-grained metering for highly flexible and detailed resource utilization
accounting. For example, flow data includes details such as IP addresses, packet and byte counts,
timestamps, and information about type of service (ToS) and application ports. Service providers might
utilize the information for billing based on time-of-day, bandwidth usage, application usage, or QoS.
Enterprise customers might utilize the information for departmental charge-back or cost allocation for
resource utilization.
Traffic Engineering
NetFlow provides autonomous system (AS) traffic engineering details. You can use NetFlow-captured
traffic data to understand source-to-destination traffic trends. This data can be used for load-balancing
traffic across alternate paths or for forwarding traffic along a preferred route. NetFlow can measure the
amount of traffic crossing peering or transit points. You can use the data to help you decide if a peering
arrangement with other service providers is fair and equitable.
3
NetFlow Reliable Export With SCTP
Information About NetFlow Reliable Export With SCTP
NetFlow Data Storage and Data Mining
NetFlow data can be stored for later retrieval and analysis in support of marketing and customer service
programs. For example, the data can be mined to find out which applications and services are being used
by internal and external users and target the users for improved service and advertising. In addition,
NetFlow data gives market researchers access to the who, what, where, and how long information
relevant to enterprises and service providers.
NetFlow Cisco IOS Packaging Information
Cisco 7200/7500/7400/MGX/AS5850
Although NetFlow functionality is included in all software images for these platforms, you must
purchase a separate NetFlow feature license. NetFlow licenses are sold on a per-node basis.
Other Routers
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Elements of a NetFlow Network Flow
A NetFlow network flow is defined as a unidirectional stream of packets between a given source and
destination. The source and destination are each defined by a network-layer IP address and
transport-layer source and destination port numbers. Specifically, a flow is defined by the combination
of the following seven key fields:
•
Source IP address
•
Destination IP address
•
Source port number
•
Destination port number
•
Layer 3 protocol type
•
Type of service
•
Input logical interface
These seven key fields define a unique flow. If a packet has one key field different from another packet,
it is considered to belong to another flow. A flow might also contain other accounting fields (such as the
AS number in the NetFlow export Version 5 flow format). The fields that a given flow contains depend
on the export record version that you configure. Flows are stored in the NetFlow cache.
NetFlow Main Cache Operation
The key components of NetFlow are the NetFlow cache that stores IP flow information and the NetFlow
export or transport mechanism that sends NetFlow data to a network management collector, such as the
NetFlow Collection Engine. NetFlow operates by creating a NetFlow cache entry (a flow record) for
each active flow. NetFlow maintains a flow record within the cache for each active flow. Each flow
record in the NetFlow cache contains values for the fields that are being monitored that can later be
exported to a collection device, such as the NetFlow Collection Engine.
4
NetFlow Reliable Export With SCTP
Information About NetFlow Reliable Export With SCTP
NetFlow Data Capture
NetFlow captures data from ingress (incoming) and egress (outgoing) packets. NetFlow gathers data for
the following ingress IP packets:
•
IP-to-IP packets
•
IP-to-Multiprotocol Label Switching (MPLS) packets
NetFlow captures data for all egress (outgoing) packets through use of the following features:
•
Egress NetFlow Accounting—NetFlow gathers data for all egress packets for IP traffic only.
•
NetFlow MPLS Egress—NetFlow gathers data for all egress MPLS-to-IP packets.
NetFlow Export Formats
NetFlow exports data in User Datagram Protocol (UDP) datagrams in one of five formats: Version 9,
Version 8, Version 7, Version 5, or Version 1. Version 9 export format, the latest version, is the most
flexible and extensible format. Version 1 was the initial NetFlow export format; Version 8 only supports
export from aggregation caches, and Version 7 is supported only on certain platforms. (Versions 2
through 4 and Version 6 were either not released or are not supported.)
•
Version 9—A flexible and extensible format, which provides the versatility needed for support of
new fields and record types. This format accommodates new NetFlow-supported technologies such
as MPLS, and Border Gateway Protocol (BGP) next hop. The distinguishing feature of the NetFlow
Version 9 format is that it is template based. Templates provide an extensible design to the record
format, a feature that should allow future enhancements to NetFlow services without requiring
concurrent changes to the basic flow-record format. Internet Protocol Information Export (IPFIX)
was based on the Version 9 export format.
•
Version 8—A format added to support data export from aggregation caches. Version 8 allows export
datagrams to contain a subset of the usual Version 5 export data, if that data is valid for a particular
aggregation cache scheme.
•
Version 7—A version supported on a Catalyst 6000 series switch with a multilayer switch feature
card (MSFC) running CatOS Release 5.5(7) and later.
On a Catalyst 6000 series switch with an MSFC, you can export using either the Version 7 or the
Version 8 format.
•
Version 5—A version that adds BGP AS information and flow sequence numbers.
•
Version 1—The initially released export format, rarely used today. Do not use the Version 1 export
format unless the legacy collection system you are using requires it. Use either the Version 9 export
format or the Version 5 export format for data export from the main cache.
NetFlow Reliable Export With SCTP
Prior to the introduction of the NetFlow Reliable Export With SCTP feature in
Cisco IOS Release 12.4(4)T exporting NetFlow information was unreliable because NetFlow
encapsulated the exported traffic in UDP packets for transmission to the NFC. Using an unreliable
transport protocol such as UDP for sending information across a network has two major disadvantages:
5
NetFlow Reliable Export With SCTP
Information About NetFlow Reliable Export With SCTP
•
Lack of congestion awareness—The exporter sends packets as fast as it can generate them, without
any regard to the bandwidth available on the network. If the link is fully congested when the
NetFlow router attempts to send, the packet might simply be dropped, either before it is put on the
exporter’s output queue or before it gets to the next hop's input queue.
•
Lack of reliability—With export over UDP, the collector has no method of signaling to the exporter
that it didn't receive an exported packet. Most versions of NetFlow export packet contain a sequence
number, so the collector often knows when it has lost a packet. But given that the exporter discards
the export packet as soon as it has been sent and that the NetFlow router lacks a mechanism to
request a retransmission of the packet, exporting over UDP can be considered to be unreliable
The NetFlow Reliable Export With SCTP feature uses the SCTP to overcome the two major
disadvantages of using UDP as the transport layer protocol:
•
SCTP has a congestion control mechanism to ensure that the router does not send data to the
collector faster than it can receive it.
•
SCTP transmits messages in a reliable manner. SCTP messages are buffered on the router until they
have been acknowledged by the collector. Messages that are not acknowledged by the collector are
retransmitted by the router.
SCTP is a reliable message-oriented transport layer protocol, which allows data to be transmitted
between two end-points in a reliable, partially reliable, or unreliable manner. An SCTP session consists
of an association between two end-points, which may contain one or more logical channels called
streams. SCTP’s stream based transmission model facilitates the export of a mix of different data types,
such as NetFlow templates and NetFlow data, over the same connection. The maximum number of
inbound and outbound streams supported by an end-point is negotiated during the SCTP association
initialization process.
When you configure the NetFlow Version 9 Export and NetFlow Reliable Export features, NetFlow
creates a minimum of two streams—stream 0 for templates and options, and one or more streams for
carrying data, as required. The following commands are not applicable when you configure the NetFlow
Version 9 Export and NetFlow Reliable Export features together because NetFlow Reliable Export
export connections use SCTP reliable stream 0 for NetFlow Version 9 Export, and these commands apply
only to NetFlow export connections that use UDP:
•
ip flow-export template refresh-rate
•
ip flow-export template timeout-rate
•
ip flow-export template options refresh-rate
•
ip flow-export template options timeout-rate
When more than one cache (main cache and one or more aggregation caches) is exporting data, each
cache creates its own streams with their own configured reliability levels. For example, you can
configure the main cache to use SCTP in full reliability mode and the NetFlow prefix aggregation cache
to use partial reliability mode to send messages to the same collector using the same SCTP port.
Note
When you are using SCTP as the transport protocol for exporting NetFlow traffic, the traffic is usually
referred to as messages instead of datagrams because SCTP is a message-oriented protocol. When you
are using UDP as the transport protocol for exporting NetFlow traffic, the traffic is usually referred to
as datagrams because UDP is a datagram-oriented protocol.
Security
SCTP contains several built-in features to counter many common security threats such as the syn-flood
type of DoS attack.
6
NetFlow Reliable Export With SCTP
Information About NetFlow Reliable Export With SCTP
SCTP uses the following techniques to resist flooding attacks:
•
A four-way start-up handshake is used to ensure that anyone opening an association is a genuine
caller, rather the someone performing a 'syn-flood' type of DoS attack.
•
Cookies are used to defer commitment of resources at the responding SCTP node until the
handshake is completed.
•
Verification Tags are used to prevent insertion of extraneous packets into the flow of an established
association.
Reliability Options
SCTP allows data to be transmitted between two end-points (a router running NetFlow SCTP export and
a collector that is receiving and acknowledging the SCTP messages) in a reliable manner. In addition to
the default behavior of full reliability, SCTP can be configured for partially-reliable or unreliable
transmission for applications that do not require full reliability.
When SCTP is operating in full reliability mode, it uses a selective-acknowledgment scheme to
guarantee the ordered delivery of messages. The SCTP protocol stack buffers messages until their receipt
has been acknowledged by the receiving end-point. (collector). SCTP has a congestion control
mechanism that can be used to limit how much memory is consumed by SCTP for buffering packets.
If a stream is specified as unreliable, then the packet is simply sent once and not buffered on the exporter.
If the packet is lost enroute to the receiver, the exporter cannot retransmit it.
When a stream is specified as partially-reliable a limit is placed on how much memory should be
dedicated to storing un-acknowledged packets. The limit on how much memory should be dedicated to
storing unacknowledged packets is configurable by means of the buffer-limit limit command. If the limit
on how much memory should be dedicated to storing unacknowledged packets is exceeded and the router
attempts to buffer another packet, the oldest unacknowledged packet is discarded. When SCTP discards
the oldest unacknowledged packet, a message called a forward-tsn (transmit sequence number) is sent
to the collector to indicate that this packet will not be received. This prevents NetFlow from consuming
all the free memory on a router when a situation has arisen which requires many packets to be buffered,
for example when SCTP is experiencing long response times from an SCTP peer connection.
When SCTP is operating in partially reliable mode, the limit on how much memory should be dedicated
to storing un-acknowledged packets should initially be set as high as possible. The limit can be reduced
if other processes on the router begin to run out of memory. Deciding on the best value for the limit
involves a trade-off between avoiding starving other processes of the memory that they require to operate
and dropping SCTP messages that have not been acknowledged by the collector.
Unreliable SCTP can be used when the collector that you are using doesn’t support UDP as a transport
protocol for receiving NetFlow export datagrams and you do not want to allocate the resources on your
router required to provide reliable, or partially reliable, SCTP connections.
Congestion Avoidance
SCTP uses congestion avoidance algorithms that are similar to those for TCP. An SCTP end-point
advertises the size of its receive window (rWnd) to ensure that a sender cannot flood it with more
messages than it can store in its input queues.
Each SCTP sender also maintains a congestion window (cWnd), which determines the number of
unacknowledged packets that can be outstanding at a given time. SCTP uses the same 'slow-start'
algorithm as TCP, in which it starts with a small cWnd and gradually increases it until it reaches its
optimum size.
Whenever a packet isn't acknowledged within the given timeout period, the value of cWnd is halved. This
method of congestion avoidance is known as added increase / multiplicative decrease and has been
shown to be the most effective congestion avoidance algorithm in most circumstances.
7
NetFlow Reliable Export With SCTP
Information About NetFlow Reliable Export With SCTP
SCTP also employs the fast-retransmit algorithm whereby it retransmits a message if it receives
acknowledgments from four messages which were sent after the message in question. This is preferable
to waiting for the timeout period to elapse and triggering a retransmit of the message.
Options for Backup Collectors
You can configure a backup collector for SCTP. It is used as a message destination in the event that the
primary collector becomes unavailable. When connectivity with the primary collector has been lost, and
a backup collector is configured, SCTP begins using the backup collector. The default period of time that
SCTP waits until it starts using the backup collector is 25 milliseconds (msec). You can configure a
different value for interval with the fail-over time command.
The router sends periodic SCTP heartbeat messages to the SCTP collectors that you have configured.
The router uses the SCTP heartbeat message acknowledgements from the collectors to monitor the status
of each collector. This allows an application, such as NetFlow, to be quickly informed when connectivity
to a collector is lost.
You can configure SCTP backup in fail-over or redundant mode. When the router is configured with
SCTP backup in fail-over mode, the router waits to activate the association with the backup collector
until the router has not received acknowledgements for the SCTP heartbeat messages from the primary
collector for the time specified by the fail-over time command (or the default of 25 msec if this
parameter has not been modified).
Note
SCTP retransmits messages that have not been acknowledged three times. The router will initiate
fail-over after three retransmissions of the same message are not acknowledged by the primary collector.
When the router is configured with SCTP backup in redundant mode, the router activates the association
with the backup collector immediately, and if NetFlow v9 export is configured the router sends the
(options) templates in advance. The router will not start sending other SCTP messages to a backup
collector in redundant mode until the router has not received acknowledgments for the SCTP heartbeat
messages from the primary collector for the time specified by the fail-over time command. Fail-over
mode is the preferred method when the backup collector is on the end of an expensive lower-bandwidth
link such as ISDN.
During the time that SCTP is using the backup collector, SCTP continues to try to restore the association
with the primary collector. This goes on until connectivity is restored or the primary SCTP collector is
removed from the configuration.
When connectivity to the primary collector is available again, the router waits for a period of time before
reverting to using it as the primary destination. You configure the value of the period of time that SCTP
waits until reverting to the primary collector with the restore-time time command. The default period
of time that SCTP waits until it reverts to the primary collector is 25 sec.
Under either fail-over mode any records which have been queued between losing connectivity with the
primary destination and establishing the association with the backup collector might be lost. A count is
maintained of how many records were lost. It can be viewed with the show ip flow export sctp verbose
command.
To avoid a flapping SCTP association with a collector (the SCTP association goes up and down in quick
succession), the time period configured with the restore-time time command should be greater than the
period of a typical connectivity problem. For example, your router is configured to use IP fast
convergence for its routing table and you have a LAN interface that is going up and down repeatedly
(flapping). That causes the IP route to the primary collector to be added and removed from the routing
table repeatedly (route flapping) every 2000 msec (2 sec). you need to configure the restore time for a
value greater than 2000 msecs.
8
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
The backup connection uses stream 0 for sending templates, options templates, and option data record.
The data stream(s) inherit the reliability settings of the primary connection.
Export to Multiple Collectors
You can configure your networking device to export NetFlow data to a maximum of two export
destinations (collectors) per cache (main and aggregation caches), using any combination of UDP and
SCTP. A destination is identified by a unique combination of hostname or IP address and port number
or port type. Table 1 shows examples of permitted multiple NetFlow export destinations for each cache.
Table 1
Examples of Permitted Multiple NetFlow Export Destinations for Each Cache
First Export Destination
Second Export Destination
ip flow-export 10.25.89.32 100 udp
ip flow-export 10.25.89.32 285 udp
ip flow-export 10.25.89.32 100 udp
ip flow-export 172.16.89.32 100 udp
ip flow-export 10.25.89.32 100 udp
ip flow-export 172.16.89.32 285 udp
ip flow-export 10.25.89.32 100 udp
ip flow-export 10.25.89.32 100 sctp
ip flow-export 10.25.89.32 100 sctp
ip flow-export 10.25.89.32 285 sctp
ip flow-export 10.25.89.32 100 sctp
ip flow-export 172.16.89.32 100 sctp
ip flow-export 10.25.89.32 100 sctp
ip flow-export 172.16.89.32 285 sctp
The most common use of the multiple-destination feature is to send the NetFlow cache entries to two
different destinations for redundancy. Therefore, in most cases the second destination IP address is not
the same as the first IP address. The port numbers can be the same when you are configuring two unique
destination IP addresses. If you want to configure both instances of the command to use the same
destination IP address, you must use unique port numbers. You receive a warning message when you
configure the two instances of the command with the same IP address. The warning message is,
“%Warning: Second destination address is the same as previous address <ip-address>”.
SCTP Support For Export Formats
SCTP based reliable transport is available for all NetFlow export formats: Versions 1, 5, 8 and 9.
How to Configure NetFlow Reliable Export with SCTP
You can configure two primary SCTP export destinations (collectors) and two backup SCTP export
destinations for each NetFlow cache (main cache and aggregation caches). The backup SCTP export
destinations inherit the reliability characteristics of the primary SCTP export destination. For example,
if you configure partial reliability with a buffer limit of 2000 packets for the primary SCTP export
destination, the backup SCTP destination also uses partial reliability and a buffer limit of 2000 packets.
You can use several permutations when you configure NetFlow Reliable Export With SCTP. The most
basic configuration requires only one SCTP export destination. The other tasks below explain how to
configure some of the more common permutations of NetFlow Reliable Export With SCTP.
•
Configuring NetFlow SCTP Export for One Export Destination, page 10
•
Configuring NetFlow SCTP Export for One Export Destination with Partial Reliability, page 11
•
Configuring NetFlow SCTP Export for One Export Destination with No Reliability, page 12
•
Configuring NetFlow SCTP Export for One Export Destination and One Backup Export Destination,
page 13
9
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
•
Configuring NetFlow SCTP Export for One Export Destination and One Backup Export Destination
With Fail-Over Mode Backup, page 15
•
Configuring NetFlow SCTP Export for Two Export Destinations and Two Backup Export
Destinations, page 17
•
Configuring NetFlow SCTP Export for One Fully Reliable and One Partially Reliable Export
Destination, page 19
•
Configuring NetFlow SCTP Export for the NetFlow Source-Prefix Aggregation Cache, page 20
•
Verifying NetFlow Reliable Export With SCTP, page 22
Configuring NetFlow SCTP Export for One Export Destination
This is the most basic NetFlow SCTP export configuration. This NetFlow SCTP export configuration
uses full reliability.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
end
5.
show ip flow export sctp verbose
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-export destination
[ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
10
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
Step 5
show ip flow export sctp verbose
Displays the status and statistics for NetFlow SCTP export. Reliability is set to the default of full.
Router# show ip flow export sctp verbose
IPv4 main cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: redundant
4 flows exported in 4 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
Configuring NetFlow SCTP Export for One Export Destination with Partial
Reliability
This NetFlow SCTP export configuration uses partial reliability.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
reliability partial buffer-limit limit
5.
end
6.
show ip flow export sctp verbose
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-export destination
[ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
11
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
reliability partial buffer-limit limit
Configures partial reliability for this SCTP export destination and sets the packet buffer limit to 3000.
Router(config-flow-export-sctp)# reliability partial buffer-limit 3000
Step 5
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 6
show ip flow export sctp verbose
Displays the status and statistics for NetFlow SCTP export. Reliability is now set to partial.
Router# show ip flow export sctp verbose
Pv4 main cache exporting to 172.16.12.200, port 100, partial
status: connected
backup mode: redundant
11 flows exported in 11 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
Configuring NetFlow SCTP Export for One Export Destination with No
Reliability
Reliability is disabled in this NetFlow SCTP export configuration.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SUMMARY STEPS
12
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
reliability none
5.
end
6.
show ip flow export sctp verbose
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-export destination [ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
reliability none
Configures partial reliability for this SCTP export destination and sets the packet buffer limit to 3000.
Router(config-flow-export-sctp)# reliability none
Step 5
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 6
show ip flow export sctp verbose
Displays the status and statistics for NetFlow SCTP export. Reliability is now set to none.
Router# show ip flow export sctp verbose
Pv4 main cache exporting to 172.16.12.200, port 100, none
status: connected
backup mode: redundant
15 flows exported in 15 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
Configuring NetFlow SCTP Export for One Export Destination and One Backup
Export Destination
This NetFlow SCTP export configuration uses full reliability, a backup SCTP export destination, and
redundant mode backup.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
13
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
backup destination [ip-address | hostname] sctp-port
5.
end
6.
show ip flow export sctp verbose
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-export destination [ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
backup destination [ip-address | hostname] sctp-port
Configures an SCTP backup destination using SCTP on port 200.
Router(config-flow-export-sctp)# backup destination 192.168.247.198 200
Step 5
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 6
show ip flow export sctp verbose
Displays the status and statistics for NetFlow SCTP export. Backup mode is redundant. The association
with the SCTP backup export destination is active (connected). The SCTP backup export destination is
not being used because the primary export destination is still active (connected).
14
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
Router# show ip flow export sctp verbose
IPv4 main cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: redundant
35 flows exported in 35 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.247.198, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
Configuring NetFlow SCTP Export for One Export Destination and One Backup
Export Destination With Fail-Over Mode Backup
This NetFlow SCTP export configuration uses full reliability, a backup SCTP export destination, and
fail-over mode backup.
Note
The backup fail-over and restore times are modified here so that you can see an example of how to
configure these commands. The values used in this example might not be suitable for your network. If
you want to override the default values for the fail-over and restore times you need to analyze the
performance of your network and the collector that you are using to determine values that are appropriate
for your network.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
backup destination [ip-address | hostname] sctp-port
5.
backup mode fail-over
6.
backup fail-over fail-over-time
7.
backup restore-time restore-time
8.
end
9.
show ip flow export sctp verbose
15
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-export destination [ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
backup destination [ip-address | hostname] sctp-port
Configures an SCTP backup destination using SCTP on port 200.
Router(config-flow-export-sctp)# backup destination 192.168.247.198 200
Step 5
backup mode fail-over
Configures the router to fail-over mode for the backup export destination.
Router(config-flow-export-sctp)# backup mode fail-over#
Step 6
backup fail-over fail-over-time
The length of time that the router will wait until failing over to the backup SCTP export destination has
been increased to 3500 msec.
Router(config-flow-export-sctp)# backup fail-over 3500
Step 7
backup restore-time restore-time
The length of time that the router will wait until reverting to the primary SCTP export destination has
been increased to 1500 msecs.
Router (config)# backup restore-time 1500
Step 8
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 9
show ip flow export sctp verbose
Displays the status and statistics for NetFlow SCTP export. Backup mode is fail-over. The association
with the SCTP backup export destination is not active (not connected) because NetFlow SCTP export
waits to activate the association with the backup destination until the primary export destination is no
longer available.
Router# show ip flow export sctp verbose
IPv4 main cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: fail-over
114 flows exported in 93 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 3500 milli-seconds
restore time:
1500 seconds
16
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
backup: 192.168.247.198, port 200
status: not connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
Configuring NetFlow SCTP Export for Two Export Destinations and Two Backup
Export Destinations
This configuration is the most basic SCTP export configuration that uses multiple export destinations.
Note
You can configure a maximum of two export destinations for every NetFlow cache.
Working with Multiple SCTP Export Destinations
Each SCTP export destination has its own area in the configuration file for the options that you can
configure for it such as fail-over mode, fail-over timers and reliability. Therefore you must make certain
that the last SCTP export destination that you entered in the router’s configuration is the SCTP export
destination that you want to modify.
For example, if you enter these commands in this order:
•
ip flow-export destination 172.16.12.200 100 sctp
•
ip flow-export destination 172.16.45.57 100 sctp
•
backup destination 192.168.100.2 200
The backup destination 192.168.100.2 200 is assigned to the ip flow-export destination 172.16.45.57
100 sctp command.
Tip
To change the SCTP export destination that you are modifying, reenter the command line for the SCTP
export destination that you want to modify.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
backup destination [ip-address | hostname] sctp-port
5.
ip flow-export destination [ip-address | hostname] port sctp
17
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
6.
backup destination [ip-address | hostname] sctp-port
7.
end
8.
show ip flow export sctp verbose
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-export destination [ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
backup destination [ip-address | hostname] sctp-port
Configures an SCTP backup destination using SCTP on port 200.
Router(config-flow-export-sctp)# backup destination 192.168.247.198 200
Step 5
ip flow-export destination
[ip-address | hostname] port sctp
Configures a second export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.45.57 100 sctp
Step 6
backup destination [ip-address | hostname] sctp-port
Configures a second SCTP backup destination using SCTP on port 200.
Router(config-flow-export-sctp)# backup destination 192.168.100.2 200
Step 7
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 8
show ip flow export sctp verbose
Displays the status and statistics for the two primary and backup NetFlow SCTP export destinations.
Reliability is set to the default of full.
Router# show ip flow export sctp verbose
IPv4 main cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: redundant
219 flows exported in 176 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 3500 milli-seconds
restore time:
10 seconds
backup: 192.168.247.198, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
18
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
0 packets dropped due to lack of SCTP resources
IPv4 main cache exporting to 172.16.45.57, port 100, full
status: connected
backup mode: redundant
66 flows exported in 47 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.100.2, port 200
status: connected
fail-overs: 1
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
Configuring NetFlow SCTP Export for One Fully Reliable and One Partially
Reliable Export Destination
This SCTP export configuration uses two SCTP export destinations. One of the export destinations uses
full reliability and the other export destination uses partial reliability.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-export destination [ip-address | hostname] port sctp
4.
ip flow-export destination [ip-address | hostname] port sctp
5.
reliability partial buffer-limit limit
6.
end
7.
show ip flow export sctp verbose
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
19
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
Step 3
ip flow-export destination [ip-address | hostname] port sctp
Configures an export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.12.200 100 sctp
Step 4
ip flow-export destination [ip-address | hostname] port sctp
Configures a second export destination using SCTP on port 100.
Router (config)# ip flow-export destination 172.16.45.57 100 sctp
Step 5
reliability partial buffer-limit limit
Configures partial reliability for this SCTP export destination and sets the packet buffer limit to 3000.
Router(config-flow-export-sctp)# reliability partial buffer-limit 3000
Step 6
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 7
show ip flow export sctp verbose
Displays the status and statistics for NetFlow export with SCTP. Reliability is set to full for SCTP export
destination 172.16.12.200 and to partial SCTP export destination 172.16.45.57.
Router# show ip flow export sctp verbose
IPv4 main cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: redundant
229 flows exported in 186 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 3500 milli-seconds
restore time:
10 seconds
backup: 192.168.247.198, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
IPv4 main cache exporting to 172.16.45.57, port 100, partial
status: connected
backup mode: redundant
76 flows exported in 57 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.100.2, port 200
status: connected
fail-overs: 1
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
Configuring NetFlow SCTP Export for the NetFlow Source-Prefix Aggregation
Cache
This SCTP export example shows how to configure NetFlow SCTP export for the NetFlow source prefix
aggregation cache.
20
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
Note
You can configure a maximum of two export destinations for every NetFlow cache.
Working With NetFlow Aggregation caches and SCTP Export Destinations
When you enter NetFlow aggregation cache configuration mode in the router the current router prompt
changes to reflect this mode.
For example, if the current router prompt is, Router(config)# and you enter the ip flow-aggregation
cache prefix command, the router prompt is changed to the NetFlow aggregation cache configuration
prompt of Router(config-flow-cache)#.
You need to pay close attention when you are configuring NetFlow SCTP export options for NetFlow
aggregation caches because the NetFlow aggregation cache configuration prompt is changed to the
NetFlow SCTP export prompt when you enter a NetFlow SCTP export command in NetFlow aggregation
cache configuration mode, even though you are still working in NetFlow aggregation cache
configuration mode.
For example, if your current prompt is the NetFlow aggregation cache configuration prompt,
Router(config-flow-cache)#, and you enter the export destination 172.16.12.200 100 sctp command,
the router prompt will change to the NetFlow SCTP export configuration mode prompt,
Router(config-flow-export-sctp)#. The NetFlow SCTP export commands that you configure are assigned
to the NetFlow aggregation cache that you are modify with NetFlow SCTP export options.
Tip
Use the configuration in the “Configuration Examples for NetFlow Reliable Export With SCTP” section
on page 25 to practice using the different configuration modes.
Prerequisites
You must have NetFlow enabled on at least one interface in your router before you can export NetFlow
data.
You must have a NetFlow collector in your network that supports NetFlow SCTP export.
SCTP Export for NetFlow Aggregation Caches
All of the NetFlow SCTP options that are available for the main NetFlow cache are also available in
NetFlow Aggregation cache mode.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip flow-aggregation cache aggregation-cache-type
4.
enable
5.
export destination [ip-address | hostname] port sctp
6.
end
7.
show ip flow export sctp verbose
21
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode.
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Router# configure terminal
Step 3
ip flow-aggregation cache aggregation-cache-type
Enters NetFlow aggregation cache mode for the cache type.
Router (config)# ip flow-aggregation cache source-prefix
Step 4
enable
Activates the NetFlow aggregation cache.
Router(config-flow-cache)# enable
Step 5
export destination [ip-address | hostname] port sctp
Configures an export destination using SCTP for the aggregation cache.
Router (config-flow-cache)# export destination 172.16.12.200 100 sctp
Step 6
end
Returns to privileged EXEC mode.
Router(config-flow-export-sctp)# end
Step 7
show ip flow export sctp verbose
Displays the status and statistics for NetFlow export with SCTP.
Router# show ip flow export sctp verbose
source-prefix cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: redundant
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
Verifying NetFlow Reliable Export With SCTP
The show ip flow export sctp [verbose] command provides information on the status and statistics of
the options that you have configured for the NetFlow Reliable Export With SCTP feature.
Cisco IOS also provides commands for monitoring and troubleshooting the status and statistics for all
of the SCTP features (including NetFlow Reliable Export With SCTP) that you have configured on the
networking device. Refer to the Stream Control Transmission Protocol (SCTP), Release 2 configuration
guide
22
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t8/ft_sctp2.htm
for more information on interpreting the output from these commands, and the other commands that are
available for monitoring and troubleshooting SCTP.
SUMMARY STEPS
1.
show ip sctp association list
2.
show ip sctp association parameters association id
3.
show ip sctp errors
4.
show ip sctp instances
5.
show ip sctp statistics
DETAILED STEPS
Step 1
show ip sctp association list
Shows the list of SCTP associations.
Router# show ip sctp association list
** SCTP Association List **
AssocID: 0, Instance ID: 0
Current state: ESTABLISHED
Local port: 51882, Addrs: 172.16.6.2
Remote port: 100, Addrs: 172.16.12.200
AssocID: 1, Instance ID: 1
Current state: ESTABLISHED
Local port: 59004, Addrs: 172.16.6.2
Remote port: 200, Addrs: 192.168.247.198
Step 2
show ip sctp association parameters association-id
Displays the current parameters for the association ID.
Router# show ip sctp association parameters 0
** SCTP Association Parameters **
AssocID: 0 Context: 1 InstanceID: 0
Assoc state: ESTABLISHED Uptime: 00:19:44.504
Local port: 51882
Peers Adaption layer indication is NOT set
Local addresses: 172.16.6.2
Remote port: 100
Primary dest addr: 172.16.12.200
Effective primary dest addr: 172.16.12.200
Destination addresses:
172.16.12.200:
State: ACTIVE(CONFIRMED)
Heartbeats: Enabled
Timeout: 500 ms
RTO/RTT/SRTT: 5000/0/3 ms
TOS: 0 MTU: 1500
cwnd: 3000 ssthresh: 9000 outstand: 0
Num retrans: 0 Max retrans: 2 Num times failed: 0
Local vertag: DAF7029F Remote vertag: A3923131
Num inbound streams: 20 outbound streams: 20
23
NetFlow Reliable Export With SCTP
How to Configure NetFlow Reliable Export with SCTP
Max assoc retrans: 2 Max init retrans: 2
CumSack timeout: 200 ms Bundle timeout: 100 ms
Min RTO: 5000 ms Max RTO: 5000 ms
Max Init RTO (T1): 1000 ms
LocalRwnd: 9000 Low: 9000
RemoteRwnd: 9000 Low: 8936
Congest levels: 0 current level: 0 high mark: 1
Step 3
show ip sctp errors
Shows any SCTP errors that have occurred.
Router# show ip sctp errors
** SCTP Error Statistics **
No SCTP errors logged.
Step 4
show ip sctp instances
Shows the details and status for the SCTP instances.
Router# show ip sctp instances
** SCTP Instances **
Instance ID: 0 Local port: 51882 State: available
Local addrs: 172.16.6.2
Default streams inbound: 20 outbound: 20
Adaption layer indication is not set
Current associations: (max allowed: 6)
AssocID: 0 State: ESTABLISHED Remote port: 100
Dest addrs: 172.16.12.200
Instance ID: 1 Local port: 59004 State: available
Local addrs: 172.16.6.2
Default streams inbound: 20 outbound: 20
Adaption layer indication is not set
Current associations: (max allowed: 6)
AssocID: 1 State: ESTABLISHED Remote port: 200
Dest addrs: 192.168.247.198
Step 5
show ip sctp statistics
Shows the SCTP overall statistics:
Router# show ip sctp statistics
** SCTP Overall Statistics **
Control Chunks
Sent: 615 Rcvd: 699
Data Chunks Sent
Total: 57 Retransmitted: 0
Ordered: 57 Unordered: 0
Total Bytes: 3648
Data Chunks Rcvd
Total: 0 Discarded: 0
Ordered: 0 Unordered: 0
Total Bytes: 0
Out of Seq TSN: 0
SCTP Dgrams
Sent: 671 Rcvd: 699
ULP Dgrams
Sent: 57 Ready: 0 Rcvd: 0
24
NetFlow Reliable Export With SCTP
Configuration Examples for NetFlow Reliable Export With SCTP
Additional Stats
Assocs Currently Estab: 2
Active Estab: 2 Passive Estab: 0
Aborts: 0 Shutdowns: 0
T1 Expired: 1 T2 Expired: 0
Configuration Examples for NetFlow Reliable Export With SCTP
The following example includes these NetFlow accounting and NetFlow SCTP export features:
•
NetFlow ingress and egress accounting
•
Multiple SCTP export destinations for the Main NetFlow cache with backup destinations
•
Multiple SCTP export destinations for the NetFlow protocol-port aggregation cache using partial
reliability and fail-over mode backup destinations
•
Multiple SCTP export destinations for the NetFlow bgp-nexthop-tos aggregation cache with
reliability disabled and redundant mode backup destinations
Router# show running-config
.
.
.
interface Ethernet0/0.1
ip address 172.16.6.2 255.255.255.0
ip flow ingress
!
!
interface Ethernet1/0.1
ip address 172.16.7.1 255.255.255.0
ip flow egress
!
ip flow-export destination 172.16.45.57 100 sctp
reliability partial buffer-limit 3000
backup destination 192.168.100.2 200
!
ip flow-export destination 172.16.12.200 100 sctp
reliability partial buffer-limit 3000
backup destination 192.168.247.198 200
!
ip flow-aggregation cache protocol-port
export destination 172.16.12.200 100 sctp
reliability partial buffer-limit 3000
backup destination 192.168.247.198 200
backup mode fail-over
export destination 172.16.45.57 100 sctp
reliability partial buffer-limit 3000
backup destination 192.168.100.2 200
backup mode fail-over
enabled
!
ip flow-aggregation cache bgp-nexthop-tos
export version 9
export destination 172.16.12.200 100 sctp
backup destination 192.168.247.198 200
export destination 172.16.45.57 100 sctp
backup destination 192.168.100.2 200
enabled
!
25
NetFlow Reliable Export With SCTP
Configuration Examples for NetFlow Reliable Export With SCTP
The display output of the show ip flow export sctp verbose command shows the status and statistics for
this configuration example:
Router# show ip flow export sctp verbose
IPv4 main cache exporting to 172.16.45.57, port 100, partial
status: connected
backup mode: redundant
104 flows exported in 84 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.100.2, port 200
status: connected
fail-overs: 2
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
IPv4 main cache exporting to 172.16.12.200, port 100, partial
status: connected
backup mode: redundant
104 flows exported in 84 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.247.198, port 200
status: connected
fail-overs: 1
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
protocol-port cache exporting to 172.16.12.200, port 100, partial
status: connected
backup mode: fail-over
19 flows exported in 18 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.247.198, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
protocol-port cache exporting to 172.16.45.57, port 100, partial
status: connected
backup mode: fail-over
15 flows exported in 15 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.100.2, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
bgp-nexthop-tos cache exporting to 172.16.12.200, port 100, full
status: connected
backup mode: redundant
20 flows exported in 10 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.247.198, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
26
NetFlow Reliable Export With SCTP
Additional References
bgp-nexthop-tos cache exporting to 172.16.45.57, port 100, full
status: connected
backup mode: redundant
20 flows exported in 10 sctp messages.
0 packets dropped due to lack of SCTP resources
fail-over time: 25 milli-seconds
restore time:
25 seconds
backup: 192.168.100.2, port 200
status: connected
fail-overs: 0
0 flows exported in 0 sctp messages.
0 packets dropped due to lack of SCTP resources
Additional References
The following sections provide references related to the NetFlow Reliable Export with SCTP feature.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
27
NetFlow Reliable Export With SCTP
Additional References
Related Topic
Document Title
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFC
Title
RFC 3954
Cisco Systems NetFlow Services Export Version 9
RFC2690
Stream Control Transmission Protocol
RFC 3578
Stream Control Transmission Protocol–Partial Reliability Extension
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
28
NetFlow Reliable Export With SCTP
Feature Information for NetFlow Reliable Transport Using SCTP
Feature Information for NetFlow Reliable Transport Using SCTP
Table 2 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the “Cisco IOS NetFlow
Features Roadmap” module.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 2
Table 2 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for NetFlow Reliable Transport Using SCTP
Feature Name
Releases
Feature Configuration Information
NetFlow Reliable Export With SCTP
12.4(4)T
The NetFlow Reliable Export With SCTP feature provides
a more robust and flexible method for exporting NetFlow
data to collectors than UDP, which was the only transport
option prior to the introduction of this feature.
NetFlow Reliable Export With SCTP has the following
benefits:
•
Backup destinations—You can configure backup
destinations for every SCTP export destination. The
backup destinations can use redundant mode (always
connected) and fail-over mode (connect as required).
Fail-over mode is more suitable for backup destinations
that are reachable over expensive dial-up links such as
ISDN.
•
Reliability—NetFlow SCTP provides a very reliable
level of transport that has error correction and flow
control. You can modify the level of reliability for each
SCTP export destination depending on the importance
of the data that you are exporting.
The following sections provide information about this
feature:
•
NetFlow Reliable Export With SCTP
•
How to Configure NetFlow Reliable Export with SCTP
The following commands were introduced or modified by
this feature: ip flow export, show ip flow export, and
export.
29
NetFlow Reliable Export With SCTP
Glossary
Glossary
CEF—Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network
performance and scalability for networks with large and dynamic traffic patterns.
BGP—Border Gateway Protocol. Interdomain routing protocol that replaces Exterior Border Gateway
Protocol (EBGP). A BGP system exchanges reachability information with other BGP systems. BGP is
defined by RFC 1163.
BGP next hop—IP address of the next hop to be used to reach a certain destination.
data record—Provides information about an IP flow that exists on the device that produced an export
packet. Each group of data records (meaning each data flowset), refers to a previously transmitted
template ID, which can be used to parse the data within the records.
dCEF—distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
export packet—A type of packet built by a device (for example, a router) with NetFlow services
enabled. The packet is addressed to another device (for example, the NetFlow Collection Engine). The
packet contains NetFlow statistics. The other device processes the packet (parses, aggregates, and stores
information on IP flows).
fast switching—A Cisco feature in which a route cache is used to expedite packet switching through a
router.
flow—A unidirectional stream of packets between a given source and destination, each of which is
defined by a network-layer IP address and transport-layer source and destination port numbers.
flowset—A collection of flow records that follow the packet header in an export packet. A flowset
contains information that must be parsed and interpreted by the NetFlow Collection Engine. There are
two different types of flowsets: template flowsets and data flowsets. An export packet contains one or
more flowsets, and both template and data flowsets can be mixed in the same export packet.
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—A Cisco application that is used with
NetFlow on Cisco routers and Catalyst 5000 series switches. The NetFlow Collection Engine collects
packets from the router that is running NetFlow and decodes, aggregates, and stores them. You can
generate reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means of carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
options data record—A special type of data record used in the NetFlow process. It is based on an
options template and has a reserved template ID that provides information about the NetFlow process
itself.
options template—A type of template record used to communicate the format of data related to the
NetFlow process.
30
NetFlow Reliable Export With SCTP
Glossary
packet header—First part of an export packet. It provides basic information about the packet (such as
the NetFlow version, number of records contained in the packet, and sequence numbering) so that lost
packets can be detected.
SCTP—Stream Control Transmission Protocol. The Stream Control Transmission Protocol (SCTP) is a
transport layer protocol defined in 2000 by the IETF Signaling Transport (SIGTRAN) working group.
The protocol is defined in RFC 2960, and an introductory text is provided by RFC 3286.
template flowset—A collection of template records that are grouped in an export packet.
template ID—A unique number that distinguishes a template record produced by an export device from
other template records produced by the same export device. A NetFlow Collection Engine application
can receive export packets from several devices. You should be aware that uniqueness is not guaranteed
across export devices. The NetFlow Collection Engine should cache the address of the export device that
produced the template ID in order to enforce uniqueness.
template record—Defines the format of subsequent data records that might be received in current or
future export packets. A template record within an export packet does not necessarily indicate the format
of data records within that same packet. A NetFlow Collection Engine application must cache any
template records received and then parse any data records it encounters by locating the appropriate
template record in the cache.
CCDE, CCENT, CCSI, Cisco Eos, Cisco Explorer, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Nurse Connect, Cisco Pulse,
Cisco SensorBase, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco TrustSec, Cisco Unified Computing System, Cisco WebEx,
DCE, Flip Channels, Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to
the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed
(Stylized), Cisco Store, Flip Gift Card, and One Million Acts of Green are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS,
Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert
logo, Cisco IOS, Cisco Lumin, Cisco Nexus, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity,
Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center, Explorer, Follow Me Browsing, GainMaker, iLYNX, IOS,
iPhone, IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking
Academy, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect, ROSA, SenderBase, SMARTnet,
Spectrum Expert, StackWise, WebEx, and the WebEx logo are registered trademarks of Cisco and/or its affiliates in the United States and certain
other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (1002R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2008 Cisco Systems, Inc. All rights reserved.
31
NetFlow Reliable Export With SCTP
Glossary
32
Detecting and Analyzing Network Threats With
NetFlow
First Published: June 19, 2006
Last Updated: October 02, 2009
This document contains information about and instructions for detecting and analyzing network threats
such as denial of service attacks (DoS) through the use of the following NetFlow features:
•
NetFlow Layer 2 and Security Monitoring Exports—This feature improves your ability to detect and
analyze network threats such as denial of service attacks (DoS) by adding 9 fields that NetFlow can
capture the values from.A few examples are:
– IP Time-to-Live field
– Packet length field
– ICMP type and code fields
•
NetFlow Dynamic Top Talkers CLI—This feature gives you an overview of the highest volume
traffic in your network by aggregating flows on a common field. For example, you can aggregate all
of the flows for a destination network by aggregating them on the destination prefix. There are over
20 fields from flows that you can aggregate the highest volume traffic on. A few examples are:
– Source or destination IP address
– Source or destination prefix
– Source or destination port
– ICMP type and code
•
NetFlow Top Talkers—This feature gives you a more detailed view of the traffic in your network
than the NetFlow Dynamic Top Talkers CLI feature because it looks at individual flows. You use the
NetFlow Dynamic Top Talkers CLI feature to quickly identify high volume traffic of interest. You
use the NetFlow Top Talkers feature to obtain more detailed information on each of the flows in the
high volume traffic.
•
NetFlow Input Filters—This feature tracks a specific subset of NetFlow traffic for the purpose of
class-based traffic analysis and monitoring. This feature is used in conjunction with the Top Talkers
feature to help you focus your analysis on the traffic that might be a network threat such as a DoS
attack.
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Detecting and Analyzing Network Threats With NetFlow
Finding Feature Information
•
Random Sampled NetFlow—This feature is typically used for statistical sampling of network traffic
for traffic engineering or capacity planning purposes. It is used in the context of monitoring and
analyzing network threats because it can be used to reduce the impact on the router using NetFlow
to monitor traffic that might be a network threat, such as a DoS attack.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Detecting and Analyzing Network Threats With NetFlow”
section on page 56.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Detecting and Analyzing Network Threats With NetFlow, page 2
•
Information About Detecting and Analyzing Network Threats With NetFlow, page 2
•
How to Configure and Use NetFlow to Detect and Analyze Network Threats, page 19
•
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow, page 40
•
Additional References, page 54
•
Feature Information for Detecting and Analyzing Network Threats With NetFlow, page 56
•
Glossary, page 58
Prerequisites for Detecting and Analyzing Network Threats
With NetFlow
Before you can use NetFlow for detecting and analyzing network threats you need to understand
NetFlow and how to configure your router to capture IP traffic status and statistics using NetFlow. See
the Cisco IOS NetFlow Overview and Configuring NetFlow and NetFlow Data Export modules for more
details.
NetFlow and Cisco Express Forwarding (CEF) or distributed CEF (dCEF) must be configured on your
system before you enable NetFlow.
Information About Detecting and Analyzing Network Threats
With NetFlow
To detect and analyze network threats with NetFlow, you should understand the following concepts:
•
2
NetFlow Layer 2 and Security Monitoring, page 3
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
•
NetFlow Top Talkers, page 13
•
Filtering and Sampling of NetFlow Traffic, page 17
NetFlow Layer 2 and Security Monitoring
The Layer 3 and Layer 2 fields supported by the NetFlow Layer 2 and Security Monitoring Exports
feature increase the amount of information that can be obtained by NetFlow about the traffic in your
network. You can use this new information for applications such as traffic engineering and usage-based
billing.
The Layer 3 IP header fields that the NetFlow Layer 2 and Security Monitoring Exports feature captures
the values of are:
•
Time-to-Live field
•
Packet Length field
•
ID field
•
ICMP type and code fields
•
Fragment offset
See the Layer 3 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports section
for more information on these Layer 3 fields.
The Layer 2 fields that NetFlow Layer 2 and Security Monitoring Exports feature captures the values of
are:
•
Source MAC address field from frames that are received by the NetFlow router
•
Destination MAC address field from frames that are transmitted by the NetFlow router
•
VLAN ID field from frames that are received by the NetFlow router
•
VLAN ID field from frames that are transmitted by the NetFlow router
•
Interface names
See the Layer 2 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports section
for more information on these Layer 2 fields.
The Layer 3 fields captured by the NetFlow Layer 2 and Security Monitoring Exports feature improve
NetFlow’s capabilities for identifying DoS attacks. The Layer 2 fields captured by the NetFlow Layer 2
and Security Monitoring Exports feature can help you identify the path that the DoS attack is taking
through the network.
The Layer 3 and Layer 2 fields captured by the NetFlow Layer 2 and Security Monitoring Exports feature
are not key fields. They provide additional information about the traffic in an existing flow. Changes in
the values of NetFlow key fields such as the source IP address from one packet to the next packet result
in the creation of a new flow. For example if the first packet captured by NetFlow has a source IP address
of 10.34.0.2 and the second packet captured by NetFlow has a source IP of 172.16.213.65, NetFlow will
create two separate flows.
Many DoS attacks consist of an attacker sending the same type of IP datagram over and over again in an
attempt to overwhelm the target systems. In such cases the incoming traffic often has similar
characteristics such as the same values in each datagram for one or more of the fields that the NetFlow
Layer 2 and Security Monitoring Exports feature can capture.
There is no easy way to identify the originator of many DoS attacks because the IP source address of the
device sending the traffic is usually forged. However by capturing the MAC address and VLAN-ID fields
using the NetFlow Layer 2 and Security Monitoring Exports feature, you can easily trace the traffic back
3
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
through the network to the router that it is arriving on. If the router that the traffic is arriving on supports
NetFlow, you can configure the NetFlow Layer 2 and Security Monitoring Exports feature on it to
identify the interface where the traffic is arriving. Figure 1 shows an example of an attack in progress.
Figure 1
DoS Attack Arriving over the Internet
DoS Attack arriving from the Internet
Email server
Host A
Router A
Switch F
Host B
Switch G
NetFlow router
Internet
Router B
Switch B
Switch A
Host C
Router C
Switch C
Switch D
127557
Router D
Switch E
CNS NetFlow
collection engine
Note
You can analyze the data captured by NetFlow directly from the router using the show ip cache verbose
flow command or remotely with the CNS NetFlow Collector Engine.
Once you have concluded that a DoS attack is taking place by analyzing the Layer 3 fields in the NetFlow
flows, you can analyze the Layer 2 fields in the flows to discover the path that the DoS attack is taking
through the network.
An analysis of the data captured by the NetFlow Layer 2 and Security Monitoring Exports feature for
the scenario shown in Figure 1 indicates that the DoS attack is arriving on Router C because the upstream
MAC address is from the interface that connects Router C to Switch A. It is also evident that there are
no routers between the target host (the email server) and the NetFlow router because the destination
MAC address of the DoS traffic that the NetFlow router is forwarding to the email server is the MAC
address of the email server.
You can find out the MAC address that Host C is using to send the traffic to Router C by configuring the
NetFlow Layer 2 and Security Monitoring Exports feature on Router C. The source MAC address will
be from Host C. The destination MAC address will be for the interface on the NetFlow router.
Once you know the MAC address that Host C is using and the interface on Router C that Host C’s DoS
attack is arriving on, you can mitigate the attack by reconfiguring Router C to block Host C’s traffic. If
Host C is on a dedicated interface you can disable the interface. If Host C is using an interface that carries
traffic from other users, you must configure your firewall, or add an ACL, to block Host C’s traffic but
still allow the traffic from the other users to flow through Router C.
4
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
The Configuration Examples for Detecting and Analyzing Network Threats With NetFlow section has
two examples for using the NetFlow Layer 2 and Security Monitoring Exports feature to identify an
attack in progress and the path that the attack is taking through a network.
Layer 3 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports
The NetFlow Layer 2 and Security Monitoring Exports feature has support for capturing five fields from
Layer 3 IP traffic in a flow:
•
Time-to-Live field
•
Packet Length field
•
ID field
•
ICMP type and code
•
Fragment offset
Figure 2 shows the fields in an IP packet header. Figure 3 shows the fields in an ICMP datagram. ICMP
datagrams are carried in the data area of an IP datagram, after the IP header.
Figure 2
Table 1
IP Packet Header Fields
IP Packet Header Fields
Field
Description
Version
The version of the IP protocol. If this field is set to 4 it is an IPv4 datagram.
If this field is set to 6 it is an IPv6 datagram.
Note
IHL (Internet Header
Length)
The IPv6 header has a different structure from an IPv4 header.
Internet Header Length is the length of the internet header in 32-bit word and
thus points to the beginning of the data.
Note
The minimum value for a correct header is 5.
ToS
ToS provides an indication of the abstract parameters of the quality of service
desired. These parameters are to be used to guide the selection of the actual
service parameters when a networking device transmits a datagram through
a particular network.
Total Length
Total length is the length of the datagram, measured in octets, including
internet header and data.
5
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Table 1
IP Packet Header Fields (continued)
Field
Description
Identification (ID)
The value in the ID field is entered by the sender. All of the fragments of an
IP datagram have the same value in the ID field. Subsequent IP datagrams
from the same sender will have different values in the ID field.
It is very common for a host to be receiving fragmented IP datagrams from
several senders concurrently. It is also common for a host to be receiving
multiple IP datagrams from the same sender concurrently.
The value in the ID field is used by the destination host to ensure that the
fragments of an IP datagram are assigned to the same packet buffer during
the IP datagram reassembly process. The unique value in the ID field is also
used to prevent the receiving host from mixing together IP datagram
fragments of different IP datagrams from the same sender during the IP
datagram reassembly process.
Flags
A sequence of 3 bits used to set and track IP datagram fragmentation
parameters.
•
001 = The IP datagram can be fragmented. There are more fragments of
the current IP datagram in transit.
•
000 = The IP datagram can be fragmented. This is the last fragment of
the current IP datagram.
•
010 = The IP Datagram cannot be fragmented. This is the entire IP
datagram.
Fragment Offset
This field indicates where in the datagram this fragment belongs.
TTL (Time-to-Live)
This field indicates the maximum time the datagram is allowed to remain in
the internet system. If this field contains the value 0, then the datagram must
be destroyed. This field is modified in internet header processing. The time
is measured in units of seconds, but since every module that processes a
datagram must decrease the TTL by at least 1 even if it processes the
datagram in less than a second, the TTL must be thought of only as an upper
bound on the time a datagram can exist. The intention is to cause
undeliverable datagrams to be discarded, and to bound the maximum
datagram lifetime.
Protocol
Indicates the type of transport packet included in the data portion of the IP
datagram. Common values are:
1 = ICMP
6 = TCP
17 = UDP
6
Header checksum
A checksum on the header only. Since some header fields, such as the
time-to-live field, change every time an IP datagram is forwarded, this value
is recomputed and verified at each point that the internet header is processed.
Source IP Address
IP address of the sending station.
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Table 1
IP Packet Header Fields (continued)
Field
Description
Destination IP Address
IP address of the destination station.
Options and Padding
The options and padding may or may not appear or not in datagrams. If they
do appear, they must be implemented by all IP modules (host and gateways).
What is optional is their transmission in any particular datagram, not their
implementation.
Figure 3
ICMP Datagram
Table 2
ICMP Packet Format
Type
Name
Codes
0
Echo reply
0—None
1
Unassigned
—
2
Unassigned
—
3
Destination unreachable
0—Net unreachable.
1—Host unreachable.
2—Protocol unreachable.
3—Port unreachable.
4—Fragmentation needed and DF bit set.
5—Source route failed.
6—Destination network unknown.
7—Destination host unknown.
8—Source host isolated.
9—Communication with destination network is
administratively prohibited.
10—Communication with destination host is administratively
prohibited.
11—Destination network unreachable for ToS.
12—Destination host unreachable for ToS.
4
Source quench
0—None.
7
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Table 2
ICMP Packet Format (continued)
Type
Name
Codes
5
Redirect
0—None.
0—Redirect datagram for the network.
1—Redirect datagram for the host.
2—Redirect datagram for the TOS and network.
3—Redirect datagram for the TOS and host.
6
Alternate host address
0—Alternate address for host.
7
Unassigned
—
8
Echo
0—None.
9
Router advertisement
0—None.
10
Router selection
0—None.
11
Time Exceeded
0—Time to live exceeded in transit.
12
Parameter problem
0—Pointer indicates the error.
1—Missing a required option.
2—Bad length.
8
13
Timestamp
0—None.
14
Timestamp reply
0—None.
15
Information request
0—None.
16
Information reply
0—None.
17
Address mask request
0—None.
18
Address mask reply
0—None.
19
Reserved (for security)
—
20–29
Reserved (for robustness
experiment)
—
30
Trace route
—
31
Datagram conversion error
—
32
Mobile host redirect
—
33
IPv6 where-are-you
—
34
IPv6 I-am-here
—
35
Mobile registration request
—
36
Mobile registration reply
—
37–255
Reserved
—
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Layer 2 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports
The NetFlow Layer 2 and Security Monitoring Exports feature has the ability to capture the values of
the MAC address and VLAN ID fields from flows. The two supported VLAN types are 802.1q and
Cisco’s Inter-Switch Link (ISL).
•
Understanding Layer 2 MAC Address Fields
•
Understanding Layer 2 VLAN ID Fields
Understanding Layer 2 MAC Address Fields
The new Layer 2 fields that the NetFlow Layer 2 and Security Monitoring Exports feature captures the
values of are:
•
The source MAC address field from frames that are received by the NetFlow router
•
The destination MAC address field from frames that are transmitted by the NetFlow router
•
The VLAN ID field from frames that are received by the NetFlow router
•
The VLAN ID field from frames that are transmitted by the NetFlow router
The Ethernet Type II and Ethernet 802.3 frame formats are shown in Figure 4. The destination address
field and the source address field in the frame formats are the MAC addresses whose values NetFlow
captures. The fields for the Ethernet frame formats are explained in Table 3.
Figure 4
Table 3
Ethernet Type II and 802.3 Frame Formats
Ethernet Type II and 802.3 Frame Fields
Field
Description
Preamble
The entry in the Preamble field is an alternating pattern of 1s and 0s that tells
receiving stations that a frame is coming. It also provides a means for the
receiving stations to synchronize their clocks with the incoming bit stream.
SOF (Start of frame )
The SOF field holds an alternating pattern of 1s and 0s, ending with two
consecutive 1-bits indicating that the next bit is the first bit of the first byte
of the destination MAC address.
9
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Table 3
Ethernet Type II and 802.3 Frame Fields (continued)
Field
Description
Destination Address
The 48-bit destination address identifies which station(s) on the LAN should
receive the frame. The first two bits of the destination MAC address are
reserved for special functions:
•
The first bit in the DA field indicates whether the address is an
individual address (0) or a group address (1).
•
The second bit indicates whether the DA is globally administered (0) or
locally administered (1).
The remaining 46 bits are a uniquely assigned value that identifies a single
station, a defined group of stations, or all stations on the network.
Source Address
The 48-bit source address identifies which station transmitted the frame. The
source address is always an individual address and the left-most bit in the SA
field is always 0.
Type
Type—In an Ethernet Type II frame this part of the frame is used for the Type
field. The Type field is used to identify the next layer protocol in the frame.
or
Length
Length—In an 802.3 Ethernet frame this part of the frame is used for the
Length field. The Length field is used to indicate the length of the Ethernet
frame. The value can be between 46 and 1500 bytes.
Data
(Ethernet type II) 46–1500 bytes of data
or
or
802.2 header and data
(802.3/802.2) 8 bytes of header and 38–1492 bytes of data.
FCS (Frame Check
Sequence)
This field contains a 32-bit cyclic redundancy check (CRC) value, which is
created by the sending station and is recalculated by the receiving station to
check for damaged frames. The FCS is generated for the DA, SA, Type, and
Data fields of the frame. The FCS does not include the data portion of the
frame.
Understanding Layer 2 VLAN ID Fields
NetFlow can capture the value in the VLAN ID field for 802.1q tagged VLANs and Cisco ISL
encapsulated VLANs. The section describes the two types of VLANs.
Note
It has become common to refer to both 802.1q and ISL as VLAN encapsulation protocols.
•
Understanding 802.1q VLANs
•
Understanding Cisco ISL VLANs
Understanding 802.1q VLANs
Devices that use 802.1q insert a four-byte tag into the original frame before it is transmitted. Figure 5
shows the format of an 802.1q tagged Ethernet frame. The fields for 802.1q VLANs are described in
Table 4.
10
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Figure 5
Table 4
802.1q Tagged Ethernet Type II or 802.3 Frame
802.1q VLAN Encapsulation Fields
Field
Description
DA, SA, Type or Length, Data, and FCS These fields are described in Table 3.
Tag Protocol ID (TPID)
This 16-bit field is set to a value of 0x8100 to identify the
frame as an IEEE 802.1q tagged frame.
Priority
Also known as user priority, this 3-bit field refers to the
802.1p priority. It indicates the frame priority level which
can be used for prioritizing traffic and is capable of
representing 8 levels (0–7).
Tag Control Information
The 2-byte Tag Control Information field is comprised of two
sub-fields:
•
(CFI)Canonical Format Indicator (CFI)—If the value of
this 1-bit field is 1, then the MAC address is in
noncanonical format. If the value of this field is 0, then
the MAC address is in canonical format.
•
VLAN ID—This 12-bit field uniquely identifies the
VLAN to which the frame belongs. It can have a value
between 0 and 4095.
Understanding Cisco ISL VLANs
ISL is a Cisco proprietary protocol for encapsulating frames on a VLAN trunk. Devices that use ISL add
an ISL header to the frame. This process is known as VLAN encapsulation. 802.1Q is the IEEE standard
for tagging frames on a VLAN trunk. Figure 6 shows the format of a Cisco ISL-encapsulated Ethernet
frame. The fields for 802.1q VLANs are described in Table 5.
11
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
#of bits in
the field
Cisco ISL Tagged Ethernet Frame
40
4
4
48
16
24
24
15
1
16
16
Field Name DA TYPE USER SA LEN AAAA03(SNAP) HSA VLAN BPDU INDEX RES
Table 5
1 to 24575
bytes
32
Enscapsulated
FCS
FRAME
127755
Figure 6
ISL VLAN Encapsulation
Field
Description
DA (destination
address)
This 40-bit field is a multicast address and is set at 0x01-00-0C-00-00 or
0x03-00-0c-00-00. The receiving host determines that the frame is
encapsulated in ISL by reading the 40-bit DA field and matching it to one of
the two ISL multicast addresses.
Type
This 4-bit field indicates the type of frame that is encapsulated and could be
used in the future to indicate alternative encapsulations.
TYPE codes:
USER
•
0000 = Ethernet
•
0001 = Token Ring
•
0010 = FDDI
•
0011 = ATM
This 4-bit field is used to extend the meaning of the Frame TYPE field. The
default USER field value is 0000. For Ethernet frames, the USER field bits
0 and 1 indicate the priority of the packet as it passes through the switch.
Whenever traffic can be handled more quickly, the packets with this bit set
should take advantage of the quicker path. Such paths however are not
required.
USER codes:
12
•
XX00 = Normal priority
•
XX01 = Priority 1
•
XX10 = Priority 2
•
XX11 = Highest priority
SA
This 48-bit field is the source address field of the ISL packet. It should be set
to the 802.3 MAC address of the switch port transmitting the frame. The
receiving device can ignore the SA field of the frame.
LEN
This 16-bit value field stores the actual packet size of the original packet.
The LEN field represents the length of the packet in bytes, excluding the DA,
TYPE, USER, SA, LEN, and FCS fields. The total length of the excluded
fields is 18 bytes, so the LEN field represents the total length minus 18 bytes.
AAAA03(SNAP)
The AAAA03 SNAP field is a 24-bit constant value of 0xAAAA03.
HSA
This 24-bit field represents the upper three bytes (the manufacturer’s ID
portion) of the SA field. It must contain the value 0x00-00-0C.
VLAN
This 15-bit field is the Virtual LAN ID of the packet. This value is used to
mark frames on different VLANs.
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Table 5
ISL VLAN Encapsulation (continued)
Field
Description
BPDU
The bit in the BPDU field is set for all BPDU packets that are encapsulated
by the ISL frame. The BPDUs are used by the spanning tree algorithm to find
out information about the topology of the network. This bit is also set for
CDP and VTP frames that are encapsulated.
INDEX
This 16-bit field indicates the port index of the source of the packet as it exits
the switch. It is used for diagnostic purposes only, and may be set to any
value by other devices. It is ignored in received packets.
RES
This 16-bit field is used when Token Ring or FDDI packets are encapsulated
with an ISL frame.
Encapsulated FRAME
This field contains the encapsulated Layer 2 frame.
FCS
The FCS field consists of 4 bytes. It includes a 32-bit CRC value, which is
created by the sending station and is recalculated by the receiving station to
check for damaged frames. The FCS covers the DA, SA, Length/Type, and
Data fields. When an ISL header is attached to a Layer 2 frame, a new FCS
is calculated over the entire ISL packet and added to the end of the frame.
Note
The addition of the new FCS does not alter the original FCS that is
contained within the encapsulated frame.
NetFlow Top Talkers
The usual implementation of NetFlow exports NetFlow data to a collector. The NetFlow Top Talkers
features can be used for security monitoring or accounting purposes for top talkers, and matching and
identifying key traffic in your network. These features are also useful for a network location where a
traditional NetFlow export operation is not possible. The NetFlow Top Talkers features do not require a
collector to obtain information regarding flows. Instead, the NetFlow data is displayed on the router
when the NetFlow Dynamic Top Talkers CLI show ip flow top command, or the NetFlow Top Talkers
show ip flow top-talkers is used.
Comparison of the NetFlow Dynamic Top Talkers CLI and NetFlow Top Talkers Features
There are two very similar NetFlow features that can be used for monitoring the highest volume traffic
in your network. The feature names are:
•
NetFlow Dynamic Top Talkers CLI
•
NetFlow Top Talkers
NetFlow Dynamic Top Talkers CLI
This feature was introduced in 12.4(4)T. The NetFlow Dynamic Top Talkers CLI feature is used to obtain
an overview of the highest volume traffic (top talkers) in your network. It provides an overview of the
traffic by aggregating the flows in the cache based on the aggregation field that you select when you use
the NetFlow Dynamic Top Talkers CLI feature.
The NetFlow Dynamic Top Talkers CLI feature does not require modifications to the configuration of
the router. The show ip flow top command is the only command that you need to use for the NetFlow
Dynamic Top Talkers CLI feature. You can invoke any of the NetFlow Dynamic Top Talkers CLI options
directly from the show ip flow top command whenever you need them.
13
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Note
The information that you want to use the NetFlow Dynamic Top Talkers CLI feature to analyze must be
available in the cache. For example, if you want to be able to identify the MAC address in the flows, you
must configure the ip flow-capture mac-addresses command in order to capture the values from the
MAC address fields in the traffic first.
The NetFlow Dynamic Top Talkers CLI feature aggregates flows and allows them to be sorted so that
they can be viewed. The flows can be aggregated on fields in the cache such as source or destination IP
address, ICMP type and code values, and so forth. For a full list of the fields that you can aggregate the
flows on, refer to the show ip flow top command in the Cisco IOS NetFlow command reference
documentation.
The aggregated top talker flows can be sorted by any of the following criteria:
•
The aggregated field in the display data
•
The number of bytes in the display data
•
The number of flows in the display data
•
The by number of packets in the display data
•
In ascending or descending order (to find the least used Top talker)
In addition to sorting top talkers, you can further organize your output by specifying criteria that the top
talkers must match, such as source or destination IP address or port. The match keyword is used to
specify this criterion. For a full list of the matching criterion that you can select, refer to the
show ip flow top command in the Cisco IOS NetFlow command reference documentation.
The NetFlow Dynamic Top Talkers CLI feature can help you quickly identify traffic that is associated
with security threats such as DoS attacks because it does not require configuration modifications. You
can change the NetFlow Dynamic Top Talkers CLI options for identifying and analyzing network threats
in the aggregated flows on-the-fly as you learn more about the traffic that is of interest. For example,
after you have identified that there is a lot of ICMP traffic in your network by using the show ip flow
top 10 aggregate icmp command you can learn what IP networks the traffic is being sent to by using
the show ip flow top 10 aggregate icmp match destination-prefix 172.0.0.0/8 command.
Note
A high volume of ICMP traffic might indicate that an ICMP-based DoS attack is in progress.
The show ip flow top command:
14
•
Does not require additional NetFlow configuration commands to display top talkers. Therefore you
do not need to supply the configuration mode password to the administrators who use the he show
ip flow top command to monitor network traffic. The only prerequisite for using the show ip flow
top command is that you have configured NetFlow on at least one interface on the router.
•
Aggregates flows automatically based on the aggregation method that you select, and independently
of any netflow aggregation cache(s).
•
Allows you to change the parameters of the command, such as the number of flows to display, the
display order, and match criterion, on-the-fly every time that you use the command without having
to change the router’s configuration.
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
•
Allows you to sort the display output in ascending or descending order based on:
– The aggregated field
– The number of bytes
– The number of flows,
– The number of packets
show ip flow top and show ip cache verbose flow
Many of the values shown in the display output of the show ip cache verbose flow command are in
hexadecimal. If you want to match these values using the show ip flow top command with the match
keyword, you must enter the field value that you want to match in hexadecimal. For example, to match
on the destination port of 00DC in the following except from the show ip cache verbose flow command,
you would use the match destination-port 0x00DC keywords and argument for the show ip flow top
command.
SrcIf
SrcIPaddress
Port Msk AS
Et0/0.1
10.10.11.4
00DC /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
DstIf
Port Msk AS
Et1/0.1
00DC /0 0
(005)
DstIPaddress
NextHop
172.16.10.8
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
Pr TOS Flgs Pkts
B/Pk Active
06 00 00
209
40
281.4
(006)
40
59
Match Criteria with the show ip flow top command
You can limit the top talkers that are displayed by the show ip flow top command by using the match
keyword and arguments. For example, you can display the IP destination address top talkers that have a
prefix of 224.0.0.0 using the show ip flow top 10 aggregate destination-address match
destination-prefix 224.0.0.0/3 command.
For a full list of the matching criterion that you can select, refer to the show ip flow top command in the
Cisco IOS NetFlow Command Reference. If you do not configure match criteria all of the flows are
considered as candidates for aggregation as top talkers based on the volume of traffic they represent.
The Order That Aggregation Occurs in
With the exception of the flows keyword, all matches are performed prior to aggregation, and only
matching flows are aggregated. For example, the show ip flow top 5 aggregate destination-address
match destination-prefix 172.16.0.0/16 command analyzes all of the available flows looking for any
flows that have destination addresses that match the destination-prefix value of 172.16.0.0/16. If it finds
any matches it aggregates them, and then displays the number of aggregated destination-address flows
that is equal to the number of top talkers that were requested in the command–in this case five.
The flows keyword matches the number of aggregated flows post-aggregation. For example, the
show ip flow top 2 aggregate destination-address match 6 command aggregates all of the flows on
the values in their destination IP address field, and then displays the top talkers that have 6 aggregated
flows.
Number of Flows Matched
If you do not specify match criteria and there is traffic in the flows that includes the field that you used
to aggregate the flows on, all of the flows will match. For example, if your router has 20 flows with IP
traffic and you enter the show ip flow top 10 aggregate destination-address command the display will
indicate that 20 of 20 flows matched, and the 10 top talkers will be displayed.
15
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
If you use the match keyword to limit the flows that are aggregated to the flows with a destination prefix
of 224.0.0.0/3, and only one flow matches this criterion the output will indicate that one out of six flows
matched. For example, if your router has 6 flows with IP traffic, but only one of them has a destination
prefix of 224.0.0.0/3, and you enter the show ip flow top 10 aggregate destination-address match
destination-prefix 224.0.0.0/3 command, the display will indicate that 1 of 6 flows matched.
If the total number of top talkers is less than the number of top talkers that were requested in the
command, the total number of top talkers is displayed. For example, if you enter a value of five for the
number of top talkers to display and there are only three top talkers that match the criteria that you used,
the display will only include three top talkers.
When a match criterion is included with the show ip flow top command, the display output will indicate
“N of M flows matched” where N <= M, N = matched flows, and M = total flows seen. The numbers of
flows seen could potentially be more than the total number of flows in the cache if some of the analyzed
flows were removed from the cache and new flows were created ahead of the current point, as the top
talkers feature sweeps through the cache. Therefore, M is NOT the total number of flows in the cache,
but rather, the number of observed flows.
If you attempt to display the top talkers by aggregating them on a field that is not in the cache you will
see the “% aggregation-field” is not available for this cache” message. For example, if you use the
show ip flow top 5 aggregate source-vlan command, and you have not enabled the capture of VLAN
IDs from the flows, you will see the “% VLAN id is not available for this cache” message.
NetFlow Top Talkers
This feature was introduced in 12.3(11)T. NetFlow Top Talkers is used to obtain information about
individual flows in the cache. It does not aggregate the flows like the NetFlow Dynamic Top Talkers CLI
feature.
The NetFlow Top Talkers feature compares all of the flows and displays information about each of the
flows that have the heaviest traffic volumes (top talkers). The show ip flow top-talkers command
requires you to pre-configure the router using the NetFlow Top Talkers configuration commands:
•
ip flow-top-talkers—Enters the NetFlow Top Talkers configuration mode.
•
sort-by—Selects the sort order for the flows in the display output.
– bytes—Sort the flows based on the numbers of bytes in each flow.
– packets—Sort the flows based on the numbers of packets in each flow.
•
top—Specifies the number of top talkers to monitor.
•
match (optional)—Specifies additional criteria, such as IP addresses, port numbers, and so forth,
that must be matched in the flow to qualify as a candidate for top talker status.
For a full list of the matching criterion that you can select, refer to the ip flow top-talkers command
in the Cisco IOS NetFlow Command Reference. If you do not configure match criteria all of the
flows are considered as candidates as top talkers based on the volume of traffic they represent.
•
show ip flow top talkers [verbose]—Displays the flows.
For more information on the NetFlow Top Talkers feature, refer to Configuring NetFlow Top Talkers
using Cisco IOS CLI Commands or SNMP Commands.
16
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Filtering and Sampling of NetFlow Traffic
NetFlow provides highly granular per-flow traffic statistics in a Cisco router. A flow is a unidirectional
stream of packets that arrive at the router on the same subinterface, have the same source and destination
IP addresses, Layer 4 protocol, TCP/UDP source and destination ports, and the same ToS (type of
service) byte in the IP headers. The router accumulates NetFlow statistics in a NetFlow cache and can
export them to an external device (such as the Cisco Networking Services (CNS) NetFlow Collection
Engine) for further processing.
Full NetFlow accounts for all traffic entering the subinterface on which it is enabled. But in some cases,
you might gather NetFlow data on only a subset of this traffic. The Random Sampled NetFlow feature
and the NetFlow Input Filters feature each provide ways to limit incoming traffic to only traffic of
interest for NetFlow processing. Random Sampled NetFlow provides NetFlow data for a subset of traffic
in a Cisco router by processing only one randomly selected packet out of n sequential packets. The
NetFlow Input Filters feature provides the capability to gather NetFlow data on only a specific
user-defined subset of traffic.
Note
Random Sampled NetFlow is more statistically accurate than Sampled NetFlow. NetFlow's ability to
sample packets was first provided by a feature named Sampled NetFlow. The methodology that the
Sampled NetFlow feature uses is deterministic sampling, which selects every nth packet for NetFlow
processing on a per-interface basis. For example, if you set the sampling rate to 1 out of 100 packets,
then Sampled NetFlow samples the 1st, 101st, 201st, 301st, and so on packets. Sampled NetFlow does
not allow random sampling and thus can make statistics inaccurate when traffic arrives in fixed patterns.
Note
The Random Sampled NetFlow algorithms are applied after input filtering.
Table 6 compares the NetFlow Input Filters feature and the NetFlow Random Sampled feature.
Table 6
Comparison of the NetFlow Input Filters Feature and the Random Sampled NetFlow Feature
Comparison Category
NetFlow Input Filters Feature
Random Sampled NetFlow Feature
Brief description
This feature enables you to gather NetFlow
data on only a specific subset of traffic. You
do this by creating filters to select flows for
NetFlow processing. For example, you can
select flows from a specific group of hosts.
This feature also lets you select various
sampling rates for selected flows.
This feature provides NetFlow data for a
subset of traffic in a Cisco router by
processing only one randomly selected packet
out of n sequential packets (n is a
user-configurable parameter). Packets are
sampled as they arrive (before any NetFlow
cache entries are made for those packets).
Main uses
You can use this feature for class-based traffic You can use this feature for traffic
engineering, capacity planning, and
analysis and monitoring on-network or
applications where full NetFlow is not needed
off-network traffic.
for an accurate view of network traffic.
This feature is also useful if you have too
much traffic and you want to limit the traffic This feature is also useful if you have too
much traffic and you want to limit the traffic
that is analyzed.
that is analyzed.
Export format support
This feature is supported in the Version 5 and This feature is supported in the Version 5 and
Version 9 NetFlow export formats.
Version 9 NetFlow export formats.
Cisco IOS release support
12.3(4)T.
12.3(2)T, 12.2(18)S, and 12.0(26)S.
17
Detecting and Analyzing Network Threats With NetFlow
Information About Detecting and Analyzing Network Threats With NetFlow
Table 6
Comparison of the NetFlow Input Filters Feature and the Random Sampled NetFlow Feature (continued)
Comparison Category
NetFlow Input Filters Feature
Random Sampled NetFlow Feature
Subinterface support
You can configure NetFlow Input Filters per You can configure the Random Sampled
subinterface as well as per physical interface. NetFlow feature per subinterface as well as
per physical interface.
You can select more than one filter per
You can not run Full NetFlow and Random
subinterface and have all of the filters run
Sampled NetFlow concurrently on the same
simultaneously.
subinterface. You must disable full NetFlow
on the subinterface before Random Sampled
NetFlow will take effect.
Traffic is collected only on the subinterfaces
on which Random Sampled NetFlow is
configured. As with full NetFlow, enabling
Random Sampled NetFlow on a physical
interface does not enable Random Sampled
NetFlow on subinterfaces automatically—you
must explicitly configure it on the
subinterfaces.
Memory impact
This feature requires no additional memory. It
allows you to use a smaller NetFlow cache
than full NetFlow, because it significantly
reduces the number of flows. This feature
requires an insignificant amount of memory
for each configured NetFlow filter.
This feature can create a smaller NetFlow
cache than full NetFlow if by reducing the
number of packets being analyzed the
numbers of flows in the cache is also reduced.
This feature requires an insignificant amount
of memory for each configured NetFlow
sampler.
Performance impact
Accounting of classified traffic saves router
resources by reducing the number of flows
being processed and exported. The amount of
bandwidth saved depends on the usage and the
class-map criteria.
Statistical traffic sampling substantially
reduces consumption of router resources
(especially CPU resources) while providing
valuable NetFlow data.
However, performance might degrade
depending on the number and complexity of
class maps configured in a policy.
This feature substantially reduces the impact
of NetFlow data export on interface traffic.
For example, a sampling rate of 1 out of 100
packets reduces the export of NetFlow data by
about 99% percent.
NetFlow Input Filters: Flow Classification
For the NetFlow Input Filters feature, classification of packets can be based on any of the following: IP
source and destination addresses, Layer 4 protocol and port numbers, incoming interface, MAC address,
IP Precedence, DSCP value, Layer 2 information (such as Frame-Relay DE bits or Ethernet 802.1p bits),
and Network-Based Application Recognition (NBAR) information. The packets are classified (filtered)
on the above criteria, and flow accounting is applied to them on subinterfaces.
The filtering mechanism uses the Modular QoS Command-Line Interface (MQC) to classify flows. You
can create multiple filters with matching samplers on a per-subinterface basis. For example, you can
subdivide subinterface traffic into multiple classes based on type of service (ToS) values or destination
prefixes (or both). For each class, you can also configure sampling at a different rate, using higher rates
for higher-priority classes of traffic and lower rates for lower-priority ones.
18
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
MQC has many policies (actions) such as bandwidth rate and queuing management. These policies are
applied only if a packet matches a criterion in a class map that is applied to the subinterface. A class map
contains a set of match clauses and instructions on how to evaluate the clauses and acts as a filter for the
policies, which are applied only if a packet’s content satisfies the match clause. The NetFlow Input
Filters feature adds NetFlow accounting to the MQC infrastructure, which means that flow accounting
is done on a packet only if it satisfies the match clauses.
Two types of filter are available:
•
ACL-based flow-mask filters
•
Fields of filter (source IP address, destination IP address, source application port, destination
application port, port protocol, ToS bits, and TCP flags)
For more information on Modular QoS Command-Line Interface (MQC) refer to the Cisco IOS Quality
of Service Solutions Configuration Guide.
Random Sampled NetFlow: Sampling Mode
Sampling mode makes use of an algorithm that selects a subset of traffic for NetFlow processing. In the
random sampling mode that the Random Sampled NetFlow feature uses, incoming packets are randomly
selected on average one out of each n sequential packets is selected for NetFlow processing. For
example, if you set the sampling rate to 1 out of 100 packets, then NetFlow might sample the 5th packet
and then the 120th, 230th, 302nd, and so on. This sample configuration provides NetFlow data on
1 percent of total traffic. The n value is a parameter that you can configure from 1 to 65535 packets.
Random Sampled NetFlow: The NetFlow Sampler Map
Random Sampled NetFlow is useful if you have too much traffic and you want to limit the traffic that is
analyzed. A NetFlow sampler map is created with the flow-sampler-map sampler-map-name command.
The sampling mode for the sampler map is configured with the mode random one-out-of sampling-rate
command. The range of values for the sampling-rate argument is 1 to 65535. Each NetFlow sampler map
can be applied to one or many subinterfaces as well as physical interfaces. The sampler map is applied
to an interface or subinterface with the flow-sampler sampler-map-name command. You can define up
to eight NetFlow sampler maps.
How to Configure and Use NetFlow to Detect and Analyze
Network Threats
Using NetFlow to detect and analyze network threats requires a combination of configuration commands
and show commands. You start by configuring the NetFlow Layer 2 and Security Monitoring Exports
feature to capture values of the additional non-key fields from the flows so that they can be displayed in
the cache by the NetFlow show commands. Capturing the values in the additional non-key fields is
required so that you can identify the path the traffic is taking through the network and other
characteristics of the traffic such as TTL values and packet length values.
After you configure the NetFlow Layer 2 and Security Monitoring Exports feature, you use the NetFlow
Dynamic Top Talkers CLI command to obtain an overview of the traffic flows the router is forwarding.
The overview displays information such as the protocol distribution in the flows, the source ip addresses
that are sending the flows, and the networks the flows are being sent to.
19
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
After you identify the type of flows that you want to focus, on such as ICMP traffic, and other
characteristics such as source IP addresses and destination network prefixes, you use the NetFlow Top
Talkers feature to obtain more focused and detailed information on the individual flows. The NetFlow
Top Talkers feature is configured with match criteria that focuses it on the types of traffic that you have
identified. If your router is keeping track of several flows and you are only interested in analyzing a
subset of them you, can configure NetFlow Input Filters to limit the flows that NetFlow is tracking.
Prerequisites
CEF or dCEF must be configured globally, and on the interface that you want to run NetFlow on, before
you configure NetFlow Layer 2 and Security Monitoring Exports.
You must have NetFlow enabled on at least one interface in the router before you configure NetFlow
Layer 2 and Security Monitoring Exports.
If you want to capture the values of the Layer 3 IP fragment offset field from the IP headers in your IP
traffic using the ip flow-capture fragment-offset command, your router must be running
Cisco IOS 12.4(2)T or later.
This section contains the following procedures:
•
Configuring NetFlow Layer 2 and Security Monitoring Exports, page 20
•
Verifying NetFlow Layer 2 and Security Monitoring Exports, page 22
•
Using NetFlow Dynamic Top Talkers CLI to Display the Protocol Distribution, page 24
•
Using NetFlow Dynamic Top Talkers CLI to Display the Source IP Address Top Talkers Sending
ICMP Traffic, page 25
•
Using NetFlow Dynamic Top Talkers CLI to Display the Destination IP Address Top Talkers
Receiving ICMP Traffic, page 27
•
Configuring NetFlow Top Talkers to Monitor Network Threats, page 28
•
Monitoring and Analyzing the NetFlow Top Talkers Flows, page 30
•
Configuring NetFlow Filtering and Sampling, page 33
•
Verify NetFlow Filtering and Sampling, page 38
•
Monitoring and Analyzing the Sampled and Filtered NetFlow Top Talkers Flows, page 39
Configuring NetFlow Layer 2 and Security Monitoring Exports
Perform the following task to configure the NetFlow Layer 2 and Security Monitoring Exports feature.
Prerequisites
To export the data captured with the NetFlow Layer 2 and Security Monitoring feature, you must
configure NetFlow to use the NetFlow Version 9 data export format.
SUMMARY STEPS
20
1.
enable
2.
configure terminal
3.
ip flow-capture fragment-offset
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
4.
ip flow-capture icmp
5.
ip flow-capture ip-id
6.
ip flow-capture mac-addresses
7.
ip flow-capture packet-length
8.
ip flow-capture ttl
9.
ip flow-capture vlan-id
10. interface interface-type interface-number
11. ip flow ingress
and/or
ip flow egress
12. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-capture fragment-offset
Enables capturing the value of the IP fragment offset field
from the first fragmented IP datagram in a flow.
Example:
Router(config)# ip flow-capture fragment-offset
Step 4
ip flow-capture icmp
Enables you to capture the value of the ICMP type and code
fields from the first ICMP datagram in a flow.
Example:
Router(config)# ip flow-capture icmp
Step 5
ip flow-capture ip-id
Enables you to capture the value of the IP-ID field from the
first IP datagram in a flow.
Example:
Router(config)# ip flow-capture ip-id
Step 6
ip flow-capture mac-addresses
Example:
Enables you to capture the values of the source and
destination MAC addresses from the first Layer 2 frame in
a flow.
Router(config)# ip flow-capture mac-addresses
Step 7
ip flow-capture packet-length
Enables you to capture the minimum and maximum values
of the packet length field from IP datagrams in a flow.
Example:
Router(config)# ip flow-capture packet-length
21
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Step 8
Command or Action
Purpose
ip flow-capture ttl
Enables you to capture the minimum and maximum values
of the Time-to-Live (TTL) field from IP datagrams in a
flow.
Example:
Router(config)# ip flow-capture ttl
Step 9
ip flow-capture vlan-id
Example:
Enables you to capture the 802.1q or ISL VLAN-ID field
from first VLAN encapsulated Layer 2 frame in a flow that
is received or transmitted on a trunk port.
Router(config)# ip flow-capture vlan-id
Step 10
interface type interface-type interface-number]
Enters interface configuration mode for the type of interface
specified in the command.
Example:
Router(config)# interface ethernet 0/0
Step 11
ip flow ingress
and/or
Enables ingress NetFlow data collection on the interface.
and/or
ip flow egress
Enables egress NetFlow data collection on the interface.
Example:
Router(config-if)# ip flow ingress
and/or
Example:
Router(config-if)# ip flow egress
Step 12
Returns to privileged EXEC mode.
end
Example:
Router(config)# end
Verifying NetFlow Layer 2 and Security Monitoring Exports
This task verifies that NetFlow Layer 2 and Security Monitoring Exports is configured correctly. The
show ip cache verbose flow command gives a detailed view of the status and statistics for flows in the
NetFlow main cache. The values for the NetFlow non-key fields that you have configured with the
NetFlow Layer 2 and Security Monitoring Exports feature are included for each flow.
To see the values of the fields that you have configured the NetFlow Layer 2 and Security Monitoring
Exports feature to capture, your router must be forwarding IP traffic that meets the criteria for these
fields. For example, if you configure the ip flow-capture vlan-id command, your router must be
forwarding IP datagrams over interfaces that are configured as VLAN trunks to capture the VLAN-ID
values from the layer-two frames carrying the IP datagrams in the flow.
Restrictions
Displaying Detailed NetFlow Cache Information on Platforms Running Distributed Cisco Express Forwarding
On platforms running dCEF, NetFlow cache information is maintained on each line card or Versatile
Interface Processor. If you want to use the show ip cache verbose flow command to display this
information on a distributed platform, you must enter the command at a line card prompt.
22
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Cisco 7500 Series Platform
To display detailed NetFlow cache information on a Cisco 7500 series router that is running distributed
dCEF, enter the following sequence of commands:
Router# if-con slot-number
LC-slot-number# show ip cache verbose flow
For Cisco IOS Releases 12.3(4)T, 12.3(6), and 12.2(20)S and later, enter the following command to
display detailed NetFlow cache information:
Router# execute-on slot-number show ip cache verbose flow
Cisco 12000 Series Platform
To display detailed NetFlow cache information on a Cisco 12000 Series Internet Router, enter the
following sequence of commands:
Router# attach slot-number
LC-slot-number# show ip cache verbose flow
For Cisco IOS Releases 12.3(4)T, 12.3(6), and 12.2(20)S and later, enter the following command to
display detailed NetFlow cache information:
Router# execute-on slot-number show ip cache verbose flow
To verify the configuration of NetFlow Layer 2 and Security Monitoring Exports use the following step.
SUMMARY STEPS
1.
show ip cache verbose flow
DETAILED STEPS
Step 1
show ip cache verbose flow
This example shows that NetFlow Layer 2 and Security Monitoring Exports is working properly because
the values have been captured from the non-key Layer 3 and Layer 2 fields in the flows. The values
captured in the flows are shown in bold text.
Router# show ip cache verbose flow
IP packet size distribution (33978 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.856 .143 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
14 active, 4082 inactive, 59 added
12452 ager polls, 0 flow alloc failures
Active flows timeout in 10 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 25736 bytes
28 active, 996 inactive, 148 added, 59 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-SMTP
2
0.0
1730
40
3.6
600.7
0.2
UDP-other
31
0.0
1
54
0.0
3.6
16.8
ICMP
12
0.0
1728
28
22.0
600.1
0.1
23
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Total:
45
0.0
SrcIf
SrcIPaddress
Port Msk AS
.
.
.
Et0/0.1
10.71.200.138
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
538
29
25.7
189.2
11.6
DstIf
Port Msk AS
DstIPaddress
NextHop
Pr TOS Flgs Pkts
B/Pk Active
Et1/0.1
0C01 /0
(005)
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
0
10
28
696
241.4
(006)
28
59
1
Using NetFlow Dynamic Top Talkers CLI to Display the Protocol Distribution
You can obtain a quick overview of the traffic in your network by viewing the protocol distribution. Use
this task to display the top talkers (aggregated flows) for these three IPv4 protocol types:
•
1—ICMP
•
6—TCP
•
17—UDP
1.
show ip flow top number aggregate aggregate-field sorted-by packets descending
SUMMARY STEPS
DETAILED STEPS
Step 1
show ip flow top number aggregate aggregate-field sorted-by packets descending
The following example looks for up to three top talkers, aggregates them on the protocol field, sorts them
by packets, and displays the output in descending order:
Router# show ip flow top 3 aggregate protocol sorted-by packets descending
There are 3 top talkers:
IPV4 PROT
=========
1
6
17
bytes
==========
406196
96560
52
15 of 15 flows matched.
24
pkts
==========
14507
2414
1
flows
==========
12
2
1
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Table 7 describes the significant fields shown in the display output.
Table 7
show ip flow top 3 aggregate protocol sorted-by packets descending Field
Descriptions
Field
Description
There are 3 top talkers
The number of top talkers is displayed.
IPV4 PROT
This position in the display output is used to show the field
that you selected to aggregate the flows on.
The protocol keyword aggregates IPv4 traffic in the flows
based on the IPv4 protocol type. In this example there are
three IPv4 protocol types in the flows:
•
1—ICMP
•
6—TCP
•
17—UDP
bytes
Displays the numbers of bytes in the aggregated flows for
each top talker.
pkts
Displays the numbers of packets in the aggregated flows for
each top talker.
flows
Displays the numbers of aggregated flows for each top talker.
15 of 15 flows matched.
Displays the number of flows that matched the command.
All 15 flows in the router are aggregated into three top talkers. In this example all of the flow traffic is
top talker traffic.
The majority of the traffic is ICMP traffic (IP protocol type 1). This might indicate an ICMP DoS attack
is in progress.
Using NetFlow Dynamic Top Talkers CLI to Display the Source IP Address Top
Talkers Sending ICMP Traffic
The display output from the show ip flow top 10 aggregate protocol sorted-by packets descending
used in Using NetFlow Dynamic Top Talkers CLI to Display the Protocol Distribution section indicates
that there is a possible ICMP-based DoS attack in progress. The next step to take is to identify the flows
that are sending the ICMP traffic. In this case the flows will be aggregated on the source IP addresses.
SUMMARY STEPS
1.
show ip flow top number aggregate aggregate-field sorted-by packets match match-field
match-value
DETAILED STEPS
Step 1
show ip flow top number aggregate aggregate-field sorted-by packets match match-field match-value
25
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
The following command looks for up to 20 top talkers, aggregates them on the source IP address, sorts
them by packets, and matches on the protocol icmp:
Router# show ip flow top 20 aggregate source-address sorted-by packets match protocol icmp
There are 6 top talkers:
IPV4 SRC-ADDR
===============
10.132.221.111
10.10.12.1
10.251.138.218
10.71.200.138
10.231.185.254
10.106.1.1
bytes
==========
90440
90440
90440
90384
90384
90356
pkts
==========
3230
3230
3230
3228
3228
3227
flows
==========
1
1
1
1
1
1
6 of 15 flows matched.
Router
Table 8 describes the significant fields shown in the display.
Table 8
show ip flow top 20 aggregate source-address sorted-by packets match protocol icmp
Field Descriptions
Field
Description
There are 6 top talkers
The number of top talkers is displayed.
Note
IPV4 SRC-ADDR
Only 6 top talkers are displayed, even though you
asked for 20, because only 6 of the 15 flows in the
cache matched the criteria you specified. The number
20 is an upper limit that will be applied in the event
that there are over 20 top talkers.
This position in the display output is used to show the field
that you selected to aggregate the flows on.
The source-address keyword aggregates flows based on the
source IP address. In this example there are 6 IP source
addresses with aggregated flows. Each of the IP addresses has
1 flow, therefore no aggregation was performed:
26
•
10.132.221.111
•
10.10.12.1
•
10.251.138.218
•
10.71.200.138
•
10.231.185.254
•
10.106.1.1
bytes
Displays the numbers of bytes in the aggregated flows for
each top talker.
pkts
Displays the numbers of packets in the aggregated flows for
each top talker.
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Table 8
show ip flow top 20 aggregate source-address sorted-by packets match protocol icmp
Field Descriptions (continued)
Field
Description
flows
Displays the numbers of aggregated flows for each top talker.
6 of 15flows matched.
Displays the number of flows that matched the command.
The ICMP traffic is aggregated into six top talkers (source IP addresses). Each top talker has one flow.
No aggregation is performed on this traffic because there is a 1-to-1 correlation of IP source addresses
and flows.
Using NetFlow Dynamic Top Talkers CLI to Display the Destination IP Address
Top Talkers Receiving ICMP Traffic
The display output from the show ip flow top 5 aggregate source-address sorted-by packets match
protocol icmp command used in Using NetFlow Dynamic Top Talkers CLI to Display the Source IP
Address Top Talkers Sending ICMP Traffic section showed the six top talkers (IP source addresses) that
are sending the 12 ICMP traffic flows. The next step to take is to identify the flows that are the target of
the ICMP traffic. In this case the flows will be aggregated on the destination IP addresses.
SUMMARY STEPS
1.
show ip flow top number aggregate aggregate-field sorted-by packets match match-field
match-value
DETAILED STEPS
Step 1
show ip flow top number aggregate aggregate-field sorted-by packets match match-field match-value
The following command looks for up to 20 top talkers, aggregates them on the destination IP address,
sorts them by packets, and matches on the protocol icmp
Router# show ip flow top 20 aggregate destination-address sorted-by packets match protocol
icmp
There is 1 top talker:
IPV4 DST-ADDR
===============
172.16.10.2
bytes
==========
407456
pkts
==========
14552
flows
==========
6
6 of 14 flows matched.
Router
Table 9 describes the significant fields shown in the display.
27
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Table 9
show ip flow top 20 aggregate destination-address sorted-by packets match protocol
icmp Field Descriptions
Field
Description
There is 1 top talker
The number of top talkers is displayed.
•
IPV4 DST-ADDR
The ICMP traffic is aggregated into 6 flows for one
destination IP addresses.
This position in the display output is used to show the field
that you selected to aggregate the flows on.
The destination-address keyword aggregates flows based on
the destination IP address. In this example there are 3 IP
destination address with aggregated flows. The IP addresses
has 8 aggregated flows:
•
172.16.10.2
bytes
Displays the numbers of bytes in the aggregated flows for
each top talker.
pkts
Displays the numbers of packets in the aggregated flows for
each top talker.
flows
Displays the numbers of aggregated flows for each top talker.
6 of 14 flows matched.
Displays the number of flows that matched the command.
The previous task identified six ICMP top talkers based on source IP addresses that each had one flow.
This task identified that there is one ICMP top talker based on destination IP addresses that is the target
for 6 individual flows. There is a 1-to-1 correlation between the number of ICMP flows in the top talkers
aggregated on the source IP address and the number of ICMP flows in the top talkers aggregated on the
destination IP address. There is a high probability that an ICMP-based DoS attack on the host with the
IP address of 172.16.10.2 is in progress.
Configuring NetFlow Top Talkers to Monitor Network Threats
The previous task (Using NetFlow Dynamic Top Talkers CLI to Display the Destination IP Address Top
Talkers Receiving ICMP Traffic) identified a probable ICMP-based DoS attack on the host with the IP
address 172.16.10.2. This task uses the NetFlow Top Talkers feature to configure the router to monitor
the DoS attack by tracking the individual ICMP flows. After you have configured the NetFlow Top
Talkers feature to focus on the DoS attack traffic, you can use the show ip flow top-talkers verbose
command to identify the path the DoS traffic is taking through the network.
Perform the following task to configure the NetFlow Top Talkers feature.
SUMMARY STEPS
28
1.
enable
2.
configure terminal
3.
ip flow-top-talkers
4.
match destination address ip-address/prefix-mask
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
5.
top number
6.
sort by [bytes | packets]
7.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-top-talkers
Enters NetFlow top talkers configuration mode.
Example:
Router(config)# ip flow-top-talkers
Step 4
match destination address
ip-address/prefix-mask
Specifies the destination IP addresses to match.
Example:
Router(config-flow-top-talkers)# match
destination address 172.16.10.2/32
Step 5
top number
Specifies the maximum number of top talkers that will be
retrieved by a NetFlow top talkers query.
Example:
Router(config-flow-top-talkers)# top 50
Step 6
sort-by [bytes | packets]
Specifies the sort criterion for the top talkers.
•
Example:
Router(config-flow-top-talkers)#
sort-by packets
Step 7
end
The top talkers can be sorted either by the total number
of packets of each top talker or the total number of
bytes of each top talker.
Exits to privileged EXEC mode.
Example:
Router(config-flow-top-talkers)# end
29
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Monitoring and Analyzing the NetFlow Top Talkers Flows
To monitor and analyze the NetFlow Top Talkers flows, use the following step.
SUMMARY STEPS
1.
show ip flow top-talkers verbose
DETAILED STEPS
Step 1
show ip flow top-talkers verbose
The following sample shows details for the six traffic flows that are being sent to the host with IP address
172.16.10.2.
Router# show ip flow top-talkers verbose
30
SrcIf
SrcIPaddress
Port Msk AS
Et0/0.1
10.106.1.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
8
IP id:
0
DstIf
Port Msk AS
Et1/0.1
0800 /0 0
(005)
DstIPaddress
NextHop
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
Pr TOS Flgs Bytes
B/Pk Active
01 00 10
9408
28
116.3
(006)
28
59
0
Et0/0.1
10.132.221.111
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
8
IP id:
0
Et1/0.1
0800 /0
(005)
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
0
Et0/0.1
10.10.12.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
0
Et0/0.1
10.251.138.218
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
0
Et0/0.1
10.71.200.138
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
0
Et0/0.1
0000 /0
Et1/0.1
0C01 /0
172.16.10.2
0.0.0.0
01 00
10.231.185.254
0
0
10
28
9408
116.4
10
28
9408
116.4
10
28
9408
116.4
10
28
9408
116.5
10
28
9408
116.5
(006)
28
59
0
(006)
28
59
1
(006)
28
59
1
(006)
28
59
1
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
(005)
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
(006)
28
59
1
6 of 50 top talkers shown. 6 of 8 flows matched.
Note
Only six of the eight flows matched because the rest of the flows are not top talker flows.
Note
The top 50 flows were requested, however there are only eight flows in the cache.
This display output contains the information required for determining the path that the DoS attack traffic
is taking through the network. This information will be used to react to the DoS attack by adding security
measures such as access-lists to the affected interfaces. Table 10 describes the significant fields in the
display from the show ip flow top-talkers verbose command for determining the network path the DoS
traffic is taking.
Table 10
Significant Field Descriptions for show ip flow top-talkers verbose
Field
Description
SrcIf
Interface on which the packet was received.
•
SrcIPaddress
DstIf
This is the source IP address of the traffic in the six top
talkers. The traffic is using 6 different IP source addresses
•
10.132.221.111
•
10.10.12.1
•
10.251.138.218
•
10.71.200.138
•
10.231.185.254
•
10.106.1.1
Interface from which the packet was transmitted.
•
Note
ICMP Type
All of the ICMP DoS traffic is being received on Et0/0.1
All of the ICMP DoS traffic is being transmitted over
Et1/0.1
If an asterisk (*) immediately follows the DstIf field,
the flow being shown is an egress flow.
The ICMP datagram types
•
8—Echo
•
12—Parameter Problem
31
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Table 10
Significant Field Descriptions for show ip flow top-talkers verbose (continued)
Field
Description
ICMP Code
The ICMP codes
•
0—None (not applicable)
•
1—Depends on the ICMP Type
– A code value of 1 for ICMP type 12 indicates that a
required option is missing
DstIPaddress
This is the destination IP address of the traffic.
Note
MAC
These are the source and destination MAC addresses from the
traffic. The source and destination MAC address are read
from left to right in the output.
•
Note
•
Note
VLAN id
172.17.10.2 is the IP address that is being attacked.
The traffic is being received from MAC address
aaa.bbb.cc03.
This MAC address is interface 1/0.1 on router R2.
The traffic is being transmitted to MAC address
aaa.bbb.cc06.
This MAC address is interface 1/0.1 on router R4.
These are the source and destination VLAN IDs. The source
and destination VLAN IDs are read from left to right in the
output.
•
The traffic is being received from VLAN 5.
•
The traffic is being transmitted to VLAN 6.
This flows in this example show only the ICMP DoS attack traffic that is destined for the host with IP
address 172.16.10.1. These flows were created specifically for documenting this task. In a real network
the host under attack might be communicating with other hosts that are using legitimate applications
such as e-mail and web sites. In this case the Top Talkers match filter on the destination IP address
(match destination address 172.16.10.2/32) that was configured in the “Configuring NetFlow Top
Talkers to Monitor Network Threats” section on page 28 will not limit the display of the show ip flow
top-talkers command to the ICMP DoS attack traffic.
Note
For more information on the fields in the display output of the show ip cache verbose flow command,
refer to the Cisco IOS NetFlow Command Reference.
If you are using the Top Talkers feature to analyze a network threat and you are not able to use the basic
match filters to limit the display of the show ip flow top-talkers command to the traffic that you are
analyzing, you can use NetFlow filtering and sampling to limit the traffic that shows up in the display of
the show ip flow top-talkers command. The process for configuring NetFlow filtering and sampling is
explained in the “Configuring NetFlow Filtering and Sampling” section on page 33.
32
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Configuring NetFlow Filtering and Sampling
If you use the show ip cache flow command or the show ip cache verbose flow command to display the
flows in the cache, you will see the ICMP flows that are selected by NetFlow filtering and sampling on
interface Ethernet0/0.1, and flows for all NetFlow supported traffic types on any other interfaces that
NetFlow is running on. The show ip flow top-talkers [verbose] command is used to display the flow
status and statistics for the traffic type you configured with the match criteria over interfaces to which
you applied the service policy. For example, in this case you configured top talkers to match on ICMP
traffic sent from any host that is arriving on Ethernet0/0.1 and destined for 172.16.10.2.
In this task the Top Talkers feature is being used more as a flow filter to separate flows of interest from
all of the flows the router is seeing, rather than a filter to display the flows with the highest traffic
volumes. Top talkers is used in this manner because in this example all of the ICMP DoS attack flows
are of interest, not just the flows with the highest volumes. This is why a large value is assigned to the
top keyword in the top talkers configuration. Setting the value for the top keyword to 50 when the largest
number of ICMP DoS attack flows tracked by the router is 12 ensures that all of the ICMP DoS attack
flows will be tracked.
If your router sees a significant number of flows involved in a DoS attack, you might want to set the
value for the top keyword to a number that is less than the total number of flows to limit the number of
flows that you see in the display when you use the show ip flow top-talkers command. This will ensure
that you are seeing the flows that have the highest volume of DoS attack traffic. However, if all of the
flows have the same traffic volume, the show ip flow top-talkers command will not be able to
differentiate between them. It displays the number of flows that you set the value of the top keyword to,
starting from the first flow in the cache.
Perform the following task to configure NetFlow Filtering and sampling.
Restrictions
Restrictions for NetFlow Input Filters
On Cisco 7500 platforms, the NetFlow Input Filters feature is supported only in distributed mode.
Restrictions for Random Sampled NetFlow
If full NetFlow is enabled on an interface, it takes precedence over Random Sampled NetFlow (which
will thus have no effect). Disable full NetFlow on an interface before enabling Random Sampled
NetFlow on that interface.
Enabling Random Sampled NetFlow on a physical interface does not automatically enable Random
Sampled NetFlow on subinterfaces; you must explicitly configure it on subinterfaces. Also, disabling
Random Sampled NetFlow on a physical interface (or a subinterface) does not enable full NetFlow. This
restriction prevents the transition to full NetFlow from overwhelming the physical interface (or
subinterface). If you want full NetFlow, you must explicitly enable it.
You must use NetFlow Version 9 if you want to use sampler option templates or view NetFlow sampler
IDs.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
flow-sampler-map sampler-map-name
4.
mode random one-out-of packet-interval
33
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
5.
exit
6.
class-map [match-all | match-any] class-map-name
7.
match access-group access-group
8.
exit
9.
policy-map policy-map-name
10. class {class-name | class-default}
11. netflow-sampler sampler-map-name
12. exit
13. exit
14. interface interface-type interface-number
15. no [ip route-cache flow | ip flow ingress]
16. service-policy {input | output} policy-map-name
17. exit
18. ip flow-top-talkers
19. top number
20. sort-by packets
21. match class-map class-name
22. no match destination address ip-address/prefix-mask
23. exit
24. access-list access-list-number permit icmp source destination
25. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
flow-sampler-map sampler-map-name
Example:
Router(config)# flow-sampler-map icmp-dos-fs-map
Defines a statistical sampling NetFlow export flow
sampler map.
•
The sampler-map-name argument is the name of
the flow sampler map to be defined.
Entering the flow-sampler-map command enables
the flow sampler configuration mode.
34
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Step 4
Command or Action
Purpose
mode random one-out-of packet-interval
Specifies a statistical sampling NetFlow export
random sampling mode and a packet interval.
Example:
•
The random keyword specifies that sampling
uses the random sampling mode.
•
The one-out-of packet-interval
argument-keyword pair specifies the packet
interval (one out of every n packets) from which
to sample. For n, you can specify from 1 to 65535
(packets).
Router(config-sampler-map)# mode random one-out-of 2
Step 5
exit
Exits back to global configuration mode.
Example:
Router(config-sampler-map)# exit
Step 6
class-map class-map-name [match-all | match-any]
Example:
Creates a class map to be used for matching packets to
a specified class.
•
The class-map-name argument is the name of the
class for the class map. The name can be a
maximum of 40 alphanumeric characters. The
class name is used for both the class map and for
configuring policy for the class in the policy map.
•
The match-all | match-any keywords determine
how packets are evaluated when multiple match
criteria exist. Packets must either meet all of the
match criteria (match-all) or only one of the
match criteria (match-any) to be considered a
member of the class.
Router(config)# class-map match-any
icmp-dos-class-map
Entering the class-map command enables class-map
configuration mode, in which you can enter one of the
match commands to configure the match criteria for
this class.
Step 7
match access-group access-group
Example:
Router(config-cmap)# match access-group 101
Step 8
exit
Configures the match criteria for a class map on the
basis of the specified access control list (ACL).
•
The access-group argument is a numbered ACL
whose contents are used as the match criteria
against which packets are checked to determine if
they belong to this class. An ACL number can be
a number from 1 to 2699.
Exits back to global configuration mode.
Example:
Router(config-cmap)# exit
35
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Step 9
Command or Action
Purpose
policy-map policy-map-name
Creates or modifies a policy map that can be attached
to one or more interfaces to specify a service policy.
Example:
•
Router(config)# policy-map icmp-dos-policy-map
The policy-map-name argument is the name of
the policy map. The name can be a maximum of
40 alphanumeric characters.
Entering the policy-map command enables quality of
service (QoS) policy-map configuration mode, in
which you can configure or modify the class policies
for that policy map
Step 10
class {class-name | class-default}
Example:
Router(config-pmap)# class icmp-dos-class-map
Specifies the name of the class whose policy you want
to create or change or specifies the default class
(commonly known as the class-default class) before
you configure its policy.
•
The class-name argument is the name of the class
for which you want to configure or modify policy.
•
The class-default keyword specifies the default
class so that you can configure or modify its
policy.
Entering the class command enables QoS policy-map
class configuration mode.
Step 11
netflow-sampler sampler-map-name
Enables a NetFlow input filter sampler.
•
Example:
Step 12
The sampler-map-name argument is the name of
the NetFlow sampler map to apply to the class.
Router(config-pmap-c)# netflow-sampler
icmp-dos-fs-map
You can assign only one NetFlow input filter sampler
to a class. Assigning another NetFlow input filter
sampler to a class overwrites the previous one.
exit
Exits back to policy-map configuration mode.
Example:
Router(config-pmap-c)# exit
Step 13
exit
Exits back to global configuration mode.
Example:
Router(config-pmap# exit
Step 14
interface interface-type
interface-number[.subinterface number]
Specifies the interface and enters subinterface
configuration mode.
•
The interface-type argument is the type of
interface to be configured.
•
The interface-number argument is the number of
the interface. Refer to the appropriate hardware
manual for slot and port information.
Example:
Router(config)# interface Ethernet0/0.1
36
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Step 15
Command or Action
Purpose
no [ip route-cache flow | ip flow ingress]
Removes the existing NetFlow command from the
interface.
Example:
Note
Router(config-subif)# no ip flow ingress
Step 16
service-policy {input | output} policy-map-name
Example:
Router(config-subif)# service-policy input
icmp-dos-policy-map
Step 17
exit
NetFlow sampling and filtering can not start if
there is another command on the interface that
is enabling NetFlow.
Attaches a policy map to an input interface or virtual
circuit (VC), or an output interface or VC, to be used
as the service policy for that interface or VC.
•
The input keyword attaches the specified policy
map to the input interface or input VC.
•
The output keyword attaches the specified policy
map to the output interface or output VC.
•
The policy-map-name is the name of a service
policy map (created through use of the
policy-map command) to be attached. The name
can be a maximum of 40 alphanumeric
characters.
Exits back to global configuration mode.
Example:
Router(config-subif)# exit
Step 18
ip flow-top-talkers
Enters NetFlow top talkers configuration mode.
Example:
Router(config)# ip flow-top-talkers
Step 19
top number
Specifies the maximum number of top talkers that will
be retrieved by a NetFlow top talkers query.
Example:
Router(config-flow-top-talkers)# top 50
Step 20
sort-by packets
Specifies the sort criterion for the top talkers.
•
Example:
Router(config-flow-top-talkers)# sort-by packets
Step 21
match class-map class-name
The top talkers can be sorted either by the total
number of packets of each top talker or the total
number of bytes of each top talker.
Specifies that the match criteria should be obtained
from the class-map.
Example:
Router(config-flow-top-talkers)# match class-map
icmp-dos-class-map
Step 22
no match destination address ip-address/prefix-mask
Example:
(Optional) If you still have a match entry for the
destination address you should remove it so that only
the class-name match criteria is used.
Router(config-flow-top-talkers)# no match
destination address 172.16.10.2/32
37
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Step 23
Command or Action
Purpose
exit
Exits back to global configuration mode.
Example:
Router(config-sampler-map)# exit
Step 24
access-list access-list-number permit icmp source
destination
Creates an extended access list that is used to track
any host that is sending ICMP traffic to 172.16.10.2.
Example:
Router(config)# access-list 101 permit icmp any host
172.16.10.2
Step 25
Exits to privileged EXEC mode.
end
Example:
Router(config)# end
Verify NetFlow Filtering and Sampling
To verify that filtering and sampling is working properly, use the following step.
SUMMARY STEPS
1.
show flow-sampler
DETAILED STEPS
Step 1
show flow-sampler
Any non-zero value in the display output below indicates that Filtering and sampling is active.
Router# show flow-sampler
Sampler : icmp-dos-fs-map, id : 1, packets matched : 63226, mode : random sampling mode
sampling interval is : 2
Router
38
Detecting and Analyzing Network Threats With NetFlow
How to Configure and Use NetFlow to Detect and Analyze Network Threats
Monitoring and Analyzing the Sampled and Filtered NetFlow Top Talkers Flows
To monitor and analyze the filtered and sampled NetFlow top talkers flows use the following step.
SUMMARY STEPS
1.
show ip flow top-talkers
2.
show ip flow top-talkers verbose
DETAILED STEPS
Step 1
show ip flow top-talkers verbose
The following sample output shows the six traffic flows that are being sent to the host with IP address
172.16.10.2.
Router# show ip flow top-talkers
SrcIf
SrcIPaddress
DstIf
DstIPaddress
Et0/0.1
10.231.185.254 Et1/0.1
172.16.10.2
Et0/0.1
10.106.1.1
Et1/0.1
172.16.10.2
Et0/0.1
10.132.221.111 Et1/0.1
172.16.10.2
Et0/0.1
10.251.138.218 Et1/0.1
172.16.10.2
Et0/0.1
10.10.12.1
Et1/0.1
172.16.10.2
Et0/0.1
10.71.200.138
Et1/0.1
172.16.10.2
6 of 50 top talkers shown. 6 of 7 flows matched.
Step 2
Pr
01
01
01
01
01
01
SrcP
0000
0000
0000
0000
0000
0000
DstP Bytes
0C01 5460
0800 5124
0800 5012
0C01 4844
0C01 4704
0C01 4396
show ip flow top-talkers verbose
The following sample output below shows the details for the six traffic flows that are being sent to the
host with IP address 172.16.10.2.
Router# show ip flow top-talkers verbose
SrcIf
SrcIPaddress
Port Msk AS
Et0/0.1
10.106.1.1
0000 /0 0
Sampler: 1 Class: 1
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
8
IP id:
0
DstIf
Port Msk AS
Et1/0.1
0800 /0 0
DstIPaddress
NextHop
172.16.10.2
0.0.0.0
Pr TOS Flgs Bytes
B/Pk Active
01 00 10
2884
28
64.6
(005)
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
(006)
28
59
0
Et0/0.1
10.132.221.111
0000 /0 0
Sampler: 1 Class: 1
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
8
IP id:
0
Et1/0.1
0800 /0
172.16.10.2
0.0.0.0
01 00
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
(006)
28
59
0
Et0/0.1
10.231.185.254
0000 /0 0
Sampler: 1 Class: 1
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
Et1/0.1
0C01 /0
172.16.10.2
0.0.0.0
01 00
aaaa.bbbb.cc06
Max plen:
Max TTL:
(006)
28
59
0
(005)
(005)
0
10
28
2828
64.6
10
28
2716
64.6
39
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
ICMP type:
IP id:
12
0
ICMP code:
Et0/0.1
10.71.200.138
0000 /0 0
Sampler: 1 Class: 1
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
Et0/0.1
10.251.138.218
0000 /0 0
Sampler: 1 Class: 1
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
Et0/0.1
10.10.12.1
0000 /0 0
Sampler: 1 Class: 1
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
28
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
0
(005)
0
(005)
(005)
0
1
172.16.10.2
0.0.0.0
01 00
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
(006)
28
59
1
172.16.10.2
0.0.0.0
01 00
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
(006)
28
59
1
172.16.10.2
0.0.0.0
01 00
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
(006)
28
59
1
10
28
2548
58.0
10
28
2436
64.6
10
28
2352
57.7
6 of 50 top talkers shown. 6 of 7 flows matched.
Configuration Examples for Detecting and Analyzing Network
Threats With NetFlow
This section provides the following configuration examples:
40
•
Configuring NetFlow Layer 2 and Security Monitoring Exports to Capture Traffic From a Simulated
FTP Attack: Example, page 41
•
Analyze an FTP DoS Attack Using the show ip cache verbose flow command: Example, page 43
•
Analyze an FTP DoS Attack Using NetFlow Dynamic Top Talkers CLI: Example, page 45
•
Configuring NetFlow Layer 2 and Security Monitoring Exports to Capture Traffic From a Simulated
ICMP Attack: Example, page 46
•
Analyze an ICMP Ping DoS Attack Using the show ip cache verbose flow command: Example,
page 48
•
Analyze an ICMP Ping DoS Attack Using NetFlow Dynamic Top Talkers CLI: Example, page 51
•
Configure NetFlow Filtering and Sampling: Example, page 53
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
Configuring NetFlow Layer 2 and Security Monitoring Exports to Capture Traffic
From a Simulated FTP Attack: Example
The following example shows how to use the NetFlow Layer 2 and Security Monitoring Exports feature
to find out whether your network is being attacked by a host that is sending fake FTP traffic in an attempt
to overwhelm the FTP server. This attack might cause end users to see a degradation in the ability of the
FTP server to accept new connections or to service existing connections.
This example uses the network shown in Figure 7. Host A is sending fake FTP packets to the FTP server.
This example also shows you how to use the Layer 2 data captured by the NetFlow Layer 2 and Security
Monitoring Exports feature to learn where the traffic is originating and what path it is taking through the
network.
Figure 7
Test Network
Simulated DoS attack
aaaa.bbbb.cc03 aaaa.bbbb.cc04 aaaa.bbbb.cc05 aaaa.bbbb.cc06
172.16.6.1
172.16.6.2
172.16.7.1
172.16.7.2
S2/0
172.16.1.2
E0/0
172.16.1.1
FTP server
S2/0
172.16.10.1
R2 E1/0.1
S3/0
E0/0.1
802.1q trunk
VLAN 5
R3
E1/0.1
E1/0.1
R4
S3/0
E0/0
172.16.10.2
802.1q trunk
VLAN 6
127556
Host A
Tip
Keep track of the MAC addresses and IP addresses of the devices in your network. You can use them to
analyze attacks and to resolve problems.
Note
This example does not include the ip flow-capture icmp command that captures the value of the ICMP
type and code fields. The use of the ip flow-capture icmp command is described in “Configuring
NetFlow Layer 2 and Security Monitoring Exports to Capture Traffic From a Simulated ICMP Attack:
Example.”
R2
!
hostname R2
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc02
ip address 172.16.1.2 255.255.255.0
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc03
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 5
41
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
ip address 172.16.6.1 255.255.255.0
!
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R3
!
hostname R3
!
ip flow-capture fragment-offset
ip flow-capture packet-length
ip flow-capture ttl
ip flow-capture vlan-id
ip flow-capture ip-id
ip flow-capture mac-addresses
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc04
no ip address
!
interface Ethernet0/0.1
encapsulation dot1Q 5
ip address 172.16.6.2 255.255.255.0
ip accounting output-packets
ip flow ingress
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc05
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.1 255.255.255.0
ip accounting output-packets
ip flow egress
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R4
!
hostname R4
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc07
ip address 172.16.10.1 255.255.255.0
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc06
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.2 255.255.255.0
!
42
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
router rip
version 2
network 172.16.0.0
no auto-summary
!
Analyze an FTP DoS Attack Using the show ip cache verbose flow command:
Example
The show ip cache verbose flow command displays the NetFlow flows. You can use this display output
to identify the path that the FTP traffic from Host A is taking as it is received and transmitted by R3.
Note
To reduce the space required to display the output from the show ip flow cache verbose flow command
only the FTP flows are shown.
Tip
Look for the flows that have FTP in them and make a note of the interfaces, MAC addresses, and VLANs
(if applicable) for the flows.
R3# show ip cache verbose flow
IP packet size distribution (189118 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.043 .610 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .173 .000 .173 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
25 active, 4071 inactive, 615 added
263794 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 25736 bytes
50 active, 974 inactive, 1648 added, 615 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-FTP
12
0.0
895
40
0.9
1363.8
5.5
TCP-FTPD
12
0.0
895
40
0.9
1363.8
5.6
Total:
590
0.0
317
383
16.1
430.1
12.4
Et0/0.1
192.168.87.200
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Et0/0.1
192.168.87.200
0014 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
Et1/0.1
0014 /0
(005)
0
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
00
40
63
94.5
00
40
63
94.5
(006)
40
59
(006)
40
59
43
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
IP id:
0
Et0/0.1
10.10.10.2
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Et0/0.1
10.10.10.2
0014 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0014 /0
(005)
0
Et0/0.1
10.234.53.1
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Et0/0.1
10.234.53.1
0014 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0014 /0
(005)
0
Et0/0.1
172.30.231.193
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Et0/0.1
172.30.231.193
0014 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
40
Min TTL:
59
IP id:
0
Et1/0.1
0014 /0
(005)
0
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 00
00
40
64
96.0
00
40
64
96.0
00
40
63
94.5
00
40
63
94.5
00
40
63
94.5
00
40
63
94.5
(006)
40
59
(006)
40
59
(006)
40
59
(006)
40
59
(006)
40
59
(006)
40
59
There are 8 FTP flows shown in the output. You can use the Layer 2 information in the flows that is
captured by the ip flow-capture command to identify the path the traffic is taking through the network.
In this example, the traffic is being sent to R3 on VLAN 5 by R2. You can demonstrate that R2 is
transmitting the traffic over interface 1/0.1 because the source MAC address (aaaa.bbb.cc03) belongs to
1/0.1 on R2. You can demonstrate that R3 is transmitting the traffic using VLAN 6 on interface 1/0.1 to
interface 1/0.1 on R4, because the destination MAC address (aaaa.bbbb.cc06) belongs to interface 1/0.1
on R4.
Note
For more information on the ip flow-capture command, and the fields in the display output of the show
ip cache verbose flow command, refer to the Cisco IOS NetFlow Command Reference.
You can use this information to mitigate this attack. One possible way to mitigate this attack is by
configuring an extended IP access list that blocks all FTP traffic from the source IP addresses that Host
A is spoofing and applying it Ethernet 0/0 on R2.
44
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
Analyze an FTP DoS Attack Using NetFlow Dynamic Top Talkers CLI: Example
You can use the NetFlow Dynamic Top Talkers CLI feature to quickly identify the FTP top talkers in the
network traffic that might be sending the traffic. This will show you the IP source addresses that Host A
is using as it sends the DoS attack traffic.
R3# show ip flow top 50 aggregate source-address sorted-by bytes descending match
destination-port min 20 max 21
There are 5 top talkers:
IPV4 SRC-ADDR
===============
10.231.185.254
10.132.221.111
10.10.12.1
10.251.138.218
10.71.200.138
bytes
==========
5640
3680
3640
3600
1880
pkts
==========
141
92
91
90
47
flows
==========
2
2
2
2
1
9 of 34 flows matched.
Note
Only source IP addresses from FTP traffic are shown because of the match destination-port min 20
max 21 criteria. The source addresses are aggregated together so only the most relevant sources are
shown.
Note
Only nine of the 34 flows matched because the rest of the flows are not FTP flows, therefore they do not
meet the match criteria (match destination-port min 20 max 21).
Tip
The top talkers are displayed in descending order of the aggregated field by default.
Tip
You can enter the port numbers in their decimal values as shown, or in their hexadecimal equivalents of
0x14 and 0x15.
After you have identified FTP top talkers traffic you need to identify the source IP addresses of IP traffic
that is being sent to the host that you believe is under attack.
R3# show ip flow top 50 aggregate source-address match destination-prefix 172.16.10.2/32
There are 6 top talkers:
IPV4 SRC-ADDR
===============
10.251.138.218
10.231.185.254
10.132.221.111
10.106.1.1
10.71.200.138
10.10.12.1
bytes
==========
6642
5068
14818
12324
12564
560
pkts
==========
18
28
25
12
18
14
flows
==========
4
4
4
2
3
2
19 of 33 flows matched.
45
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
Tip
You can specify the host that you believe is under attack by using a prefix value of 32 with the match
destination-prefix command.
Note
Only 19 of the 33 flows matched because the rest of the flows do not contain traffic that is destined for
the host with the IP address of 172.16.10.2, therefore they do not meet the match criteria (match
destination-prefix 172.16.10.2/32).
The final step is to cross reference the source IP addresses of any hosts that are sending any IP traffic to
the host under attack with the list of source IP addresses from the FTP top talkers. This is required
because the show ip flow top command does not support multiple match criteria. Therefore you cannot
limit the top talkers to FTP traffic being sent to a specific host with a single show ip flow top command
(match destination-port min 20 max 21 <and> match destination-prefix 172.16.10.2/32).
The host with the IP address of 10.106.1.1 is apparently not involved in this DoS attack because it is not
in the display output from the show ip flow top 50 aggregate source-address sorted-by bytes
descending match destination-port min 20 max 21 command. This means that it is not sending FTP
traffic to the host that is under attack.
Therefore the host IP addressees involved in this FTP DoS attack are likely to be:
•
10.231.185.254
•
10.132.221.111
•
10.10.12.1
•
10.251.138.218
•
10.71.200.138
Now that you know the source addresses of the FTP traffic you can configure an extended access list that
blocks FTP traffic from these address, and applying it to the interface that is closest to the point the
traffic in entering your network.
Note
Unless you recognize that some of the source IP addresses are not legitimate IP addresses for your
network it might not be possible to identify legitimate FTP traffic from FTP DoS attack traffic.
Configuring NetFlow Layer 2 and Security Monitoring Exports to Capture Traffic
From a Simulated ICMP Attack: Example
The following example shows how to use the NetFlow Layer 2 and Security Monitoring Exports feature
to find out that your network is being attacked by ICMP traffic. It uses the network shown in Figure 8.
Host A is sending ICMP ping packets to the FTP server.
46
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
Figure 8
Test Network
Simulated DoS attack
aaaa.bbbb.cc03 aaaa.bbbb.cc04 aaaa.bbbb.cc05 aaaa.bbbb.cc06
172.16.6.1
172.16.6.2
172.16.7.1
172.16.7.2
S2/0
172.16.1.2
E0/0
172.16.1.1
172.16.10.1
R2 E1/0.1
S3/0
E0/0.1
802.1q trunk
VLAN 5
Tip
FTP server
S2/0
R3
E1/0.1
E1/0.1
R4
S3/0
E0/0
172.16.10.2
802.1q trunk
VLAN 6
127556
Host A
Keep track of the MAC addresses and IP addresses of the devices in your network. You can use them to
analyze attacks and to resolve problems.
R2
!
hostname R2
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc02
ip address 172.16.1.2 255.255.255.0
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc03
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 5
ip address 172.16.6.1 255.255.255.0
!
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R3
!
hostname R3
!
ip flow-capture fragment-offset
ip flow-capture packet-length
ip flow-capture ttl
ip flow-capture vlan-id
ip flow-capture icmp
ip flow-capture ip-id
ip flow-capture mac-addresses
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc04
no ip address
47
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
!
interface Ethernet0/0.1
encapsulation dot1Q 5
ip address 172.16.6.2 255.255.255.0
ip accounting output-packets
ip flow ingress
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc05
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.1 255.255.255.0
ip accounting output-packets
ip flow egress
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R4
!
hostname R4
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc07
ip address 172.16.10.1 255.255.255.0
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc06
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.2 255.255.255.0
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
Analyze an ICMP Ping DoS Attack Using the show ip cache verbose flow
command: Example
The show ip cache verbose flow command displays the NetFlow flows. You can use this display output
to identify the path that the ICMP traffic from Host A is taking as it is received and transmitted by R3.
Note
48
To reduce the space required to display the output from the show ip flow cache verbose flow command
only the ICMP flows are shown.
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
Tip
Look for the flows that have ICMP in them and make a note of the interfaces, MAC addresses, and
VLANs (if applicable) for the flows.
R3# show ip cache verbose flow
IP packet size distribution (122369 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.065 .665 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .134 .000 .134 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
24 active, 4072 inactive, 404 added
176657 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 25736 bytes
48 active, 976 inactive, 1088 added, 404 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
ICMP
27
0.0
1131
763
3.9
1557.4
3.6
Total:
380
0.0
267
257
13.0
382.8
12.6
SrcIf
Port Msk AS
Et0/0.1
0000 /0 0
MAC: (VLAN id)
Min plen:
Min TTL:
ICMP type:
IP id:
SrcIPaddress
DstIf
Port Msk AS
Et1/0.1
0800 /0 0
(005)
DstIPaddress
NextHop
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
Et0/0.1
10.71.200.138
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
554
Min TTL:
59
ICMP type:
0
IP id:
0
Et1/0.1
0000 /0
(005)
0
172.16.10.2
01 00 00
0.0.0.0
554
aaaa.bbbb.cc06 (006)
Max plen:
554
Max TTL:
59
ICMP code:
0
FO:
185
864
1090.0
Et0/0.1
10.231.185.254
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
554
Min TTL:
59
ICMP type:
0
IP id:
0
Et1/0.1
0000 /0
(005)
0
172.16.10.2
01 00 00
0.0.0.0
554
aaaa.bbbb.cc06 (006)
Max plen:
554
Max TTL:
59
ICMP code:
0
FO:
185
864
1090.0
Et0/0.1
10.10.12.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
554
Min TTL:
59
ICMP type:
0
IP id:
0
Et1/0.1
0000 /0
(005)
0
172.16.10.200
01 00 00
0.0.0.0
554
aaaa.bbbb.cc06 (006)
Max plen:
554
Max TTL:
59
ICMP code:
0
FO:
185
864
1090.0
Et0/0.1
Et1/0.1
10.106.1.1
aaaa.bbbb.cc03
1500
59
8
0
10.132.221.111
172.16.10.2
Pr TOS Flgs Pkts
B/Pk Active
01 00 10
864
1500 1089.9
(006)
1500
59
0
01 00
10
864
49
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
50
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
1500
Min TTL:
59
ICMP type:
8
IP id:
0
0800 /0
(005)
0
Et0/0.1
10.251.138.218
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
554
Min TTL:
59
ICMP type:
0
IP id:
0
Et1/0.1
0000 /0
(005)
0
Et0/0.1
10.10.12.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
1500
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
0
Et0/0.1
10.106.1.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
554
Min TTL:
59
ICMP type:
0
IP id:
0
Et1/0.1
0000 /0
(005)
0
Et0/0.1
10.251.138.218
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
1500
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
0
Et0/0.1
10.71.200.138
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
1500
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
0
Et0/0.1
10.132.221.111
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
554
Min TTL:
59
ICMP type:
0
IP id:
0
Et1/0.1
0000 /0
(005)
0
Et0/0.1
10.231.185.254
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
1500
Min TTL:
59
ICMP type:
12
IP id:
0
Et1/0.1
0C01 /0
(005)
0
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
1500
1089.9
172.16.10.2
01 00 00
0.0.0.0
554
aaaa.bbbb.cc06 (006)
Max plen:
554
Max TTL:
59
ICMP code:
0
FO:
185
864
1089.9
172.16.10.200
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
10
1500
864
1090.0
172.16.10.2
01 00 00
0.0.0.0
554
aaaa.bbbb.cc06 (006)
Max plen:
554
Max TTL:
59
ICMP code:
0
FO:
185
864
1089.9
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
10
1500
864
1089.9
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
01 00
10
1500
864
1090.0
172.16.10.2
01 00 00
0.0.0.0
554
aaaa.bbbb.cc06 (006)
Max plen:
554
Max TTL:
59
ICMP code:
0
FO:
185
864
1089.9
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
ICMP code:
864
1090.0
(006)
1500
59
0
01 00
(006)
1500
59
1
(006)
1500
59
1
(006)
1500
59
1
01 00
(006)
1500
59
1
10
1500
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
There are 12 ICMP flows shown in the output. You can use the Layer 2 information in the flows that is
captured by the ip flow-capture command to identify the path the traffic is taking through the network.
In this example, the traffic is being sent to R3 on VLAN 5 by R2. You can demonstrate that R2 is
transmitting the traffic over interface 1/0.1 because the source MAC address (aaaa.bbb.cc03) belongs to
1/0.1 on R2. You can demonstrate that R3 is transmitting the traffic using VLAN 6 on interface 1/0.1 to
interface 1/0.1 on R4, because the destination MAC address (aaaa.bbbb.cc06) belongs to interface 1/0.1
on R4.
Note
For more information on the ip flow-capture command, and the fields in the display output of the show
ip cache verbose flow command, refer to the Cisco IOS NetFlow Command Reference.
You can use this information to mitigate this attack. One possible way to mitigate this attack is by
configuring an extended IP access list that blocks all ICMP traffic from the source IP addresses that Host
A is spoofing and applying it Ethernet 0/0 on R2.
Analyze an ICMP Ping DoS Attack Using NetFlow Dynamic Top Talkers CLI:
Example
You can use the NetFlow Dynamic Top Talkers CLI feature to quickly identify the ICMP top talkers in
the network traffic that might be sending the traffic. This will show you the IP source addresses that Host
A is using as it sends the DoS attack traffic.
R3# show ip flow top 50 aggregate icmp
There are 3 top talkers:
ICMP TYPE
=========
12
8
0
ICMP CODE
=========
1
0
0
bytes
==========
2466000
1233000
1366164
pkts
==========
1644
822
2466
flows
==========
4
2
6
12 of 25 flows matched.
Note
Only 12 of the 25 flows matched because the rest of the flows are not ICMP flows.
Tip
The top talkers are displayed in descending order of the aggregated field by default.
After you have identified the ICMP types and code values in the network traffic, you need to determine
the source IP addresses for the ICMP traffic that being sent to the FTP server.
R3# show ip flow top 50 aggregate source-address match icmp type 12 code 1
There are 4 top talkers:
IPV4 SRC-ADDR
===============
10.251.138.218
10.231.185.254
10.71.200.138
10.10.12.1
bytes
==========
867000
865500
865500
867000
pkts
==========
578
577
577
578
flows
==========
1
1
1
1
51
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
4 of 24 flows matched.
Note
Only source IP addresses from ICMP traffic are shown because of the match icmp type 12 code 1
criteria. No aggregation is performed on the source IP addresses because there is only one flow for IP
each address.
Note
Only four of the 24 flows matched because the rest of the flows did not meet the match criteria
(match icmp type 12 code 1).
R3# show ip flow top 50 aggregate source-address match icmp type 8 code 0
There are 2 top talkers:
IPV4 SRC-ADDR
===============
10.132.221.111
10.106.1.1
bytes
==========
1095000
1095000
pkts
==========
730
730
flows
==========
1
1
2 of 24 flows matched.
Note
Only source IP addresses from ICMP traffic are shown because of the match icmp type 8 code 0 criteria.
No aggregation is performed on the source IP addresses because there is only one flow for IP each
address.
Note
Only two of the 24 flows matched because the rest of the flows did not meet the match criteria
(match icmp type 8 code 0).
R3# show ip flow top 50 aggregate source-address match icmp type 0 code 0
There are 6 top talkers:
IPV4 SRC-ADDR
===============
10.251.138.218
10.231.185.254
10.132.221.111
10.106.1.1
10.71.200.138
10.10.12.1
bytes
==========
416608
416608
416608
416608
416608
416608
pkts
==========
752
752
752
752
752
752
flows
==========
1
1
1
1
1
1
6 of 24 flows matched.
Note
52
Only source IP addresses from ICMP traffic are shown because of the match icmp type 0 code 0 criteria.
No aggregation is performed on the source IP addresses because there is only one flow for IP each
address.
Detecting and Analyzing Network Threats With NetFlow
Configuration Examples for Detecting and Analyzing Network Threats With NetFlow
Note
Only six of the 24 flows matched because the rest of the flows did not meet the match criteria
(match icmp type 0 code 0).
The next step is to create a list of the source IP addresses that Host A is using.
•
10.251.138.218
•
10.231.185.254
•
10.71.200.138
•
10.10.12.1
•
10.132.221.111
•
10.106.1.1.
Now that you know the source addresses of the ICMP DoS attack traffic you can mitigate this attack by
configuring an extended access list that blocks ICMP traffic from these address and applying it to the
interface that is closest to the point the traffic in entering your network.
Configure NetFlow Filtering and Sampling: Example
This example configuration contains the configuration commands required to use NetFlow filtering and
sampling on the NetFlow router.
!
hostname Router
!
ip cef
!
flow-sampler-map icmp-dos-fs-map
mode random one-out-of 2
!
!
class-map match-any icmp-dos-class-map
match access-group 101
!
!
policy-map icmp-dos-policy-map
class icmp-dos-class-map
netflow-sampler icmp-dos-fs-map
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc04
no ip address
!
interface Ethernet0/0.1
encapsulation dot1Q 5
ip address 172.16.6.2 255.255.255.0
service-policy input icmp-dos-policy-map
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.1 255.255.255.0
ip flow egress
!
ip flow-capture fragment-offset
ip flow-capture packet-length
ip flow-capture ttl
ip flow-capture vlan-id
53
Detecting and Analyzing Network Threats With NetFlow
Where to Go Next
ip flow-capture icmp
ip flow-capture ip-id
ip flow-capture mac-addresses
!
ip flow-top-talkers
top 5
sort-by bytes
match class-map icmp-dos-class-map
!
access-list 101 permit icmp any host 172.16.10.2
!
end
Where to Go Next
See the “Related Documents” section on page 54 for links to configuration information about additional
NetFlow features and services.
Additional References
The following sections provide references related to NetFlow Layer 2 and Security Monitoring Exports.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
“Cisco IOS NetFlow Overview”
List of the features documented in the Book Title
configuration guide
“Cisco IOS NetFlow Features Roadmap”
The minimum information about and tasks required for “Getting Started with Configuring NetFlow and NetFlow Data
configuring NetFlow and NetFlow Data Export
Export”
Tasks for configuring NetFlow to capture and export
network traffic data
“Configuring NetFlow and NetFlow Data Export”
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring Random Sampled NetFlow
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring NetFlow aggregation caches
“Configuring NetFlow Aggregation Caches”
Tasks for configuring NetFlow BGP next hop support
“Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis”
Tasks for configuring NetFlow multicast support
“Configuring NetFlow Multicast Accounting”
54
Detecting and Analyzing Network Threats With NetFlow
Additional References
Related Topic
Document Title
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
“NetFlow Layer 2 and Security Monitoring Exports”
Tasks for configuring the SNMP NetFlow MIB
“Configuring SNMP and using the NetFlow MIB to Monitor
NetFlow Data”
Tasks for configuring the NetFlow MIB and Top
Talkers feature
“Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands”
Information for installing, starting, and configuring the “Cisco CNS NetFlow Collection Engine Documentation”
CNS NetFlow Collection Engine
Standards
Standards
Title
There are no new or modified standards associated with —
this feature
MIBs
MIBs
MIBs Link
There are no new or modified MIBs associated with
this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
There are no new or modified RFCs associated with this —
feature.
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
55
Detecting and Analyzing Network Threats With NetFlow
Feature Information for Detecting and Analyzing Network Threats With NetFlow
Feature Information for Detecting and Analyzing Network
Threats With NetFlow
Table 11 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Releases12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 11
Table 11 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for NetFlow Layer 2 and Security Monitoring Exports
Feature Name
Releases
Feature Configuration Information
NetFlow Layer 2 and Security Monitoring
Exports
12.3(14)T
The NetFlow Layer 2 and Security Monitoring Exports
feature enables the capture of values from fields in Layer 3
and Layer 2 of IP traffic for accounting and security
analysis.
The following sections provide information about this
feature:
•
NetFlow Layer 2 and Security Monitoring, page 3
•
Configuring NetFlow Layer 2 and Security Monitoring
Exports, page 20
•
Verifying NetFlow Layer 2 and Security Monitoring
Exports, page 22
The following commands were modified by this feature: ip
flow-capture, ip flow-export and show ip cache verbose
flow.
Support for capturing the value from the
fragment offset field of IP headers added to
NetFlow Layer 2 and Security Monitoring
Exports1
56
12.4(2)T
The fragment-offset keyword for the ip flow-capture
command enables capturing the value of the IP fragment
offset field from the first fragmented IP datagram in a flow.
Detecting and Analyzing Network Threats With NetFlow
Feature Information for Detecting and Analyzing Network Threats With NetFlow
Table 11
Feature Information for NetFlow Layer 2 and Security Monitoring Exports (continued)
Feature Name
Releases
Feature Configuration Information
NetFlow Top Talkers
12.3(11)T,
This document references the Top Talkers feature from the
NetFlow MIB and Top Talkers feature documentation.
12.2(25)S
Please refer to Configuring NetFlow Top Talkers using
Cisco IOS CLI Commands or SNMP Commands for
complete information on using this feature.
Top Talkers uses NetFlow functionality to obtain
information regarding heaviest traffic patterns and
most-used applications in the network.
The following sections provide information about this
feature:
•
Configuring NetFlow Top Talkers to Monitor Network
Threats, page 28
The following commands were introduced by this feature:
cache-timeout, ip flow-top-talkers, match, show ip flow
top-talkers, sort-by, and top.
NetFlow Dynamic Top Talkers CLI
12.4(4)T
The NetFlow Dynamic Top Talkers CLI allows you to se an
overview of the traffic characteristics on your router by
aggregating flows based on the fields such as source IP
address, destination prefix, and so forth.
The following sections provide information about this
feature:
•
Using NetFlow Dynamic Top Talkers CLI to Display
the Protocol Distribution, page 24
•
Using NetFlow Dynamic Top Talkers CLI to Display
the Source IP Address Top Talkers Sending ICMP
Traffic, page 25
•
Using NetFlow Dynamic Top Talkers CLI to Display
the Destination IP Address Top Talkers Receiving
ICMP Traffic, page 27
•
Monitoring and Analyzing the NetFlow Top Talkers
Flows, page 30
•
Analyze an FTP DoS Attack Using NetFlow Dynamic
Top Talkers CLI: Example, page 45
•
Analyze an ICMP Ping DoS Attack Using NetFlow
Dynamic Top Talkers CLI: Example, page 51
57
Detecting and Analyzing Network Threats With NetFlow
Glossary
Table 11
Feature Information for NetFlow Layer 2 and Security Monitoring Exports (continued)
Feature Name
Releases
Feature Configuration Information
NetFlow Input Filters
12.3(4)T,
12.2(25)S
This document references the NetFlow Input Filters feature
from the NetFlow Filtering and Sampling feature
documentation.
Refer to Using NetFlow Filtering or Sampling to Select the
Network Traffic to Track for complete information on using
this feature.
The following sections provide information about this
feature:
Random Sampled NetFlow
12.3(4)T,
12.2(18)S,
12.0(26)S
•
Configuring NetFlow Filtering and Sampling, page 33
•
Configure NetFlow Filtering and Sampling: Example,
page 53
This document references the Random Sampled NetFlow
feature from the NetFlow Filtering and Sampling feature
documentation.
Refer to Using NetFlow Filtering or Sampling to Select the
Network Traffic to Track for complete information on using
this feature.
The following sections provide information about this
feature:
•
Configuring NetFlow Filtering and Sampling, page 33
1. This is a minor enhancement. Minor enhancements are not typically listed in Feature Navigator.
Glossary
data flowset—A collection of data records that are grouped in an export packet.
export packet—A type of packet built by a device (for example, a router) with NetFlow services
enabled. The packet is addressed to another device (for example, the NetFlow Collection Engine). The
packet contains NetFlow statistics. The other device processes the packet (parses, aggregates, and stores
information about IP flows).
flow—A set of packets with the same source IP address, destination IP address, protocol,
source/destination ports, and type-of-service, and the same interface on which flow is monitored. Ingress
flows are associated with the input interface, and egress flows are associated with the output interface.
flowset—A collection of flow records that follow the packet header in an export packet. A flowset
contains information that must be parsed and interpreted by the NetFlow Collection Engine. There are
two types of flowsets: template flowsets and data flowsets. An export packet contains one or more
flowsets, and both template and data flowsets can be mixed in the same export packet.
NetFlow—Cisco IOS accounting feature that maintains per-flow information.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
58
Detecting and Analyzing Network Threats With NetFlow
Glossary
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means of carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
template—Describes the layout of a data flowset.
template flowset—A collection of template records that are grouped in an export packet.
CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect,
Cisco Pulse, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco Unified Computing System, Cisco WebEx, DCE, Flip Channels,
Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to the Human Network
are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed (Stylized), Cisco Store,
and Flip Gift Card are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP,
CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems,
Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center,
Explorer, Fast Step, Follow Me Browsing, FormShare, GainMaker, GigaDrive, HomeLink, iLYNX, Internet Quotient, IOS, iPhone, iQuick Study,
IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers,
Networking Academy, Network Registrar, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect,
ROSA, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx,
and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (0908R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2009 Cisco Systems, Inc. All rights reserved.
59
Detecting and Analyzing Network Threats With NetFlow
Glossary
60
Configuring NetFlow Aggregation Caches
First Published: June 19, 2006
Last Updated: August 09, 2010
This module contains information about and instructions for configuring NetFlow aggregation caches.
The NetFlow main cache is the default cache used to store the data captured by NetFlow. By maintaining
one or more extra caches, called aggregation caches, the NetFlow Aggregation feature allows limited
aggregation of NetFlow data export streams on a router. The aggregation scheme that you select
determines the specific kinds of data that are exported to a remote host.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring NetFlow Aggregation Caches” section on page 36.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Configuring NetFlow Aggregation Caches, page 2
•
Restrictions for Configuring NetFlow Aggregation Caches, page 2
•
Information About Configuring NetFlow Aggregation Caches, page 3
•
How to Configure NetFlow Aggregation Caches, page 24
•
Configuration Examples for Configuring NetFlow Aggregation Caches, page 30
•
Additional References, page 34
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring NetFlow Aggregation Caches
Prerequisites for Configuring NetFlow Aggregation Caches
•
Feature Information for Configuring NetFlow Aggregation Caches, page 36
•
Glossary, page 38
Prerequisites for Configuring NetFlow Aggregation Caches
NetFlow Aggregation Caches
Before you enable NetFlow you must:
•
Configure the router for IP routing
•
Ensure that one of the following is enabled on your router, and on the interfaces that you want to
configure NetFlow on: Cisco Express Forwarding (CEF), distributed CEF, or fast switching
•
Understand the resources required on your router because NetFlow consumes additional memory
and CPU resources
If you intend to use Version 8 export format with an aggregation cache, configure Version 5 export
format for the main cache.
If you need autonomous system (AS) information from the aggregation, make sure to specify either the
peer-as or origin-as keyword in your export command if you have not configured an export format
version.
You must explicitly enable each NetFlow aggregation cache by entering the enabled keyword from
aggregation cache configuration mode.
Router-based aggregation must be enabled for minimum masking.
Restrictions for Configuring NetFlow Aggregation Caches
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
Memory Impact
During times of heavy traffic, the additional flows can fill up the global flow hash table. If you need to
increase the size of the global flow hash table, increase the memory of the router.
Performance Impact
Configuring Egress NetFlow accounting with the ip flow egress command might adversely affect
network performance because of the additional accounting-related computation that occurs in the
traffic-forwarding path of the router.
2
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
NetFlow Data Export
Restrictions for NetFlow Version 9 Data Export
•
Backward compatibility—Version 9 is not backward-compatible with Version 5 or Version 8. If you
need Version 5 or Version 8, you must configure it.
•
Export bandwidth—Export bandwidth use increases for Version 9 (because of template flowsets)
versus Version 5. The increase in bandwidth usage versus Version 5 varies with the frequency with
which template flowsets are sent. The default is to resend templates every 20 packets, which has a
bandwidth cost of about 4 percent. If necessary, you can lower the resend rate with the ip
flow-export template refresh-rate packets command.
•
Performance impact—Version 9 slightly decreases overall performance, because generating and
maintaining valid template flowsets require additional processing.
Restrictions for NetFlow Version 8 Export Format
Version 8 export format is available only for aggregation caches, and it cannot be expanded to support
new features.
Information About Configuring NetFlow Aggregation Caches
Before configuring the NetFlow main cache, NetFlow aggregation caches and NetFlow aggregation
schemes, you should understand the following information:
•
NetFlow Aggregation Caches, page 2
•
NetFlow Data Export Format Versions 9, and 8 for NetFlow Aggregation Caches: Overview, page 24
NetFlow Aggregation Caches
•
NetFlow Cache Aggregation Benefits, page 4
•
NetFlow Cache Aggregation Schemes, page 4
•
NetFlow Aggregation Scheme Fields, page 5
•
NetFlow AS Aggregation Scheme, page 7
•
NetFlow AS-ToS Aggregation Scheme, page 8
•
NetFlow Destination Prefix Aggregation Scheme, page 9
•
NetFlow Destination Prefix-ToS Aggregation Scheme, page 11
•
NetFlow Prefix Aggregation Scheme, page 12
•
NetFlow Prefix-Port Aggregation Scheme, page 14
•
NetFlow Prefix-ToS Aggregation Scheme, page 16
•
NetFlow Protocol Port Aggregation Scheme, page 18
•
NetFlow Protocol-Port-ToS Aggregation Scheme, page 19
•
NetFlow Source Prefix Aggregation Scheme, page 20
•
NetFlow Source Prefix-ToS Aggregation Scheme, page 22
3
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
NetFlow Cache Aggregation Benefits
Aggregation of export data is typically performed by NetFlow collection tools on management
workstations. Router-based aggregation allows limited aggregation of NetFlow export records to occur
on the router. Thus, you can summarize NetFlow export data on the router before the data is exported to
a NetFlow data collection system, which has the following benefits:
•
Reduces the bandwidth required between the router and the workstations
•
Reduces the number of collection workstations required
•
Improves performance and scalability on high flow-per-second routers
NetFlow Cache Aggregation Schemes
Cisco IOS NetFlow aggregation maintains one or more extra caches with different combinations of fields
that determine which flows are grouped together. These extra caches are called aggregation caches. The
combinations of fields that make up an aggregation cache are referred to as schemes. As flows expire from
the main cache, they are added to each enabled aggregation cache.
You can configure each aggregation cache with its individual cache size, cache ager timeout parameter,
export destination IP address, and export destination UDP port. As data flows expire in the main cache
(depending on the aggregation scheme configured), relevant information is extracted from the expired
flow and the corresponding flow entry in the aggregation cache is updated. The normal flow ager process
runs on each active aggregation cache the same way it runs on the main cache. On-demand aging is also
supported. Each aggregation cache contains different field combinations that determine which data flows
are grouped. The default aggregation cache size is 4096 bytes.
You configure a cache aggregation scheme through the use of arguments to the ip flow-aggregation
cache command. NetFlow supports the following five non-ToS based cache aggregation schemes:
•
Autonomous system (AS) aggregation scheme
•
Destination prefix aggregation scheme
•
Prefix aggregation scheme
•
Protocol port aggregation scheme
•
Source prefix aggregation scheme
The NetFlow Type of Service (ToS)-Based Router Aggregation feature introduced support for additional
cache aggregation schemes, all of which include the ToS byte as one of the fields in the aggregation
cache. The following are the six ToS-based aggregation schemes:
•
AS-ToS aggregation scheme
•
Destination prefix-ToS aggregation scheme
•
Prefix-port aggregation scheme
•
Prefix-ToS aggregation scheme
•
Protocol-port-ToS aggregation scheme
•
Source prefix-ToS aggregation scheme
Figure 1 shows an example of how the main NetFlow cache can be aggregated into multiple aggregation
caches based upon user-configured aggregation schemes.
4
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Figure 1
Building a NetFlow Aggregation Cache
NetFlow main cache
Flow entries
Flow 1
• Flow expired
• Cache full
• Timer expired
Flow 2
Flow 3
Export V5
buffer
UDP
Export V8
buffer
UDP
Aggreg. cache
Flow entries
• Flow expired
• Cache full
• Timer expired
Note
• Cache full
• Timer expired
Flow entries
60155
Flow entries
To collector
Figure 2 through Figure 12 illustrate the Version 8 export formats of the aggregation schemes listed
above. Additional export formats (for instance, Version 9) are also supported. If you are using Version 9,
the formats will be different from those shown in the figures. For more information about Version 9
export formats, see Configuring NetFlow and NetFlow Data Export.
NetFlow Aggregation Scheme Fields
Each cache aggregation scheme contains field combinations that differ from any other cache aggregation
scheme. The combination of fields determines which data flows are grouped and collected when a flow
expires from the main cache. A flow is a set of packets that has common fields, such as the source IP
address, destination IP address, protocol, source and destination ports, type-of-service, and the same
interface on which the flow is monitored. To manage flow aggregation on your router, you need to
configure the aggregation cache scheme that groups and collects the fields from which you want to
examine data. Table 1 and Table 2 show the NetFlow fields that are grouped and collected for non-ToS
and ToS based cache aggregation schemes.
Table 1 shows the NetFlow fields used in the non-TOS based aggregation schemes.
Table 1
NetFlow Fields Used in the Non-ToS Based Aggregations Schemes
Field
AS
Protocol
Port
Source
Prefix
Destination
Prefix
Prefix
Source prefix
X
X
Source prefix mask
X
X
Destination prefix
X
X
Destination prefix mask
X
X
Source app port
X
Destination app port
X
5
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 1
NetFlow Fields Used in the Non-ToS Based Aggregations Schemes (continued)
Field
AS
Input interface
X
Output interface
X
IP protocol
Protocol
Port
Source
Prefix
Destination
Prefix
Prefix
X
X
X
X
X
Source AS
X
X
Destination AS
X
First time stamp
X
X
Last time stamp
X
Number of flows
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Number of packets
X
X
X
X
X
Number of bytes
X
X
X
X
X
Table 2 shows the NetFlow fields used in the TOS based aggregation schemes.
Table 2
NetFlow Fields Used in the ToS Based Aggregation Schemes
Field
AS-ToS
Source
Prefix-ToS
Destination
Prefix-ToS Prefix-ToS
Prefix-Port
Source prefix
X
X
X
Source prefix mask
X
X
X
Destination prefix
X
X
X
Destination prefix mask
X
X
X
Source app port
X
X
Destination app port
X
X
Input interface
X
X
Output interface
X
X
IP protocol
6
Protocol
Port-ToS
X
X
X
X
X
X
X
Source AS
X
Destination AS
X
ToS
X
X
First time stamp
X
Last time stamp
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Number of flows
X
X
X
X
X
Number of packets
X
X
X
X
X
Number of bytes
X
X
X
X
X
X
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
NetFlow AS Aggregation Scheme
The NetFlow AS aggregation scheme reduces NetFlow export data volume substantially and generates
AS-to-AS traffic flow data. The scheme groups data flows that have the same source BGP AS,
destination BGP AS, input interface, and output interface.
The aggregated NetFlow data export records report the following:
•
Source and destination BGP AS
•
Number of packets summarized by the aggregated record
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Source interface
•
Destination interface
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
Figure 2 shows the data export format for the AS aggregation scheme. For a definition of the data export
terms used in the aggregation scheme, see Table 3.
Data Export Format for AS Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source AS
Destination AS
24
Source interface
Destination interface
26462
Figure 2
Table 3 lists definitions for the data export record fields used in the AS aggregation scheme.
Table 3
Data Export Record Field Definitions for AS Aggregation Scheme
Field
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
7
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 3
Data Export Record Field Definitions for AS Aggregation Scheme (continued)
Field
Definition
Source AS
Autonomous system of the source IP address (peer or origin)
Destination AS
Autonomous system of the destination IP address (peer or
origin)
Source interface
SNMP index of the input interface
Destination interface
SNMP index of the output interface
NetFlow AS-ToS Aggregation Scheme
The NetFlow AS-ToS aggregation scheme groups flows that have the same source BGP AS, destination
BGP AS, source and destination interfaces, and ToS byte. The aggregated NetFlow export record based
on the AS-ToS aggregation scheme reports the following:
•
Source BGP AS
•
Destination BGP AS
•
ToS byte
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by this aggregated record
•
Number of packets summarized by this aggregation record
•
Source and destination interface
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
This aggregation scheme is particularly useful for generating AS-to-AS traffic flow data, and for
reducing NetFlow export data volume substantially. Figure 3 show the data export format for the AS-ToS
aggregation scheme. For a definition of the data export terms used in the aggregation scheme, see
Table 4.
8
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Data Export Format for AS-ToS Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source AS
Destination AS
24
Source interface
Destination interface
28
ToS
PAD
Reserved
135069
Figure 3
Table 4 lists definitions for the data export record terms used in the AS-ToS aggregation scheme.
Table 4
Data Export Record Term Definitions for AS-ToS Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Source AS
Autonomous system of the source IP address (peer or origin)
Destination AS
Autonomous system of the destination IP address (peer or
origin)
Source interface
SNMP index of the input interface
Destination interface
SNMP index of the output interface
ToS
Type of service byte
PAD
Zero field
Reserved
Zero field
NetFlow Destination Prefix Aggregation Scheme
The destination prefix aggregation scheme generates data so that you can examine the destinations of
network traffic passing through a NetFlow-enabled device. The scheme groups data flows that have the
same destination prefix, destination prefix mask, destination BGP AS, and output interface.
The aggregated NetFlow data export records report the following:
9
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
•
Destination prefix
•
Destination prefix mask
•
Destination BGP AS
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregated record
•
Output interface
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
Figure 4 shows the data export format for the destination prefix aggregation scheme. For a definition of
the data export terms used in the aggregation scheme, see Table 5.
Destination Prefix Aggregation Data Export Record Format
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Destination prefix
24
Destination mask
bits
28
Destination AS
PAD
Reserved
Destination interface
26463
Figure 4
Table 5 lists definitions for the data export record terms used in the destination prefix aggregation
scheme.
Table 5
10
Data Export Record Term Definitions for Destination Prefix Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Destination prefix
Destination IP address ANDed with the destination prefix mask
Destination mask bits
Number of bits in the destination prefix
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 5
Data Export Record Term Definitions for Destination Prefix Aggregation Scheme
Term
Definition
PAD
Zero field
Destination AS
Autonomous system of the destination IP address (peer or
origin)
Destination interface
SNMP index of the output interface
Reserved
Zero field
NetFlow Destination Prefix-ToS Aggregation Scheme
The NetFlow destination prefix-ToS aggregation scheme groups flows that have the same destination
prefix, destination prefix mask, destination BGP AS, ToS byte, and output interface. The aggregated
NetFlow export record reports the following:
•
Destination IP address
•
Destination prefix mask
•
Destination AS
•
ToS byte
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregated record
•
Output interface
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
This aggregation scheme is particularly useful for capturing data with which you can examine the
destinations of network traffic passing through a NetFlow-enabled device. Figure 5 shows the data
export format for the Destination prefix-ToS aggregation scheme. For a definition of the data export
terms used in the aggregation scheme, see Table 6.
11
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Data Export Format for Destination Prefix-ToS Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Destination prefix
24 Destination mask bits
28
Destination AS
ToS
Reserved
Destination interface
135070
Figure 5
Table 6 lists definitions for the data export record terms used in the destination prefix-ToS aggregation
scheme.
Table 6
Data Export Record Term Definitions for Destination Prefix-ToS Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Destination prefix
Destination IP address ANDed with the destination prefix mask
Dest mask bits
Number of bits in the destination prefix
ToS
Type of service byte
Destination AS
Autonomous system of the destination IP address (peer or
origin)
Destination interface
SNMP index of the output interface
Reserved
Zero field
NetFlow Prefix Aggregation Scheme
The NetFlow prefix aggregation scheme generates data so that you can examine the sources and
destinations of network traffic passing through a NetFlow-enabled device. The scheme groups data flows
that have the same source prefix, destination prefix, source prefix mask, destination prefix mask, source
BGP AS, destination BGP AS, input interface, and output interface. See Figure 6.
12
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
The aggregated NetFlow data export records report the following:
•
Source and destination prefix
•
Source and destination prefix mask
•
Source and destination BGP AS
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregated record
•
Input and output interfaces
•
Time stamp when the first packet is switched and time stamp when the last packet is switched
Figure 6 shows the data export format for the prefix aggregation scheme. For a definition of the data
export terms used in the aggregation scheme, see Table 7.
Data Export Format for Prefix Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source prefix
24
Destination prefix
28
Destination mask
bits
Source mask
bits
Reserved
32
Source AS
Destination AS
36
Source interface
Destination interface
26464
Figure 6
13
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 7 lists definitions for the data export record terms used in the prefix aggregation scheme.
Table 7
Data Export Record Terms and Definitions for Prefix Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Source prefix
Source IP address ANDed with the source prefix mask, or the
prefix to which the source IP address of the aggregated flows
belongs
Destination prefix
Destination IP address ANDed with the destination prefix mask
Destination mask bits
Number of bits in the destination prefix
Source mask bits
Number of bits in the source prefix
Reserved
Zero field
Source AS
Autonomous system of the source IP address (peer or origin)
Destination AS
Autonomous system of the destination IP address (peer or
origin)
Source interface
SNMP index of the input interface
Destination interface
SNMP index of the output interface
NetFlow Prefix-Port Aggregation Scheme
The NetFlow prefix-port aggregation scheme groups flows that have a common source prefix, source
mask, destination prefix, destination mask, source port and destination port when applicable, input
interface, output interface, protocol, and ToS byte. The aggregated NetFlow export record reports the
following:
14
•
Source prefix
•
Source prefix mask
•
Destination prefix
•
Destination prefix mask
•
Source port
•
Destination port
•
Source interface
•
Destination interface
•
Protocol
•
ToS byte
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregation record
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
This aggregation scheme is particularly useful for capturing data with which you can examine the
sources and destinations of network traffic passing through a NetFlow-enabled device. Figure 7 shows
the data export record for the prefix-port aggregation scheme. For a definition of the data export terms
used in the aggregation scheme, see Table 8.
Data Export Record for Prefix-Port Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source prefix
24
Destination prefix
28 Destination mask bits Source mask bits
ToS
Protocol
32
Source port
Destination port
36
Source interface
Destination interface
135071
Figure 7
Table 8 lists definitions for the data export record terms used in the prefix-port aggregation scheme.
Table 8
Data Export Record Term Definitions for Prefix-Port Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Source prefix
Source IP address ANDed with the source prefix mask, or the
prefix to which the source IP address of the aggregated flows
belongs
Destination prefix
Destination IP address ANDed with the destination prefix mask
Destination mask bits
Number of bits in the destination prefix
Source mask bits
Number of bits in the source prefix
15
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 8
Data Export Record Term Definitions for Prefix-Port Aggregation Scheme (continued)
Term
Definition
ToS
Type of service byte
Protocol
IP protocol byte
Source port
Source UDP or TCP port number if applicable
Destination port
Destination User Datagram Protocol (UDP) or TCP port
number
Source interface
SNMP index of the input interface
Destination interface
SNMP index of the output interface
NetFlow Prefix-ToS Aggregation Scheme
The NetFlow prefix-tos aggregation scheme groups together flows that have a common source prefix,
source mask, destination prefix, destination mask, source BGP AS, destination BGP AS, input interface,
output interface, and ToS byte. The aggregated NetFlow export record reports the following:
•
Source prefix
•
Source prefix mask
•
Destination prefix
•
Destination prefix mask
•
Source AS
•
Destination AS
•
Source interface
•
Destination interface
•
ToS byte
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregated record
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
This aggregation scheme is particularly useful for capturing data so that you can examine the sources
and destinations of network traffic passing through a NetFlow-enabled device. Figure 8 displays the data
export format for the prefix-tos aggregation scheme. For a definition of the data export terms used in the
aggregation scheme, see Table 9.
16
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Data Export Format for Prefix-ToS Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source prefix
24
Destination prefix
28 Destination mask bits Source mask bits
ToS
PAD
32
Source AS
Destination AS
36
Source interface
Destination interface
135072
Figure 8
Table 9 lists definitions for the data export record terms used in the prefix-ToS aggregation scheme.
Table 9
Data Export Record Term Definitions for Prefix-ToS Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Source prefix
Source IP address ANDed with the source prefix mask, or the
prefix to which the source IP address of the aggregated flows
belongs
Destination prefix
Destination IP address ANDed with the destination prefix mask
Destination mask bits
Number of bits in the destination prefix
Source mask bits
Number of bits in the source prefix
ToS
Type of service byte
Pad
Zero field
Source AS
Autonomous system of the source IP address (peer or origin)
Destination AS
Autonomous system of the destination IP address (peer or
origin)
17
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 9
Data Export Record Term Definitions for Prefix-ToS Aggregation Scheme (continued)
Term
Definition
Source interface
SNMP index of the input interface
Destination interface
SNMP index of the output interface
NetFlow Protocol Port Aggregation Scheme
The NetFlow protocol port aggregation scheme captures data so that you can examine network usage by
traffic type. The scheme groups data flows with the same IP protocol, source port number, and (when
applicable) destination port number.
The aggregated NetFlow data export records report the following:
•
Source and destination port numbers
•
IP protocol (where 6 = TCP, 17 = UDP, and so on)
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregated record
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
Figure 9 shows the data export format for the protocol port aggregation scheme. For a definition of the
data export terms used in the aggregation scheme, see Table 10.
Data Export Format for Protocol Port Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
24
Protocol
PAD
Source port
Reserved
Destination port
26465
Figure 9
Table 10 lists definitions for the data export record terms used in the protocol port aggregation scheme.
18
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 10
Data Export Record Term Definitions for Protocol Port Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Protocol
IP protocol byte
PAD
Zero field
Reserved
Zero field
Source port
Source UDP or TCP port number if applicable
Destination port
Destination User Datagram Protocol (UDP) or TCP port
number
NetFlow Protocol-Port-ToS Aggregation Scheme
The NetFlow protocol-port-tos aggregation scheme groups flows that have a common IP protocol, ToS
byte, source and (when applicable) destination port numbers, and source and destination interfaces. The
aggregated NetFlow Export record reports the following:
•
Source application port number
•
Destination port number
•
Source and destination interface
•
IP protocol
•
ToS byte
•
Number of flows summarized by the aggregated record
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregation record
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
This aggregation scheme is particularly useful for capturing data so that you can examine network usage
by type of traffic. Figure 10 shows the data export format for the protocol-port-tos aggregation scheme.
For a definition of the data export terms used in the aggregation scheme, see Table 11.
19
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Data Export Format for Protocol-Port-ToS Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Protocol
ToS
Reserved
24
Source port
Destination port
28
Source interface
Destination interface
135073
Figure 10
Table 11 lists definitions for the data export record terms used in the protocol-port-ToS aggregation
scheme.
Table 11
Data Export Record Term Definitions for Protocol-Port-ToS Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Protocol
IP protocol byte
ToS
Type of service byte
Reserved
Zero field
Source port
Source UDP or TCP port number if applicable
Destination port
Destination User Datagram Protocol (UDP) or TCP port
number
Source interface
SNMP index of the input interface
Destination interface
SNMP index of the output interface
NetFlow Source Prefix Aggregation Scheme
The NetFlow source prefix aggregation scheme captures data so that you can examine the sources of
network traffic passing through a NetFlow-enabled device. The scheme groups data flows that have the
same source prefix, source prefix mask, source BGP AS, and input interface.
20
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
The aggregated NetFlow data export records report the following:
•
Source prefix
•
Source prefix mask
•
Source BGP AS
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregated record
•
Input interface
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
Figure 11 show the data export format for the source prefix aggregation scheme. For a definition of the
data export terms used in the aggregation scheme, see Table 12.
Data Export Format for Source Prefix Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source prefix
24
Source mask
bits
28
PAD
Source AS
Reserved
Source interface
26466
Figure 11
Table 12 lists definitions for the data export record terms used in the source prefix aggregation scheme.
Table 12
Data Export Record Term Definitions for Source Prefix Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Source prefix
Source IP address ANDed with the source prefix mask, or the
prefix to which the source IP address of the aggregated flows
belongs
21
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Table 12
Data Export Record Term Definitions for Source Prefix Aggregation Scheme
Term
Definition
Source mask bits
Number of bits in the source prefix
PAD
Zero field
Source AS
Autonomous system of the source IP address (peer or origin)
Source interface
SNMP index of the input interface
Reserved
Zero field
NetFlow Source Prefix-ToS Aggregation Scheme
The NetFlow source prefix-ToS aggregation scheme groups flows that have a common source prefix,
source prefix mask, source BGP AS, ToS byte, and input interface. The aggregated NetFlow export
record reports the following:
•
Source prefix
•
Source prefix mask
•
Source AS
•
ToS byte
•
Number of bytes summarized by the aggregated record
•
Number of packets summarized by the aggregation record
•
Input interface
•
Time stamp when the first packet was switched and time stamp when the last packet was switched
This aggregation scheme is particularly useful for capturing data so that you can examine the sources of
network traffic passing through a NetFlow-enabled device. Figure 12 show the data export format for the
source prefix-ToS aggregation scheme. For a definition of the data export terms used in the aggregation
scheme, see Table 13.
Note
22
When a router does not have a prefix for the source IP address in the flow, NetFlow uses 0.0.0.0 with 0
mask bits rather than making /32 entries. This prevents DOS attacks that use random source addresses
from thrashing the aggregation caches. This is also done for the destination in the destination prefix-ToS,
the prefix-ToS, and prefix-port aggregation schemes.
Configuring NetFlow Aggregation Caches
Information About Configuring NetFlow Aggregation Caches
Data Export Format for Source Prefix-ToS Aggregation Scheme
0
Flows
4
Packets
8
Bytes
12
First time stamp
16
Last time stamp
20
Source prefix
24
Source mask bits
28
ToS
Source AS
Source interface
Reserved
135074
Figure 12
Table 13 lists definitions for the data export record terms used in the source prefix-ToS aggregation
scheme.
Table 13
Data Export Record Term Definitions for Source Prefix-ToS Aggregation Scheme
Term
Definition
Flows
Number of main cache flows that were aggregated
Packets
Number of packets in the aggregated flows
Bytes
Number of bytes in the aggregated flows
First time stamp
System uptime when the first packet was switched
Last time stamp
System uptime when the last packet was switched
Source prefix
Source IP address ANDed with the source prefix mask, or the
prefix to which the source IP address of the aggregated flows
belongs
Source mask bits
Number of bits in the source prefix
ToS
Type of service byte
Source AS
Autonomous system of the source IP address (peer or origin)
Source interface
SNMP index of the input interface
Reserved
Zero field
23
Configuring NetFlow Aggregation Caches
How to Configure NetFlow Aggregation Caches
NetFlow Data Export Format Versions 9, and 8 for NetFlow Aggregation Caches:
Overview
Export formats available for NetFlow aggregation caches are the Version 9 export format and the Version
8 export format.
•
Version 9—A flexible and extensible format, which provides the versatility needed for support of
new fields and record types. This format accommodates new NetFlow-supported technologies such
as Multicast, Multiprotocol Label Switching (MPLS), and Border Gateway Protocol (BGP)
next hop. Version 9 export format enables you to use the same version for main and aggregation
caches, and the format is extendable, so you can use the same export format with future features.
•
Version 8—A format added to support data export from aggregation caches. Export datagrams
contain a subset of the usual Version 5 export data, which is valid for the particular aggregation
cache scheme. Version 8 is the default export version for aggregation caches when data export is
configured.
The Version 9 export format is flexible and extensible, which provides the versatility needed for the
support of new fields and record types. You can use the Version 9 export format for both main and
aggregation caches.
The Version 8 export format was added to support data export from aggregation caches. This format
allows export datagrams to contain a subset of the Version 5 export data that is valid for the cache
aggregation scheme.
Refer to the NetFlow Data Export section for more details.
How to Configure NetFlow Aggregation Caches
This section is broken down into the following subsections:
•
Configuring NetFlow Aggregation Caches, page 24 (required)
•
Verifying the Aggregation Cache Configuration, page 28 (optional)
Configuring NetFlow Aggregation Caches
Perform the steps in this required to enable NetFlow and configure a NetFlow aggregation cache.
SUMMARY STEPS
24
1.
enable
2.
configure terminal
3.
ip flow-aggregation cache {as | as-tos | bgp-nexthop-tos | destination-prefix |
destination-prefix-tos | prefix | prefix-port | prefix-tos | protocol-port | protocol-port-tos |
source-prefix | source-prefix-tos}
4.
cache entries number
5.
cache timeout active minutes
6.
cache timeout inactive seconds
7.
export destination {{ip-address | hostname} udp-port}
Configuring NetFlow Aggregation Caches
How to Configure NetFlow Aggregation Caches
8.
Repeat Step 7 once to configure a second export destination
9.
export version [9 | 8]
10. enabled
11. exit
12. interface interface-type interface-number
13. ip flow {ingress | egress}
14. exit
15. Repeat Steps 12 through 14 to enable NetFlow on other interfaces
16. end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
25
Configuring NetFlow Aggregation Caches
How to Configure NetFlow Aggregation Caches
Step 3
Command or Action
Purpose
ip flow-aggregation cache {as | as-tos |
bgp-nexthop-tos | destination-prefix |
destination-prefix-tos | prefix | prefix-port |
prefix-tos | protocol-port | protocol-port-tos
| source-prefix | source-prefix-tos}
(Required) Specifies the aggregation cache scheme and
enables aggregation cache configuration mode.
Example:
Router(config)# ip flow-aggregation cache
destination-prefix
Step 4
cache entries number
Example:
•
The as keyword configures the AS aggregation cache.
•
The as-tos keyword configures the AS ToS aggregation
cache.
•
The bgp-nexthop-tos keyword configures the BGP
nexthop aggregation cache.
•
The destination-prefix keyword configures the
destination prefix aggregation cache.
•
The destination-prefix-tos keyword configures the
destination prefix ToS aggregation cache.
•
The prefix keyword configures the prefix aggregation
cache.
•
The prefix-port keyword configures the prefix port
aggregation cache.
•
The prefix-tos keyword configures the prefix ToS
aggregation cache.
•
The protocol-port keyword configures the protocol
port aggregation cache.
•
The protocol-port-tos keyword configures the
protocol port ToS aggregation cache.
•
The source-prefix keyword configures the source
prefix aggregation cache.
•
The source-prefix-tos keyword configures the source
prefix ToS aggregation cache.
(Optional) Configures aggregation cache operational
parameters.
•
Router(config-flow-cache)# cache entries 2048
Step 5
cache timeout active minutes
Example:
(Optional) Configures aggregation cache operational
parameters.
•
The timeout keyword dissolves the session in the
aggregation cache.
•
The active minutes keyword-argument pair specifies
the number of minutes that an entry is active. The range
is from 1 to 60 minutes. The default is 30 minutes.
Router(config-flow-cache)# cache timeout active
15
26
The entries number keyword-argument pair is the
number of cached entries allowed in the aggregation
cache. The range is from 1024 to 524288. The default
is 4096.
Configuring NetFlow Aggregation Caches
How to Configure NetFlow Aggregation Caches
Step 6
Command or Action
Purpose
cache timeout inactive seconds
(Optional) Configures aggregation cache operational
parameters.
Example:
•
The timeout keyword dissolves the session in the
aggregation cache.
•
The inactive seconds keyword-argument pair specifies
the number of seconds that an inactive entry stays in the
aggregation cache before the entry times out. The range
is from 10 to 600 seconds. The default is 15 seconds.
Router(config-flow-cache)# cache timeout
inactive 300
Step 7
export destination {{ip-address | hostname}
udp-port}
(Optional) Enables the exporting of information from
NetFlow aggregation caches.
•
The ip-address | hostname argument is the destination
IP address or hostname.
•
The port argument is the destination UDP port.
Example:
Router(config-flow-cache)# export destination
172.30.0.1 991
Step 8
Repeat Step 7 once to configure a second export
destination.
(Optional) You can configure a maximum of two export
destinations for each NetFlow aggregation cache.
Step 9
export version [9 | 8]
(Optional) Specifies data export format Version.
•
Example:
The version 9 keyword specifies that the export packet
uses the Version 9 format.
Router(config-flow-cache)# export version 9
Step 10
enabled
(Required) Enables the aggregation cache.
Example:
Router(config-flow-cache)# enabled
Step 11
exit
(Required) Exits NetFlow aggregation cache configuration
mode and returns to global configuration mode.
Example:
Router(config-if)# exit
Step 12
interface interface-type interface-number
(Required) Specifies the interface that you want to enable
NetFlow on and enters interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
Step 13
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—captures traffic that is being received by the
interface
•
egress—captures traffic that is being transmitted by the
interface.
Example:
Router(config-if)# ip flow ingress
or
Example:
Router(config-if)# ip flow egress
Step 14
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
Router(config-if)# exit
You only need to use this command if you want to
enable NetFlow on another interface.
27
Configuring NetFlow Aggregation Caches
How to Configure NetFlow Aggregation Caches
Command or Action
Purpose
Step 15
Repeat Steps 12 through 14 to enable NetFlow on other (Optional) —
interfaces
Step 16
end
Exits the current configuration mode and returns to
privileged EXEC mode.
Example:
Router(config-if)# end
Verifying the Aggregation Cache Configuration
Perform the steps in this optional task to verify that:
•
The NetFlow aggregation cache is operational
•
NetFlow Data Export for the aggregation cache is operational
•
To view the aggregation cache statistics.
1.
show ip cache [ip-address-prefix prefix-mask] flow aggregation {as | as-tos | bgp-nexthop-tos |
destination-prefix | destination-prefix-tos | prefix | prefix-port | prefix-tos | protocol-port |
protocol-port-tos | source-prefix | source-prefix-tos}
2.
show ip flow export
SUMMARY STEPS
DETAILED STEPS
Step 1
show ip cache flow aggregation {as | as-tos | bgp-nexthop-tos | destination-prefix |
destination-prefix-tos | prefix | prefix-port | prefix-tos | protocol-port | protocol-port-tos |
source-prefix | source-prefix-tos}
Use the show ip cache flow aggregation destination-prefix command to verify the configuration of an
destination-prefix aggregation cache. For example:
Router# show ip cache flow aggregation destination-prefix
IP Flow Switching Cache, 139272 bytes
5 active, 2043 inactive, 9 added
841 ager polls, 0 flow alloc failures
Active flows timeout in 15 minutes
Inactive flows timeout in 300 seconds
IP Sub Flow Cache, 11144 bytes
5 active, 507 inactive, 9 added, 9 added to flow
0 alloc failures, 0 force free
1 chunk, 2 chunks added
Dst If
Null
Et0/0.1
Et1/0.1
Et0/0.1
Et1/0.1
Router#
28
Dst Prefix
0.0.0.0
172.16.6.0
172.16.7.0
172.16.1.0
172.16.10.0
Msk
/0
/24
/24
/24
/24
AS
0
0
0
0
0
Flows
5
1
3
16
9
Pkts
13
1
31K
104K
99K
B/Pk
52
56
1314
1398
1412
Active
138.9
0.0
187.3
188.4
183.3
Configuring NetFlow Aggregation Caches
How to Configure NetFlow Aggregation Caches
Use the show ip cache verbose flow aggregation source-prefix command to verify the configuration
of a source-prefix aggregation cache. For example:
Router# show ip cache verbose flow aggregation source-prefix
IP Flow Switching Cache, 278544 bytes
4 active, 4092 inactive, 4 added
51 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 21640 bytes
4 active, 1020 inactive, 4 added, 4 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
Src If
Et1/0.1
Et0/0.1
Et1/0.1
Et0/0.1
Router#
Src Prefix
172.16.10.0
172.16.6.0
172.16.7.0
172.16.1.0
Msk
/24
/24
/24
/24
AS
0
0
0
0
Flows Pkts
4
35K
2
5
2 3515
2
20K
B/Pk
1391
88
1423
1416
Active
67.9
60.6
58.6
71.9
Use the show ip cache verbose flow aggregation protocol-port command to verify the configuration
of a protocol-port aggregation cache. For example:
Router# show ip cache verbose flow aggregation protocol-port
IP Flow Switching Cache, 278544 bytes
4 active, 4092 inactive, 4 added
158 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 21640 bytes
0 active, 1024 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
Protocol
0x01
0x11
0x01
0x01
Router#
Step 2
Source Port
0x0000
0x0208
0x0000
0x0000
Dest Port
0x0000
0x0208
0x0800
0x0B01
Flows
6
1
2
2
Packets
52K
3
846
10
Bytes/Packet
1405
52
1500
56
Active
104.3
56.9
59.8
63.0
show ip flow export
Use the show ip flow export command to verify that NetFlow Data Export is operational for the
aggregation cache. For example:
Router# show ip flow export
Flow export v1 is disabled for main cache
Version 1 flow records
Cache for protocol-port aggregation:
Exporting flows to 172.16.20.4 (991) 172.30.0.1 (991)
Exporting using source IP address 172.16.6.2
Cache for source-prefix aggregation:
Exporting flows to 172.16.20.4 (991) 172.30.0.1 (991)
Exporting using source IP address 172.16.6.2
Cache for destination-prefix aggregation:
Exporting flows to 172.16.20.4 (991) 172.30.0.1 (991)
Exporting using source IP address 172.16.6.2
40 flows exported in 20 udp datagrams
0 flows failed due to lack of export packet
20 export packets were sent up to process level
29
Configuring NetFlow Aggregation Caches
Configuration Examples for Configuring NetFlow Aggregation Caches
0
0
0
0
export
export
export
export
packets
packets
packets
packets
were
were
were
were
dropped
dropped
dropped
dropped
due
due
due
due
to
to
to
to
no fib
adjacency issues
fragmentation failures
encapsulation fixup failures
Router#
Configuration Examples for Configuring NetFlow Aggregation
Caches
This section provides the following examples for configuring an aggregation cache:
•
Configuring an AS Aggregation Cache: Example, page 30
•
Configuring a Destination Prefix Aggregation Cache: Example, page 31
•
Configuring a Prefix Aggregation Cache: Example, page 31
•
Configuring a Protocol Port Aggregation Cache: Example, page 31
•
Configuring a Source Prefix Aggregation Cache: Example, page 32
•
Configuring an AS-ToS Aggregation Cache: Example, page 32
•
Configuring a Prefix-ToS Aggregation Cache: Example, page 32
•
Configuring the Minimum Mask of a Prefix Aggregation Scheme: Example, page 32
•
Configuring the Minimum Mask of a Destination Prefix Aggregation Scheme: Example, page 33
•
Configuring the Minimum Mask of a Source Prefix Aggregation Scheme: Example, page 33
•
Configuring NetFlow Version 9 Data Export for Aggregation Caches: Example, page 33
•
Configuring NetFlow Version 8 Data Export for Aggregation Caches: Example, page 34
Configuring an AS Aggregation Cache: Example
The following example shows how to configure an AS aggregation cache with a cache size of 2046, an
inactive timeout of 200 seconds, a cache active timeout of 45 minutes, an export destination IP address
of 10.42.42.1, and a destination port of 9992:
configure terminal
!
ip flow-aggregation cache as
cache entries 2046
cache timeout inactive 200
cache timeout active 45
export destination 10.42.42.1 9992
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
30
Configuring NetFlow Aggregation Caches
Configuration Examples for Configuring NetFlow Aggregation Caches
Configuring a Destination Prefix Aggregation Cache: Example
The following example shows how to configure a destination prefix aggregation cache with a cache size
of 2046, an inactive timeout of 200 seconds, a cache active timeout of 45 minutes, an export destination
IP address of 10.42.42.1, and a destination port of 9992:
configure terminal
!
ip flow-aggregation cache destination-prefix
cache entries 2046
cache timeout inactive 200
cache timeout active 45
export destination 10.42.42.1 9992
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring a Prefix Aggregation Cache: Example
The following example shows how to configure a prefix aggregation cache with a cache size of 2046, an
inactive timeout of 200 seconds, a cache active timeout of 45 minutes, an export destination IP address
of 10.42.42.1, and a destination port of 9992:
configure terminal
!
ip flow-aggregation cache prefix
cache entries 2046
cache timeout inactive 200
cache timeout active 45
export destination 10.42.42.1 9992
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring a Protocol Port Aggregation Cache: Example
The following example shows how to configure a protocol port aggregation cache with a cache size of
2046, an inactive timeout of 200 seconds, a cache active timeout of 45 minutes, an export destination IP
address of 10.42.42.1, and a destination port of 9992:
configure terminal
!
ip flow-aggregation cache protocol-port
cache entries 2046
cache timeout inactive 200
cache timeout active 45
export destination 10.42.42.1 9992
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
31
Configuring NetFlow Aggregation Caches
Configuration Examples for Configuring NetFlow Aggregation Caches
Configuring a Source Prefix Aggregation Cache: Example
The following example shows how to configure a source prefix aggregation cache with a cache size of
2046, an inactive timeout of 200 seconds, a cache active timeout of 45 minutes, an export destination IP
address of 10.42.42.1, and a destination port of 9992:
configure terminal
!
ip flow-aggregation cache source-prefix
cache entries 2046
cache timeout inactive 200
cache timeout active 45
export destination 10.42.42.1 9992
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring an AS-ToS Aggregation Cache: Example
The following example shows how to configure an AS-ToS aggregation cache with a cache active
timeout of 20 minutes, an export destination IP address of 10.2.2.2, and a destination port of 9991:
configure terminal
!
ip flow-aggregation cache as-tos
cache timeout active 20
export destination 10.2.2.2 9991
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring a Prefix-ToS Aggregation Cache: Example
The following example shows how to configure a prefix-ToS aggregation cache with an export
destination IP address of 10.4.4.4 and a destination port of 9995:
configure terminal
!
ip flow-aggregation cache prefix-tos
export destination 10.4.4.4 9995
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring the Minimum Mask of a Prefix Aggregation Scheme: Example
The following example shows how to configure the minimum mask for a prefix aggregation scheme:
configure terminal
!
ip flow-aggregation cache prefix
32
Configuring NetFlow Aggregation Caches
Configuration Examples for Configuring NetFlow Aggregation Caches
mask source minimum 24
mask destination minimum 28
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring the Minimum Mask of a Destination Prefix Aggregation Scheme: Example
The following example shows how to configure the minimum mask for a destination prefix aggregation
scheme:
configure terminal
!
ip flow-aggregation cache destination-prefix
mask destination minimum 32
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring the Minimum Mask of a Source Prefix Aggregation Scheme: Example
The following example shows how to configure the minimum mask for a source prefix aggregation
scheme:
configure terminal
!
ip flow-aggregation cache source-prefix
mask source minimum 30
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Configuring NetFlow Version 9 Data Export for Aggregation Caches: Example
The following example shows how to configure NetFlow Version 9 data export for an AS aggregation
cache scheme:
configure terminal
!
ip flow-aggregation cache as
export destination 10.42.42.2 9991
export template refresh-rate 10
export version 9
export template timeout-rate 60
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
33
Configuring NetFlow Aggregation Caches
Additional References
Configuring NetFlow Version 8 Data Export for Aggregation Caches: Example
The following example shows how to configure NetFlow Version 8 data export for an AS aggregation
cache scheme:
configure terminal
!
ip flow-aggregation cache as
export destination 10.42.42.2 9991
export destination 10.42.41.1 9991
export version 8
enabled
!
interface Ethernet0/0
ip flow ingress
!
end
Additional References
The following sections provide references related to configuring NetFlow aggregation caches and
schemes.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
34
Configuring NetFlow Aggregation Caches
Additional References
Related Topic
Document Title
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
Standards
Standards
Title
—
No new or modified standards are supported by this
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBS are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
35
Configuring NetFlow Aggregation Caches
Feature Information for Configuring NetFlow Aggregation Caches
Feature Information for Configuring NetFlow Aggregation
Caches
Table 14 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later version
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
36
Table 14 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Configuring NetFlow Aggregation Caches
Feature Information for Configuring NetFlow Aggregation Caches
Table 14
Feature Information for Configuring NetFlow Aggregation Caches
Feature Name
Releases
Feature Configuration Information
NetFlow ToS-Based Router
Aggregation
12.0(15)S
12.2(4)T
12.2(14)S
15.0(1)S
The NetFlow ToS-Based Router Aggregation feature
enables you to limit router-based type of service (ToS)
aggregation of NetFlow export data. The aggregation of
export data provides a summarized NetFlow export data
that can be exported to a collection device. The result is
lower bandwidth requirements for NetFlow export data
and reduced platform requirements for NetFlow data
collection devices.
The following sections provide information about this
feature:
•
NetFlow Cache Aggregation Benefits, page 4
•
NetFlow Cache Aggregation Schemes, page 4
•
NetFlow Data Export Format Versions 9, and 8 for
NetFlow Aggregation Caches: Overview, page 24
•
NetFlow Aggregation Scheme Fields, page 5
•
NetFlow AS-ToS Aggregation Scheme, page 8
•
NetFlow Destination Prefix-ToS Aggregation
Scheme, page 11
•
NetFlow Prefix-Port Aggregation Scheme, page 14
•
NetFlow Prefix-ToS Aggregation Scheme, page 16
•
NetFlow Protocol-Port-ToS Aggregation Scheme,
page 19
•
NetFlow Source Prefix-ToS Aggregation Scheme,
page 22
•
Configuring NetFlow Aggregation Caches, page 24
The following commands were modified by this
feature: ip flow-aggregation cache, show ip cache
verbose flow aggregation, and show ip flow export.
37
Configuring NetFlow Aggregation Caches
Glossary
Table 14
Feature Information for Configuring NetFlow Aggregation Caches (continued)
Feature Name
Releases
Feature Configuration Information
NetFlow Minimum Prefix Mask for
Router-Based Aggregation
12.0(11)S
12.1(2)T
The NetFlow Minimum Prefix Mask for Router-Based
Aggregation feature allows you to set a minimum mask
size for prefix aggregation, destination prefix
aggregation, and source prefix aggregation schemes.
The following sections provide configuration
information about this feature:
•
NetFlow Destination Prefix Aggregation Scheme,
page 9
•
NetFlow Destination Prefix-ToS Aggregation
Scheme, page 11
•
NetFlow Destination Prefix Aggregation Scheme,
page 9
•
NetFlow Prefix Aggregation Scheme, page 12
•
NetFlow Prefix-ToS Aggregation Scheme, page 16
The following commands were modified by this
feature: ip flow-aggregation cache, mask destination,
mask source, and show ip cache flow aggregation.
Glossary
AS—autonomous system. A collection of networks under a common administration sharing a common
routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned
a unique 16-bit number by the Internet Assigned Numbers Authority (IANA).
CEF—Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network
performance and scalability for networks with large and dynamic traffic patterns.
dCEF—Distributed Cisco Express Forwarding. Type of CEF switching in which line cards maintain an
identical copy of the forwarding information base (FIB) and adjacency tables. The line cards perform
the express forwarding between port adapters; this relieves the Route Switch Processor of involvement
in the switching operation.
export packet—Type of packet built by a device (for example, a router) with NetFlow services enabled.
The packet contains NetFlow statistics and is addressed to another device (for example, the NetFlow
Collection Engine). The other device processes the packet (parses, aggregates, and stores information on
IP flows).
flow—A set of packets with the same source IP address, destination IP address, protocol,
source/destination ports, and type-of-service, and the same interface on which flow is monitored. Ingress
flows are associated with the input interface, and egress flows are associated with the output interface.
flowset—Collection of flow records that follow the packet header in an export packet. A flowset contains
information that must be parsed and interpreted by the NetFlow Collection Engine. There are two
different types of flowsets: template flowsets and data flowsets. An export packet contains one or more
flowsets, and both template and data flowsets can be mixed in the same export packet.
NetFlow—Cisco IOS accounting feature that maintains per-flow information.
38
Configuring NetFlow Aggregation Caches
Glossary
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
QoS—quality of service. A measure of performance for a transmission system that reflects its
transmission quality and service availability.
template flowset—One or more template records that are grouped in an export packet.
ToS—type of service. The second byte in the IP header. It indicates the desired quality of service (QoS)
for a particular datagram.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2010 Cisco Systems, Inc. All rights reserved.
39
Configuring NetFlow Aggregation Caches
Glossary
40
Using NetFlow Filtering or Sampling to Select the
Network Traffic to Track
First Published: June 19, 2006
Last Updated: August 09, 2010
This module contains information about and instructions for selecting the network traffic to track
through the use of NetFlow filtering or sampling. The NetFlow Input Filtering and Random Sampled
NetFlow features, described in this module, allow you to collect data from specific subsets of traffic.
•
The NetFlow Input Filters feature provides NetFlow data for a specific subset of traffic by letting
you create filters to select flows for NetFlow processing. For example, you can select flows from a
specific group of hosts.
•
The Random Sampled NetFlow feature provides NetFlow data for a subset of traffic in a Cisco router
by processing only one randomly selected packet out of n sequential packets (n is a
user-configurable parameter).
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Using NetFlow Filtering or Sampling to Select Network Traffic
to Track” section on page 21.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Contents
Contents
•
Prerequisites for Using NetFlow Filtering or Sampling to Select Network Traffic to Track, page 2
•
Restrictions for Using NetFlow Filtering or Sampling to Select Network Traffic to Track, page 3
•
Information About Using NetFlow Filtering or Sampling to Select Network Traffic to Track, page 3
•
How to Configure NetFlow Filtering or Sampling, page 7
•
Configuration Examples for Configuring NetFlow Filtering and Sampling, page 16
•
Additional References, page 18
•
Feature Information for Using NetFlow Filtering or Sampling to Select Network Traffic to Track,
page 21
•
Glossary, page 22
Prerequisites for Using NetFlow Filtering or Sampling to Select
Network Traffic to Track
Prerequisites for NetFlow Input Filters
Before you can configure the NetFlow Input Filters feature, you must
Note
•
Configure the router for IP routing
•
Configure Cisco Express Forwarding (CEF) switching or distributed CEF (dCEF) switching on the
router and on the interfaces that you want to enable NetFlow Input Filters on (fast switching is not
supported)
•
Create traffic classes and define NetFlow sampler maps
The NetFlow Input Filters feature is supported in the Version 5 and Version 9 NetFlow export formats.
Prerequisites for Random Sampled NetFlow
Before you can configure the Random Sampled NetFlow feature, you must:
2
•
Configure the router for IP routing
•
Configure Cisco Express Forwarding (CEF) switching or distributed CEF (dCEF) switching on the
router and on the interfaces that you want to enable Random Sampled NetFlow on (fast switching is
not supported)
•
Configure NetFlow Version 5 or Version 9 data export if you want to export NetFlow data
(otherwise, NetFlow data is visible in the cache, but is not exported)
•
Configure NetFlow Version 9 if you want to use sampler option templates or view NetFlow sampler
IDs
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Restrictions for Using NetFlow Filtering or Sampling to Select Network Traffic to Track
Restrictions for Using NetFlow Filtering or Sampling to Select
Network Traffic to Track
Restrictions for NetFlow Input Filters
On Cisco 7500 platforms, the NetFlow Input Filters feature is supported only in distributed mode.
Restrictions for Random Sampled NetFlow
If full NetFlow is enabled on an interface, it takes precedence over Random Sampled NetFlow (which
will thus have no effect). This means that you should disable full NetFlow on an interface before
enabling Random Sampled NetFlow on that interface.
Enabling Random Sampled NetFlow on a physical interface does not automatically enable Random
Sampled NetFlow on subinterfaces; you must explicitly configure it on subinterfaces. Also, disabling
Random Sampled NetFlow on a physical interface (or a subinterface) does not enable full NetFlow. This
restriction prevents the transition to full NetFlow from overwhelming the physical interface (or
subinterface). If you want full NetFlow, you must explicitly enable it.
If you enable Random Sampled NetFlow with Version 5 data export, sampler option templates are not
exported, and sampler IDs are exported in the least significant three bits of the last byte of the Version 5
record pad field. Use NetFlow Version 9 if you want to use sampler option templates or view NetFlow
sampler IDs.
Information About Using NetFlow Filtering or Sampling to Select
Network Traffic to Track
Before configuring NetFlow sampling or filtering, you should understand the following:
•
Roadmap: Using NetFlow Filtering or Sampling to Select the Network Traffic to Track, page 3
•
Filtering and Sampling of NetFlow Traffic, page 4
•
NetFlow Input Filters: Flow Classification, page 6
•
Random Sampled NetFlow: Sampling Mode, page 6
•
Random Sampled NetFlow: The NetFlow Sampler, page 6
Roadmap: Using NetFlow Filtering or Sampling to Select the Network Traffic to
Track
Table 1 provides a roadmap for this section that includes links to associated information and
configuration instruction for selecting traffic of interest.
3
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Information About Using NetFlow Filtering or Sampling to Select Network Traffic to Track
Table 1
Roadmap: Selecting the Network Traffic to Track Using Sampling and Filtering
Traffic of Interest
Links to Associated Information and Configuration Instructions
Associated information:
A specific subset of NetFlow traffic for the
purpose of class-based traffic analysis and
• Filtering and Sampling of NetFlow Traffic, page 4
monitoring (including on-network or off-network
• NetFlow Input Filters: Flow Classification, page 6
traffic)
•
Prerequisites for NetFlow Input Filters, page 2
•
Restrictions for NetFlow Input Filters, page 3
Configuration instructions:
•
Statistical sampling of network traffic for traffic
engineering or capacity planning purposes
Configuring NetFlow Input Filters to Reduce the Impact of NetFlow
Data Export, page 7
Associated information:
•
Filtering and Sampling of NetFlow Traffic, page 4
•
Random Sampled NetFlow: Sampling Mode, page 6
•
Prerequisites for Random Sampled NetFlow, page 2
•
Restrictions for Random Sampled NetFlow, page 3
Configuration instructions:
•
Configuring NetFlow Input Filters to Reduce the Impact of NetFlow
Data Export, page 7
Filtering and Sampling of NetFlow Traffic
NetFlow provides highly granular per-flow traffic statistics in a Cisco router. A flow is a unidirectional
stream of packets that arrive at the router on the same subinterface, have the same source and destination
IP addresses, Layer 4 protocol, TCP/UDP source and destination ports, and the same ToS (type of
service) byte in the IP headers. The router accumulates NetFlow statistics in a NetFlow cache and can
export them to an external device (such as the Cisco Networking Services (CNS) NetFlow Collection
Engine) for further processing.
Full NetFlow accounts for all traffic entering the subinterface on which it is enabled. But in some cases,
you might gather NetFlow data on only a subset of this traffic. The Random Sampled NetFlow feature
and the NetFlow Input Filters feature each provide ways to limit incoming traffic to only traffic of
interest for NetFlow processing. Random Sampled NetFlow provides NetFlow data for a subset of traffic
in a Cisco router by processing only one randomly selected packet out of n sequential packets. The
NetFlow Input Filters feature provides the capability to gather NetFlow data on only a specific
user-defined subset of traffic.
Note
4
Random Sampled NetFlow is more statistically accurate than Sampled NetFlow. NetFlow's ability to
sample packets was first provided by a feature named Sampled NetFlow. The methodology that the
Sampled NetFlow feature uses is deterministic sampling, which selects every nth packet for NetFlow
processing on a per-interface basis. For example, if you set the sampling rate to 1 out of 100 packets,
then Sampled NetFlow samples the 1st, 101st, 201st, 301st, and so on packets. Sampled NetFlow does
not allow random sampling and thus can make statistics inaccurate when traffic arrives in fixed patterns.
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Information About Using NetFlow Filtering or Sampling to Select Network Traffic to Track
Note
The Random Sampled NetFlow algorithms are applied after input filtering.
Table 2 compares the NetFlow Input Filters feature and the NetFlow Random Sampled feature.
Table 2
Comparison of the NetFlow Input Filters Feature and the Random Sampled NetFlow Feature
Comparison Category
NetFlow Input Filters Feature
Random Sampled NetFlow Feature
Brief description
This feature enables you to gather NetFlow
data on only a specific subset of traffic. You
do this by creating filters to select flows for
NetFlow processing. For example, you can
select flows from a specific group of hosts.
This feature also lets you select various
sampling rates for selected flows.
This feature provides NetFlow data for a
subset of traffic in a Cisco router by
processing only one randomly selected packet
out of n sequential packets (n is a
user-configurable parameter). Packets are
sampled as they arrive (before any NetFlow
cache entries are made for those packets).
Main uses
You can use this feature for class-based traffic You can use this feature for traffic
analysis and monitoring on-network or
engineering, capacity planning, and
off-network traffic.
applications where full NetFlow is not needed
for an accurate view of network traffic.
Export format support
This feature is supported in the Version 5 and This feature is supported in the Version 5 and
Version 9 NetFlow export formats.
Version 9 NetFlow export formats.
Cisco IOS release support
12.3(4)T.
Subinterface support
You can configure NetFlow Input Filters per You can configure the Random Sampled
subinterface as well as per physical interface. NetFlow feature per subinterface as well as
per physical interface.
You can select more than one filter per
Traffic is collected only on the subinterfaces
subinterface and have all of the filters run
on which Random Sampled NetFlow is
simultaneously.
configured. As with full NetFlow, enabling
Random Sampled NetFlow on a physical
interface does not enable Random Sampled
NetFlow on subinterfaces automatically—you
must explicitly configure it on the
subinterfaces.
Memory impact
This feature requires no additional memory. It
allows you to use a smaller NetFlow cache
than full NetFlow, because it significantly
reduces the number of flows. This feature
requires an insignificant amount of memory
for each configured NetFlow sampler.
This feature allows a smaller NetFlow cache
than full NetFlow, because it significantly
reduces the number of flows. This feature
requires an insignificant amount of memory
for each configured NetFlow sampler.
Performance impact
Accounting of classified traffic saves router
resources by reducing the number of flows
being processed and exported. The amount of
bandwidth saved depends on the usage and the
class-map criteria.
Statistical traffic sampling substantially
reduces consumption of router resources
(especially CPU resources) while providing
valuable NetFlow data.
However, performance might degrade
depending on the number and complexity of
class maps configured in a policy.
12.3(2)T, 12.2(18)S, and 12.0(26)S.
This feature substantially reduces the impact
of NetFlow data export on interface traffic.
For example, a sampling rate of 1 out of 100
packets reduces the export of NetFlow data by
about 50 percent.
5
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Information About Using NetFlow Filtering or Sampling to Select Network Traffic to Track
NetFlow Input Filters: Flow Classification
For the NetFlow Input Filters feature, classification of packets can be based on any of the following: IP
source and destination addresses, Layer 4 protocol and port numbers, incoming interface, MAC address,
IP Precedence, DSCP value, Layer 2 information (such as Frame-Relay DE bits or Ethernet 802.1p bits),
and Network-Based Application Recognition (NBAR) information. The packets are classified (filtered)
on the above criteria, and flow accounting is applied to them on subinterfaces.
The filtering mechanism uses the Modular QoS Command-Line Interface (MQC) to classify flows. You
can create multiple filters with matching samplers on a per-subinterface basis. For example, you can
subdivide subinterface traffic into multiple classes based on type of service (ToS) values or destination
prefixes (or both). For each class, you can also configure sampling at a different rate, using higher rates
for higher-priority classes of traffic and lower rates for lower-priority ones.
MQC has many policies (actions) such as bandwidth rate and queuing management. These policies are
applied only if a packet matches a criterion in a class map that is applied to the subinterface. A class map
contains a set of match clauses and instructions on how to evaluate the clauses and acts as a filter for the
policies, which are applied only if a packet’s content satisfies the match clause. The NetFlow Input
Filters feature adds NetFlow accounting to the MQC infrastructure, which means that flow accounting
is done on a packet only if it satisfies the match clauses.
Two types of filter are available:
•
ACL-based flow-mask filters
•
Fields of filter (source IP address, destination IP address, source application port, destination
application port, port protocol, ToS bits, and TCP flags)
Random Sampled NetFlow: Sampling Mode
Sampling mode makes use of an algorithm that selects a subset of traffic for NetFlow processing. In the
random sampling mode that the Random Sampled NetFlow feature uses, incoming packets are randomly
selected so that one out of each n sequential packets is selected on average for NetFlow processing. For
example, if you set the sampling rate to 1 out of 100 packets, then NetFlow might sample the 5th packet
and then the 120th, 199th, 302nd, and so on. This sample configuration provides NetFlow data on
1 percent of total traffic. The n value is a parameter from 1 to 65535 packets that you can configure.
Random Sampled NetFlow: The NetFlow Sampler
A NetFlow sampler map defines a set of properties (such as the sampling rate and NetFlow sampler
name) for NetFlow sampling. Each NetFlow sampler map can be applied to one or many subinterfaces
as well as physical interfaces. You can define up to eight NetFlow sampler maps.
For example, you can create a NetFlow sampler map named mysampler1 with the following properties:
random sampling mode and a sampling rate of 1 out of 100 packets. This NetFlow sampler map can be
applied to any number of subinterfaces, each of which would refer to mysampler1 to perform NetFlow
sampling. Traffic from these subinterfaces is merged (from a sampling point of view). This introduces
even more “randomness” than random per-subinterface NetFlow sampling does, but statistically it
provides the same sampling rate of 1 out of 100 packets for each participating subinterface.
The sampling in random sampled NetFlow is done by NetFlow samplers. A NetFlow sampler is defined
as an instance of a NetFlow sampler map that has been applied to a physical interface or subinterface. If
full NetFlow is configured on a physical interface, it overrides random sampled NetFlow on all subinterfaces
of this physical interface.
6
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
How to Configure NetFlow Filtering or Sampling
Perform the procedures in this section to configure NetFlow filtering or sampling:
Note
•
Configuring NetFlow Input Filters to Reduce the Impact of NetFlow Data Export, page 7
•
Configuring Random Sampled NetFlow to Reduce the Impact of NetFlow Data Export, page 12
You need to configure input filtering before you apply the random sampled NetFlow algorithms.
Configuring NetFlow Input Filters to Reduce the Impact of NetFlow Data Export
Perform the following tasks to configure NetFlow input filters. Configuring NetFlow input filters
reduces the impact of NetFlow data export.
•
Creating a Class Map for a Policy Map for NetFlow Input Filtering, page 7 (required)
•
Creating a Sampler Map for a Policy Map for NetFlow Input Filtering, page 9 (required)
•
Creating a Class-Based Policy Containing NetFlow Sampling Actions, page 10 (required)
•
Applying a Policy Containing NetFlow Sampling Actions to an Interface, page 11 (required)
Creating a Class Map for a Policy Map for NetFlow Input Filtering
Perform the steps in this required task to create a class map for a policy map for NetFlow input filtering.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
class-map class-map-name [match-all | match-any]
4.
match access-group access-group
5.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
7
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
Step 3
Command or Action
Purpose
class-map class-map-name [match-all | match-any]
(Required) Creates a class map to be used for
matching packets to a specified class.
Example:
•
The class-map-name argument is the name of the
class for the class map. The name can be a
maximum of 40 alphanumeric characters. The
class name is used for both the class map and for
configuring policy for the class in the policy map.
•
The match-all | match-any keywords determine
how packets are evaluated when multiple match
criteria exist. Packets must either meet all of the
match criteria (match-all) or only one of the
match criteria (match-any) to be considered a
member of the class.
Router(config)# class-map my_high_importance_class
Entering the class-map command enables class-map
configuration mode, in which you can enter one of the
match commands to configure the match criteria for
this class.
Step 4
match access-group access-group
Example:
Router(config-cmap)# match access-group 101
Step 5
end
Example:
Router(config-cmap)# end
8
(Required) Configures the match criteria for a class
map on the basis of the specified access control list
(ACL).
•
The access-group argument is a numbered ACL
whose contents are used as the match criteria
against which packets are checked to determine if
they belong to this class. An ACL number can be
a number from 1 to 2699.
(Required) Exits the current configuration mode and
returns to privileged EXEC mode.
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
Creating a Sampler Map for a Policy Map for NetFlow Input Filtering
Perform the steps in this required task to create a sampler map for a policy map for NetFlow input
filtering.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
flow-sampler-map sampler-map-name
4.
mode random one-out-of packet-interval
5.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
flow-sampler-map sampler-map-name
Example:
(Required) Defines a statistical sampling NetFlow
export flow sampler map.
•
Router(config)# flow-sampler-map my_high_sampling
The sampler-map-name argument is the name of
the flow sampler map to be defined.
Entering the flow-sampler-map command enables
the flow sampler configuration mode.
Step 4
mode random one-out-of packet-interval
Example:
(Required) Specifies a statistical sampling NetFlow
export random sampling mode and a packet interval.
•
The random keyword specifies that sampling
uses the random sampling mode.
•
The one-out-of packet-interval
argument-keyword pair specifies the packet
interval (one out of every n packets) from which
to sample. For n, you can specify from 1 to 65535
(packets).
Router(config-sampler-map)# mode random one-out-of
100
Step 5
end
(Required) Exits the current configuration mode and
returns to privileged EXEC mode.
Example:
Router(config-sampler-map)# end
9
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
Creating a Class-Based Policy Containing NetFlow Sampling Actions
Perform the steps in this required task to create a class-based policy containing NetFlow sampling
actions.
You can assign only one NetFlow input filters sampler to a class. Assigning a subsequent NetFlow input
filters sampler to a class overwrites the previous sampler. Removing a NetFlow sampler map also
removes the NetFlow input filters sampler from the corresponding policy map.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
policy-map policy-map-name
4.
class {class-name | class-default}
5.
netflow-sampler map-name
6.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
policy-map policy-map-name
Example:
Router(config)# policy-map mypolicymap
(Required) Creates or modifies a policy map that can
be attached to one or more interfaces to specify a
service policy.
•
The policy-map-name argument is the name of
the policy map. The name can be a maximum of
40 alphanumeric characters.
Entering the policy-map command enables quality of
service (QoS) policy-map configuration mode, in
which you can configure or modify the class policies
for that policy map.
10
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
Step 4
Command or Action
Purpose
class {class-name | class-default}
(Required) Specifies the name of the class whose
policy you want to create or change or specifies the
default class (commonly known as the class-default
class) before you configure its policy.
Example:
Router(config-pmap)# class my_high_importance_class
•
The class-name argument is the name of the class
for which you want to configure or modify policy.
•
The class-default keyword specifies the default
class so that you can configure or modify its
policy.
Entering the class command enables QoS policy-map
class configuration mode.
Step 5
netflow-sampler sampler-map-name
(Required) Enables a NetFlow input filter sampler.
•
Example:
Step 6
The sampler-map-name argument is the name of
the NetFlow sampler map to apply to the class.
Router(config-pmap-c)# netflow-sampler high_sampling
You can assign only one NetFlow input filter sampler
to a class. Assigning another NetFlow input filter
sampler to a class overwrites the previous one.
end
(Required) Exits the current configuration mode and
returns to privileged EXEC mode.
Example:
Router(config-pmap-c)# end
Applying a Policy Containing NetFlow Sampling Actions to an Interface
Perform the steps in this required task to apply a policy containing NetFlow sampling actions to an
interface.
After you define a service policy with the policy-map command, you use the service-policy command
in interface configuration mode to attach it to one or more interfaces, thus specifying the service policy
for those interfaces. Although you can assign the same service policy to multiple interfaces, each
interface can have only one service policy attached. You can apply the service policy only in the input
direction.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface interface-type interface-number
4.
service-policy {input | output} policy-map-name
5.
end
11
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface interface-type interface-number
(Required) Specifies the interface and enters interface
configuration mode.
Example:
Router(config)# interface POS 1/0
Step 4
service-policy {input | output} policy-map-name
Example:
Router(config-if)# service-policy input
mypolicymap
Step 5
(Required) Attaches a policy map to an input interface or
virtual circuit (VC), or an output interface or VC, to be
used as the service policy for that interface or VC.
•
The input keyword attaches the specified policy map
to the input interface or input VC.
•
The output keyword attaches the specified policy
map to the output interface or output VC.
•
The policy-map-name is the name of a service policy
map (created through use of the policy-map
command) to be attached. The name can be a
maximum of 40 alphanumeric characters.
(Required) Exits the current configuration mode and
returns to privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
Use the debug flow-sampler class-based command to display debugging output for NetFlow input
filters.
Configuring Random Sampled NetFlow to Reduce the Impact of NetFlow Data
Export
Perform the following required and optional tasks to configure and verify the configuration for the
Random Sampled NetFlow feature:
12
•
Defining a NetFlow Sampler Map (Required), page 13
•
Applying a NetFlow Sampler Map to an Interface (Required), page 13
•
Verifying the Configuration of Random Sampled NetFlow (Optional), page 14
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
Defining a NetFlow Sampler Map (Required)
Perform the following task to define a NetFlow sampler map.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
flow-sampler-map sampler-map-name
4.
mode random one-out-of sampling-rate
5.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
flow-sampler-map sampler-map-name
(Required) Defines a NetFlow sampler map and enters flow
sampler map configuration mode.
•
Example:
Router(config)# flow-sampler-map mysampler1
Step 4
mode random one-out-of sampling-rate
Example:
(Required) Enables random mode and specifies a sampling
rate for the NetFlow sampler.
•
The random keyword specifies that sampling uses the
random mode.
•
The one-out-of sampling-rate keyword-argument pair
specifies the sampling rate (one out of every n packets)
from which to sample. For n, you can specify from 1 to
65535 (packets).
Router(config-sampler)# mode random one-out-of
100
Step 5
The sampler-map-name argument is the name of the
NetFlow sampler map to be defined.
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
end
Example:
Router(config-sampler)# end
Applying a NetFlow Sampler Map to an Interface (Required)
Perform the following task to apply a NetFlow sampler map to an interface.
You can apply a NetFlow sampler map to a physical interface (or a subinterface) to create a NetFlow
sampler.
13
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface interface-type interface-number
4.
flow-sampler sampler-map-name
5.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface interface-type interface-number
(Required) Specifies the interface and enters interface
configuration mode.
Example:
Router(config)# ethernet 1/0.2
Step 4
flow-sampler sampler-map-name
•
Example:
Router(config-if)# flow-sampler mysampler1
Step 5
(Required) Applies a NetFlow sampler map to the interface
to create the NetFlow sampler.
The sampler-map-name argument is the name of the
NetFlow sampler map to apply to the interface.
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
end
Example:
Router(config-if)# end
Verifying the Configuration of Random Sampled NetFlow (Optional)
Perform the following tasks to verify the configuration of random sampled NetFlow.
SUMMARY STEPS
1.
show flow-sampler
2.
show ip cache verbose flow
3.
show ip flow export template
DETAILED STEPS
Step 1
14
show flow-sampler
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
How to Configure NetFlow Filtering or Sampling
Use this command to display attributes (including mode, sampling rate, and number of sampled packets)
of one or all Random Sampled NetFlow samplers to verify the sampler configuration. For example:
Router# show flow-sampler
Sampler : mysampler1, id : 1, packets matched : 10, mode : random sampling mode
sampling interval is : 100
Sampler : myflowsampler2, id : 2, packets matched : 5, mode : random sampling mode
sampling interval is : 200
To verify attributes for a particular NetFlow sampler, use the show flow-sampler sampler-map-name
command. For example, enter the following for a NetFlow sampler named mysampler1:
Router# show flow-sampler mysampler1
Sampler : mysampler1, id : 1, packets matched : 0, mode : random sampling mode
sampling interval is : 100
Step 2
show ip cache verbose flow
Use this command to display additional NetFlow fields in the header when Random Sampled NetFlow
is configured. For example:
Router# show ip cache verbose flow
...
SrcIf
SrcIPaddress
DstIf
Port Msk AS
Port Msk AS
DstIPaddress
NextHop
BGP: BGP NextHop
Et1/0
8.8.8.8
Et0/0*
9.9.9.9
0000 /8 302
0800 /8 300
3.3.3.3
BGP: 2.2.2.2
Sampler: 1 Class: 1 FFlags: 01
Pr TOS Flgs Pkts
B/Pk Active
01 00
10
100
3
0.1
This example shows the NetFlow output of the show ip cache verbose flow command in which the
sampler, class-id, and general flags are set. What is displayed for a flow depends on what flags are set
in the flow. If the flow was captured by a sampler, the output shows the sampler ID. If the flow was
marked by MQC, the display includes the class ID. If any general flags are set, the output includes the
flags.
NetFlow flags (FFlags) that might appear in the show ip cache verbose flow command output are:
•
FFlags: 01 (#define FLOW_FLAGS_OUTPUT 0x0001)—Egress flow
•
FFlags: 02 (#define FLOW_FLAGS_DROP 0x0002)—Dropped flow (for example, dropped by an
ACL)
•
FFlags: 04 (#define FLOW_FLAGS_MPLS 0x0004)—MPLS flow
•
FFlags: 08 (#define FLOW_FLAGS_IPV6 0x0008)—IPv6 flow
•
FFlags: 10 (#define FLOW_FLAGS_RSVD 0x0010)—Reserved
IPv6 and RSVD FFlags are seldom used. If FFlags is zero, the line is omitted from the output. If multiple
flags are defined (logical ORed together), then both sets of flags are displayed in hexadecimal format.
Step 3
show ip flow export template
Use this command to display the statistics for the NetFlow data export (such as template timeout and
refresh rate) for the template-specific configurations. For example:
Router# show ip flow export template
Template Options Flag = 0
Total number of Templates added = 0
Total active Templates = 0
15
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Configuration Examples for Configuring NetFlow Filtering and Sampling
Flow Templates active = 0
Flow Templates added = 0
Option Templates active = 0
Option Templates added = 0
Template ager polls = 0
Option Template ager polls = 0
Main cache version 9 export is enabled
Template export information
Template timeout = 30
Template refresh rate = 20
Option export information
Option timeout = 30
Option refresh rate = 20
Troubleshooting Tips
Use the debug flow-sampler command to display debugging output for Random Sampled NetFlow.
Configuration Examples for Configuring NetFlow Filtering and
Sampling
This section contains the following examples for configuring NetFlow filtering and sampling:
•
Configuring NetFlow Input Filters to Reduce the Impact of NetFlow Data Export: Examples,
page 16
•
Configuring Random Sampled NetFlow to Reduce the Impact of NetFlow Data Export: Examples,
page 18
Configuring NetFlow Input Filters to Reduce the Impact of NetFlow Data Export:
Examples
This section contains the following configuration examples:
•
Creating a Class Map for a Policy Map for NetFlow Input Filtering: Example, page 16
•
Creating a Sampler Map for a Policy Map for NetFlow Input Filtering: Example, page 17
•
Creating a Policy Containing NetFlow Sampling Actions: Example, page 17
•
Applying a Policy to an Interface: Example, page 17
Creating a Class Map for a Policy Map for NetFlow Input Filtering: Example
The following example shows how to create a class map for a policy map for NetFlow input filtering. In
the example, class maps named my_high_importance_class and my_medium_importance_class are
created:
configure terminal
!
class-map my_high_importance_class
match access-group 101
exit
16
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Configuration Examples for Configuring NetFlow Filtering and Sampling
!
class-map my_medium_importance_class
match access-group 102
end
Creating a Sampler Map for a Policy Map for NetFlow Input Filtering: Example
The following example shows how to create a sampler map for a policy map for NetFlow input filtering.
In the following example, sampler maps called my_high_sampling, my_medium sampling, and
my_low_samplng are created for use with a policy map for NetFlow input filtering:
configure terminal
!
flow-sampler-map my_high_sampling
mode random one-out-of 1
exit
!
flow-sampler-map my_medium_sampling
mode random one-out-of 100
exit
!
flow-sampler-map my_low_sampling
mode random one-out-of 1000
end
Creating a Policy Containing NetFlow Sampling Actions: Example
The following example shows how to create a class-based policy containing three NetFlow sampling
actions. In this example, a sampling action named my_high_sampling is applied to a class named
my_high_importance_class, a sampling action named my_medium_sampling is applied to a class named
my_medium_importance_class, and a sampling action named my_low_sampling is applied to the default
class.
configure terminal
!
policy-map mypolicymap
class my_high_importance_class
netflow sampler my_high_sampling
exit
!
class my_medium_importance_class
netflow-sampler my_medium_sampling
exit
!
class class-default
netflow-sampler my_low_sampling
end
Applying a Policy to an Interface: Example
The following example shows how to apply a policy containing NetFlow sampling actions to an
interface. In this example, a policy named mypolicymap is attached to interface POS1/0 and also to
interface ATM2/0:
configure terminal
!
interface POS1/0
service-policy input mypolicymap
exit
17
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Additional References
!
interface ATM2/0
service-policy input mypolicymap
end
Configuring Random Sampled NetFlow to Reduce the Impact of NetFlow Data
Export: Examples
This section contains the following configuration examples:
•
Defining a NetFlow Sampler Map: Example, page 18
•
Applying a NetFlow Sampler Map to an Interface: Example, page 18
Defining a NetFlow Sampler Map: Example
The following example shows how to define a NetFlow sampler map named mysampler1:
configure terminal
!
flow-sampler-map mysampler1
mode random one-out-of 100
end
Applying a NetFlow Sampler Map to an Interface: Example
The following example shows how to enable CEF switching and apply a NetFlow sampler map named
mysampler1 to Ethernet interface 1 to create a NetFlow sampler on that interface:
configure terminal
!
ip cef
!
interface ethernet 1/0
flow-sampler mysampler1
end
Additional References
The following sections provide references related to configuring NetFlow filtering and sampling.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
18
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Additional References
Related Topic
Document Title
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
“Configuring NetFlow Multicast Accounting”
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
19
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Additional References
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
The Cisco Support website provides extensive online
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies.
http://www.cisco.com/cisco/web/support/index.html
To receive security and technical information about
your products, you can subscribe to various services,
such as the Product Alert Tool (accessed from Field
Notices), the Cisco Technical Services Newsletter, and
Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website
requires a Cisco.com user ID and password.
20
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Feature Information for Using NetFlow Filtering or Sampling to Select Network Traffic to Track
Feature Information for Using NetFlow Filtering or Sampling to
Select Network Traffic to Track
Table 3 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 3
Table 3 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for Using NetFlow Filtering or Sampling to Select Network Traffic to Track
Feature Name
Releases
Feature Configuration Information
NetFlow Input Filters
12.3(4)T,
12.2(25)S
12.2(27)SBC
15.0(1)S
The NetFlow Input Filters feature provides NetFlow
data for a specific subset of traffic by letting you create
filters to select flows for NetFlow processing. For
example, you can select flows from a specific group of
hosts. This feature also lets you select various sampling
rates for selected flows. The NetFlow Input Filters
feature is used, for example, for class-based traffic
analysis and monitoring on-network or off-network
traffic.
The following sections provide information about this
feature:
•
Roadmap: Using NetFlow Filtering or Sampling to
Select the Network Traffic to Track, page 3
•
Filtering and Sampling of NetFlow Traffic, page 4
•
NetFlow Input Filters: Flow Classification, page 6
•
Configuring NetFlow Input Filters to Reduce the
Impact of NetFlow Data Export, page 7
The following commands were introduced or modified
by this feature: netflow-sampler and debug
flow-sampler.
21
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Glossary
Table 3
Feature Information for Using NetFlow Filtering or Sampling to Select Network Traffic to Track (continued)
Feature Name
Releases
Feature Configuration Information
Random Sampled NetFlow
12.3(4)T,
12.2(18)S,
12.0(26)S,
12.2(27)SBC
Random Sampled NetFlow provides NetFlow data for a
subset of traffic in a Cisco router by processing only
one randomly selected packet out of n sequential
packets (n is a user-configurable parameter). Packets
are sampled as they arrive (before any NetFlow cache
entries are made for those packets). Statistical traffic
sampling substantially reduces consumption of router
resources (especially CPU resources) while providing
valuable NetFlow data. The main uses of Random
Sampled NetFlow are traffic engineering, capacity
planning, and applications where full NetFlow is not
needed for an accurate view of network traffic.
The following sections provide information about this
feature:
•
Roadmap: Using NetFlow Filtering or Sampling to
Select the Network Traffic to Track, page 3
•
Filtering and Sampling of NetFlow Traffic, page 4
•
Random Sampled NetFlow: Sampling Mode,
page 6
•
Random Sampled NetFlow: The NetFlow Sampler,
page 6
•
Configuring Random Sampled NetFlow to Reduce
the Impact of NetFlow Data Export, page 12
The following commands were introduced by this
feature: debug flow-sampler, flow-sampler,
flow-sampler-map, mode (flow sampler map
configuration), and show flow-sampler.
The following command was modified by this feature:
ip flow-export.
Glossary
ACL—Access control list. A roster of users and groups of users kept by a router. The list is used to
control access to or from the router for a number of services.
BGP—Border Gateway Protocol. Interdomain routing protocol that replaces Exterior Gateway Protocol
(EGP). A BGP system exchanges reachability information with other BGP systems. BGP is defined by
RFC 1163.
BGP next hop—IP address of the next hop to be used to reach a certain destination.
CEF—Cisco Express Forwarding. Layer 3 IP switching technology that optimizes network performance
and scalability for networks with large and dynamic traffic patterns.
22
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Glossary
dCEF—Distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
fast switching—Cisco feature in which a route cache is used to expedite packet switching through a
router.
flow—Unidirectional stream of packets between a given source and destination. Source and destination
are each defined by a network-layer IP address and transport-layer source and destination port numbers.
MQC—Modular QoS command-line interface. A CLI structure that lets you create traffic polices and
attach them to interfaces. A traffic policy contains a traffic class and one or more QoS features. The QoS
features in the traffic policy determine how the classified traffic is treated.
NBAR—Network-Based Application Recognition. A classification engine in Cisco IOS software that
recognizes a wide variety of applications, including web-based applications and client/server
applications that dynamically assign Transmission Control Protocol (TCP) or User Datagram Protocol
(UDP) port numbers. After the application is recognized, the network can invoke specific services for
that application. NBAR is a key part of the Cisco Content Networking architecture and works with QoS
features to let you use network bandwidth efficiently.
NetFlow—Cisco IOS security and accounting feature that maintains per-flow information.
NetFlow sampler—A set of properties that are defined in a NetFlow sampler map that has been applied
to at least one physical interface or subinterface.
NetFlow sampler map—The definition of a set of properties (such as the sampling rate) for NetFlow
sampling.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
ToS—type of service. Second byte in the IP header that indicates the desired quality of service for a
specific datagram.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2010 Cisco Systems, Inc. All rights reserved.
23
Using NetFlow Filtering or Sampling to Select the Network Traffic to Track
Glossary
24
NetFlow Layer 2 and Security Monitoring Exports
First Published: June 19, 2006
Last Updated: June 11, 2010
The NetFlow Layer 2 and Security Monitoring Exports feature improves your ability to detect and
analyze network threats such as denial of service (DoS) attacks by increasing the number of fields from
which NetFlow can capture values.
NetFlow is a Cisco IOS technology that provides statistics on packets flowing through a router. NetFlow
is the standard for acquiring IP operational data from IP networks. NetFlow provides network and
security monitoring, network planning, traffic analysis, and IP accounting.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, use the “Feature Information for NetFlow Layer 2 and Security Monitoring Exports” section on
page 34.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for NetFlow Layer 2 and Security Monitoring Exports, page 2
•
Restrictions for NetFlow Layer 2 and Security Monitoring Exports, page 2
•
Information About NetFlow Layer 2 and Security Monitoring Exports, page 2
•
How to Configure NetFlow Layer 2 and Security Monitoring Exports, page 14
•
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports, page 19
•
Additional References, page 33
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
NetFlow Layer 2 and Security Monitoring Exports
Prerequisites for NetFlow Layer 2 and Security Monitoring Exports
•
Feature Information for NetFlow Layer 2 and Security Monitoring Exports, page 34
•
Glossary, page 36
Prerequisites for NetFlow Layer 2 and Security Monitoring
Exports
Before you configure NetFlow Layer 2 and Security Monitoring Exports, you should understand
NetFlow accounting and how to configure your router to capture IP traffic accounting statistics using
NetFlow. See the “Cisco IOS NetFlow Overview” and “Configuring NetFlow and NetFlow Data Export”
modules for more details.
NetFlow and Cisco Express Forwarding (CEF), distributed CEF (dCEF), or fast switching must be
configured on your system.
Restrictions for NetFlow Layer 2 and Security Monitoring
Exports
If you want to export the data captured with the NetFlow Layer 2 and Security Monitoring feature, you
must configure NetFlow to use the NetFlow Version 9 data export format.
Information About NetFlow Layer 2 and Security Monitoring
Exports
To configure NetFlow Layer 2 and Security Monitoring Exports, you should understand the following
concepts:
•
NetFlow Layer 2 and Security Monitoring, page 2
•
NBAR Data Export, page 13
NetFlow Layer 2 and Security Monitoring
The Layer 2 and Layer 3 fields supported by the NetFlow Layer 2 and Security Monitoring Exports
feature increase the amount of information that can be obtained by NetFlow about the traffic in your
network. You can use this new information for applications such as traffic engineering and usage-based
billing.
The Layer 3 IP header fields for which the NetFlow Layer 2 and Security Monitoring Exports feature
captures the values are as follows:
2
•
Time-to-live (TTL) field
•
Packet length field
•
ID field
•
ICMP type and code fields
•
Fragment offset
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
See the “Layer 3 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports” section
for more information on these Layer 3 fields.
The Layer 2 fields for which NetFlow Layer 2 and Security Monitoring Exports feature captures the
values are as follows:
•
Source MAC address field from frames that are received by the NetFlow router
•
Destination MAC address field from frames that are transmitted by the NetFlow router
•
VLAN ID field from frames that are received by the NetFlow router
•
VLAN ID field from frames that are transmitted by the NetFlow router
See the “Layer 2 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports” section
for more information about these Layer 2 fields.
The Layer 3 fields captured by the NetFlow Layer 2 and Security Monitoring Exports feature improve
the capabilities of NetFlow for identifying DoS attacks. The Layer 2 fields captured by the NetFlow
Layer 2 and Security Monitoring Exports feature can help you identify the path that the DoS attack is
taking through the network.
The Layer 2 and Layer 3 fields captured by the NetFlow Layer 2 and Security Monitoring Exports feature
are not key fields. They provide additional information about the traffic in an existing flow. Changes in
the values of NetFlow key fields such as the source IP address from one packet to the next packet result
in the creation of a new flow. For example, if the first packet captured by NetFlow has a source IP address
of 10.34.0.2 and the second packet captured has a source IP address of 172.16.213.65, then NetFlow will
create two separate flows.
Many DoS attacks consist of an attacker sending the same type of IP datagram again and again in an
attempt to overwhelm the target systems. In such cases the incoming traffic often has similar
characteristics, such as the same values in each datagram for one or more of the fields that the NetFlow
Layer 2 and Security Monitoring Exports feature can capture.
There is no easy way to identify the originator of many DoS attacks because the IP source address of the
device sending the traffic is usually forged. However, you can easily trace the traffic back through the
network to the router on which it is arriving by capturing the MAC address and VLAN-ID fields using
the NetFlow Layer 2 and Security Monitoring Exports feature. If the router on which the traffic is
arriving supports NetFlow, you can configure the NetFlow Layer 2 and Security Monitoring Exports
feature on it to identify the interface where the traffic is arriving. Figure 1 shows an example of an attack
in progress.
3
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Figure 1
DoS Attack Arriving over the Internet
DoS Attack arriving from the Internet
Email server
Host A
Router A
Switch F
Host B
Switch G
NetFlow router
Internet
Router B
Switch B
Switch A
Host C
Router C
Switch C
Switch D
127557
Router D
Switch E
CNS NetFlow
collection engine
Note
You can analyze the data captured by NetFlow directly from the router using the show ip cache verbose
flow command or the CNS NetFlow Collector Engine.
Once you have concluded that a DoS attack is taking place by analyzing the Layer 3 fields in the NetFlow
flows, you can analyze the Layer 2 fields in the flows to discover the path that the DoS attack is taking
through the network.
An analysis of the data captured by the NetFlow Layer 2 and Security Monitoring Exports feature for
the scenario shown in Figure 1 indicates that the DoS attack is arriving on Router C because the upstream
MAC address is from the interface that connects Router C to Switch A. It is also evident that there are
no routers between the target host (the e-mail server) and the NetFlow router because the destination
MAC address of the DoS traffic that the NetFlow router is forwarding to the email server is the MAC
address of the e-mail server.
You can find out the MAC address that Host C is using to send the traffic to Router C by configuring the
NetFlow Layer 2 and Security Monitoring Exports feature on Router C. The source MAC address will
be from Host C. The destination MAC address will be for the interface on the NetFlow router.
Once you know the MAC address that Host C is using and the interface on Router C on which Host C’s
DoS attack is arriving, you can mitigate the attack by reconfiguring Router C to block Host C’s traffic.
If Host C is on a dedicated interface, you disable the interface. If Host C is using an interface that carries
traffic from other users, you must configure your firewall to block Host C’s traffic but still allow the
traffic from the other users to flow through Router C.
The “Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports” section has two
examples for using the NetFlow Layer 2 and Security Monitoring Exports feature to identify an attack
in progress and the path that the attack is taking through a network.
4
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Layer 3 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports
The NetFlow Layer 2 and Security Monitoring Exports feature has support for capturing five fields from
Layer 3 IP traffic in a flow:
•
Time-to-live field
•
Packet length field
•
ID field
•
ICMP type and code
•
Fragment offset
Figure 2 shows the fields in an IP packet header.
Figure 2
IP Packet Header Fields
Table 1 describes the header fields in Figure 2.
Table 1
IP Packet Header Fields
Field
Description
Version
The version of the IP protocol. If this field is set to 4 it is an IPv4 datagram.
If this field is set to 6 it is an IPv6 datagram.
Note
IHL (Internet Header
Length)
The IPv6 header has a different structure from an IPv4 header.
Internet Header Length is the length of the Internet header in 32-bit word
format and thus points to the beginning of the data.
Note
The minimum value for a correct header is 5.
ToS
Type of service (ToS) provides an indication of the abstract parameters of the
quality of service desired. These parameters are to be used to guide the
selection of the actual service parameters when a networking device
transmits a datagram through a particular network.
Total Length
Total length is the length of the datagram, measured in octets, including
Internet header and data.
5
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Table 1
IP Packet Header Fields (continued)
Field
Description
Identification (ID)
The value in the ID field is entered by the sender. All of the fragments of an
IP datagram have the same value in the ID field. Subsequent IP datagrams
from the same sender will have different values in the ID field.
It is very common for a host to be receiving fragmented IP datagrams from
several senders concurrently. It is also common for a host to be receiving
multiple IP datagrams from the same sender concurrently.
The value in the ID field is used by the destination host to ensure that the
fragments of an IP datagram are assigned to the same packet buffer during
the IP datagram reassembly process. The unique value in the ID field is also
used to prevent the receiving host from mixing together IP datagram
fragments of different IP datagrams from the same sender during the IP
datagram reassembly process.
Flags
A sequence of 3 bits used to set and track IP datagram fragmentation
parameters.
•
001 = The IP datagram can be fragmented. There are more fragments of
the current IP datagram in transit.
•
000 = The IP datagram can be fragmented. This is the last fragment of
the current IP datagram.
•
010 = The IP Datagram cannot be fragmented. This is the entire IP
datagram.
Fragment Offset
This field indicates where in the datagram this fragment belongs.
TTL (Time-to-Live)
This field indicates the maximum time the datagram is allowed to remain in
the Internet system. If this field contains the value 0, then the datagram must
be destroyed. This field is modified in Internet header processing. The time
is measured in units of seconds, but since every module that processes a
datagram must decrease the TTL by at least 1 even if it processes the
datagram in less than a second, the TTL must be thought of only as an upper
bound on the time a datagram can exist. The intention is to cause
undeliverable datagrams to be discarded and to bound the maximum
datagram lifetime.
Protocol
Indicates the type of transport packet included in the data portion of the IP
datagram. Common values are:
1 = ICMP
6 = TCP
17 = UDP
6
Header checksum
A checksum on the header only. Since some header fields, such as the
time-to-live field, change every time an IP datagram is forwarded, this value
is recomputed and verified at each point that the Internet header is processed.
Source IP Address
IP address of the sending station.
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Table 1
IP Packet Header Fields (continued)
Field
Description
Destination IP Address
IP address of the destination station.
Options and Padding
The options and padding may or may not appear or not in datagrams. If they
do appear, they must be implemented by all IP modules (host and gateways).
What is optional is their transmission in any particular datagram, not their
implementation.
Figure 3 shows the fields in an ICMP datagram.
Figure 3
ICMP Datagram
Table 2 interprets the packet format in Figure 3. ICMP datagrams are carried in the data area of an IP
datagram, after the IP header.
Table 2
ICMP Packet Format
Type
Name
Codes
0
Echo reply
0—None
1
Unassigned
—
2
Unassigned
—
3
Destination unreachable
0—Net unreachable.
1—Host unreachable.
2—Protocol unreachable.
3—Port unreachable.
4—Fragmentation needed and DF bit set.
5—Source route failed.
6—Destination network unknown.
7—Destination host unknown.
8—Source host isolated.
9—Communication with destination network is
administratively prohibited.
10—Communication with destination host is administratively
prohibited.
11—Destination network unreachable for ToS.
12—Destination host unreachable for ToS.
4
Source quench
0—None.
7
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Table 2
ICMP Packet Format (continued)
Type
Name
Codes
5
Redirect
0—None.
0—Redirect datagram for the network.
1—Redirect datagram for the host.
2—Redirect datagram for the ToS and network.
3—Redirect datagram for the ToS and host.
6
Alternate host address
0—Alternate address for host.
7
Unassigned
—
8
Echo
0—None.
9
Router advertisement
0—None.
10
Router selection
0—None.
11
Time Exceeded
0—Time to live exceeded in transit.
12
Parameter problem
0—Pointer indicates the error.
1—Missing a required option.
2—Bad length.
8
13
Timestamp
0—None.
14
Timestamp reply
0—None.
15
Information request
0—None.
16
Information reply
0—None.
17
Address mask request
0—None.
18
Address mask reply
0—None.
19
Reserved (for security)
—
20–29
Reserved (for robustness
experiment)
—
30
Trace route
—
31
Datagram conversion error
—
32
Mobile host redirect
—
33
IPv6 where-are-you
—
34
IPv6 I-am-here
—
35
Mobile registration request
—
36
Mobile registration reply
—
37–255
Reserved
—
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Layer 2 Information Capture Using NetFlow Layer 2 and Security Monitoring Exports
The NetFlow Layer 2 and Security Monitoring Exports feature has the ability to capture the values of
the MAC address and VLAN ID fields from flows. The two supported VLAN types are 802.1q and the
Cisco Inter-Switch Link (ISL) protocol. This section explains the following concepts:
•
Understanding Layer 2 MAC Address Fields
•
Understanding Layer 2 VLAN ID Fields
Understanding Layer 2 MAC Address Fields
The new Layer 2 fields for which the NetFlow Layer 2 and Security Monitoring Exports feature captures
the values are as follows:
•
The source MAC address field from frames that are received by the NetFlow router
•
The destination MAC address field from frames that are transmitted by the NetFlow router
•
The VLAN ID field from frames that are received by the NetFlow router
•
The VLAN ID field from frames that are transmitted by the NetFlow router
Figure 4 shows the Ethernet Type II and Ethernet 802.3 frame formats. The destination address field and
the source address field in the frame formats are the MAC addresses values that are captured by NetFlow.
Figure 4
Ethernet Type II and 802.3 Frame Formats
Table 3 explains the fields for the Ethernet frame formats.
Table 3
Ethernet Type II and 802.3 Frame Fields
Field
Description
Preamble
The entry in the Preamble field is an alternating pattern of 1s and 0s that tells
receiving stations that a frame is coming. It also provides a means for the
receiving stations to synchronize their clocks with the incoming bit stream.
SOF (Start of frame)
The SOF field holds an alternating pattern of 1s and 0s, ending with two
consecutive 1-bits indicating that the next bit is the first bit of the first byte
of the destination MAC address.
9
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Table 3
Ethernet Type II and 802.3 Frame Fields (continued)
Field
Description
Destination Address
The 48-bit destination address identifies which station(s) on the LAN should
receive the frame. The first two bits of the destination MAC address are
reserved for special functions:
•
The first bit in the DA field indicates whether the address is an
individual address (0) or a group address (1).
•
The second bit indicates whether the DA is globally administered (0) or
locally administered (1).
The remaining 46 bits are a uniquely assigned value that identifies a single
station, a defined group of stations, or all stations on the network.
Source Address
The 48-bit source address identifies which station transmitted the frame. The
source address is always an individual address, and the leftmost bit in the SA
field is always 0.
Type
Type—In an Ethernet Type II frame, this part of the frame is used for the
Type field. The Type field is used to identify the next layer protocol in the
frame.
or
Length
Length—In an 802.3 Ethernet frame, this part of the frame is used for the
Length field. The Length field is used to indicate the length of the Ethernet
frame. The value can be from 46 to 1500 bytes.
Data
(Ethernet type II) 46 to 1500 bytes of data
or
or
802.2 header and data
(802.3/802.2) 8 bytes of header and 38 to 1492 bytes of data.
FCS (Frame Check
Sequence)
This field contains a 32-bit cyclic redundancy check (CRC) value, which is
created by the sending station and is recalculated by the receiving station to
check for damaged frames. The FCS is generated for the DA, SA, Type, and
Data fields of the frame. The FCS does not include the data portion of the
frame.
Understanding Layer 2 VLAN ID Fields
NetFlow can capture the value in the VLAN ID field for 802.1q tagged VLANs and Cisco ISL
encapsulated VLANs. This section describes the two types of VLANs:
Note
•
Understanding 802.1q VLANs
•
Understanding Cisco ISL VLANs
ISL and 802.1q are commonly called VLAN encapsulation protocols.
Understanding 802.1q VLANs
Devices that use 802.1q insert a four-byte tag into the original frame before it is transmitted. Figure 5
shows the format of an 802.1q tagged Ethernet frame.
10
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Figure 5
802.1q Tagged Ethernet Type II or 802.3 Frame
Table 4 describes the fields for 802.1q VLANs.
Table 4
802.1q VLAN Encapsulation Fields
Field
Description
DA, SA, Type or Length, Data, and FCS Table 3 describes these fields.
Tag Protocol ID (TPID)
This 16-bit field is set to a value of 0x8100 to identify the
frame as an IEEE 802.1q tagged frame.
Priority
Also known as user priority, this 3-bit field refers to the
802.1p priority. It indicates the frame priority level used for
prioritizing traffic and is capable of representing 8 levels
(0–7).
Tag Control Information
The 2-byte Tag Control Information field consists of two
subfields:
•
Canonical Format Indicator (CFI)—If the value of this
1-bit field is 1, then the MAC address is in noncanonical
format. If the value of this field is 0, then the MAC
address is in canonical format.
•
VLAN ID—This 12-bit field uniquely identifies the
VLAN to which the frame belongs. It can have a value
from 0 to 4095.
Understanding Cisco ISL VLANs
ISL is a Cisco-proprietary protocol for encapsulating frames on a VLAN trunk. Devices that use ISL add
an ISL header to the frame. This process is known as VLAN encapsulation. 802.1Q is the IEEE standard
for tagging frames on a VLAN trunk. Figure 6 shows the format of a Cisco ISL-encapsulated Ethernet
frame.
11
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
#of bits in
the field
Cisco ISL Tagged Ethernet Frame
40
4
4
48
16
24
24
15
1
16
16
Field Name DA TYPE USER SA LEN AAAA03(SNAP) HSA VLAN BPDU INDEX RES
1 to 24575
bytes
32
Enscapsulated
FCS
FRAME
127755
Figure 6
Table 5 describes The fields for 802.1q VLANs.
Table 5
ISL VLAN Encapsulation
Field
Description
DA (destination
address)
This 40-bit field is a multicast address and is set at 0x01-00-0C-00-00 or
0x03-00-0c-00-00. The receiving host determines that the frame is
encapsulated in ISL by reading the 40-bit DA field and matching it to one of
the two ISL multicast addresses.
TYPE
This 4-bit field indicates the type of frame that is encapsulated and could be
used in the future to indicate alternative encapsulations.
TYPE codes:
USER
•
0000 = Ethernet
•
0001 = Token Ring
•
0010 = FDDI
•
0011 = ATM
This 4-bit field is used to extend the meaning of the Frame TYPE field. The
default USER field value is 0000. For Ethernet frames, the USER field bits
0 and 1 indicate the priority of the packet as it passes through the switch.
Whenever traffic can be handled more quickly, the packets with this bit set
should take advantage of the quicker path. However, such paths are not
required.
USER codes:
12
•
XX00 = Normal priority
•
XX01 = Priority 1
•
XX10 = Priority 2
•
XX11 = Highest priority
SA
This 48-bit field is the source address field of the ISL packet. It should be set
to the 802.3 MAC address of the switch port transmitting the frame. The
receiving device can ignore the SA field of the frame.
LEN
This 16-bit value field stores the actual packet size of the original packet.
The LEN field represents the length of the packet in bytes, excluding the DA,
TYPE, USER, SA, LEN, and FCS fields. The total length of the excluded
fields is 18 bytes, so the LEN field represents the total length minus 18 bytes.
AAAA03(SNAP)
The AAAA03 SNAP field is a 24-bit constant value of 0xAAAA03.
HSA
This 24-bit field represents the upper three bytes (the manufacturer’s ID
portion) of the SA field. It must contain the value 0x00-00-0C.
VLAN
This 15-bit field is the virtual LAN ID of the packet. This value is used to
mark frames on different VLANs.
NetFlow Layer 2 and Security Monitoring Exports
Information About NetFlow Layer 2 and Security Monitoring Exports
Table 5
ISL VLAN Encapsulation (continued)
Field
Description
BPDU
The bit in the BPDU field is set for all BPDU packets that are encapsulated
by the ISL frame. The BPDUs are used by the spanning tree algorithm to find
out information about the topology of the network. This bit is also set for
CDP and VTP frames that are encapsulated.
INDEX
This 16-bit field indicates the port index of the source of the packet as it exits
the switch. It is used for diagnostic purposes only, and may be set to any
value by other devices. It is ignored in received packets.
RES
This 16-bit field is used when Token Ring or FDDI packets are encapsulated
with an ISL frame.
Encapsulated FRAME
This field contains the encapsulated Layer 2 frame.
FCS
The FCS field consists of 4 bytes. It includes a 32-bit CRC value, which is
created by the sending station and is recalculated by the receiving station to
check for damaged frames. The FCS covers the DA, SA, Length/Type, and
Data fields. When an ISL header is attached to a Layer 2 frame, a new FCS
is calculated over the entire ISL packet and added to the end of the frame.
Note
The addition of the new FCS does not alter the original FCS that is
contained within the encapsulated frame.
NBAR Data Export
Network Based Application Recognition (NBAR) is a classification engine that recognizes and classifies
a wide variety of protocols and applications, including web-based and other difficult-to-classify
applications and protocols that use dynamic TCP/UDP port assignments.
When NBAR recognizes and classifies a protocol or application, the network can be configured to apply
the appropriate application mapping with that protocol.
With Cisco IOS Release 12.2(18)ZYA2 on the Catalyst 6500 series switch equipped with a
Supervisor 32/programmable intelligent services accelerator (PISA), the NBAR flow can be exported
along with NetFlow export records.
The application-aware NetFlow feature integrates NBAR with NetFlow to provide the ability to export
application information collected by NBAR using NetFlow. The application IDs created for the NetFlow
Version 9 attribute export application names along with the standard attributes such as IP address and
TCP/UDP port information. The NetFlow collector collects these flows based on source IP address and
ID. The source ID refers to the unique identification for flows exported from a particular device.
The NBAR data exported to the NetFlow collector contains application mapping information. Using the
NetFlow Data export options, the table containing the application IDs mapped to their application names
is exported to the NetFlow collector. The mapping table is sent using the ip flow-export template
options nbar command. The mapping information is refreshed every 30 minutes by default. You can
configure the refresh interval by using the ip flow-export template options timeout-rate command.
Netflow export uses several aging mechanisms to manage the NetFlow cache. However, the NBAR data
export intervals do not use NetFlow aging parameters.
13
NetFlow Layer 2 and Security Monitoring Exports
How to Configure NetFlow Layer 2 and Security Monitoring Exports
Benefits of NBAR NetFlow Integration
NBAR enables network administrators to track variety of protocols and the amount of traffic generated
by each protocol. NBAR also allows them to organize traffic into classes. These classes can then be used
to provide different levels of service for network traffic, thereby allowing better network management
by providing the right level of network resources for network traffic.
How to Configure NetFlow Layer 2 and Security Monitoring
Exports
This section contains the following procedures:
•
Configuring NetFlow Layer 2 and Security Monitoring Exports, page 14
•
Verifying NetFlow Layer 2 and Security Monitoring Exports, page 16 (Optional)
•
Configuring NBAR Support for NetFlow Exports
Configuring NetFlow Layer 2 and Security Monitoring Exports
Prerequisites
CEF, dCEF, or fast switching for IP must be configured on your system before you configure the
NetFlow Layer 2 and Security Monitoring Exports feature.
The optional “Verifying NetFlow Layer 2 and Security Monitoring Exports” task uses the show ip cache
verbose flow command to display the values of the fields that you have configured the NetFlow Layer 2
and Security Monitoring Exports feature to capture. In order for you to view the values of the fields that
you configured the NetFlow Layer 2 and Security Monitoring Exports feature to capture, your router
must forward the IP traffic that meets the criteria for these fields. For example, if you configure the ip
flow-capture ipid command, your router must be forwarding IP datagrams to capture the IP ID values
from the IP datagrams in the flow.
If you want to capture the values of the Layer 3 IP fragment offset field from the IP headers in your IP
traffic using the ip flow-capture fragment-offset command, your router must be running
Cisco IOS 12.4(2)T or later release.
SUMMARY STEPS
14
1.
enable
2.
configure terminal
3.
ip flow-capture fragment-offset
4.
ip flow-capture icmp
5.
ip flow-capture ip-id
6.
ip flow-capture mac-addresses
7.
ip flow-capture packet-length
8.
ip flow-capture ttl
9.
ip flow-capture vlan-id
NetFlow Layer 2 and Security Monitoring Exports
How to Configure NetFlow Layer 2 and Security Monitoring Exports
10. interface type [number | slot/port]
11. ip flow ingress
and/or
ip flow egress
12. exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-capture fragment-offset
(Optional) Enables capturing the value of the IP fragment
offset field from the first fragmented IP datagram in a flow.
Example:
Router(config)# ip flow-capture fragment-offset
Step 4
ip flow-capture icmp
(Optional) Enables you to capture the value of the ICMP
type and code fields from ICMP datagrams in a flow.
Example:
Router(config)# ip flow-capture icmp
Step 5
ip flow-capture ip-id
(Optional) Enables you to capture the value of the IP-ID
field from the first IP datagram in a flow.
Example:
Router(config)# ip flow-capture ip-id
Step 6
ip flow-capture mac-addresses
(Optional) Enables you to capture the values of the source
and destination MAC addresses from the traffic in a flow.
Example:
Router(config)# ip flow-capture mac-addresses
Step 7
ip flow-capture packet-length
Example:
(Optional) Enables you to capture the minimum and
maximum values of the packet length field from IP
datagrams in a flow.
Router(config)# ip flow-capture packet-length
Step 8
ip flow-capture ttl
Example:
(Optional) Enables you to capture the minimum and
maximum values of the time-to-live (TTL) field from IP
datagrams in a flow.
Router(config)# ip flow-capture ttl
Step 9
ip flow-capture vlan-id
Example:
(Optional) Enables you to capture the 802.1q or ISL
VLAN-ID field from VLAN encapsulated frames in a flow
that are received or transmitted on trunk ports.
Router(config)# ip flow-capture vlan-id
15
NetFlow Layer 2 and Security Monitoring Exports
How to Configure NetFlow Layer 2 and Security Monitoring Exports
Step 10
Command or Action
Purpose
interface type [number | slot/port]
Enters interface configuration mode for the type of interface
specified in the command.
Example:
Router(config)# interface ethernet 0/0
Step 11
ip flow ingress
Enables ingress NetFlow data collection on the interface.
and/or
and/or
ip flow egress
Enables egress NetFlow data collection on the interface.
Example:
Router(config-if)# ip flow ingress
and/or
Example:
Router(config-if)# ip flow egress
Step 12
Exits global configuration mode.
exit
Example:
Router(config)# exit
Verifying NetFlow Layer 2 and Security Monitoring Exports
Perform this task to verify the configuration of NetFlow Layer 2 and Security Monitoring Exports.
Restrictions
The “Verifying NetFlow Layer 2 and Security Monitoring Exports” uses the show ip cache verbose flow
command. The following restrictions apply to using the show ip cache verbose flow command.
Displaying Detailed NetFlow Cache Information on Platforms Running Distributed Cisco Express Forwarding
On platforms running dCEF, NetFlow cache information is maintained on each line card or Versatile
Interface Processor. If you want to use the show ip cache verbose flow command to display this
information on a distributed platform, you must enter the command at a line card prompt.
Cisco 7500 Series Platform
To display detailed NetFlow cache information on a Cisco 7500 series router that is running distributed
dCEF, enter the following sequence of commands:
Router# if-con slot-number
LC-slot-number# show ip cache verbose flow
For Cisco IOS Releases 12.3(4)T, 12.3(6), and 12.2(20)S and later, enter the following command to
display detailed NetFlow cache information:
Router# execute-on slot-number show ip cache verbose flow
16
NetFlow Layer 2 and Security Monitoring Exports
How to Configure NetFlow Layer 2 and Security Monitoring Exports
Cisco 12000 Series Platform
To display detailed NetFlow cache information on a Cisco 12000 Series Internet Router, enter the
following sequence of commands:
Router# attach slot-number
LC-slot-number# show ip cache verbose flow
For Cisco IOS Releases 12.3(4)T, 12.3(6), and 12.2(20)S and later, enter the following command to
display detailed NetFlow cache information:
Router#
execute-on slot-number show ip cache verbose flow.
SUMMARY STEPS
1.
show ip cache verbose flow
DETAILED STEPS
Step 1
show ip cache verbose flow
The following output shows the working of NetFlow Layer 2 and Security Monitoring Exports feature
by capturing the values from the Layer 2 and Layer 3 fields in the flows.
Router# show ip cache verbose flow
IP packet size distribution (25229 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .206 .793 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
6 active, 4090 inactive, 17 added
505 ager polls, 0 flow alloc failures
Active flows timeout in 1 minutes
Inactive flows timeout in 10 seconds
IP Sub Flow Cache, 25736 bytes
12 active, 1012 inactive, 39 added, 17 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-Telnet
1
0.0
362
940
2.7
60.2
0.0
TCP-FTP
1
0.0
362
840
2.7
60.2
0.0
TCP-FTPD
1
0.0
362
840
2.7
60.1
0.1
TCP-SMTP
1
0.0
361 1040
2.7
60.0
0.1
UDP-other
5
0.0
1
66
0.0
1.0
10.6
ICMP
2
0.0
8829 1378
135.8
60.7
0.0
Total:
11
0.0
1737 1343
147.0
33.4
4.8
SrcIf
Port Msk AS
Et0/0.1
0015 /0 0
MAC: (VLAN id)
Min plen:
Min TTL:
IP id:
SrcIPaddress
10.251.138.218
aaaa.bbbb.cc03
840
59
0
DstIf
Port Msk AS
Et1/0.1
0015 /0 0
(005)
DstIPaddress
NextHop
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
Pr TOS Flgs Pkts
B/Pk Active
06 80 00
65
840
10.8
(006)
840
59
17
NetFlow Layer 2 and Security Monitoring Exports
How to Configure NetFlow Layer 2 and Security Monitoring Exports
Configuring NBAR Support for NetFlow Exports
Perform this task to export NBAR data to NetFlow Collector.
Prerequisites
You must enable NetFlow Version 9 and NBAR before you configure NBAR data export.
You must add and configure the following fields to the Cisco NetFlow Collector Software to identify the
flow exported by the NBAR data export feature:
•
app_id field as an integer with NumericID of 95
•
app_name field as a UTF-8 String with NumericID of 96
•
sub_app_id field as an Integer with NumericID of 97
•
biflowDirection field as an Integer with NumericID of 239
Note
The biflowDirection field provides information about the host that initiates the session. The size
of this field is one byte. RFC 5103 provides details for using this field.
Restrictions
NBAR support can be configured only with NetFlow Version 9 format. If you try to configure NBAR
data export with other versions, the following error message appears:
1d00h: %FLOW : Export version 9 not enabled
The NBAR data export does not use NetFlow aging parameters.
SUMMARY STEPS
18
1.
enable
2.
configure terminal
3.
ip flow-export version
4.
ip flow-capture nbar
5.
ip flow-export template options nbar
6.
exit
7.
show ip flow export nbar
8.
clear ip flow stats nbar
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
DETAILED STEPS
Step 1
Enables privileged EXEC mode.
enable
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-export version 9
Enables the Version 9 format to export NetFlow cache
entries.
Example:
Router(config)# ip flow-capture version 9
Step 4
ip flow-capture nbar
Enables you to capture the NBAR data in NetFlow export
records.
Example:
Router(config)# ip flow-capture nbar
Step 5
ip flow-export template options nbar
Exports application mapping information to NetFlow data
collector.
Example:
Router(config)# ip flow-export template options
nbar
Step 6
Exits global configuration mode.
exit
Example:
Router(config)# exit
Step 7
show ip flow export nbar
(Optional) Displays NBAR export records.
Example:
Router # show ip flow export nbar
Step 8
clear ip flow stats nbar
(Optional) Clears NetFlow accounting statistics for NBAR.
Example:
Router# clear ip flow stats nbar
Configuration Examples for NetFlow Layer 2 and Security
Monitoring Exports
This section provides the following configuration examples:
•
Configuring and Using NetFlow Layer 2 and Security Monitoring Exports to Analyze a Simulated
FTP Attack: Example, page 20
•
Configuring and Using NetFlow Layer 2 and Security Monitoring Exports to Analyze a Simulated
ICMP Ping Attack: Example, page 26
19
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Configuring and Using NetFlow Layer 2 and Security Monitoring Exports to
Analyze a Simulated FTP Attack: Example
The following example shows how to use the NetFlow Layer 2 and Security Monitoring Exports feature
to find out whether your network is being attacked by a host that is sending fake FTP traffic in an attempt
to overwhelm the FTP server. This attack might cause end users to see a degradation in the ability of the
FTP server to accept new connections or to service existing connections.
This example uses the network shown in Figure 7. Host A is sending fake FTP packets to the FTP server.
This example also shows you how to use the Layer 2 data captured by the NetFlow Layer 2 and Security
Monitoring Exports feature to learn where the traffic is originating and what path it is taking through the
network.
Figure 7
Test Network
Simulated DoS attack
aaaa.bbbb.cc03 aaaa.bbbb.cc04 aaaa.bbbb.cc05 aaaa.bbbb.cc06
172.16.6.1
172.16.6.2
172.16.7.1
172.16.7.2
S2/0
172.16.1.2
E0/0
172.16.1.1
172.16.10.1
R2 E1/0.1
S3/0
E0/0.1
R3
802.1q trunk
VLAN 5
E1/0.1
E1/0.1
802.1q trunk
VLAN 6
R4
S3/0
E0/0
172.16.10.2
Tip
Keep track of the MAC addresses and IP addresses of the devices in your network. You can use them to
analyze attacks and to resolve problems.
Note
This example does not include the ip flow-capture icmp command, which captures the value of the
ICMP type and code fields. The use of the ip flow-capture icmp command is described in “Configuring
and Using NetFlow Layer 2 and Security Monitoring Exports to Analyze a Simulated ICMP Ping Attack:
Example.”
R2
!
hostname R2
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc02
ip address 172.16.1.2 255.255.255.0
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc03
no ip address
!
interface Ethernet1/0.1
20
FTP server
S2/0
127556
Host A
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
encapsulation dot1Q 5
ip address 172.16.6.1 255.255.255.0
!
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R3
!
hostname R3
!
ip flow-capture fragment-offset
ip flow-capture packet-length
ip flow-capture ttl
ip flow-capture vlan-id
ip flow-capture ip-id
ip flow-capture mac-addresses
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc04
no ip address
!
interface Ethernet0/0.1
encapsulation dot1Q 5
ip address 172.16.6.2 255.255.255.0
ip accounting output-packets
ip flow ingress
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc05
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.1 255.255.255.0
ip accounting output-packets
ip flow egress
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R4
!
hostname R4
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc07
ip address 172.16.10.1 255.255.255.0
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc06
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.2 255.255.255.0
21
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
The show ip cache verbose flow command displays the NetFlow flows that have been captured from the
FTP traffic that Host A is sending.
The fields that have the values captured by the ip flow-capture command are in Table 9. These are the
fields and the values that are used to analyze the traffic for this example. The other fields captured by
the show ip cache verbose flow command are explained in Table 6, Table 7, and Table 8.
R3# show ip cache verbose flow
IP packet size distribution (3596 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .003 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .995 .000 .000 .000 .000 .000 .000 .000
The preceding output shows the percentage distribution of packets by size. In this display, 99.5 percent
of the packets fall in the 1024-byte size range, and 0.3 percent fall in the 64-byte range.
The next section of the output can be divided into four parts. The section and the table corresponding to
each are as follows:
•
Field Descriptions in the NetFlow Cache Section of the Output (Table 6 on page 23)
•
Field Descriptions in the Activity by Protocol Section of the Output (Table 7 on page 24)
•
Field Descriptions in the NetFlow Record Section of the Output (Table 8 on page 24)
•
NetFlow Layer 2 and Security Monitoring Exports Fields in the NetFlow Record Section of the
Output (Table 9 on page 25)
IP Flow Switching Cache, 278544 bytes
5 active, 4091 inactive, 25 added
719 ager polls, 0 flow alloc failures
Active flows timeout in 1 minutes
Inactive flows timeout in 10 seconds
IP Sub Flow Cache, 25736 bytes
10 active, 1014 inactive, 64 added, 25 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
TCP-FTP
5
0.0
429
840
6.6
58.1
1.8
Total:
5
0.0
129
835
6.6
17.6
7.9
SrcIf
Port Msk AS
Et0/0.1
0015 /0 0
MAC: (VLAN id)
Min plen:
Min TTL:
IP id:
SrcIPaddress
10.132.221.111
aaaa.bbbb.cc03
840
59
0
Et0/0.1
10.251.138.218
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
22
DstIf
Port Msk AS
Et1/0.1
0015 /0 0
(005)
DstIPaddress
NextHop
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
Pr TOS Flgs Pkts
B/Pk Active
06 80 00
198
840
41.2
(006)
840
59
Et1/0.1
0015 /0
(005)
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
06 80
0
(006)
00
840
198
41.2
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Min plen:
Min TTL:
IP id:
840
59
0
Et0/0.1
10.10.12.1
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
840
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Et0/0.1
10.231.185.254
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
840
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Et0/0.1
10.71.200.138
0015 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
840
Min TTL:
59
IP id:
0
Et1/0.1
0015 /0
(005)
0
Max plen:
Max TTL:
840
59
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 80
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 80
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Max plen:
Max TTL:
06 80
00
840
203
42.2
00
840
203
42.2
00
840
203
42.2
(006)
840
59
(006)
840
59
(006)
840
59
R3#
Table 6 describes the significant fields shown in the NetFlow cache section of the output.
Table 6
Field Descriptions in the NetFlow Cache Section of the Output
Field
Description
bytes
Number of bytes of memory used by the NetFlow cache.
active
Number of active flows in the NetFlow cache at the time this command was
entered.
inactive
Number of flow buffers that are allocated in the NetFlow cache but that were
not assigned to a specific flow at the time this command was entered.
added
Number of flows created since the start of the summary period.
ager polls
Number of times the NetFlow code caused entries to expire (used by Cisco
Customer Support Engineers (CSE) for diagnostic purposes).
flow alloc failures
Number of times the NetFlow code tried to allocate a flow but could not.
last clearing of statistics The period of time that has passed since the clear ip flow stats privileged
EXEC command was last executed. The standard time output format of
hours, minutes, and seconds (hh:mm:ss) is used for a period of time less than
24 hours. This time output changes to hours and days after the time exceeds
24 hours.
23
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Table 7 describes the significant fields shown in the activity by protocol section of the output.
Table 7
Field Descriptions in the Activity by Protocol Section of the Output
Field
Description
Protocol
IP protocol and the well-known port number. (Refer to http://www.iana.org,
Protocol Assignment Number Services, for the latest RFC values.)
Note
Only a small subset of all protocols is displayed.
Total Flows
Number of flows for this protocol since the last time statistics were cleared.
Flows/Sec
Average number of flows for this protocol per second; equal to the total flows
divided by the number of seconds for this summary period.
Packets/Flow
Average number of packets for the flows for this protocol; equal to the total
packets for this protocol divided by the number of flows for this protocol for
this summary period.
Bytes/Pkt
Average number of bytes for the packets for this protocol; equal to the total
bytes for this protocol divided by the total number of packets for this protocol
for this summary period.
Packets/Sec
Average number of packets for this protocol per second; equal to the total
packets for this protocol divided by the total number of seconds for this
summary period.
Active(Sec)/Flow
Number of seconds from the first packet to the last packet of an expired flow
divided by the number of total flows for this protocol for this summary period.
Idle(Sec)/Flow
Number of seconds observed from the last packet in each nonexpired flow for
this protocol until the time at which the show ip cache verbose flow
command was entered divided by the total number of flows for this protocol
for this summary period.
Table 8 describes the significant fields in the NetFlow record section of the output.
Table 8
Field Descriptions in the NetFlow Record Section of the Output
Field
Description
SrcIf
Interface on which the packet was received.
Port Msk AS
Source port number (displayed in hexadecimal format), IP address mask, and
autonomous system number. This is always set to 0 in MPLS flows.
SrcIPaddress
This is the source IP address of the traffic in the five flows. The traffic is
using five different IP source addresses
DstIf
•
10.132.221.111
•
10.251.138.218
•
10.10.12.1
•
10.231.185.254
•
10.71.200.138
Interface from which the packet was transmitted.
Note
24
If an asterisk (*) immediately follows the DstIf field, the flow being
shown is an egress flow.
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Table 8
Field Descriptions in the NetFlow Record Section of the Output (continued)
Field
Description
Port Msk AS
Source port number (displayed in hexadecimal format), IP address mask, and
autonomous system number. The value of this field is always set to 0 in
Multiprotocol Label Switching (MPLS) flows.
DstIPaddress
This is the destination IP address of the traffic.
Note
172.17.10.2 is the IP address of the FTP server.
NextHop
The Border Gateway Protocol (BGP) next-hop address. This is always set to
0 in MPLS flows.
Pr
IP protocol “well-known” port number, displayed in hexadecimal format.
(Refer to http://www.iana.org, Protocol Assignment Number Services, for
the latest RFC values.)
ToS
Type of service, displayed in hexadecimal format.
B/Pk
Average number of bytes observed for the packets seen for this flow.
Flgs
TCP flags, shown in hexadecimal format. This value is the result of bitwise
OR of the TCP flags from all packets in the flow.
Pkts
Number of packets in this flow.
Active
Time the flow has been active.
Table 9 describes the fields and values for the NetFlow Traffic Classification and Identification fields for
the NetFlow record section of the output.
Table 9
NetFlow Layer 2 and Security Monitoring Exports Fields in the NetFlow Record
Section of the Output
Field
Description
MAC
These are the source and destination MAC addresses from the traffic. The
source and destination MAC address are read from left to right in the output.
•
Note
•
Note
VLAN id
Min plen
The traffic is being received from MAC address aaa.bbb.cc03.
This MAC address is interface 1/0.1 on router R2.
The traffic is being transmitted to MAC address aaa.bbb.cc06.
This MAC address is interface 1/0.1 on router R4.
These are the source and destination VLAN IDs. The source and destination
VLAN IDs are read from left to right in the output.
•
The traffic is being received from VLAN 5.
•
The traffic is being transmitted to VLAN 6.
This is the minimum packet length for the packets captured in the five flows.
The current value is 840.
Max plen
This is the maximum packet length for the packets captured in the five flows.
The current value is 840.
25
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Table 9
NetFlow Layer 2 and Security Monitoring Exports Fields in the NetFlow Record
Section of the Output (continued)
Field
Description
Min TTL
This is the minimum time-to-live (TTL) for the packets captured in the five
flows.
The current value is 59.
Max TTL
This is the maximum TTL for the packets captured in the five flows.
The current value is 59.
IP id
This is the IP identifier field for the traffic in the five flows.
The current value is 0.
The fact that the Layer 3 TTL, identifier, and packet length fields in the five flows have the same values
is a good indication that this traffic is a DoS attack. If this data had been captured from real traffic, the
values would typically be different. The fact that all six of these flows have a TTL value of 59 indicates
that this traffic is originating from points that are the same distance away from R3. Real user traffic
would normally be arriving from many different distances away; therefore the TTL values would be
different.
If this traffic is identified as a DoS attack (based on the data captured in the Layer 3 fields), you can use
the Layer 2 information in the flows to identify the path the traffic is taking through the network. In this
example, the traffic is being sent to R3 on VLAN 5 by R2. You can demonstrate that R2 is transmitting
the traffic over interface 1/0.1 because the source MAC address (aaaa.bbb.cc03) belongs to 1/0.1 on R2.
You can identify that R3 is transmitting the traffic using VLAN 6 on interface 1/0.1 to interface 1/0.1 on
R4 because the destination MAC address (aaaa.bbbb.cc06) belongs to interface 1/0.1 on R4.
You can use this information to develop a plan to mitigate this attack. One possible way to mitigate this
attack is by configuring an extended IP access list that blocks FTP traffic from any host with a source
address that is on the 10.0.0.0 network. Another possible solution is to configure a default route for the
10.0.0.0 network that points to the null interface on the router.
Caution
Each of these solutions blocks traffic from legitimate hosts on the 10.0.0.0 network. Therefore these
solutions should be used only temporarily while you identify the point of origin of the attack and decide
how to stop it there.
Configuring and Using NetFlow Layer 2 and Security Monitoring Exports to
Analyze a Simulated ICMP Ping Attack: Example
The following example shows how to use the NetFlow Layer 2 and Security Monitoring Exports feature
to find out that your network is being attacked by ICMP traffic. It uses the network shown in Figure 7.
Host A is sending very large ICMP ping packets to the FTP server.
R2
!
hostname R2
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc02
ip address 172.16.1.2 255.255.255.0
26
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc03
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 5
ip address 172.16.6.1 255.255.255.0
!
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R3
!
hostname R3
!
ip flow-capture fragment-offset
ip flow-capture packet-length
ip flow-capture ttl
ip flow-capture vlan-id
ip flow-capture icmp
ip flow-capture ip-id
ip flow-capture mac-addresses
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc04
no ip address
!
interface Ethernet0/0.1
encapsulation dot1Q 5
ip address 172.16.6.2 255.255.255.0
ip accounting output-packets
ip flow ingress
!
interface Ethernet1/0
mac-address aaaa.bbbb.cc05
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.1 255.255.255.0
ip accounting output-packets
ip flow egress
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
R4
!
hostname R4
!
interface Ethernet0/0
mac-address aaaa.bbbb.cc07
ip address 172.16.10.1 255.255.255.0
!
27
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
interface Ethernet1/0
mac-address aaaa.bbbb.cc06
no ip address
!
interface Ethernet1/0.1
encapsulation dot1Q 6
ip address 172.16.7.2 255.255.255.0
!
router rip
version 2
network 172.16.0.0
no auto-summary
!
The show ip cache verbose flow command displays the NetFlow flows that have been captured from the
ICMP traffic that Host A is sending.
The fields that have their values captured by the ip flow-capture command are explained in Table 13.
These are the fields and the values that are used to analyze the traffic for this example. The other fields
captured by the show ip cache verbose flow command are explained in Table 10, Table 11 and Table 12.
R3# show ip cache verbose flow
IP packet size distribution (5344 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .166 .832 .000 .000 .000 .000 .000 .000
The preceding output shows the percentage distribution of packets by size. In this display, 16.6 percent
of the packets fall in the 1024-byte size range and 83.2 percent fall in the 1536-byte range.
The next section of the output can be divided into four sections. The section and the table corresponding
to each are as follows:
•
Field Descriptions in the NetFlow Cache Section of the Output (Table 10 on page 29)
•
Field Descriptions in the Activity by Protocol Section of the Output (Table 11 on page 29)
•
Field Descriptions in the NetFlow Record Section of the Output (Table 12 on page 30)
•
NetFlow Layer 2 and Security Monitoring Exports Fields in the NetFlow Record Section of the
Output (Table 13 on page 31)
IP Flow Switching Cache, 278544 bytes
3 active, 4093 inactive, 7 added
91 ager polls, 0 flow alloc failures
Active flows timeout in 1 minutes
Inactive flows timeout in 10 seconds
IP Sub Flow Cache, 25736 bytes
7 active, 1017 inactive, 17 added, 7 added to flow
0 alloc failures, 0 force free
1 chunk, 0 chunks added
last clearing of statistics 00:01:13
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
ICMP
2
0.0
1500 1378
42.8
11.4
10.9
Total:
2
0.0
600 1378
42.9
11.5
10.8
SrcIf
SrcIPaddress
Port Msk AS
Et0/0.1
10.106.1.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
28
DstIf
Port Msk AS
Et1/0.1
0800 /0 0
(005)
DstIPaddress
NextHop
172.16.10.2
0.0.0.0
aaaa.bbbb.cc06
Pr TOS Flgs Pkts
B/Pk Active
01 00 10
391
1500
8.6
(006)
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Min plen:
Min TTL:
ICMP type:
IP id:
1500
59
8
13499
Max plen:
Max TTL:
ICMP code:
Et0/0.1
10.106.1.1
0000 /0 0
MAC: (VLAN id) aaaa.bbbb.cc03
Min plen:
772
Min TTL:
59
ICMP type:
0
IP id:
13499
Et1/0.1
0000 /0
(005)
0
1500
59
0
172.16.10.2
01 00 00
0.0.0.0
1354
aaaa.bbbb.cc06 (006)
Max plen:
1500
Max TTL:
59
ICMP code:
0
FO:
185
1950
8.6
R3#
Table 10 describes the significant fields shown in the NetFlow cache lines of the output.
Table 10
Field Descriptions in the NetFlow Cache Section of the Output
Field
Description
bytes
Number of bytes of memory used by the NetFlow cache.
active
Number of active flows in the NetFlow cache at the time this command was
entered.
inactive
Number of flow buffers that are allocated in the NetFlow cache but that were
not assigned to a specific flow at the time this command was entered.
added
Number of flows created since the start of the summary period.
ager polls
Number of times the NetFlow code caused entries to expire (used by Cisco
Customer Support Engineers (CSE) for diagnostic purposes).
flow alloc failures
Number of times the NetFlow code tried to allocate a flow but could not.
last clearing of
statistics
The period of time that has passed since the clear ip flow stats privileged
EXEC command was last executed. The standard time output format of hours,
minutes, and seconds (hh:mm:ss) is used for a period of time less than 24
hours. This time output changes to hours and days after the time exceeds
24 hours.
Table 11 describes the significant fields shown in the activity by protocol lines of the output.
Table 11
Field Descriptions in the Activity by Protocol Section of the Output
Field
Description
Protocol
IP protocol and the well-known port number. (Refer to http://www.iana.org,
Protocol Assignment Number Services, for the latest RFC values.)
Note
Only a small subset of all protocols is displayed.
Total Flows
Number of flows for this protocol since the last time statistics were cleared.
Flows/Sec
Average number of flows for this protocol per second; equal to the total flows
divided by the number of seconds for this summary period.
Packets/Flow
Average number of packets for the flows for this protocol; equal to the total
packets for this protocol divided by the number of flows for this protocol for
this summary period.
29
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Table 11
Field Descriptions in the Activity by Protocol Section of the Output (continued)
Field
Description
Bytes/Pkt
Average number of bytes for the packets for this protocol; equal to the total
bytes for this protocol divided by the total number of packets for this protocol
for this summary period.
Packets/Sec
Average number of packets for this protocol per second; equal to the total
packets for this protocol divided by the total number of seconds for this
summary period.
Active(Sec)/Flow
Number of seconds from the first packet to the last packet of an expired flow
divided by the total number of flows for this protocol for this summary period.
Idle(Sec)/Flow
Number of seconds observed from the last packet in each nonexpired flow for
this protocol until the time at which the show ip cache verbose flow
command was entered divided by the total number of flows for this protocol
for this summary period.
Table 12 describes the significant fields in the NetFlow record lines of the output.
Table 12
Field Descriptions in the NetFlow Record Section of the Output
Field
Description
SrcIf
Interface on which the packet was received.
Port Msk AS
Source port number (displayed in hexadecimal format), IP address mask, and
autonomous system number. The value of this field is always set to 0 in
MPLS flows.
SrcIPaddress
IP address of the device that transmitted the packet. The sending host is using
10.106.1.1 as the source IP address.
DstIf
Interface from which the packet was transmitted.
Note
30
If an asterisk (*) immediately follows the DstIf field, the flow being
shown is an egress flow.
Port Msk AS
Destination port number (displayed in hexadecimal format), IP address
mask, and autonomous system. This is always set to 0 in MPLS flows.
DstIPaddress
IP address of the destination device.
NextHop
The BGP next-hop address. This is always set to 0 in MPLS flows.
Pr
IP protocol “well-known” port number, displayed in hexadecimal format.
(Refer to http://www.iana.org, Protocol Assignment Number Services, for the
latest RFC values.)
ToS
Type of service, displayed in hexadecimal format.
B/Pk
Average number of bytes observed for the packets seen for this flow.
Flgs
TCP flags, shown in hexadecimal format. This value is the result of bitwise
OR of the TCP flags from all packets in the flow.
Pkts
Number of packets in this flow.
Active
Time the flow has been active.
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
Table 13 describes the fields and values for the NetFlow Traffic Classification and Identification fields
for the NetFlow record lines of the output.
Table 13
NetFlow Layer 2 and Security Monitoring Exports Fields in the NetFlow Record
Section of the Output
Field
Description
MAC
These are the source and destination MAC addresses from the traffic. The
source and destination MAC address are read from left to right in the output.
•
Note
•
Note
VLAN id
Min plen
The traffic is being received from MAC address aaa.bbb.cc03.
This MAC address is interface 1/0.1 on router R2.
The traffic is being transmitted to MAC address aaa.bbb.cc06.
This MAC address is interface 1/0.1 on router R4.
These are the source and destination VLAN IDs. The source and destination
VLAN IDs are read from left to right in the output.
•
The traffic is being received from VLAN 5.
•
The traffic is being transmitted to VLAN 6.
This is the minimum packet length for the packets captured in the two flows.
The current value for the first flow is 1500.
The current value for the second flow is 772.
Max plen
This is the maximum packet length for the packets captured in the two flows.
The current value for the first flow is 1500.
The current value for the second flow is 1500.
Min TTL
This is the minimum time-to-live (TTL) for the packets captured in the two
flows.
The current value is 59.
Max TTL
This is the maximum TTL for the packets captured in the two flows.
The current value is 59.
IP id
This is the IP identifier field for the traffic in the flows. The current value is
0 for all three flows.
ICMP type
This is the Internet Control Message Protocol (ICMP) type field from the
ICMP datagram captured in the first flow.
The value is: 8
ICMP code
This is the ICMP code field from the ICMP datagram captured in the third
flow.
The value is: 0
FO
This is the value of the fragment offset field from the first fragmented
datagram in the second flow.
The value is: 185
31
NetFlow Layer 2 and Security Monitoring Exports
Configuration Examples for NetFlow Layer 2 and Security Monitoring Exports
There are two ICMP flows shown in the output. You can tell that they are from the same ICMP datagram
because they have the same IP ID field value of 13499. When two ICMP flows have the same IP ID value,
the ICMP datagram being analyzed has been fragmented. The first flow has the ICMP type field set to
8, which indicates that this is an ICMP echo request (ping) datagram. The value of 185 in the fragment
offset (FO) field in the second flow shows where this fragment will be placed in the memory buffer of
the FTP server as the server reassembles the ICMP datagram. The value of 185 is applicable only to the
first fragment of this datagram. The subsequent values will be greater because they take into account the
previous fragments.
The value of 0 in the ICMP type field of the second flow does not mean that this flow is an ICMP echo
reply as Table 2 shows. In this case the ICMP type field value is set to 0 because the ICMP headers for
fragments of ICMP datagrams do not have the type and code fields. The default value of 0 is inserted
instead.
Note
If this data were captured from a real ICMP attack, it would probably have more than one flow.
Although, you cannot find out the original size of the ICMP datagram from the information shown by
the show ip cache verbose flow, the fact that it was large enough to be fragmented in transit is a good
indication that this is not a normal ICMP datagram. Notice the values in the minimum and maximum
packet length fields for both flows. The values for both fields are set to 1500 for the first flow. The value
for the minimum packet length is set to 772 and the value for the maximum packet length is set to 1500
for the second flow.
If this traffic is identified as a DoS attack based on the data captured in the Layer 3 fields, you can use
the Layer 2 information in the flows to identify the path that the traffic is taking through the network. In
this example, the traffic is being sent to R3 on VLAN 5 by R2. You can demonstrate that R2 is
transmitting the traffic over interface 1/0.1 because the source MAC address (aaaa.bbb.cc03) belongs to
1/0.1 on R2. You can demonstrate that R3 is transmitting the traffic using VLAN 6 on interface 1/0.1 to
interface 1/0.1 on R4, because the destination MAC address (aaaa.bbbb.cc06) belongs to interface 1/0.1
on R4.
You can use this information to mitigate this attack. One possible way to mitigate this attack is by
configuring an extended IP access list that blocks ICMP traffic from any host with a source address that
is on the 10.0.0.0 network. Another possible solution is to configure a default route for the 10.0.0.0
network that points to the null interface on the router.
Caution
Each of these solutions blocks traffic from legitimate hosts on the 10.0.0.0 network. Therefore these
solutions should only be used temporarily while you identify the point of origin of the attack and decide
how to stop it there.
Configuring NBAR Support for NetFlow Exports: Example
The following example shows how to configure NBAR support for NetFlow exports:
Router(config)# ip flow-export version 9
Router(config)# ip flow-capture nbar
Router(config)# ip flow-export template options nbar
Router# exit
32
NetFlow Layer 2 and Security Monitoring Exports
Additional References
The following example shows sample output of the show ip flow export nbar command:
Router # show ip flow export nbar
Nbar netflow is enabled
10 nbar flows exported
0 nbar flows failed to export due to lack of internal buffers
The following example shows how to clear NBAR data from NetFlow accounting statistics:
Router # clear ip flow stats nbar
Additional References
The following sections provide references related to NetFlow Layer 2 and Security Monitoring Exports.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
Cisco IOS NetFlow Features Roadmap
Overview of NBAR
Classifying Network Traffic Using NBAR
Configuring NBAR
Configuring NBAR Using the MQC
Configuring NBAR using protocol-discovery
Enabling Protocol Discovery
NetFlow commands
Cisco IOS NetFlow Command Reference
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
Standards
Standards
Title
There are no new or modified standards associated with —
this feature
MIBs
MIBs
MIBs Link
There are no new or modified MIBs associated with
this feature
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
33
NetFlow Layer 2 and Security Monitoring Exports
Feature Information for NetFlow Layer 2 and Security Monitoring Exports
RFCs
RFC
Title
5103
Bidirectional Flow Export Using IP Flow Information Export
(IPFIX)
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
Feature Information for NetFlow Layer 2 and Security
Monitoring Exports
Table 14 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Releases12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the Cisco IOS NetFlow
Features Roadmap.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
34
Table 14 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
NetFlow Layer 2 and Security Monitoring Exports
Feature Information for NetFlow Layer 2 and Security Monitoring Exports
Table 14
Feature Information for NetFlow Layer 2 and Security Monitoring Exports
Feature Name
Releases
Feature Configuration Information
NetFlow Layer 2 and Security Monitoring
Exports
12.3(14)T
12.2(33)SRA
The NetFlow Layer 2 and Security Monitoring Exports
feature enables the capture of values from fields in Layer 2
and Layer 3 of IP traffic for accounting and security
analysis.
The following sections provide information about this
feature:
•
NetFlow Layer 2 and Security Monitoring, page 2
•
Configuring NetFlow Layer 2 and Security Monitoring
Exports, page 14
•
Verifying NetFlow Layer 2 and Security Monitoring
Exports, page 16
The following commands were modified by this feature: ip
flow-capture, ip flow-export and show ip cache verbose
flow.
Support for capturing the value from the
fragment offset field of IP headers added to
NetFlow Layer 2 and Security Monitoring
Exports1
12.4(2)T
The fragment-offset keyword for the ip flow-capture
command enables capturing the value of the IP fragment
offset field from the first fragmented IP datagram in a flow.
Application-aware NetFlow
12.2(18)ZYA2
The application-aware NetFlow feature enables the capture
of application information collected by PISA NBAR and
exports using NetFlow Version 9.
The following sections provide information about this
feature:
•
NBAR Data Export
•
Configuring NBAR Support for NetFlow Exports
The following commands were modified by this feature: ip
flow-capture, ip flow-export template options, show ip
flow export, and clear ip flow stats.
1. This is a minor enhancement. Minor enhancements are not typically listed in Feature Navigator.
35
NetFlow Layer 2 and Security Monitoring Exports
Glossary
Glossary
export packet—A type of packet built by a device (for example, a router) with NetFlow services
enabled. The packet is addressed to another device (for example, the NetFlow Collection Engine). The
packet contains NetFlow statistics. The other device processes the packet (parses, aggregates, and stores
information about IP flows).
flow—A set of packets with the same source IP address, destination IP address, protocol,
source/destination ports, and type-of-service, and the same interface on which flow is monitored. Ingress
flows are associated with the input interface, and egress flows are associated with the output interface.
NBAR—A classification engine in Cisco IOS Software that recognizes a wide variety of applications,
including web-based and client/server applications.
NetFlow—Cisco IOS accounting feature that maintains per-flow information.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on a Cisco IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly NetFlow FlowCollector)—Cisco application that is used with
NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets
from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate
reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means of carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any
examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only.
Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
© 2009-2010 Cisco Systems, Inc. All rights reserved.
36
Configuring MPLS-aware NetFlow
First Published: June 19, 2006
Last Updated: August 09, 2010
This module contains information about and instructions for configuring Multiprotocol Label Switching
(MPLS)-aware NetFlow. MPLS-aware NetFlow is an extension of the NetFlow accounting feature that
provides highly granular traffic statistics for Cisco routers.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring MPLS-aware NetFlow” section on page 21.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Configuring MPLS-aware NetFlow, page 2
•
Restrictions for Configuring MPLS-aware NetFlow, page 3
•
Information About Configuring MPLS-aware NetFlow, page 4
•
How to Configure MPLS-aware NetFlow, page 10
•
Configuration Examples for MPLS-aware NetFlow, page 16
•
Additional References, page 19
•
Feature Information for Configuring MPLS-aware NetFlow, page 21
•
Glossary, page 23
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring MPLS-aware NetFlow
Prerequisites for Configuring MPLS-aware NetFlow
Prerequisites for Configuring MPLS-aware NetFlow
Before you can configure the MPLS-aware NetFlow feature, you must:
•
Configure NetFlow on the label switch router (LSR).
•
Configure MPLS on the LSR.
•
Configure Cisco Express Forwarding (CEF) or Distributed CEF (dCEF) enabled on the LSR and the
interfaces that you want to enable NetFlow on.
If you are exporting data to a Cisco NetFlow collector, the following requirements apply:
•
NetFlow Version 9 export format configured on the LSR
•
NetFlow collector and analyzer capable of using MPLS-aware NetFlow export packets in Version 9
format
Table 1 describes the Cisco 12000 Series Internet Router line card support for Cisco IOS 12.0 S releases
of MPLS-aware NetFlow.
Table 1
2
Cisco 12000 Series Line Card Support for MPLS-aware NetFlow in Cisco IOS 12.0 S
Releases
Type
Line Card
Ethernet
1-Port GE1
8-Port FE1
3-Port GE
1-Port 10-GE
Modular GE
Packet Over Sonet
(POS)
4-Port OC-3 POS2
1-Port OC-12 POS2
1-Port OC-48 POS
4-Port OC-12 POS
4-Port OC-12 POS ISE
1-Port OC-48 POS ISE
4-Port OC-3 POS ISE
8-Port OC-3 POS ISE
16-Port OC-3 POS ISE
1-Port OC-192 POS ES (Edge Release)
4-Port OC-48 POS ES (Edge Release)
Channelized
interfaces
1-Port CHOC-12 (DS3)2
1-Port CHOC-12 (OC-3)2
6-Port Ch T3 (DS1)2
2-Port CHOC-32
1-Port CHOC-48 ISE
4-Port CHOC-12 ISE
Electrical interface
6-Port DS32
12-Port DS3 2
6-Port E32
12-Port E32
Configuring MPLS-aware NetFlow
Restrictions for Configuring MPLS-aware NetFlow
Table 1
Cisco 12000 Series Line Card Support for MPLS-aware NetFlow in Cisco IOS 12.0 S
Releases (continued)
Type
Line Card
Dynamic packet
transport
1-Port OC-12 DPT1
1-Port OC-48 DPT
4-Port OC-48 DPT
1-Port OC-192 DPT
Asynchronous
Transfer Mode
(ATM)
4-Port OC-3 ATM2
1-Port OC-12 ATM2
8-Port OC-3 STM-1 ATM2
1. This Cisco 12000 Series Internet Router line card does not support MPLS-aware NetFlow.
2. This Cisco 12000 Series Internet Router line card supports MPLS-aware NetFlow enabled in either full or sampled mode.
Line cards not marked with a footnote character support MPLS-aware NetFlow in sampled mode only. In general,
Cisco 12000 line cards support MPLS-aware NetFlow in the same mode as they support NetFlow.
Restrictions for Configuring MPLS-aware NetFlow
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
MPLS-aware NetFlow
The following restrictions apply to the MPLS-aware NetFlow feature:
•
No more than three MPLS labels are allowed to be captured and exported for this implementation.
•
MPLS-aware NetFlow reports the following fields in MPLS flows as 0: IP next-hop, source and
destination Border Gateway Protocol (BGP) autonomous system (AS) numbers, and source and
destination prefix masks.
•
For MPLS packets that contain non-IP packets under the MPLS label stack, MPLS-aware NetFlow
reports the following flow fields as 0: source and destination IP addresses, protocol, ToS, ports, and
TCP flags.
•
The IP addresses associated with the top label for traffic engineering (TE) tunnel midpoints and Any
Transport over MPLS (AToM) are reported as 0.0.0.0.
•
The top label type and IP address are obtained at the moment of flow export. Either can be incorrect
if the top label was deleted or reassigned after the creation of the flow in the NetFlow cache.
•
The following points hold true for the Cisco 12000 1-Port 10-GE, Modular GE, 1-Port OC-192 POS
ES (Edge Release), and 4-Port OC-48 POS ES (Edge Release) line cards:
– MPLS-aware NetFlow samples both IP and MPLS packets, but reports only MPLS packets that
have one label per packet, ignoring all other packets (that is, IP and MPLS packets with more
than one label).
– MPLS-aware NetFlow does not report application (TCP/UDP) port numbers.
– MPLS-aware NetFlow reports experimental bits in MPLS labels as 0.
3
Configuring MPLS-aware NetFlow
Information About Configuring MPLS-aware NetFlow
•
The Cisco 12000 1-Port OC-48 POS, 4-Port OC-12 POS, 16-Port OC-3 POS, 3-Port GE, and
1-Port OC-48 DPT line cards support MPLS-aware NetFlow in sampled mode in all microcode
bundles that include IP-sampled NetFlow.
Information About Configuring MPLS-aware NetFlow
The following sections contain useful information for understanding how to configure and use the
MPLS-aware NetFlow feature:
•
MPLS-aware NetFlow Overview, page 4
•
MPLS Label Stack, page 4
•
MPLS-aware NetFlow Capture of MPLS Labels, page 6
•
MPLS-aware NetFlow Display of MPLS Labels, page 7
•
Information Captured and Exported by MPLS-aware NetFlow, page 8
•
Full and Sampled MPLS-aware NetFlow Support, page 9
MPLS-aware NetFlow Overview
MPLS-aware NetFlow is an extension of the NetFlow accounting feature that provides highly granular
traffic statistics for Cisco routers. MPLS-aware NetFlow collects statistics on a per-flow basis just as
NetFlow does.
A flow is a unidirectional set of packets (IP or MPLS) that arrive at the router on the same subinterface,
have the same source and destination IP addresses, the same Layer 4 protocol, the same TCP/UDP
source and destination ports, and the same type of service (TOS) byte in the IP header.
An MPLS flow contains up to three of the same incoming MPLS labels of interest with experimental bits
and end-of-stack bits in the same positions in the packet label stack. MPLS-aware NetFlow captures
MPLS traffic that contains both IP and non-IP packets. It reports non-IP packets, but sets the IP NetFlow
fields to 0. It can also be configured to capture and report IP packets, setting to 0 the IP NetFlow fields.
MPLS-aware NetFlow uses the NetFlow Version 9 export format. MPLS-aware NetFlow exports up to
three labels of interest from the incoming label stack, the IP address associated with the top label, and
traditional NetFlow data.
MPLS-aware NetFlow statistics can be used for detailed MPLS traffic studies and analysis that can
provide information for a variety of purposes such as MPLS network management, network planning,
and enterprise accounting.
A network administrator can turn on MPLS-aware NetFlow inside an MPLS cloud on a subset of
provider backbone (P) routers. These routers can export MPLS-aware NetFlow data to an external
NetFlow collection device for further processing and analysis or you can display NetFlow cache data on
a router terminal.
MPLS Label Stack
As packets move through an MPLS network, LSRs can add labels to the MPLS label stack. LSRs in an
MPLS cloud can add up to six labels to the MPLS label stack. An LSR adds the MPLS labels to the top
of the IP packet. Figure 1 shows an example of an incoming MPLS label stack that LSRs added to an
IP packet as it traversed an MPLS cloud.
4
Configuring MPLS-aware NetFlow
Information About Configuring MPLS-aware NetFlow
Example of an MPLS Label Stack Added to an IP Packet in an MPLS Cloud
MPLS labels
33
B
Top-level label
42 B 16
Label Label type Location
in stack
B Lb4–Lb6 B IP Header
Data
IP packet
Miscellaneous bits
33
LDP
1 (top)
42
CSC
2
16
VPN
3
88306
Figure 1
In the example of an MPLS label stack in Figure 1:
•
The 33 represents the top label of this packet.
This label was the last label added to the MPLS label stack and the label that MPLS-aware NetFlow
captures if you indicate the label of interest as 1.
•
The 42 represents the second label in the MPLS stack.
MPLS-aware NetFlow captures this label if you indicate 2 (second from the top) as a label of
interest.
•
The 16 represents the third label in the MPLS label stack.
MPLS-aware NetFlow captures this label if you indicate 3 (third from the top) as a label of interest.
•
Lb4–Lb6 represents the fourth to sixth labels in the MPLS stack. LSRs in an MPLS cloud add up to
six labels to the MPLS label stack.
MPLS-aware NetFlow captures these labels if you indicate 4, 5, or 6 as labels of interest.
•
The B represents miscellaneous bits. These include the following:
– Exp—Three bits reserved for experimental use
– S—End-of-stack bits, set to 1 for the last entry in the stack and to 0 for every other entry
– Time To Live (TTL)—Eight bits used to encode a hop count (or time to live) value
Figure 2 shows a sample Carrier Supporting Carrier (CSC) topology and the incoming MPLS label stack
on multiple LSRs as the packet travels through the network. Figure 2 shows what the stack might look
like at a provider core LSR.
5
Configuring MPLS-aware NetFlow
Information About Configuring MPLS-aware NetFlow
Figure 2
Provider and Customer Networks and MPLS Label Imposition
Carrier's carrier
MPLS
Backbone MPLS
Carrier's carrier
MPLS
IP
16
IP
25
42
33
25 16
IP
Lx VPN
33 42 16
IP
LDP CSC VPN
CSC VPN IP
VPN IP
88307
Label 16
stack VPN IP
Label Label type Location
in stack
33
LDP
1 (top)
42
CSC
2
16
VPN
3
In the example in Figure 2, a hierarchical VPN is set up between two customer edge (CE) routers.
•
Traffic flows from the CE router to a provider edge (PE) router, possibly one belonging to an Internet
service provider (ISP). Here, a VPN label (16) is imposed on the inbound IP packet.
•
The ISP network eventually connects to an Internet backbone provider where a CSC label (42) is
imposed on the label stack.
•
As packets traverse the backbone network, a Label Distribution Protocol (LDP) label (33) is
imposed on the label stack.
At the inbound interface shown in Figure 2, MPLS-aware NetFlow captures the MPLS label stack and
reports that the top label (33) is an LDP label, the second label (42) is a CSC label, and the third
label (16) is a VPN label.
With NetFlow and MPLS-aware NetFlow enabled on the P router, you can determine the label type for
the specified labels, and the IP address associated with the top label on the incoming interface (see the
“MPLS-aware NetFlow Capture of MPLS Labels” section on page 6). Thus, you can track specific types
of MPLS traffic, such as TE, LDP, or Virtual Private Networks (VPNs).
MPLS-aware NetFlow Capture of MPLS Labels
When you configure the MPLS-aware NetFlow feature, you select the MPLS label positions in the
incoming label stack that you are interested in monitoring. You can capture up to three labels from
positions 1 to 6 in the MPLS label stack. Label positions are counted from the top of the stack. For
example, the position of the top label is 1, the position of the next label is 2, and so on. You enter the
stack location value as an argument to the following command:
ip flow-cache mpls label-positions [label-position-1 [label-position-2
[label-position-3]]]
6
Configuring MPLS-aware NetFlow
Information About Configuring MPLS-aware NetFlow
The label-position-n argument represents the position of the label on the incoming label stack. For
example, the ip flow-cache mpls label-positions 1 3 4 command configures MPLS-aware NetFlow to
capture and export the first (top), third, and fourth labels. If you enter this command and the label stack
consists of two MPLS labels, MPLS-aware NetFlow captures only the first (top) label. If some of the
labels you requested are not available, they are not captured or reported.
Note
For this implementation, MPLS-aware NetFlow allows the capture of up to three labels.
In addition to capturing MPLS labels from the label stack, MPLS-aware NetFlow records the following
MPLS label information:
Note
•
Type of top label—The type can be any of the following: unknown, TE tunnel midpoint, AToM,
VPN, BGP, or LDP.
•
The IP address associated with the top label—The route prefix to which the label maps.
For this implementation, the IP address for any TE tunnel midpoint or AToM top label is reported as
0.0.0.0.
MPLS-aware NetFlow is enabled globally on the router. However, NetFlow is enabled per interface and
must be enabled in either full or sampled mode on the interfaces where you choose to capture and export
MPLS and IP NetFlow data.
Note
See Table 1 on page 2 for information on Cisco 12000 Series Internet Router line card support for
NetFlow (full and sampled modes).
MPLS-aware NetFlow Display of MPLS Labels
The MPLS-aware NetFlow feature allows the display of a snapshot of the NetFlow cache, including
MPLS flows, on a terminal through the use of the show ip cache verbose flow command. For example,
output like the following from a provider core router (P router) shows position, value, experimental bits,
and end-of-stack bit for each MPLS label of interest. It also shows the type of the top label and the IP
address associated with the top label.
SrcIf
SrcIPaddress
DstIf
DstIPaddress
Port Msk AS
Port Msk AS
NextHop
PO3/0
10.1.1.1
PO5/1
10.2.1.1
0100 /0 0
0200 /0 0
0.0.0.0
Pos:Lbl-Exp-S 1:12305-6-0 (LDP/10.10.10.10) 2:12312-6-1
Pr TOS Flgs Pkts
B/Pk Active
01 00 10
9
100
0.0
In this example from a P router:
•
The value of the top label is 12305.
•
The experimental bits value is 6 and the end-of-stack bit is 0.
•
The label type is LDP and the IP address associated with the label is 10.10.10.10.
•
The value of the second label is 12312, the experimental bits value is 6, and the end-of-stack bit is 1.
To fully understand and use the information gathered on the P router, you need information from the
label forwarding information base (LFIB) on the PE router.
7
Configuring MPLS-aware NetFlow
Information About Configuring MPLS-aware NetFlow
Note
The MPLS application owner for a label is not reported by MPLS-aware NetFlow for any MPLS
label except for the top label. IP information, the label number, and the MPLS application are
reported for the top label. Only IP information and the label number are reported for labels other
than the top label. Therefore, you need to understand your network if you are interested in
identifying the MPLS application owner for labels other than the top MPLS label.
Using MPLS-aware NetFlow, you can monitor various labels in the MPLS label stack. You can also
export this information to a NetFlow collector for further processing with a data analyzer and look at
MPLS traffic patterns in your network.
Information Captured and Exported by MPLS-aware NetFlow
MPLS-aware NetFlow captures and reports on other information in addition to MPLS labels. It provides
per-flow statistics for both incoming IP and MPLS traffic.
•
For MPLS traffic, MPLS-aware NetFlow captures and reports up to three labels of interest and the
label type and associated IP address of the top label, along with a subset of NetFlow data.
•
For IP traffic, MPLS-aware NetFlow provides the regular NetFlow data.
MPLS-aware NetFlow uses Version 9 format to export both IP and MPLS NetFlow data.
MPLS-aware NetFlow provides the following traditional NetFlow per-flow statistics:
•
Number of packets
•
Number of bytes, counting either MPLS payload size only or MPLS payload size plus MPLS label
stack size
•
Time stamp of the first packet
•
Time stamp of the last packet
In addition to these statistics, MPLS-aware NetFlow exports values for the following fields for each flow,
using Version 9 NetFlow export format:
•
Regular NetFlow fields:
– Source IP address
– Destination IP address
– Transport layer protocol
– Source application port number
– Destination application port number
– IP type of service (ToS)
– TCP flags
– Input interface
– Output interface
Note
8
With the exception of the input interface and output interface fields, these regular NetFlow fields
are not included in a flow if the no-ip-fields keyword is specified in the ip flow-cache mpls
label-positions command.
Configuring MPLS-aware NetFlow
Information About Configuring MPLS-aware NetFlow
•
Additional fields:
– Up to three incoming MPLS labels with experimental bits and an end-of-stack bit
– Positions of the above labels in the label stack
– Type of the top label
– An address prefix associated with the top label specific to the label type:
TE–This is always set to "0.0.0.0" because tunnel label addresses are not supported.
LDP–The address prefix is the IP address of the next-hop.
VPN–If the VRFs do not have overlapping IP addresses, the address prefix is the destination
prefix. If the VRFs have overlapping IP addresses the destination prefix given may be
ambiguous.
Note
Unlike NetFlow, MPLS-aware NetFlow reports a 0 value for IP next-hop, source and destination BGP
autonomous system numbers, or source and destination prefix masks for MPLS packets.
Note
If you are exporting MPLS data to a NetFlow collector or a data analyzer, the collector must support
NetFlow Version 9 flow export format, and you must configure NetFlow export in Version 9 format on
the router.
Full and Sampled MPLS-aware NetFlow Support
Table 2 shows MPLS-aware NetFlow full and sampled NetFlow support. Information in the table is
based on the Cisco IOS release and includes the commands to implement the functionality on a
supported platform.
Table 2
MPLS-aware NetFlow Full and Sampled NetFlow Support
Cisco IOS
Release
Full or Sampled Cisco 12000 Series Commands
NetFlow
to Implement
Cisco 7500/7200 Series Commands
to Implement1
12.0(24)S
Sampled
ip route-cache flow sampled
—
Full
—
—
Sampled
ip route-cache flow sampled
flow-sampler-map sampler-map-name
12.0(26)S
mode random one-of packet-interval
interface type number
flow-sampler sampler-map-name
Full
—
ip route-cache flow
1. NetFlow sampling on the Cisco 7500/7200 platforms is performed by a feature called Random Sampled NetFlow.
9
Configuring MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
This section contains the following procedures for configuring MPLS-aware NetFlow:
•
Configuring MPLS-aware NetFlow on a Router, page 10 (required)
•
Configuring Sampling for MPLS-aware NetFlow, page 12 (optional)
•
Verifying the NetFlow Sampler Configuration, page 14 (optional)
•
Displaying MPLS-aware NetFlow Information on a Router, page 14 (optional)
Configuring MPLS-aware NetFlow on a Router
Perform the steps in this required task to configure MPLS-aware NetFlow on a router.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface interface-type interface-number
4.
ip flow {ingress}
5.
exit
6.
Repeat Steps 3 through 5 for each interface you want to configure NetFlow on.
7.
ip flow-export version 9 [origin-as | peer-as] [bgp-nexthop]
8.
ip flow-cache mpls label-positions [label-position-1 [label-position-2 [label-position-3]]]
[no-ip-fields] [mpls-length]
9.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface interface-type interface-number
Example:
Router(config)# interface pos 3/0
10
(Required) Specifies the interface and enters interface
configuration mode.
Configuring MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
Step 4
Command or Action
Purpose
ip flow {ingress}
(Required) Enables NetFlow on the interface.
•
Example:
ingress—captures traffic that is being received by the
interface
Router(config-if)# ip flow ingress
Step 5
exit
(Optional) Exits interface configuration mode and returns to
global configuration mode.
Example:
Note
You only need to use this command if you want to
enable NetFlow on another interface.
Router(config-if)# exit
Step 6
Repeat Steps 3 through 5 to enable NetFlow on other
interfaces.
(Optional) —
Step 7
ip flow-export version 9 [origin-as | peer-as]
[bgp-nexthop]
(Optional) Enables the export of information in NetFlow
cache entries.
•
The version 9 keyword specifies that the export packet
uses the Version 9 format.
•
The origin-as keyword specifies that export statistics
include the origin autonomous system (AS) for the
source and destination.
•
The peer-as keyword specifies that export statistics
include the peer AS for the source and destination.
•
The bgp-nexthop keyword specifies that export
statistics include BGP next hop related information.
Example:
Router(config)# ip flow-export version 9
origin-as
Caution
Entering this command on a Cisco 12000 Series
Internet Router causes packet forwarding to stop
for a few seconds while NetFlow reloads the
route processor and line card CEF tables. To
avoid interruption of service to a live network,
apply this command during a change window, or
include it in the startup-config file to be executed
during a router reboot.
11
Configuring MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
Step 8
Command or Action
Purpose
ip flow-cache mpls label-positions
[label-position-1 [label-position-2
[label-position-3]]] [no-ip-fields]
[mpls-length]
(Required) Enables MPLS-aware NetFlow.
•
The label-position-n argument identifies the position of
an MPLS label of interest in the incoming label stack.
Label positions are counted from the top of the stack,
starting with 1.
•
The no-ip-fields keyword controls the capture and
reporting of MPLS flow fields. If the no-ip-fields
keyword is specified, the following IP-related flow
fields are not included:
Example:
Router(config)# ip flow-cache mpls
label-positions 1 2 3
– Source IP address
– Destination IP address
– Transport layer protocol
– Source application port number
– Destination application port number
– IP type of service (ToS)
– TCP flag (the result of a bitwise OR of TCP)
If the no-ip-fields keyword is not specified, the IP
related fields are captured and reported.
•
The mpls-length keyword controls the reporting of
packet length. If the mpls-length keyword is specified,
the reported length represents the sum of the MPLS
packet payload length and the MPLS label stack length.
If the mpls-length keyword is not specified, only the
length of the MPLS packet payload is reported.
Step 9
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
exit
Example:
Router(config)# exit
Configuring Sampling for MPLS-aware NetFlow
Perform the steps in this optional task to configure sampling for MPLS-aware NetFlow.
SUMMARY STEPS
12
1.
enable
2.
configure terminal
3.
flow-sampler-map sampler-map-name
4.
mode random one-out-of packet-interval
5.
exit
6.
interface interface-type interface-number
Configuring MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
7.
flow-sampler sampler-map-name
8.
end
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
flow-sampler-map sampler-map-name
Example:
(Required) Defines a named object representing a NetFlow
sampler.
•
Router(config)# flow-sampler-map mysampler
Step 4
mode random one-out-of packet-interval
Example:
(Required) Specifies the sampling mode for the NetFlow
sampler.
•
The random keyword specifies the random sampling
mode.
•
The one-out-of packet-interval keyword argument
combination defines the interval selected for random
sampling. The packet interval is from 1 to 65535.
Router(config-sampler-map)# mode random
one-out-of 100
Step 5
exit
The sampler-map-name argument is the name of the
NetFlow sampler.
(Required) Exits sampler map configuration mode and
returns to global configuration mode.
Example:
Router(config-sampler-map)# exit
Step 6
interface interface-type interface-number
(Required) Specifies the interface that you want to enable
NetFlow on and enters interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
Step 7
flow-sampler sampler-map-name
Example:
Router(config-if)# flow-sampler mysampler
Step 8
end
(Required) Enables sampled NetFlow accounting on the
interface.
•
The sampler-map-name argument is the name of the
NetFlow sampler.
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
13
Configuring MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
Troubleshooting Tips
Use the show-sampler sampler-map-name command to verify the configuration of NetFlow sampling,
including the NetFlow sampling mode, sampling mode parameters, and number of packets sampled by the
NetFlow sampler.
For more information on NetFlow export sampling, see the “Using NetFlow Filtering or Sampling to
Select the Network Traffic to Track” module.
Verifying the NetFlow Sampler Configuration
Perform the steps in this optional task to verify the NetFlow sampler configuration on your router:
SUMMARY STEPS
1.
show flow-sampler [sampler-map-name]
2.
show flow sampler
DETAILED STEPS
Step 1
show flow-sampler [sampler-map-name]
Use this command to verify the following information about a specific NetFlow sampler: sampling mode,
sampling parameters (such as packet sampling interval), and number of packets selected by the sampler for
NetFlow processing. For example:
Router# show flow-sampler mysampler
Sampler : mysampler, id : 1, packets matched : 10, mode : random sampling mode
sampling interval is : 100
Step 2
show flow-sampler
Use the following command to verify the configuration for all Netflow samplers on the router:
Router# show flow-sampler
Sampler : mysampler, id : 1, packets matched : 10, mode : random sampling mode
sampling interval is : 100
Sampler : mysampler1, id : 2, packets matched : 5, mode : random sampling mode
sampling interval is : 200
Displaying MPLS-aware NetFlow Information on a Router
Perform the steps in this optional task to display a snapshot of the MPLS-aware NetFlow cache on a
router.
14
Configuring MPLS-aware NetFlow
How to Configure MPLS-aware NetFlow
SUMMARY STEPS
1.
enable
2.
attach slot-number (Cisco 12000 series routers only) or if-con slot-number (Cisco 7500 series
routers only)
3.
show ip cache verbose flow
4.
show ip cache flow
5.
exit (Cisco 12000 Series Internet routers only) or if-quit (Cisco 7500 series routers only)
DETAILED STEPS
Step 1
enable
Use this command to enable privileged EXEC mode. Enter your password if required. For example:
Router> enable
Router#
Step 2
attach slot-number (Cisco 12000 Series Internet routers only) or if-con slot-number (Cisco 7500 series
routers only)
Use the attach command to access the Cisco IOS on the line card of a Cisco 12000 Series Internet
Router. For example:
Router# attach 3
LC-Slot3#
Use the if-con command to access the Cisco IOS on the line card of a Cisco 7500 series router. For
example:
Router# if-con 3
LC-Slot3#
Step 3
show ip cache verbose flow
Use this command to display IP and MPLS flow records in the NetFlow cache on a Cisco 12000 Series
Internet Router or Cisco 7500 series router. For example:
LC-Slot3# show ip cache verbose flow
...
SrcIf
SrcIPaddress
DstIf
DstIPaddress
Port Msk AS
Port Msk AS
NextHop
PO3/0
10.1.1.1
PO5/1
10.2.1.1
0100 /0 0
0200 /0 0
0.0.0.0
Pos:Lbl-Exp-S 1:12305-6-0 (LDP/10.10.10.10) 2:12312-6-1
Pr TOS Flgs Pkts
B/Pk Active
01 00 10
9
100
0.0
In this example, the value of the top label is 12305, the experimental bits value is 6, and the end-of-stack
bit is 0. The label is LDP and it has an associated IP address of 10.10.10.10. The value of the next from
the top label is 12312, the experimental bits value is 6, and the end-of-stack bit is 1. The 1 indicates that
this is the last MPLS label in the stack.
Use this command to display IP and MPLS flow records in the NetFlow cache on a Cisco 7200 series
router. For example:
Router# show ip cache verbose flow
...
SrcIf
SrcIPaddress
DstIf
DstIPaddress
Pr TOS Flgs
Pkts
15
Configuring MPLS-aware NetFlow
Configuration Examples for MPLS-aware NetFlow
Port Msk AS
Port Msk AS
NextHop
PO3/0
10.1.1.1
PO5/1
10.2.1.1
0100 /0 0
0200 /0 0
0.0.0.0
Pos:Lbl-Exp-S 1:12305-6-0 (LDP/10.10.10.10) 2:12312-6-1
01 00
B/Pk
10
100
Active
9
0.0
In this example, the value of the top label is 12305, the experimental bits value is 6, and the end-of-stack
bit is 0. The label is LDP and has an associated IP address of 10.10.10.10. The value of the next from
the top label is 12312, the experimental bits value is 6, and the end-of-stack bit is 1. The 1 indicates that
this is the last MPLS label in the stack.
Step 4
show ip cache flow
Use this command to display a summary of the IP and MPLS flow records in the NetFlow cache on a
Cisco 12000 Series Internet Router or Cisco 7500 series router. For example, the following output of the
show ip cache flow command shows the IP portion of the MPLS flow record in the NetFlow cache:
LC-Slot3# show ip cache flow
...
SrcIf
PO3/0
...
SrcIPaddress
10.1.1.1
DstIf
PO5/1
DstIPaddress
10.2.1.1
Pr SrcP DstP
01 0100 0200
Pkts
9
Use this command to display a summary of the IP and MPLS flow records in the NetFlow cache on a
Cisco 7200 series router. For example:
Router# show ip cache flow
...
SrcIf
PO3/0
...
Step 5
SrcIPaddress
10.1.1.1
DstIf
PO5/1
DstIPaddress
10.2.1.1
Pr SrcP DstP
01 0100 0200
Pkts
9
exit (Cisco 12000 series routers only) or if-quit (Cisco 7500 series routers only)
Use the exit command to exit from the line card to privileged EXEC mode of a Cisco 12000 Series
Internet Router. For example:
LC-Slot3# exit
Router#
Use the if-quit command to exit from the line card to privileged EXEC mode of a Cisco 7500 Series
Router. For example:
LC-Slot3# if-quit
Router#
Configuration Examples for MPLS-aware NetFlow
This section contains the following configuration examples for MPLS-aware NetFlow:
16
•
Configuring MPLS-aware NetFlow on a Router: Examples, page 17
•
Configuring Sampling for MPLS-aware NetFlow: Examples, page 18
Configuring MPLS-aware NetFlow
Configuration Examples for MPLS-aware NetFlow
Configuring MPLS-aware NetFlow on a Router: Examples
The following example shows MPLS-aware NetFlow configured globally and NetFlow enabled on an
interface on a Cisco 12000 series P router with Cisco IOS Release 12.0(24)S and later:
configure terminal
!
interface pos 3/0
ip address 10.10.10.2 255.255.255.0
ip route-cache flow sampled
exit
!
ip flow-export version 9 origin-as
ip flow-sampling-mode packet-interval 101
ip flow-cache mpls label-positions 1 2 3
exit
The following examples show MPLS-aware NetFlow configured globally and NetFlow enabled on an
interface on a Cisco 7200 or 7500 series P router with Cisco IOS 12.0S releases:
configure terminal
!
interface pos 3/0
ip address 10.10.10.2 255.255.255.0
ip route-cache flow sampled
exit
!
ip flow-export version 9 origin-as
ip flow-sampling-mode packet-interval 101
ip flow-cache mpls label-positions 1 2 3
exit
The following examples show MPLS-aware NetFlow configured globally and NetFlow enabled on an
interface on a router with a Cisco IOS Release 12.2(14)S, 12.2(15)T, or 12.0(22)S or later:
configure terminal
!
interface pos 3/0
ip address 10.10.10.2 255.255.255.0
ip flow ingress
exit
!
ip flow-export version 9 origin-as
ip flow-sampling-mode packet-interval 101
ip flow-cache mpls label-positions 1 2 3
exit
To export MPLS-aware NetFlow data from the router, you need to configure NetFlow Version 9 export
format. This example shows the NetFlow Version 9 export format configuration options for MPLS-aware
NetFlow and IP NetFlow data export along with an explanation of what each command configures:
configure terminal
ip flow-export version 9 origin-as
ip flow-export template options sampling
ip flow-export template options
export-stats
Enters global configuration mode and requests
Version 9 flow export, reports origin-as for
IP packets.
Specifies the template option sampling
configuration.
Reports the number of export packets sent and the
number of flows exported.
17
Configuring MPLS-aware NetFlow
Configuration Examples for MPLS-aware NetFlow
ip flow-export template options timeout 5
Exports template options every 5 minutes.
ip flow-export template timeout 5
Resends templates to the collector every
5 minutes.
ip flow-export destination 10.21.32.25
9996
Specifies export destination and UDP port.
ip flow-export source Loopback0
Specifies export source.
ip flow-sampling-mode packet-interval 101
Configures the sampling mode packet interval.
ip flow-cache mpls label-positions 1 2 3
Configured the MPLS-aware NetFlow feature to
report the top 3 labels.
interface pos 3/0
ip route-cache flow [sampled]
end
Enables full or sampled IP and MPLS-aware
NetFlow on interface POS 3/0 and returns to
privileged EXEC mode.
Note
The combination of sampled IP and
MPLS-aware NetFlow is supported on the
Cisco 12000 Series Internet Router only.
Configuring Sampling for MPLS-aware NetFlow: Examples
The following examples show how to define a Netflow sampler that randomly selects 1 out of 100
packets for NetFlow processing, and how to apply this sampler to an interface on a Cisco 7500 or 7200
series router.
Defining the NetFlow Sampler
The following example shows how to define a NetFlow sampler called mysampler that randomly selects
1 out of 100 packets for NetFlow processing:
configure terminal
!
flow-sampler-map mysampler
mode random one-out-of 100
end
exit
Applying the NetFlow Sampler to an Interface
The following example shows how to apply the NetFlow sampler named mysampler to an interface:
configure terminal
!
interface FastEthernet 2/0
flow-sampler mysampler
end
exit
18
Configuring MPLS-aware NetFlow
Additional References
Additional References
The following sections provide references related to configuring MPLS-aware NetFlow.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
“Cisco IOS NetFlow Overview”
List of the features documented in the Cisco IOS
NetFlow Configuration Guide configuration guide
“Cisco IOS NetFlow Features Roadmap”
The minimum information about and tasks required for “Getting Started with Configuring NetFlow and NetFlow Data
configuring NetFlow and NetFlow Data Export
Export”
Tasks for configuring NetFlow to capture and export
network traffic data
“Configuring NetFlow and NetFlow Data Export”
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring Random Sampled NetFlow
“Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track”
Tasks for configuring NetFlow aggregation caches
“Configuring NetFlow Aggregation Caches”
Tasks for configuring NetFlow BGP next hop support
“Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis”
Tasks for configuring NetFlow multicast support
“Configuring NetFlow Multicast Accounting”
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
“NetFlow Layer 2 and Security Monitoring Exports”
Tasks for configuring the SNMP NetFlow MIB
“Configuring SNMP and using the NetFlow MIB to Monitor
NetFlow Data”
Tasks for configuring the NetFlow MIB and Top
Talkers feature
“Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands”
Information for installing, starting, and configuring the “Cisco CNS NetFlow Collection Engine Documentation”
CNS NetFlow Collection Engine
Standards
Standard
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
19
Configuring MPLS-aware NetFlow
Additional References
MIBs
MIB
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFC
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
The Cisco Support website provides extensive online
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies.
http://www.cisco.com/cisco/web/support/index.html
To receive security and technical information about
your products, you can subscribe to various services,
such as the Product Alert Tool (accessed from Field
Notices), the Cisco Technical Services Newsletter, and
Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website
requires a Cisco.com user ID and password.
20
Configuring MPLS-aware NetFlow
Feature Information for Configuring MPLS-aware NetFlow
Feature Information for Configuring MPLS-aware NetFlow
Table 3 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the “Cisco IOS NetFlow
Features Roadmap” module.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 3 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
21
Configuring MPLS-aware NetFlow
Feature Information for Configuring MPLS-aware NetFlow
Table 3
Feature Information for Configuring MPLS-aware NetFlow
Feature Name
Releases
Feature Configuration Information
MPLS-aware NetFlow
12.0(24)S,
12.3(8)T
15.0(1)S
Multiprotocol Label Switching (MPLS)-aware NetFlow is an
extension of the NetFlow accounting feature that provides
highly granular traffic statistics for Cisco routers.
MPLS-aware NetFlow collects statistics on a per-flow basis
just as NetFlow does. MPLS-aware NetFlow uses the
NetFlow Version 9 export format.
The following sections provide information about this
feature:
•
MPLS-aware NetFlow Overview, page 4
•
MPLS Label Stack, page 4
•
MPLS-aware NetFlow Capture of MPLS Labels, page 6
•
MPLS-aware NetFlow Display of MPLS Labels, page 7
•
Information Captured and Exported by MPLS-aware
NetFlow, page 8
•
Full and Sampled MPLS-aware NetFlow Support, page 9
•
Configuring MPLS-aware NetFlow on a Router, page 10
•
Configuring Sampling for MPLS-aware NetFlow,
page 12
•
Verifying the NetFlow Sampler Configuration, page 14
•
Displaying MPLS-aware NetFlow Information on a
Router, page 14
The following commands were modified by this feature:
ip flow-cache mpls label-positions and show ip cache
verbose flow.
22
Configuring MPLS-aware NetFlow
Glossary
Glossary
AToM—Any Transport over MPLS. A protocol that provides a common framework for encapsulating
and transporting supported Layer 2 traffic types over a Multiprotocol Label Switching (MPLS) network
core.
BGP—Border Gateway Protocol. An interdomain routing protocol that replaces Exterior Gateway
Protocol (EGP). A BGP system exchanges reachability information with other BGP systems. It is
defined by RFC 1163.
CE router—customer edge router. A router that is part of a customer network and that interfaces to a
provider edge (PE) router. CE routers do not have routes to associated Virtual Private Networks (VPNs)
in their routing tables.
core router—In a packet-switched star topology, a router that is part of the backbone and that serves as
the single pipe through which all traffic from peripheral networks must pass on its way to other
peripheral networks.
EGP—Exterior Gateway Protocol. Internet protocol for exchanging routing information between
autonomous systems. It is documented in RFC 904. This term is not to be confused with the general term
exterior gateway protocol. EGP is an obsolete protocol that was replaced by Border Gateway Protocol
(BGP).
export packet—(NetFlow) A packet from a device (for example, a router) with NetFlow services
enabled that is addressed to another device (for example, a NetFlow collector). This other device
processes the packet (parses, aggregates, and stores information on IP flows).
FEC—Forward Equivalency Class. A set of packets that can be handled equivalently for the purpose of
forwarding and thus is suitable for binding to a single label. The set of packets destined for an address
prefix is one example of an FEC. A flow is another example.
flow—A unidirectional set of packets (IP or Multiprotocol Label Switching [MPLS]) that arrive at the
router on the same subinterface and have the same source and destination IP addresses, the same Layer 4
protocol, the same TCP/UDP source and destination ports, and the same type of service (ToS) byte in
the IP header.
IPv6—IP Version 6. Replacement for the current version of IP (Version 4). IPv6 includes support for
flow ID in the packet header, which can be used to identify flows. Formerly called IPng (next
generation).
label—A short, fixed-length identifier that tells switching nodes how the data (packets or cells) should
be forwarded.
label imposition—The act of putting a label or labels on a packet.
LDP—Label Distribution Protocol. A standard protocol that operates between Multiprotocol Label
Switching (MPLS)-enabled routers to negotiate the labels (addresses) used to forward packets. The
Cisco proprietary version of this protocol is the Tag Distribution Protocol (TDP).
LFIB—label forwarding information base. A data structure and way of managing forwarding in which
destinations and incoming labels are associated with outgoing interfaces and labels.
LSR—label switch router. A router that forwards packets in a Multiprotocol Label Switching (MPLS)
network by looking only at the fixed-length label.
MPLS—Multiprotocol Label Switching. A switching method in which IP traffic is forwarded through
use of a label. This label instructs the routers and the switches in the network where to forward the
packets. The forwarding of MPLS packets is based on preestablished IP routing information.
23
Configuring MPLS-aware NetFlow
Glossary
MPLS flow—A unidirectional sequence of Multiprotocol Label Switching (MPLS) packets that arrive
at a router on the same subinterface and have the same source and destination IP addresses, the same
Layer 4 protocol, the same TCP/UDP source and destination ports, and the same type of service (ToS)
byte in the IP header. A TCP session is an example of a flow.
packet header— (NetFlow) The first part of an export packet that provides basic information about the
packet, such as the NetFlow version, number of records contained within the packet, and sequence
numbering. The header information enables lost packets to be detected.
PE router—provider edge router. A router that is part of a service provider’s network connected to a
customer edge (CE) router. All Virtual Private Network (VPN) processing occurs in the PE router.
P router—provider core or backbone router. A router that is part of a service provider's core or backbone
network and is connected to the provider edge (PE) routers.
TDP—Tag Distribution Protocol. The Cisco proprietary version of the protocol (label distribution
protocol) between Multiprotocol Label Switching (MPLS)-enabled routers to negotiate the labels
(addresses) used to forward packets.
TE—traffic engineering. Techniques and processes that cause routed traffic to travel through the
network on a path other than the one that would have been chosen if standard routing methods were used.
TE tunnel—traffic engineering tunnel. A label-switched tunnel that is used for traffic engineering. Such
a tunnel is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path
different from the one that Layer 3 routing could cause the tunnel to take.
VPN—Virtual Private Network. A secure IP-based network that shares resources on one or more
physical networks. A VPN contains geographically dispersed sites that can communicate securely over
a shared backbone.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2006–2010 Cisco Systems, Inc. All rights reserved.
24
Configuring NetFlow Multicast Accounting
First Published: June 19, 2006
Last Updated: April 21, 2008
This document contains information about and instructions for configuring NetFlow multicast
accounting. NetFlow multicast accounting allows you to capture multicast-specific data (both packets
and bytes) for multicast flows.
NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring NetFlow Multicast Accounting” section on page 12.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
This document includes the following sections:
•
Prerequisites for Configuring NetFlow Multicast Accounting, page 2
•
Restrictions for Configuring NetFlow Multicast Accounting, page 2
•
Information About Configuring NetFlow Multicast Accounting, page 2
•
How to Configure NetFlow Multicast Accounting, page 3
•
Configuration Examples for NetFlow Multicast Accounting, page 9
•
Additional References, page 11
•
Glossary, page 14
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring NetFlow Multicast Accounting
Prerequisites for Configuring NetFlow Multicast Accounting
•
Feature Information for Configuring NetFlow Multicast Accounting, page 12
Prerequisites for Configuring NetFlow Multicast Accounting
Before you can configure NetFlow multicast accounting, you must:
•
Configure the router for IP routing
•
Configure Multicast fast switching or multicast distributed fast switching (MDFS); multicast Cisco
Express Forwarding (CEF) switching is not supported.
•
Configure Multicast routing.
•
Configure NetFlow v9 (Version 9) data export (otherwise, multicast data is visible in the cache but
is not exported).
Restrictions for Configuring NetFlow Multicast Accounting
Memory Impact
If traffic is heavy, the additional flows might fill the global flow hash table. If you must increase the size
of the global flow hash table, you must also add memory to the router.
NetFlow has a maximum cache size of 65,536 flow record entries of 64 bytes each. To deduce the
packet-replication factor, multicast accounting adds 16 bytes (for a total of 80 bytes) to each multicast
flow record.
Performance Impact
Ingress multicast accounting does not greatly affect performance. Because of the additional
accounting-related computation that occurs in the traffic-forwarding path of the router, egress NetFlow
multicast accounting might degrade network performance slightly, but it does not limit the functionality
of the router.
Multicast Addresses
NetFlow data cannot be exported to multicast addresses.
Information About Configuring NetFlow Multicast Accounting
To configure NetFlow multicast accounting, you must understand the following concepts:
2
•
NetFlow Multicast Benefits, page 3
•
Multicast Ingress and Multicast Egress Accounting, page 3
•
NetFlow Multicast Flow Records, page 3
Configuring NetFlow Multicast Accounting
How to Configure NetFlow Multicast Accounting
NetFlow Multicast Benefits
NetFlow multicast allows you to capture multicast-specific data (both packets and bytes) for multicast
flows. For example, you can capture the packet-replication factor for a specific flow as well as for each
outgoing stream. NetFlow multicast provides complete end-to-end usage information about network
traffic for a complete multicast traffic billing solution.
You can use NetFlow multicast accounting to identify and count multicast packets on the ingress side or
the egress side (or both sides) of a router. Multicast ingress accounting provides information about the
source and how many times the traffic was replicated. Multicast egress accounting monitors the
destination of the traffic flow.
NetFlow multicast lets you enable NetFlow statistics to account for all packets that fail the reverse path
forwarding (RPF) check and that are dropped in the core of the service provider network. Accounting
for RPF-failed packets provides more accurate traffic statistics and patterns.
Multicast Ingress and Multicast Egress Accounting
NetFlow multicast lets you select either multicast ingress accounting, in which a replication factor (equal
to the number of output interfaces) indicates the load, or multicast egress accounting, in which all
outgoing multicast streams are counted as separate streams, or both multicast ingress and multicast
egress accounting.
NetFlow multicast lets you collect information about how much data is leaving the interfaces of the
router (egress and multicast ingress accounting) or how much multicast data is received (multicast
ingress accounting).
On the ingress side, multicast packets are counted as with unicast packets, but with two additional fields
(for number of replicated packets and byte count). With multicast ingress accounting, the destination
interface field is set to null, and the IP next hop field is set to 0 for multicast flows.
NetFlow Multicast Flow Records
Multicast ingress accounting creates one flow record that indicates how many times each packet is
replicated. Multicast egress accounting creates a unique flow record for each outgoing interface.
How to Configure NetFlow Multicast Accounting
Perform the following tasks to configure NetFlow multicast accounting:
•
Configuring NetFlow Multicast Accounting in Cisco IOS Releases 12.4(12), 12.4(11)T,
12.2(33)SRB, 12.2(33)SXH, 12.2(33)SB, and Newer Releases, page 4
•
Configuring NetFlow Multicast Accounting in Cisco IOS Releases Prior to 12.4(12), 12.4(11)T,
12.2(33)SRB, 12.2(33)SXH, and 12.2(33)SB, page 5
•
Verifying the NetFlow Multicast Accounting Configuration, page 8 (optional)
3
Configuring NetFlow Multicast Accounting
How to Configure NetFlow Multicast Accounting
Configuring NetFlow Multicast Accounting in Cisco IOS Releases 12.4(12),
12.4(11)T, 12.2(33)SRB, 12.2(33)SXH, 12.2(33)SB, and Newer Releases
Perform the steps in this required task to configure NetFlow multicast accounting.
Prerequisites
You must have already configured IP multicast on the networking devices in your network. See the Cisco
IOS IP Multicast Configuration Guide, for more information on configuring IP multicast.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip multicast-routing [vrf vrf-name] [distributed]
4.
ip multicast netflow rpf-failure
5.
ip multicast netflow output-counters
6.
interface type number
7.
ip flow ingress
8.
end
DETAILED STEPS
Step 1
Command
Purpose
enable
Enters privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip multicast-routing [vrf vrf-name]
[distributed]
Enables IP multicast routing.
•
The vrf keyword supports the multicast Virtual
Private Network (VPN) routing/forwarding instance
(VRF).
•
The vrf-name argument is the name assigned to the
VRF.
•
The distributed keyword enables Multicast
Distributed Switching (MDS).
Example:
Router(config)# ip multicast-routing
Step 4
ip multicast netflow rpf-failure
Example:
Router(config)# ip multicast netflow rpf-failure
4
Enables accounting for multicast data that fails the RPF
check.
Configuring NetFlow Multicast Accounting
How to Configure NetFlow Multicast Accounting
Step 5
Command
Purpose
ip multicast netflow output-counters
Enables accounting for the number of bytes and packets
forwarded.
Example:
Router(config)# ip multicast netflow
output-counters
Step 6
interface type number
Specifies the interface and enters interface configuration
mode.
Example:
Router(config)# interface fastethernet 0/0
Step 7
Enables NetFlow ingress accounting.
ip flow ingress
Example:
Router(config-if)# ip flow ingress
Step 8
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
If there are no multicast flow records in the NetFlow cache, check the multicast switching counters for
the existence of process-switched packets (NetFlow exports only fast-switched or MDFS-switched
packets). If process-switched packets are present, check the MDFS routing table to help determine
potential problems.
Configuring NetFlow Multicast Accounting in Cisco IOS Releases Prior to
12.4(12), 12.4(11)T, 12.2(33)SRB, 12.2(33)SXH, and 12.2(33)SB
•
Configuring NetFlow Multicast Egress Accounting, page 5
•
Configuring NetFlow Multicast Ingress Accounting, page 7
Configuring NetFlow Multicast Egress Accounting
Perform the steps in this required task to configure NetFlow multicast egress accounting.
Prerequisites
You must have already configured IP multicast on the networking devices in your network. See the Cisco
IOS IP Multicast Configuration Guide, for more information on configuring IP multicast.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip multicast-routing [vrf vrf-name] [distributed]
5
Configuring NetFlow Multicast Accounting
How to Configure NetFlow Multicast Accounting
4.
ip multicast netflow rpf-failure
5.
interface type number
6.
ip multicast netflow egress
7.
end
DETAILED STEPS
Step 1
Command
Purpose
enable
Enters privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip multicast-routing [vrf vrf-name]
[distributed]
Enables IP multicast routing.
•
The vrf keyword supports the multicast Virtual
Private Network (VPN) routing/forwarding instance
(VRF).
•
The vrf-name argument is the name assigned to the
VRF.
•
The distributed keyword enables Multicast
Distributed Switching (MDS).
Example:
Router(config)# ip multicast-routing
Step 4
ip multicast netflow rpf-failure
Enables accounting for multicast data that fails the RPF
check.
Example:
Router(config)# ip multicast netflow rpf-failure
Step 5
interface type number
Specifies the interface and enters interface configuration
mode.
Example:
Router(config)# interface fastethernet 0/0
Step 6
ip multicast netflow egress
Enables NetFlow multicast egress accounting.
Example:
Router(config-if)# ip multicast netflow egress
Step 7
end
Example:
Router(config-if)# end
6
Exits the current configuration mode and returns to
privileged EXEC mode.
Configuring NetFlow Multicast Accounting
How to Configure NetFlow Multicast Accounting
Troubleshooting Tips
If there are no multicast flow records in the NetFlow cache, check the multicast switching counters for
the existence of process-switched packets (NetFlow exports only fast-switched or MDFS-switched
packets). If process-switched packets are present, check the MDFS routing table to help determine
potential problems.
Configuring NetFlow Multicast Ingress Accounting
Perform the steps in this required task to configure NetFlow multicast ingress accounting.
Multicast ingress NetFlow accounting is enabled by default.
Prerequisites
You must have already configured IP multicast on the networking devices in your network. See the Cisco
IOS IP Multicast Configuration Guide, for more information on configuring IP multicast.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip multicast-routing [vrf vrf-name] [distributed]
4.
ip multicast netflow rpf-failure
5.
interface type number
6.
ip multicast netflow ingress
7.
end
DETAILED STEPS
Step 1
Command
Purpose
enable
Enters privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip multicast-routing [vrf vrf-name]
[distributed]
Example:
Enables IP multicast routing.
•
The vrf keyword supports the multicast VRF.
•
The vrf-name argument is the name assigned to the
VRF.
•
The distributed keyword enables Multicast
Distributed Switching (MDS).
Router(config)# ip multicast-routing
7
Configuring NetFlow Multicast Accounting
How to Configure NetFlow Multicast Accounting
Step 4
Command
Purpose
ip multicast netflow rpf-failure
Enables accounting for multicast data that fails the RPF
check.
Example:
Router(config)# ip multicast netflow rpf-failure
Step 5
interface type number
Specifies the interface and enters interface configuration
mode.
Example:
Router(config)# interface fastethernet 0/0
Step 6
ip multicast netflow ingress
Enables NetFlow multicast ingress accounting.
Example:
Router(config-if)# ip multicast netflow ingress
Step 7
Exits the current configuration mode and returns to
privileged EXEC mode.
end
Example:
Router(config-if)# end
Troubleshooting Tips
If there are no multicast flow records in the NetFlow cache, check the multicast switching counters for
the existence of process-switched packets (NetFlow exports only fast-switched or MDFS-switched
packets). If process-switched packets are present, check the MDFS routing table to help determine
potential problems.
Verifying the NetFlow Multicast Accounting Configuration
Perform the steps in this optional task to verify the NetFlow multicast accounting configuration.
SUMMARY STEPS
1.
enable
2.
show ip cache verbose flow
DETAILED STEPS
Step 1
enable
Use this command to enable privileged EXEC mode. Enter your password if required. For example:
Router> enable
Router#
Step 2
show ip cache verbose flow
Use this command to verify that NetFlow multicast accounting is configured. Look for the two additional
fields related to multicast data, that is, the number of IP multicast output packet and byte counts. For
example:
Router# show ip cache verbose flow
8
Configuring NetFlow Multicast Accounting
Configuration Examples for NetFlow Multicast Accounting
IP packet size distribution (5149 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.997 .002 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
2 active, 4094 inactive, 14 added
468 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 25800 bytes
1 active, 1023 inactive, 1 added, 1 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol
Total
Flows
Packets Bytes Packets Active(Sec) Idle(Sec)
-------Flows
/Sec
/Flow /Pkt
/Sec
/Flow
/Flow
UDP-other
12
0.0
1
52
0.0
0.1
15.6
Total:
12
0.0
1
52
0.0
0.1
15.6
SrcIf
Port Msk AS
IPM: OPkts
Et0/0
0000 /0 0
IPM:
15K
Et0/0
0208 /0 0
Router#
SrcIPaddress
OBytes
10.1.1.1
309K
10.1.1.1
DstIf
Port Msk AS
DstIPaddress
NextHop
Pr TOS Flgs Pkts
B/Pk Active
Null
0000 /0
224.192.16.1
0.0.0.0
01 55
0
10
20
5164
262.8
Null
0208 /0
0
255.255.255.255 11 C0
0.0.0.0
10
52
1
0.0
The Opkts column displays the number of IP multicast (IPM) output packets, the OBytes column
displays the number of IPM output bytes, and the DstIPaddress column displays the destination IP
address for the IPM output packets.
Configuration Examples for NetFlow Multicast Accounting
This section provides the following configuration examples for NetFlow multicast accounting:
•
Configuring NetFlow Multicast Accounting in Cisco IOS Releases 12.4(12), 12.4(11)T,
12.2(33)SRB, 12.2(33)SXH, 12.2(33)SB, and Newer Releases, page 9
•
Configuring NetFlow Multicast Accounting in Cisco IOS Releases Prior to 12.4(12), 12.4(11)T,
12.2(33)SRB, 12.2(33)SXH, and 12.2(33)SB, page 10
Configuring NetFlow Multicast Accounting in Cisco IOS Releases 12.4(12),
12.4(11)T, 12.2(33)SRB, 12.2(33)SXH, 12.2(33)SB, and Newer Releases
The following example shows how to configure multicast NetFlow accounting:
configure terminal
ip multicast-routing
ip multicast netflow rpf-failure
ip multicast netflow output-counters
!
9
Configuring NetFlow Multicast Accounting
Configuration Examples for NetFlow Multicast Accounting
interface ethernet 0/0
ip flow ingress
end
Configuring NetFlow Multicast Accounting in Cisco IOS Releases Prior to
12.4(12), 12.4(11)T, 12.2(33)SRB, 12.2(33)SXH, and 12.2(33)SB
•
Configuring NetFlow Multicast Egress Accounting: Example, page 10
•
Configuring NetFlow Multicast Ingress Accounting: Example, page 10
Configuring NetFlow Multicast Egress Accounting: Example
The following example shows how to configure multicast egress NetFlow accounting on the egress
Ethernet 0/0 interface:
configure terminal
ip multicast-routing
ip multicast netflow rpf-failure
!
interface ethernet 0/0
ip multicast netflow egress
end
Configuring NetFlow Multicast Ingress Accounting: Example
The following example shows how to configure multicast ingress NetFlow accounting on the ingress
Ethernet 1/0 interface:
configure terminal
ip multicast-routing
ip multicast netflow rpf-failure
!
interface ethernet 1/0
ip multicast netflow ingress
end
10
Configuring NetFlow Multicast Accounting
Additional References
Additional References
The following sections provide references related to configuring NetFlow multicast accounting:
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Tasks for configuring the NetFlow MIB and Top
Talkers feature
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands
or SNMP Commands
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
11
Configuring NetFlow Multicast Accounting
Feature Information for Configuring NetFlow Multicast Accounting
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBS are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
Feature Information for Configuring NetFlow Multicast
Accounting
Table 1 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the “Cisco IOS NetFlow
Features Roadmap” module.
12
Configuring NetFlow Multicast Accounting
Feature Information for Configuring NetFlow Multicast Accounting
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
Table 1
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for Configuring NetFlow Multicast Accounting
Feature Name
Releases
Feature Configuration Information
NetFlow Multicast Support
12.3(1), 12.2(18)S,
12.2(27)SBC,
12.2(33)SXF,
12.2(33)SRB
The NetFlow Multicast Support feature lets you capture
multicast-specific data (both packets and bytes) for
multicast flows. For example, you can capture the
packet-replication factor for a specific flow as well as
for each outgoing stream. This feature provides
complete end-to-end usage information about network
traffic for a complete multicast traffic billing solution.
The following sections provide information about this
feature:
•
NetFlow Multicast Benefits, page 3
•
Multicast Ingress and Multicast Egress
Accounting, page 3
•
NetFlow Multicast Flow Records, page 3
•
Configuring NetFlow Multicast Accounting in
Cisco IOS Releases 12.4(12), 12.4(11)T,
12.2(33)SRB, 12.2(33)SXH, 12.2(33)SB, and
Newer Releases, page 4
•
Configuring NetFlow Multicast Accounting in
Cisco IOS Releases Prior to 12.4(12), 12.4(11)T,
12.2(33)SRB, 12.2(33)SXH, and 12.2(33)SB,
page 5
•
Verifying the NetFlow Multicast Accounting
Configuration, page 8
The following commands were introduced by this
feature: ip multicast netflow egress, ip multicast
netflow ingress, and ip multicast netflow rpf-failure.
NetFlow Multicast Support1
12.4(11)T, 12.4(12),
12.(33)SRB, 12.2(33)SB,
12.2(33)SXH
The ip multicast netflow [ingress | egress] interface
configuration command was replaced by the
ip multicast netflow output-counters global
configuration command.
1. This was a minor modification to the existing NetFlow Multicast Support feature. Minor feature modifications are not included in Feature Navigator.
13
Configuring NetFlow Multicast Accounting
Glossary
Glossary
CEF—Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network
performance and scalability for networks with large and dynamic traffic patterns.
dCEF—distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as
Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information
base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters;
this relieves the Route Switch Processor of involvement in the switching operation.
egress traffic—Traffic leaving the network.
fast switching—Cisco feature in which a route cache is used for expediting packet switching through a
router.
ingress traffic—Traffic entering the network.
multicast data—Single packets copied by the network and sent to a specific subset of network
addresses. These addresses are specified in the Destination Address field.
NetFlow—A Cisco IOS application that provides statistics on packets flowing through the router. It is
emerging as a primary network accounting and security technology.
NetFlow Aggregation—A NetFlow feature that lets you summarize NetFlow export data on an IOS
router before the data is exported to a NetFlow data collection system such as the NetFlow Collection
Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform
requirements for NetFlow data collection devices.
NetFlow Collection Engine (formerly called NetFlow FlowCollector)—A Cisco application that is used
with NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects
packets from the router that is running NetFlow and decodes, aggregates, and stores them. You can
generate reports on various aggregations that can be set up on the NetFlow Collection Engine.
NetFlow v9—NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow
records from a network node to a collector. NetFlow Version 9 has definable record types and is
self-describing for easier NetFlow Collection Engine configuration.
RPF—Reverse Path Forwarding. Multicasting technique in which a multicast datagram is forwarded out
of all but the receiving interface if the receiving interface is the one used to forward unicast datagrams
to the source of the multicast datagram.
ToS byte—type of service byte. Second byte in the IP header that indicates the desired quality of service
(QoS) for a particular datagram.
CCDE, CCENT, CCSI, Cisco Eos, Cisco Explorer, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Nurse Connect, Cisco Pulse,
Cisco SensorBase, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco TrustSec, Cisco Unified Computing System, Cisco WebEx,
DCE, Flip Channels, Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to
the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed
(Stylized), Cisco Store, Flip Gift Card, and One Million Acts of Green are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS,
Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert
logo, Cisco IOS, Cisco Lumin, Cisco Nexus, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity,
Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center, Explorer, Follow Me Browsing, GainMaker, iLYNX, IOS,
iPhone, IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking
Academy, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect, ROSA, SenderBase, SMARTnet,
Spectrum Expert, StackWise, WebEx, and the WebEx logo are registered trademarks of Cisco and/or its affiliates in the United States and certain
other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (1002R)
14
Configuring NetFlow Multicast Accounting
Glossary
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2008 Cisco Systems, Inc. All rights reserved.
15
Configuring NetFlow Multicast Accounting
Glossary
16
Configuring NetFlow Top Talkers using
Cisco IOS CLI Commands or SNMP Commands
First Published: May 02, 2005
Last Updated: October 02, 2009
This module contains information about and instructions for configuring NetFlow Top Talkers feature.
The NetFlow Top Talkers feature can be configured using the Cisco IOS command-line interface (CLI)
or with SNMP commands using the NetFlow MIB. The NetFlow Top Talkers feature uses NetFlow
functionality to obtain information regarding heaviest traffic patterns and most-used applications in the
network. The NetFlow MIB allows you to configure NetFlow and the NetFlow Top Talkers feature using
SNMP commands from a network management workstation.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Configuring NetFlow Top Talkers using the Cisco IOS CLI or
SNMP Commands” section on page 26.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Note
If you are searching in Feature Navigator, the feature documented in this module is named NetFlow MIB
and Top Talkers.
Contents
•
Prerequisites for Configuring NetFlow Top Talkers, page 2
•
Restrictions for Configuring NetFlow Top Talkers, page 2
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Prerequisites for Configuring NetFlow Top Talkers
•
Information About Configuring NetFlow Top Talkers, page 2
•
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands,
page 4
•
Configuration Examples for NetFlow Top Talkers, page 23
•
Additional References, page 24
•
Feature Information for Configuring NetFlow Top Talkers using the Cisco IOS CLI or SNMP
Commands, page 26
Prerequisites for Configuring NetFlow Top Talkers
Before you enable NetFlow and NetFlow Top Talkers, you must:
•
Configure the router for IP routing
•
Ensure that one of the following is enabled on your router, and on the interfaces that you want to
configure NetFlow on: Cisco Express Forwarding (CEF), distributed CEF, or fast switching
•
Understand the resources required on your router because NetFlow consumes additional memory
and CPU resources.
Restrictions for Configuring NetFlow Top Talkers
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the
ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress
command is used to enable NetFlow on an interface.
Cisco IOS Release 12.2(33)SXH
Some of the keywords and arguments for the commands used to configure the NetFlow MIB and Top
Talkers feature are not supported in 112.2(33)SXH. See the syntax descriptions for the commands in the
command reference (URL for the 12.2SX NF CR to be added later) for details.
Information About Configuring NetFlow Top Talkers
To configure the NetFlow MIB and Top Talkers feature, you should understand the following concepts:
2
•
Overview of the NetFlow MIB and Top Talkers Feature, page 3
•
Benefits of the NetFlow MIB and Top Talkers Feature, page 3
•
Cisco IOS Release 12.2(33)SXH on Cisco 6500 Series Switches, page 3
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Information About Configuring NetFlow Top Talkers
Overview of the NetFlow MIB and Top Talkers Feature
NetFlow collects traffic flow statistics on routing devices. NetFlow has been used for a variety of
applications, including traffic engineering, usage-based billing, and monitoring for denial-of-service
(DoS) attacks.
The flows that are generating the heaviest system traffic are known as the “top talkers.”
The NetFlow Top Talkers feature allows flows to be sorted so that they can be viewed. The top talkers
can be sorted by either of the following criteria:
•
By the total number of packets in each top talker
•
By the total number of bytes in each top talker
The usual implementation of NetFlow exports NetFlow data to a collector. The NetFlow MIB and Top
Talkers feature performs security monitoring and accounting for top talkers and matches and identifyies
key users of the network. This feature is also useful for a network location where a traditional NetFlow
export operation is not possible. The NetFlow MIB and Top Talkers feature does not require a collector
to obtain information regarding flows. Instead, these flows are placed in a special cache where they can
be viewed. The NetFlow MIB part of the NetFlow MIB and Top Talkers feature allows you to configure
the NetFlow Top Talkers feature using SNMP.
In addition to sorting top talkers, you can further organize your output by specifying criteria that the top
talkers must match, such as source or destination IP address or port. The match command is used to
specify this criterion. For a full list of the matching criteria that you can select, refer to the
match command in the Cisco IOS command reference documentation.
Benefits of the NetFlow MIB and Top Talkers Feature
Top talkers can be useful for analyzing network traffic in any of the following ways:
•
Security—You can view the list of top talkers to see if traffic patterns consistent with DoS attack are
present in your network.
•
Load balancing—You can identify the most heavily used parts of the system and move network
traffic over to less-used parts of the system.
•
Traffic analysis—Consulting the data retrieved from the NetFlow MIB and Top Talkers feature can
assist you in general traffic study and planning for your network.
An additional benefit of the NetFlow MIB and Top Talkers feature is that it can be configured for a router
either by entering CLI commands or by entering SNMP commands on a network management system
(NMS) workstation. The SNMP commands are sent to the router and processed by a MIB. You do not
have to be connected to the router console to extract the list of top talkers information if an NMS
workstation is configured to communicate using SNMP to your network device. For more information
on configuring your network device to use MIB functionality for the NetFlow MIB and Top Talkers
feature, see Configuring SNMP Support on the Networking Device.
Cisco IOS Release 12.2(33)SXH on Cisco 6500 Series Switches
The show ip flow top-talkers command was modified in Cisco IOS Release 12.2(33)SXH for the Cisco
6500 Series switches to support displaying the top talkers for a specific module. The show ip flow
top-talkers module number command displays the top talkers for that module. The show ip flow
top-talkers command without the module keyword shows the top talkers in the hardware switched path
3
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
(a merged list of top lists from all modules) and then software switched top talkers. The NetFlow MIB
can be used to request the top talker list and to set and/or get the configuration parameters for the
NetFlow MIB Top Talkers feature.
How to Configure NetFlow Top Talkers using Cisco IOS CLI
Commands or SNMP Commands
Note
Some of the tasks in this section include examples of the SNMP CLI syntax used to set configuration
parameters on the router and to read values from MIB objects on the router. These SNMP CLI syntax
examples are taken from a Linux workstation using public-domain SNMP tools. The SNMP CLI syntax
for your workstation might be different. Refer to the documentation that was provided with your SNMP
tools for the correct syntax for your network management workstation.
This section contains the following subsections:
•
Configuring SNMP Support on the Networking Device, page 4
•
Configuring Parameters for the NetFlow Main Cache, page 6
•
Identifying the Interface Number to Use for Enabling NetFlow with SNMP, page 9
•
Configuring NetFlow on a Cisco 6500 Series Switch, page 9
•
Configuring NetFlow on Cisco Routers, page 12
•
Configuring NetFlow Top Talkers, page 13
•
Configuring NetFlow Top Talkers Match Criteria, page 16
•
Verifying the NetFlow Top Talkers Configuration, page 21
Configuring SNMP Support on the Networking Device
If you want to configure the NetFlow Top Talkers feature using the Cisco IOS CLI, you do not have to
perform this task.
If you want to configure the NetFlow Top Talkers feature using the NetFlow MIB and SNMP, you must
perform this task.
Before you can use SNMP commands to configure the Top Talkers feature you must configure SNMP
support on your networking device. To enable SNMP support on the networking device perform the steps
in this task.
4
Note
The SNMP community read-only (RO) string for the examples is public. The SNMP community
read-write (RW) string for the examples is private. You should use more complex strings for these
values in your configurations.
Note
For more information on configuring SNMP support on your networking device, refer to the
“Configuring SNMP Support” chapter of the Cisco IOS Configuration Fundamentals and Network
Management Configuration Guide.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
snmp-server community string ro
4.
snmp-server community string rw
5.
end
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
snmp-server community string ro
Example:
(Required) Sets up the community access string to permit
access to SNMP.
•
The string argument is a community string that consists
of from 1 to 32 alphanumeric characters and functions
much like a password, permitting access to the SNMP
protocol. Blank spaces are not permitted in the
community string.
•
The ro keyword specifies read-only access. SNMP
management stations using this string can retrieve MIB
objects.
Router(config)# snmp-server community public ro
5
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Step 4
Command or Action
Purpose
snmp-server community string rw
(Required) Sets up the community access string to permit
access to SNMP.
Example:
•
The string argument is a community string that consists
of from 1 to 32 alphanumeric characters and functions
much like a password, permitting access to the SNMP
protocol. Blank spaces are not permitted in the
community string.
•
The rw keyword specifies read-write access. SNMP
management stations using this string can retrieve and
modify MIB objects.
Note
The string argument must be different from the
read-only string argument specified in the
preceding step (Step 3).
Router(config)# snmp-server community private
rw
Step 5
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
end
Example:
Router(config)# end
Configuring Parameters for the NetFlow Main Cache
This optional task describes the procedure for modifying the parameters for the NetFlow main cache.
Perform the steps in this optional task using either the router CLI commands or the SNMP commands to
modify the parameters for the NetFlow main cache.
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
ip flow-cache entries number
4.
ip flow-cache timeout active minutes
5.
ip flow-cache timeout inactive seconds
6.
end
SNMP Commands
6
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCICacheEntries.type unsigned number
2.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCIActiveTimeOut.type unsigned
number
3.
snmpset -c private -m all -v2c [ip-address | hostname] ccnfCIInactiveTimeOut.type unsigned
number
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-cache entries number
Example:
(Optional) Specifies the maximum number of entries to be
captured for the main flow cache.
•
Router(config)# ip flow-cache entries 4000
Step 4
ip flow-cache timeout active minutes
Example:
(Optional) Configures operational parameters for the main
cache.
•
The timeout keyword dissolves the session in the
cache.
•
The active minutes keyword-argument pair is the
number of minutes that an entry is active. The range is
from 1 to 60 minutes. The default is 30 minutes.
Router(config)# ip flow-cache timeout active 30
Step 5
ip flow-cache timeout inactive seconds
Example:
(Optional) Configures operational parameters for the main
cache.
•
The timeout keyword dissolves the session in the main
cache.
•
The inactive seconds keyword-argument pair is the
number of seconds that an inactive entry will stay in the
main cache before it times out. The range is from
10 to 600 seconds. The default is 15 seconds.
Router(config)# ip flow-cache timeout inactive
100
Step 6
end
The range for the number argument is from 1024 to
524288 entries.
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config)# end
7
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCICacheEntries.type unsigned
number
(Optional) Defines the maximum number of entries to be
captured for the main flow cache.
•
The value for the type argument in
cnfCICacheEntries.type unsigned number is 0 for the
main cache.
•
The value for the number argument in
cnfCICacheEntries.type number is the maximum
number of cache entries.
•
The range for the number argument is from 1024 to
524288 entries.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCICacheEntries.0 unsigned 4000
Step 2
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCIActiveTimeOut.type unsigned
number
(Optional) Specifies the number of seconds that an active
flow remains in the main cache before it times out.
•
The value for the type argument in
cnfCIActiveTimeout.type unsigned number is 0 for
the main cache.
•
The value for the number argument in
cnfCIActiveTimeout.type unsigned number is the
number of seconds that an active flow remains in the
cache before it times out.
•
The range for the number argument is from 1 to 60
minutes. The default is 30 minutes.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCIActiveTimeOut.0 unsigned 60
Step 3
snmpset -c private -m all -v2c [ip-address |
hostname] ccnfCIInactiveTimeOut.type unsigned
number
(Optional) Specifies the number of seconds that an inactive
flow remains in the main cache before it times out.
•
The value for the type argument in
cnfCIInactiveTimeout.type unsigned number is 0 for
the main cache.
•
The value for the number argument in
cnfCIInactiveTimeout.type unsigned number is the
number of seconds that an inactive flow remains in the
main cache before it times out.
•
The range for the number argument is from
10 to 600 seconds. The default is 15 seconds.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCIInactiveTimeOut.0 unsigned 30
8
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Identifying the Interface Number to Use for Enabling NetFlow with SNMP
If you want to configure the NetFlow Top Talkers feature using the Cisco IOS CLI, you do not have to
perform this task.
If you want to configure the NetFlow Top Talkers feature using the NetFlow MIB and SNMP, you must
perform this task.
Before you can use SNMP to enable NetFlow on an interface, you must identify the SNMP interface
number on the router. To identify the interface number for the interface on which you want to enable
NetFlow, perform the steps in this required task.
SUMMARY STEPS
1.
enable
2.
show snmp mib ifmib ifindex type number
3.
Repeat Step 2 to identify the SNMP interface number for any other interfaces on which you plan to
enable NetFlow.
DETAILED STEPS
Step 1
enable
Enters privileged EXEC mode. Enter the password if prompted.
Router> enable
Step 2
show snmp mib ifmib ifindex type number
Displays the SNMP interface number for the interface specified.
Router# show snmp mib ifmib ifindex GigabitEthernet6/2
Ethernet0/0: Ifindex = 60
Step 3
Repeat Step 2 to identify the SNMP interface number for any other interfaces on which you plan to
enable NetFlow.
Configuring NetFlow on a Cisco 6500 Series Switch
To enable NetFlow on the switch, perform the steps in this required task using either the CLI commands
or the SNMP commands.
Note
This task provides the minimum information required to configure NetFlow on your Cisco 6500 series
switch. See the Catalyst 6500 Series Cisco IOS Software Configuration Guide, for more information of
configuring NetFlow on your switch.
SUMMARY STEPS
Router CLI Commands
1.
enable
9
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
2.
configure terminal
3.
mls flow {ip | ipv6} {destination | destination-source | full | interface-destination-source |
interface-full | source}
4.
interface type number
5.
ip flow {ingress | egress}
6.
exit
7.
Repeat Steps 4 through 6 to enable NetFlow on other interfaces.
8.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cseFlowIPFlowMask integer [1 | 2 | 3 | 4 |
5 | 6]
2.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCINetflowEnable.interface-number
integer [0 | 1 | 2 | 3]
3.
Repeat Step 2 to enable NetFlow on other interfaces.
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
mls flow {ip | ipv6} {destination |
destination-source | full |
interface-destination-source | interface-full |
source}
Specifies the NetFlow flow mask for IPv4 traffic.
Example:
Router(config)# mls flow ip interface-full
Step 4
interface type number
Example:
Router(config)# interface GigabitEthernet6/2
10
(Required) Specifies the interface on which you want to
enable NetFlow and enters interface configuration mode.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Step 5
Command or Action
Purpose
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—Captures traffic that is being received by the
interface
•
egress—Captures traffic that is being transmitted by
the interface.
Example:
Router(config-if)# ip flow ingress
and/or
Example:
Router(config-if)# ip flow egress
Step 6
exit
Example:
(Optional) Exits interface configuration mode and returns to
global configuration mode.
•
Router(config-if)# exit
Use this command only if you want to enable NetFlow
on another interface.
Step 7
Repeat Steps 4 through 6 to enable NetFlow on other
interfaces.
(Optional) —
Step 8
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
DETAILED STEPS: SNMP Commands
Step 1
Step 2
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cseFlowIPFlowMask integer [1 | 2 | 3
| 4 | 5 | 6]
Specifies the NetFlow flow mask for IPv4 traffic.
•
1—destination-only
•
2—source-destination
Example:
•
3—full-flow
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCINetflowEnable.60 integer 1
•
4—source-only
•
5—interface-source-destination
•
6—interface-full
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCINetflowEnable.interface-number
integer [0 | 1 | 2 | 3]
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCINetflowEnable.60 integer 1
(Required) Configures NetFlow for an interface.
•
The value for the interface-number argument is found
by entering the router CLI command show snmp mib
ifmib ifindex on the router in privileged EXEC mode.
•
The values for the direction argument are:
– 0—Disable NetFlow
– 1—Enable Ingress NetFlow
– 2—Enable Egress NetFlow
– 3—Enable Ingress and Egress NetFlow
Step 3
Repeat Step 2 to enable NetFlow on other interfaces
(Optional) —
11
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Configuring NetFlow on Cisco Routers
To enable NetFlow on the router, perform the steps in this required task using either the CLI commands
or the SNMP commands .
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
interface type number
4.
ip flow {ingress | egress}
5.
exit
6.
Repeat Steps 3 through 5 to enable NetFlow on other interfaces.
7.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfCINetflowEnable.interface-number
integer [0 | 1 | 2 | 3]
2.
Repeat Step 1 to enable NetFlow on other interfaces.
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Example:
Router(config)# interface GigabitEthernet6/2
12
(Required) Specifies the interface on which you want to
enable NetFlow and enters interface configuration mode.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Step 4
Command or Action
Purpose
ip flow {ingress | egress}
(Required) Enables NetFlow on the interface.
•
ingress—Captures traffic that is being received by the
interface
•
egress—Captures traffic that is being transmitted by
the interface.
Example:
Router(config-if)# ip flow ingress
and/or
Example:
Router(config-if)# ip flow egress
Step 5
(Optional) Exits interface configuration mode and returns to
global configuration mode.
exit
•
Example:
Router(config-if)# exit
Use this command only if you want to enable NetFlow
on another interface.
Step 6
Repeat Steps 3 through 5 to enable NetFlow on other
interfaces.
(Optional) —
Step 7
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-if)# end
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfCINetflowEnable.interface-number
integer [0 | 1 | 2 | 3]
(Required) Configures NetFlow for an interface.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfCINetflowEnable.60 integer 1
•
The value for the interface-number argument is found
by entering the router CLI command show snmp mib
ifmib ifindex on the router in privileged EXEC mode.
•
The values for the direction argument are:
– 0—Disable NetFlow
– 1—Enable Ingress NetFlow
– 2—Enable Egress NetFlow
– 3—Enable Ingress and Egress NetFlow
Step 2
Repeat Step 1 to enable NetFlow on other interfaces
(Optional) —
Configuring NetFlow Top Talkers
This task describes the procedure for configuring the NetFlow Top Talkers feature. Perform the steps in
this required task using either the router CLI commands or the SNMP commands to configure the
NetFlow Top Talkers feature on the router.
13
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
ip flow-top-talkers
4.
top number
5.
sort by [bytes | packets]
6.
cache-timeout milliseconds
7.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfTopFlowsTopN.0 unsigned number
2.
snmpset -c private -m all -v2c [ip-address | hostname] cnfTopFlowsSortBy.0 integer [1 | 2 | 3]
3.
snmpset -c private -m all -v2c [ip-address | hostname] cnfTopFlowsCacheTimeout.0 unsigned
milliseconds
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-top-talkers
(Required) Enters NetFlow Top Talkers configuration
mode.
Example:
Router(config)# ip flow-top-talkers
Step 4
top number
Example:
(Required) Specifies the maximum number of top talkers
that will be retrieved by a NetFlow top talkers query.
•
Router(config-flow-top-talkers)# top 50
Step 5
sort-by [bytes | packets]
(Required) Specifies the sort criterion for the top talkers.
•
Example:
Router(config-flow-top-talkers)#
sort-by packets
14
The range for the number argument is from 1 to 200
entries.
The top talkers can be sorted either by the total number
of packets of each top talker or the total number of
bytes of each top talker.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Step 6
Command or Action
Purpose
cache-timeout milliseconds
(Optional) Specifies the amount of time that the list of top
talkers is retained.
Example:
•
Reentering the top, sort-by, or cache-timeout
command resets the timeout period, and the list of top
talkers is recalculated the next time they are requested.
•
The list of top talkers is lost when the timeout period
expires. You should configure a timeout period for at
least as long as it takes the network management
system (NMS) to retrieve all the required NetFlow top
talkers.
•
If this timeout value is too large, the list of top talkers
might not be updated quickly enough to display the
latest top talkers. If a request to display the top talkers
is made more than once during the timeout period, the
same results will be displayed for each request. To
ensure that the latest information is displayed while
conserving CPU time, configure a large value for the
timeout period and change the parameters of the
cache-timeout, top, or sort-by command when a new
list of top talkers is required.
•
The range for the number argument is from 1 to
3,600,000 milliseconds. The default is 5000 (5
seconds).
Router(config-flow-top-talkers)#
cache-timeout 30000
Step 7
end
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Example:
Router(config-flow-top-talkers)# end
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfTopFlowsTopN.0 unsigned number
(Required) Specifies the maximum number of top talkers
that will be retrieved by a NetFlow top talkers query.
•
The value for the number argument in
cnfTopFlowsTopN.0 number is the maximum number
of top talkers that will be retrieved by a NetFlow top
talkers query.
•
The range for the number argument is from 1 to 200
entries.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfTopFlowsTopN.0 unsigned 50
15
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Step 2
snmpset -c private -m all -v2c [ip-address |
hostname] cnfTopFlowsSortBy.0 integer [1 | 2 |
3]
(Required) Specifies the sort criteria for the top talkers.
•
Values for sort-option in cnfTopFlowsSortBy.0 [1 | 2 |
3] are
– 1—No sorting will be performed and that the
Example:
NetFlow MIB and Top Talkers feature will be
disabled.
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfTopFlowsSortBy.0 integer 2
– 2—Sorting will be performed by the total number
of packets of each top talker.
– 3—Sorting will be performed by the total number
of bytes of each top talker.
Step 3
snmpset -c private -m all -v2c [ip-address |
hostname] cnfTopFlowsCacheTimeout.0 unsigned
milliseconds
(Optional) Specifies the amount of time that the list of top
talkers is retained.
•
Reentering the top, sort-by, or cache-timeout
command resets the timeout period, and the list of top
talkers is recalculated the next time they are requested.
•
The list of top talkers will be lost when the timeout
period expires. You should configure a timeout period
for at least as long as it takes the network management
system (NMS) to retrieve all the required NetFlow top
talkers.
•
If this timeout value is too large, the list of top talkers
might not be updated quickly enough to display the
latest top talkers. If a request to display the top talkers
is made more than once during the timeout period, the
same results will be displayed for each request. To
ensure that the latest information is displayed while
conserving CPU time, configure a large value for the
timeout period and change the parameters of the
cache-timeout, top, or sort-by command when a new
list of top talkers is required.
•
The range for the number argument is from 1 to
3,600,000 milliseconds. The default is 5000 (5
seconds).
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfTopFlowsCacheTimeout.0 unsigned
30000
Configuring NetFlow Top Talkers Match Criteria
You can limit the traffic that is displayed by the NetFlow Top Talkers feature by configuring match
criteria. The match criteria are applied to data in the main cache. The data in the main cache that meets
the match criteria is displayed when you enter the show ip flow top-talkers command. To limit the
traffic that is displayed by the NetFlow MIB and Top Talkers feature, perform the steps in this optional
task.
Before configuring NetFlow MIB and Top Talkers match criteria, you should understand the following:
16
•
NetFlow Top Talkers Match Criteria Specified by CLI Commands, page 17
•
NetFlow Top Talkers Match Criteria Specified by SNMP Commands, page 17
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
NetFlow Top Talkers Match Criteria Specified by CLI Commands
You can use the match CLI command to specify match criteria to restrict the display of top talkers for
the NetFlow MIB and Top Talkers feature. If you do not provide matching criteria, all top talkers are
displayed.
Note
When configuring a matching source, destination or nexthop address, both the address and a mask must
be configured. The configuration will remain unchanged until both have been specified.
Note
cnfTopFlowsMatchSampler matches flows from a named flow sampler. cnfTopFlowsMatchClass
matches flows from a named class map.
Note
When you are configuring the Top Talkers feature to match bytes and packets, the values that are
matched are the total number of bytes and packets in the flow so far. For example, it is possible to match
flows containing a specific number of packets, or flows with more or less than a set number of bytes.
For more information on using the match command, see the Cisco IOS NetFlow Command Reference.
NetFlow Top Talkers Match Criteria Specified by SNMP Commands
If you are using SNMP commands to configure NetFlow Top Talkers, see Table 1 for router CLI
commands and equivalent SNMP commands.
Note
Some of the SNMP match criteria options, such as the cnfTopFlowsMatchSrcAddress option, require
that you enter more than one SNMP commands on the same line. For example, snmpset -c private -m
all -v2c 10.4.9.62 cnfTopFlowsMatchSrcAddressType.0 integer 1 cnfTopFlowsMatchSrcAddress.0
decimal 172.16.10.0 cnfTopFlowsMatchSrcAddressMask.0 unsigned 24.
Table 1
Router CLI Commands and Equivalent SNMP Commands
Router CLI Command
SNMP Command
match source address [ip-address] [mask | /nn]
cnfTopFlowsMatchSrcAddress decimal
ip-address
cnfTopFlowsMatchSrcAddressType integer
type1
cnfTopFlowsMatchSrcAddressMask unsigned
mask
match destination address [ip-address] [mask |
/nn]
cnfTopFlowsMatchDstAddress decimal
ip-address
cnfTopFlowsMatchDstAddressType integer
type1
cnfTopFlowsMatchDstAddressMask unsigned
mask
17
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Table 1
Router CLI Commands and Equivalent SNMP Commands (continued)
Router CLI Command
SNMP Command
match nexthop address [ip-address] [mask | /nn] cnfTopFlowsMatchNhAddress decimal
ip-address
cnfTopFlowsMatchNhAddressType integer
type1
cnfTopFlowsMatchNhAddressMask unsigned
mask
match source port min port
cnfTopFlowsMatchSrcPortLo integer port
match source port max port
cnfTopFlowsMatchSrcPortHi integer port
match destination port min port
cnfTopFlowsMatchDstPortLo integer port
match destination port max port
cnfTopFlowsMatchDstPortHi integer port
match source as as-number
cnfTopFlowsMatchSrcAS integer as-number
match destination as as-number
cnfTopFlowsMatchDstAS integer as-number
match input-interface interface
cnfTopFlowsMatchInputIf integer interface
match output-interface interface
cnfTopFlowsMatchOutputIf integer interface
match tos [tos-value | dscp dscp-value |
precedence precedence-value]
cnfTopFlowsMatchTOSByte integer tos-value2
match protocol [protocol-number | tcp | udp]
cnfTopFlowsMatchProtocol integer
protocol-number
match flow-sampler flow-sampler-name
cnfTopFlowsMatchSampler string
flow-sampler-name
match class-map class
cnfTopFlowsMatchClass string class
match packet-range min minimum-range
cnfTopFlowsMatchMinPackets unsigned
minimum-range
match packet-range max maximum-range
cnfTopFlowsMatchMaxPackets unsigned
maximum-range
match byte-range min minimum-range
cnfTopFlowsMatchMinBytes unsigned
minimum-range
match byte-range max maximum-range
cnfTopFlowsMatchMaxPackets unsigned
maximum-range
1. The only IP version type that is currently supported is IPv4 (type 1).
2. tos-value is 6 bits for DSCP, 3 bits for precedence, and 8 bits (one byte) for ToS.
Configuring Source IP Address Top Talkers Match Criteria
Perform the steps in this optional task using either the router CLI commands or the SNMP commands to
add source IP address match criteria to the Top Talkers configuration.
For information on configuring other Top Talkers match criteria see the following resources:
18
•
Cisco IOS NetFlow Command Reference.
•
CISCO-NETFLOW-MIB at the following URL: http://www.cisco.com/go/mibs/. Select SNMP
Object Locator. Then select View & Download MIBs.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Prerequisites
You must configure NetFlow Top Talkers before you perform this task.
SUMMARY STEPS
Router CLI Commands
1.
enable
2.
configure terminal
3.
ip flow-top-talkers
4.
match source address {ip-address/nn | ip-address mask}
5.
end
SNMP Commands
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfTopFlowsMatchSrcAddressType.0
integer 1 cnfTopFlowsMatchSrcAddress.0 decimal ip-address
cnfTopFlowsMatchSrcAddressMask.0 unsigned mask
DETAILED STEPS: Router CLI Commands
Step 1
Command or Action
Purpose
enable
(Required) Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
(Required) Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip flow-top-talkers
(Required) Enters NetFlow Top Talkers configuration
mode.
Example:
Router(config)# ip flow-top-talkers
19
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Step 4
Command or Action
Purpose
match source address {ip-address/nn |
ip-address mask}
(Required) Specifies a match criterion.
Example:
Router(config-flow-top-talkers)# match source
address 172.16.10.0/24
Step 5
end
Example:
Router(config-flow-top-talkers)# end
20
•
The source address keyword specifies that the match
criterion is based on the source IP address.
•
The ip-address argument is the IP address of the source,
destination, or next-hop address to be matched.
•
The mask argument is the address mask, in dotted
decimal format.
•
The /nn argument is the address mask as entered in
CIDR format. The match source address
172.16.10.0/24 is equivalent to the match source
address 172.16.10.0 255.255.255.0 command.
Note
You must configure at least one of the possible
match criteria before matching can be used to limit
the traffic that is displayed by the NetFlow Top
Talkers feature. Additional match criteria are
optional.
Note
For a full list of the matching criteria that you can
select, refer to NetFlow Top Talkers Match Criteria
Specified by CLI Commands.
(Required) Exits the current configuration mode and returns
to privileged EXEC mode.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
DETAILED STEPS: SNMP Commands
Step 1
Command or Action
Purpose
snmpset -c private -m all -v2c [ip-address |
hostname] cnfTopFlowsMatchSrcAddressType.0
integer 1 cnfTopFlowsMatchSrcAddress.0 decimal
ip-address cnfTopFlowsMatchSrcAddressMask.0
unsigned mask
(Required) Specifies a match criterion.
•
The IP address type of 1 in the
cnfTopFlowsMatchSrcAddressType.0 integer 1
command specifies an IP version 4 (IPv4) address for
the IP address type. IPv4 is currently the only IP
version that is supported.
•
The ip-address argument in
cnfTopFlowsMatchSrcAddress.0 decimal ip-address
is the IPv4 source IP address to match in the traffic that
is being analyzed.
•
The mask argument in
cnfTopFlowsMatchSrcAddressMask.0 unsigned
mask is the number of bits in the mask for the IPv4
source IP address to match in the traffic that is being
analyzed.
Example:
workstation% snmpset -c private -m all -v2c
10.4.9.62 cnfTopFlowsMatchSrcAddressType.0
integer 1 cnfTopFlowsMatchSrcAddress.0 decimal
172.16.10.0 cnfTopFlowsMatchSrcAddressMask.0
unsigned 24
Note
You must configure at least one of the possible
match criteria before matching can be used to limit
the traffic that is displayed by the Top talkers
feature. Additional match criteria are optional.
Note
To remove the cnfTopFlowsMatchSrcAddress
match criterion from the configuration, specify an
IP address type of 0 (unknown) with the
cnfTopFlowsMatchSrcAddressType.0 integer 0
command.
Note
For a list of router CLI commands and their
corresponding SNMP commands, see Table 1.
Verifying the NetFlow Top Talkers Configuration
To verify the NetFlow Top Talkers configuration, perform the steps in this optional task using either the
router CLI command or the SNMP commands.
SUMMARY STEPS
Router CLI Commands
1.
show ip flow top-talkers
SNMP Command
1.
snmpset -c private -m all -v2c [ip-address | hostname] cnfTopFlowsGenerate.0 integer 1
2.
snmpwalk -c public -m all -v2c [ip-address | hostname] cnfTopFlowsReportAvailable
3.
snmpwalk -c public -m all -v2c [ip-address | hostname] cnfTopFlowsTable
21
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
How to Configure NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
DETAILED STEPS: Router CLI Commands
Step 1
show ip flow top-talkers
Use this command to verify that the NetFlow MIB and Top Talkers feature is operational. For example:
Router# show ip flow top-talkers
SrcIf
SrcIPaddress
DstIf
DstIPaddress
Et3/0
10.1.1.3
Local
10.1.1.2
Et3/0
10.1.1.4
Local
10.1.1.2
Et3/0
10.1.1.5
Local
10.1.1.2
3 of 10 top talkers shown. 3 flows processed.
Pr
01
01
01
SrcP
0000
0000
0000
DstP Bytes
0000 4800
0000 4800
0000
800
In this example, even though a maximum of ten top talkers is configured by the top command, only three
top talkers were transmitting data in the network. Therefore, three top talkers are shown, and the “3 flows
processed” message is displayed in the output. If you expect more top talkers to be displayed than are
being shown, this condition may possibly be the result of matching criteria, specified by the match
command, that are overly restrictive.
DETAILED STEPS: SNMP Commands
Step 1
snmpset -c private -m all -v2c [ip-address | hostname] cnfTopFlowsGenerate.0 integer 1
Use this command to initiate a generation of the top talkers statistics:
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfTopFlowsGenerate.0 integer 1
CISCO-NETFLOW-MIB::cnfTopFlowsGenerate.0 = INTEGER: true(1)
Step 2
snmpget -c public -m all -v2c [ip-address | hostname] cnfTopFlowsReportAvailable
Use this command to verify that the top talkers statistics are available:
workstation% snmpwalk -c public -m all -v2c 10.4.9.62 cnfTopFlowsReportAvailable
CISCO-NETFLOW-MIB::cnfTopFlowsReportAvailable.0 = INTEGER: true(1)
Step 3
snmpwalk -c public -m all -v2c [ip-address | hostname] cnfTopFlowsTable
Use this command to display the NetFlow top talkers:
workstation% snmpwalk -c public -m all -v2c 10.4.9.62 cnfTopFlowsTable
CISCO-NETFLOW-MIB::cnfTopFlowsSrcAddressType.1 = INTEGER: ipv4(1)
CISCO-NETFLOW-MIB::cnfTopFlowsSrcAddress.1 = Hex-STRING: 0A 04 09 08
CISCO-NETFLOW-MIB::cnfTopFlowsSrcAddressMask.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsDstAddressType.1 = INTEGER: ipv4(1)
CISCO-NETFLOW-MIB::cnfTopFlowsDstAddress.1 = Hex-STRING: 0A 04 09 A7
CISCO-NETFLOW-MIB::cnfTopFlowsDstAddressMask.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsNhAddressType.1 = INTEGER: ipv4(1)
CISCO-NETFLOW-MIB::cnfTopFlowsNhAddress.1 = Hex-STRING: 00 00 00 00
CISCO-NETFLOW-MIB::cnfTopFlowsSrcPort.1 = Gauge32: 32773
CISCO-NETFLOW-MIB::cnfTopFlowsDstPort.1 = Gauge32: 161
CISCO-NETFLOW-MIB::cnfTopFlowsSrcAS.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsDstAS.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsInputIfIndex.1 = INTEGER: 1
CISCO-NETFLOW-MIB::cnfTopFlowsOutputIfIndex.1 = INTEGER: 0
CISCO-NETFLOW-MIB::cnfTopFlowsFirstSwitched.1 = Timeticks: (12073160) 1 day, 9:32:11.60
CISCO-NETFLOW-MIB::cnfTopFlowsLastSwitched.1 = Timeticks: (12073160) 1 day, 9:32:11.60
CISCO-NETFLOW-MIB::cnfTopFlowsTOS.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsProtocol.1 = Gauge32: 17
22
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Configuration Examples for NetFlow Top Talkers
CISCO-NETFLOW-MIB::cnfTopFlowsTCPFlags.1 = Gauge32: 16
CISCO-NETFLOW-MIB::cnfTopFlowsSamplerID.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsClassID.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsFlags.1 = Gauge32: 0
CISCO-NETFLOW-MIB::cnfTopFlowsBytes.1 = Gauge32: 75
CISCO-NETFLOW-MIB::cnfTopFlowsPackets.1 = Gauge32: 1
Tip
You must convert the source and destination IP addresses from hexadecimal to dotted decimal format
used in the display output before you can correlate them to source and destination hosts on your network.
For example, in the display output above: 0A 04 09 02 = 10.4.9.2 and 0A 04 09 AF = 10.4.9.175.
Configuration Examples for NetFlow Top Talkers
This section provides the following configuration examples:
•
Configuring NetFlow Top Talkers Using SNMP Commands: Example, page 23
•
Configuring NetFlow Top Talkers Match Criteria Using SNMP Commands: Example, page 24
Configuring NetFlow Top Talkers Using SNMP Commands: Example
The following output from the network management workstation shows the command and the response
for enabling NetFlow on interface GigabitEthernet6/2 (ifindex number 60):
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfCINetflowEnable.60 integer 1
CISCO-NETFLOW-MIB::cnfCINetflowEnable.60 = INTEGER: interfaceDirIngress(1)
The following output from the network management workstation shows the command and the response
for specifying 5 as the maximum number of top talkers that will be retrieved by a NetFlow top talkers
query:
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfTopFlowsTopN.0 unsigned 5
CISCO-NETFLOW-MIB::cnfTopFlowsTopN.0 = Gauge32: 5
The following output from the network management workstation shows the command and the response
for specifying the sort criteria for the top talkers:
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfTopFlowsSortBy.0 integer 2
CISCO-NETFLOW-MIB::cnfTopFlowsSortBy.0 = INTEGER: byPackets(2)
The following output from the network management workstation shows the command and the response
for specifying the amount of time that the list of top talkers is retained:
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfTopFlowsCacheTimeout.0 unsigned
2000
CISCO-NETFLOW-MIB::cnfTopFlowsCacheTimeout.0 = Gauge32: 2000 milliseconds
23
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Additional References
Configuring NetFlow Top Talkers Match Criteria Using SNMP Commands:
Example
The following output from the network management workstation shows the snmpset command and the
response for specifying the following NetFlow Top Talkers match criteria:
•
Source IP address–172.16.23.0
•
Source IP address mask–255.255.255.0 (/24)
•
IP address type–IPv4
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfTopFlowsMatchSrcAddress.0 decimal
172.16.23.0 cnfTopFlowsMatchSrcAddressMask.0 unsigned 24 cnfTopFlowsMatchSrcAddressType.0
integer 1
CISCO-NETFLOW-MIB::cnfTopFlowsMatchSrcAddress.0 = Hex-STRING: AC 10 17 00
CISCO-NETFLOW-MIB::cnfTopFlowsMatchSrcAddressMask.0 = Gauge32: 24
CISCO-NETFLOW-MIB::cnfTopFlowsMatchSrcAddressType.0 = INTEGER: ipv4(1)
The following output from the network management workstation shows the snmpset command and the
response for specifying the class-map my-class-map as aNetFlow Top Talkers match criterion:
workstation% snmpset -c private -m all -v2c 10.4.9.62 cnfTopFlowsMatchClass.0 s
my-class-map
CISCO-NETFLOW-MIB::cnfTopFlowsMatchClass.0 = STRING: my-class-map.
Additional References
The following sections provide references related to the NetFlow MIB and Top Talkers feature.
Related Documents
Related Topic
Document Title
Overview of Cisco IOS NetFlow
Cisco IOS NetFlow Overview
List of the features documented in the Book Title
configuration guide
Cisco IOS NetFlow Features Roadmap
The minimum information about and tasks required for Getting Started with Configuring NetFlow and NetFlow Data Export
configuring NetFlow and NetFlow Data Export
Tasks for configuring NetFlow to capture and export
network traffic data
Configuring NetFlow and NetFlow Data Export
Tasks for configuring Configuring MPLS Aware
NetFlow
Configuring MPLS Aware NetFlow
Tasks for configuring MPLS egress NetFlow
accounting
Configuring MPLS Egress NetFlow Accounting and Analysis
Tasks for configuring NetFlow input filters
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
Tasks for configuring Random Sampled NetFlow
Using NetFlow Filtering or Sampling to Select the Network Traffic
to Track
24
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Additional References
Related Topic
Document Title
Tasks for configuring NetFlow aggregation caches
Configuring NetFlow Aggregation Caches
Tasks for configuring NetFlow BGP next hop support
Configuring NetFlow BGP Next Hop Support for Accounting and
Analysis
Tasks for configuring NetFlow multicast support
Configuring NetFlow Multicast Accounting
Tasks for detecting and analyzing network threats with Detecting and Analyzing Network Threats With NetFlow
NetFlow
Tasks for configuring NetFlow Reliable Export With
SCTP
NetFlow Reliable Export With SCTP
Tasks for configuring NetFlow Layer 2 and Security
Monitoring Exports
NetFlow Layer 2 and Security Monitoring Exports
Tasks for configuring the SNMP NetFlow MIB
Configuring SNMP and using the NetFlow MIB to Monitor NetFlow
Data
Information for installing, starting, and configuring the Cisco CNS NetFlow Collection Engine Documentation
CNS NetFlow Collection Engine
Standards
Standards
Title
—
No new or modified standards are supported by this
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
CISCO-NETFLOW-MIB
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL (requires CCO login account):
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
25
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Feature Information for Configuring NetFlow Top Talkers using the Cisco IOS CLI or SNMP Commands
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support website contains
thousands of pages of searchable technical content,
including links to products, technologies, solutions,
technical tips, and tools. Registered Cisco.com users
can log in from this page to access even more content.
Feature Information for Configuring NetFlow Top Talkers using
the Cisco IOS CLI or SNMP Commands
Table 2 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(1) or 12.0(3)S or a later release
appear in the table.
Not all commands may be available in your Cisco IOS software release. For details on when support for
a specific command was introduced, see the command reference documentation.
For information on a feature in this technology that is not documented here, see the “Cisco IOS NetFlow
Features Roadmap” module.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image
support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on
Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at
the login dialog box and follow the instructions that appear.
Note
26
Table 2 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Feature Information for Configuring NetFlow Top Talkers using the Cisco IOS CLI or SNMP Commands
Table 2
Feature Information for Configuring NetFlow Top Talkers using the Cisco IOS CLI or SNMP Commands
Feature Name
Releases
Feature Configuration Information
NetFlow MIB
12.3(7)T,
12.2(25)S
12.2(27)SBC
The NetFlow MIB feature provides MIB objects to allow
users to monitor NetFlow cache information, the current
NetFlow configuration, and statistics.
The following command was introduced by this feature: ip
flow-cache timeout.
NetFlow MIB and Top Talkers
12.3(11)T,
12.2(25)S
12.2(27)SBC
12.2(33)SXH
The NetFlow MIB feature that was originally released in
Cisco IOS Release12.3(7)T was modified in Cisco IOS
Release 12.3(11)T to support the new NetFlow Top Talkers
feature. The modifications to the NetFlow MIB and the new
Top Talkers feature were released under the feature name
NetFlow MIB and Top Talkers.
The NetFlow MIB and Top Talkers feature uses NetFlow
functionality to obtain information regarding heaviest
traffic patterns and most-used applications (top talkers) in
the network. The NetFlow MIB component of the NetFlow
MIB and Top Talkers feature enables you to configure top
talkers and view the top talker statistics using SNMP.
The following sections provide information about this
feature:
•
Information About Configuring NetFlow Top Talkers,
page 2
•
How to Configure NetFlow Top Talkers using Cisco
IOS CLI Commands or SNMP Commands, page 4
The following commands were introduced by this feature:
cache-timeout, ip flow-top-talkers, match, show ip flow
top-talkers, sort-by, and top.
CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, Cisco IronPort, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect,
Cisco Pulse, Cisco StackPower, Cisco StadiumVision, Cisco TelePresence, Cisco Unified Computing System, Cisco WebEx, DCE, Flip Channels,
Flip for Good, Flip Mino, Flipshare (Design), Flip Ultra, Flip Video, Flip Video (Design), Instant Broadband, and Welcome to the Human Network
are trademarks; Changing the Way We Work, Live, Play, and Learn, Cisco Capital, Cisco Capital (Design), Cisco:Financed (Stylized), Cisco Store,
and Flip Gift Card are service marks; and Access Registrar, Aironet, AllTouch, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP,
CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems,
Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, Continuum, EtherFast, EtherSwitch, Event Center,
Explorer, Fast Step, Follow Me Browsing, FormShare, GainMaker, GigaDrive, HomeLink, iLYNX, Internet Quotient, IOS, iPhone, iQuick Study,
IronPort, the IronPort logo, Laser Link, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers,
Networking Academy, Network Registrar, PCNow, PIX, PowerKEY, PowerPanels, PowerTV, PowerTV (Design), PowerVu, Prisma, ProConnect,
ROSA, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx,
and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply
a partnership relationship between Cisco and any other company. (0908R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2005–2009 Cisco Systems, Inc. All rights reserved.
27
Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands
Feature Information for Configuring NetFlow Top Talkers using the Cisco IOS CLI or SNMP Commands
28
Configuring NetFlow v9 for IPv6
First Published: February 27, 2007
Last Updated: August 11, 2010
This module contains information about and instructions for configuring NetFlow and NetFlow Data
Export (NDE) for capturing and exporting data from IP version 6 (IPv6) traffic flows using the NetFlow
version 9 (v9) export format.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for NetFlow v9 for IPv6” section on page 8.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for NetFlow v9 for IPv6, page 2
•
Information About NetFlow v9 for IPv6, page 2
•
How to Configure NetFlow v9 for IPv6, page 4
•
Configuration Examples for NetFlow v9 for IPv6, page 6
•
Additional References, page 7
•
Feature Information for NetFlow v9 for IPv6, page 8
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
Configuring NetFlow v9 for IPv6
Prerequisites for NetFlow v9 for IPv6
Prerequisites for NetFlow v9 for IPv6
Your router must be running Cisco IOS release 12.2(33)SRB or later to configure the NDE for VRF
Interfaces feature.
Information About NetFlow v9 for IPv6
Before you configure the NDE for VRF Interfaces feature, you should understand the following
concepts:
•
NetFlow and NDE on the PFC, page 2
•
NetFlow Export Format Version 9, page 2
NetFlow and NDE on the PFC
The NetFlow cache on the PFC captures statistics for flows routed in hardware.
The PFC uses one of these flow masks to create NetFlow entries:
•
source-only—The cache contains one entry for each source IP address. All flows from a given
source IP address use this entry.
•
destination—The cache contains one entry for each destination IP address. All flows to a given
destination IP address use this entry.
•
destination-source—The cache contains one entry for each source and destination IP address pair.
All flows between the same source and destination IP addresses use this entry.
•
destination-source-interface—Adds the source VLAN SNMP ifIndex to the information in the
destination-source flow mask.
•
full—A separate cache entry is created for each IP flow. A full entry includes the source IP address,
destination IP address, protocol, and protocol interfaces.
•
full-interface—Adds the source VLAN SNMP ifIndex to the information in the full flow mask.
See the “Configuring NetFlow and NDE” chapter of the Cisco 7600 Series Cisco IOS Software
Configuration Guide, Release 12.2SR, for detailed information on NetFlow flow masks and flow
records.
NetFlow Export Format Version 9
For all NetFlow export versions, the NetFlow export datagram consists of a header and a sequence of
flow records. The header contains information such as sequence number, record count, and system
uptime. The flow record contains flow information, such as IP addresses, ports, and routing information.
NetFlow version 9 export format is the newest NetFlow export format. The distinguishing feature of the
NetFlow version 9 export format is that it is template based. Templates make the record format
extensible. NetFlow version 9 export format allows future enhancements to NetFlow without requiring
concurrent changes to the basic flow-record format.
The NetFlow version 9 export record format is different from the traditional NetFlow fixed format export
record. In NetFlow version 9, a template describes the NetFlow data, and the flow set contains the actual
data. This arrangement allows for flexible export.
2
Configuring NetFlow v9 for IPv6
Information About NetFlow v9 for IPv6
The use of templates with the NetFlow version 9 export format provides several other key benefits:
•
You can export almost any information from a router or switch, including Layer 2 through 7
information, routing information, IP version 6 (IPv6), IP version 4 (IPv4), multicast, and
Multiprotocol Label Switching (MPLS) information. This new information allows new applications
for export data and new views of network behavior.
•
Third-party business partners who produce applications that provide NetFlow collector or
display services for NetFlow are not required to recompile their applications each time a new
NetFlow export field is added. Instead, they can use an external data file that documents the known
template formats.
•
New features can be added to NetFlow more quickly, without breaking current implementations.
•
NetFlow is “future-proofed” against new or developing protocols, because the version 9 export
format can be adapted to provide support for them and for other non-NetFlow-based approaches to
data collection.
The NetFlow version 9 export packet header format is shown in Table 1.
Table 1
NetFlow Version 9 Export Packet Header Field Names and Descriptions
Bytes
Field Name
Description
0–1
Version
The version of NetFlow records exported in this packet; for version 9,
this value is 0x0009.
2–3
Count
Number of FlowSet records (both template and data) contained within
this packet.
4–7
System Uptime
Time in milliseconds since this device was first booted.
8–11
UNIX Seconds
Seconds since 0000 Coordinated Universal Time (UTC) 1970.
12–15
Sequence Number
Incremental sequence counter of all export packets sent by this export
device; this value is cumulative, and it can be used to find out whether
any export packets have been missed.
This is a change from the NetFlow version 5 and version 8 headers,
where this number represented “total flows.”
16–19
Source ID
The Source ID field is a 32-bit value that is used to guarantee uniqueness for each flow exported from a particular device. (The Source ID
field is the equivalent of the engine type and engine ID fields found in
the NetFlow version 5 and version 8 headers.) The format of this field
is vendor specific. In Cisco’s implementation, the first two bytes are
reserved for future expansion and are always zero. Byte 3 provides
uniqueness with respect to the routing engine on the exporting device.
Byte 4 provides uniqueness with respect to the particular line card or
Versatile Interface Processor on the exporting device. Collector
devices should use the combination of the source IP address and the
Source ID field to associate an incoming NetFlow export packet with a
unique instance of NetFlow on a particular device.
3
Configuring NetFlow v9 for IPv6
How to Configure NetFlow v9 for IPv6
Figure 1 shows a typical example of exporting data using the NetFlow version 9 export format.
NetFlow Version 9 Export Format Packet Example
Header
First Template FlowSet
Template Record
First Record FlowSet
(Template ID 256)
First data Record
Second Data Record
Second Template Flow Set
Template Record
Template Record
Second Record FlowSet
(Template ID 257)
Data Record
Data Record
Data Record
Data Record
NetFlow Version 9 Header: 32 bits
Version 9
Count = 4 (FlowSets)
System Uptime
UNIX Seconds
Package Sequence
Source ID
Template FlowSet 16 bits
FlowSet ID = 0
Length = 28 bytes
Template ID = 256
Field Count = 5
IPv4_SRCADDR (0x0008)
Length = 4
IPv4_DSTADDR (0x000C)
Length = 4
IPv4_NEXT_HOP (0x000E)
Length = 4
PKTS_32 (0x0002)
Length = 4
BYTES_32 (0x0001)
Length = 4
Data FlowSet: 32 bits
FlowSet
Length =
ID = 256
64 bytes
192.168.1.12
10.5.12.254
192.168.1.1
5009
5344365
192.168.1.27
10.5.12.23
192.168.1.1
748
388934
192.168.1.56
10.5.12.65
192.168.1.1
5
6534
121979
Figure 1
Additional information about the NetFlow export format version 9 and the export format architecture is
available in the NetFlow version 9 Flow-Record Format document.
How to Configure NetFlow v9 for IPv6
Perform the steps in this required task to configure the NDE for VRF Interfaces feature.
SUMMARY STEPS
4
1.
enable
2.
configure terminal
3.
ipv6 unicast-routing
4.
mls flow {ip | ipv6} {destination | destination-source | full | interface-destination-source |
interface-full | source}
5.
mls nde sender
6.
ip flow-export version 9
7.
ip flow-export destination {ip-address | hostname} udp-port
Configuring NetFlow v9 for IPv6
How to Configure NetFlow v9 for IPv6
8.
interface type number
9.
ipv6 address ip-address/mask
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ipv6 unicast-routing
Enables the forwarding of IPv6 unicast datagrams.
Example:
Router(config)# ipv6 unicast-routing
Step 4
mls flow {ip | ipv6} {destination |
destination-source | full |
interface-destination-source | interface-full |
source}
Specifies the NetFlow flow mask for IPv6 traffic.
Example:
Router(config)# mls flow ipv6 interface-full
Step 5
mls nde sender
Enables NDE globally on the router.
Note
Example:
Route(config)# mls nde sender
Step 6
ip flow-export version 9
NDE does not start exporting data until you specify
a destination for the exported traffic. The
destination for exported traffic is specified in Step
7.
Configures NDE to use the NetFlow version 9 export
format.
Example:
Router(config)# ip flow-export version 9
Step 7
ip flow-export destination {ip-address |
hostname} udp-port
Specifies the IP address or the hostname of the NetFlow
collector and the UDP port on which the NetFlow collector
is listening.
Example:
Router(config)# ip flow-export destination
172.16.10.2 88
5
Configuring NetFlow v9 for IPv6
Configuration Examples for NetFlow v9 for IPv6
Step 8
Command or Action
Purpose
interface type number
Specifies the interface that you want to enable NetFlow on
and enters interface configuration mode.
Example:
Router(config)# interface fastethernet 1/1
Step 9
ipv6 address ip-address/mask
Configure an IPv6 address on the interface.
Example:
Router(config-if)# ipv6 address
2001:0DB8:AB::2/64
Examples
The following output of the show mls nde command verifies that NDE is enabled on the router.
Router#show mls nde
NetFlow Data Export enabled
Exporting flows to 10.30.30.2 (12345) 172.16.10.2 (88)
Exporting flows from 10.4.9.149 (58970)
Version: 9
Layer2 flow creation is disabled
Layer2 flow export is disabled
Include Filter not configured
Exclude Filter not configured
Total NetFlow Data Export Packets are:
0 packets, 0 no packets, 0 records
Total NetFlow Data Export Send Errors:
IPWRITE_NO_FIB = 0
IPWRITE_ADJ_FAILED = 0
IPWRITE_PROCESS = 0
IPWRITE_ENQUEUE_FAILED = 0
IPWRITE_IPC_FAILED = 0
IPWRITE_OUTPUT_FAILED = 0
IPWRITE_MTU_FAILED = 0
IPWRITE_ENCAPFIX_FAILED = 0
NetFlow Aggregation Disabled
Configuration Examples for NetFlow v9 for IPv6
This section contains the following configuration example:
•
Configuring the NetFlow v9 for IPv6 Feature: Example, page 6
Configuring the NetFlow v9 for IPv6 Feature: Example
The following example shows how to configure the router for NetFlow and NDE for IPv6 traffic using
NetFlow export format version 9.
ipv6 unicast-routing
mls flow ipv6 interface-full
mls nde sender
ip flow-export version 9
ip flow-export destination 172.16.10.2 88
interface FastEthernet1/1
6
Configuring NetFlow v9 for IPv6
Additional References
ipv6 address 2001:0DB8::1/64
Additional References
The following sections provide references related to the NDE for VRF Interfaces feature.
Related Documents
Related Topic
Document Title
Platform-independent NetFlow commands, complete Cisco IOS NetFlow Command Reference, Release 12.2SR
command syntax, command mode, defaults, command
history, usage guidelines, and examples.
Standards
Standard
Title
There are no standards associated with this feature.
—
MIBs
MIB
MIBs Link
There are no MIBs associated with this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFC
Title
RFC 3954
Cisco Systems NetFlow Services Export Version 9.
Technical Assistance
Description
Link
http://www.cisco.com/techsupport
The Cisco Technical Support & Documentation
website contains thousands of pages of searchable
technical content, including links to products,
technologies, solutions, technical tips, tools, and
technical documentation. Registered Cisco.com users
can log in from this page to access even more content.
7
Configuring NetFlow v9 for IPv6
Feature Information for NetFlow v9 for IPv6
Feature Information for NetFlow v9 for IPv6
Table 2 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a
specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support.
Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images
support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 2
Table 2 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for NetFlow v9 for IPv6
Feature Name
Releases
Feature Information
Netflow v9 for IPv6
12.2(33)SRB
The NetFlow v9 for IPv6 feature enables the export of NetFlow
flow information for IPv6 traffic.
In 12.2(33)SRB, support for this feature was introduced on the
Cisco 7600 series routers.
The following sections provide information about this feature:
•
Information About NetFlow v9 for IPv6, page 2
•
How to Configure NetFlow v9 for IPv6, page 4
The following commands were introduced or modified: mls
flow, mls nde sender.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2007–2010 Cisco Systems, Inc. All rights reserved.
8
NDE for VRF Interfaces
First Published: February 27, 2007
Last Updated: August 09, 2010
The NetFlow data export (NDE) for VRF Interfaces feature enables the creation and export of hardware
NetFlow cache entries for traffic entering a router on the last multi-protocol label switching (MPLS) hop
of an IPv4 MPLS virtual private network (VPN). The NDE for VRF Interfaces feature also ensures that
the data collected in the hardware NetFlow cache for traffic that is received on an IPv4 interface
configured for a per-site forwarding table (VRF) contains the routing information specific to the VRF.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for NDE for VRF Interfaces” section on page 17.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for NDE for VRF Interfaces, page 2
•
Restrictions for NDE for VRF Interfaces, page 2
•
Information About NDE for VRF Interfaces, page 2
•
How to Configure NDE for VRF Interfaces for an MPLS VPN, page 6
•
Configuration Examples for NDE for VRF Interfaces, page 11
•
Where to Go Next, page 15
•
Additional References, page 16
•
Feature Information for NDE for VRF Interfaces, page 17
Americas Headquarters:
Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA 95134-1706 USA
NDE for VRF Interfaces
Prerequisites for NDE for VRF Interfaces
Prerequisites for NDE for VRF Interfaces
Your router must be running Cisco IOS release 12.2(33)SRB or later to configure the NDE for VRF
Interfaces feature.
Restrictions for NDE for VRF Interfaces
The NDE for VRF Interfaces feature supports only IPv4 traffic.
When you configure the NDE for VRF Interfaces feature for a MPLS VPN, the router assigns a reserved
VLAN ID to the MPLS VPN. This will limit the number of VLAN IDs available for other features that
you configure on the router and that require VLAN IDs.
Information About NDE for VRF Interfaces
Before configuring the NDE for VRF Interfaces feature, you should understand the following concepts:
•
Example of an MPLS VPN Network, page 2
•
Analysis of Traffic Exiting the MPLS VPN Network with NetFlow, page 3
•
MPLS Aggregate Labels, page 3
•
NetFlow Cache Population, page 4
•
VRF Name as the Source Interface in the NetFlow Cache, page 6
Example of an MPLS VPN Network
Figure 1 is an example of a simple MPLS virtual private network (VPN). Routers PE1 and PE2 are
configured to support an MPLS VPN to carry the customer’s traffic between the sites where routers CE1
and CE2 are located. Routers PE1 and PE2 use multi-protocol iBGP peers for routing traffic on the
MPLS VPNs. The NDE for VRF Interfaces feature is applicable to routers PE1 and PE2 in this example.
Figure 1
Example of a simple MPLS VPN network
IP
network
MPLS
network
MPLS
network
IP
network
Host A
Host B
PE1
P1
P2
PE2
CE2
119118
CE1
Owned by
service provider
Cisco IOS NetFlow Configuration Guide
2
NDE for VRF Interfaces
Information About NDE for VRF Interfaces
For more information about configuring MPLS on Cisco 7600 series routers, see the chapter Configuring
PFC3BXL and PFC3B Multiprotocol Label Switching (MPLS) in the Cisco 7600 Series Cisco IOS
Software Configuration Guide.
Analysis of Traffic Exiting the MPLS VPN Network with NetFlow
The NDE for VRF Interfaces feature captures traffic received by the router on the MPLS VPN VRF
interface as it exits the MPLS network. For example, when you configure the NDE for VRF Interfaces
feature on VPN Red on PE2 as shown in Figure 2, and the traffic to and from CE2 is assigned to VRF
Red, the traffic is added to the NetFlow cache and shown as being received on VPN Red.
Figure 2
Example of a Router (PE2) Receiving Traffic over a MPLS VPN VRF Interface
VPN red
FE0/1
10.2.0.2/24
CE2
MPLS core
Hosts
10.2.0.1/24
FE0/0
FE0/0
172.16.2.2/24
MPLS traffic
PE2
VRF VPN red
10.3.0.1/24
FE0/1
FE0/1
10.3.0.2/24
Hosts
230539
CE3
MPLS Aggregate Labels
There are two types of VPN MPLS labels:
•
Aggregate labels for traffic on which a routing decision must be made
•
Non aggregate (specific) labels.
When you configure a MPLS VPN on a PE router the router allocates an aggregate MPLS label for the
VPN.
Since aggregate MPLS labels correspond to the VRF to which a packet belongs, the router must consult
the routing table for a VRF to determine the correct next hop IP address within the VPN domain in order
to forward the packet. The next-hop IP address is required before the router can forward the packet
because VPN domains are capable of supporting multiple next hop routers. For example, in Figure 2
there are two CE routers: CE2 and CE3. MPLS traffic arriving on VPN Red on PE1 could be destined to
hosts attached to either CE2 or CE3. PE2 must perform another lookup to identify the correct CE router
to which the traffic must be forwarded. The method that PE2 uses to perform the next-hop IP address
lookup depends on the number of MPLS aggregate labels that the router has stored.
Cisco IOS NetFlow Configuration Guide
3
NDE for VRF Interfaces
Information About NDE for VRF Interfaces
Stored MPLS Aggregate Labels
Traffic that uses one of the first 511 aggregate MPLS labels is forwarded by the router based on the entry
for the MPLS VPN label in the VPN content addressable memory (CAM).
The following steps are performed by a PE router to forward MPLS traffic that uses one of the first 511
aggregate MPLS labels:
1.
An MPLS packet carrying an aggregation label arrives at the egress PE router.
2.
A lookup in the VPN CAM is performed for the MPLS aggregation label.
3.
The MPLS aggregation label is removed and the corresponding VPN ID for the packet is identified.
4.
The index from the VPN CAM is used to reference the MPLS VPN routing table.
5.
A lookup is performed for the destination IP prefix in the VPN VRF that was derived from the MPLS
VPN table. The lookup result contains the next hop IP address and all other rewrite information
needed for forwarding the packet to the correct CE router.
More Than 511 Stored MPLS Aggregate Labels
When the number of MPLS aggregate labels in the network exceeds 511, the router can no longer store
some MPLS aggregate labels in its VPN CAM. In this situation the router consults the MPLS FIB, strips
off the label to reveal the IPv4 packet encapsulated inside, and recirculates the packet, at which point the
VRF FIB determines the next hop.
Note
The first 511 MPLS aggregate labels remain in the VPN CAM and are processed based on the steps in
the “Stored MPLS Aggregate Labels” section on page 4.
The following steps are performed by a PE router to forward MPLS traffic when the aggregate MPLS
label is not in the VPN CAM:
1.
A lookup is performed in the TCAM and FIB.
2.
The MPLS label is popped and the reserved VLAN associated with the MPLS aggregation label is
assigned to the packet.
Note
When the number of MPLS aggregate labels exceeds 511, a reserved VLAN interface is assigned
for each new MPLS aggregate label.
3.
The VPN ID for the reserved VLAN ID is derived from the VLAN RAM. The VPN ID is used as a
part of the lookup key for the IP VRF Cisco express forwarding (CEF) lookup.
4.
The IP VRF CEF lookup result contains the next hop IP address and all other rewrite information
needed for forwarding the packet to the correct CE router.
NetFlow Cache Population
When the NDE for VRF Interfaces feature is configured for an MPLS VPN, a VLAN interface is
reserved and NetFlow is enabled on the VLAN interface. The method used by the router to process the
MPLS VPN IPv4 traffic and populate the NetFlow cache depends on the number of MLS aggregate
labels that the router has stored.
Cisco IOS NetFlow Configuration Guide
4
NDE for VRF Interfaces
Information About NDE for VRF Interfaces
MPLS Aggregate Labels in VPN CAM
When there are fewer than 512 VPN aggregate MPLS labels, the label and associated VPN are
programmed in the MPLS VPN CAM, and packet recirculation is not required. The policy feature card
(PFC) receives the packet as an IP packet. The PFC NetFlow function sees flows as sourced at the MPLS
VPN not at the interface on which the traffic was received.
When there are fewer than 512 VPN aggregate MPLS labels (all MPLS aggregate labels are stored in the
VPN CAM), the NetFlow cache is populated for the MPLS traffic that is using the MPLS aggregate
labels by enabling NetFlow on the MPLS interface with the ip flow ingress command. For example, to
enable NetFlow for the traffic that is being forwarded based on the MPLS aggregation labels in the VPN
CAM in router PE2 in Figure 2, you must configure the ip flow ingress command on interface
FastEthernet0/0. This is sufficient to populate the cache. To cause the router to export the NetFlow data
to a collector, the flow hardware mpls-vpn ip vrf-id command must be issued in global configuration
mode.
MPLS Aggregate Labels Not in VPN CAM
When the number of MPLS aggregate labels in the network exceeds 511, the VPN CAM is full. Traffic
must be recirculated if it does not use one of the MPLS aggregate labels stored in the VPN CAM. The
packets are processed by the policy feature card (PFC) once to strip the MPLS label, and processed by
the PFC a second time with the VLAN specified as the reserved VPN VLAN that was assigned when the
NDE for VRF Interfaces feature was enabled. The VLAN RAM maps this VLAN to the VPN for use in
routing. The PFC netflow function sees flows as sourced at the reserved VRF VLAN. The ternary content
addressable memory (TCAM) entry for the reserved VLAN interface provides the flow mask to NetFlow.
Flows for MPLS VPN traffic received with aggregate label that is not in the VPN CAM are populated in
the NetFlow cache by configuring the flow hardware mpls-vpn ip vrf-id command for each VPN VRF
on the router in global configuration mode.
MPLS-Specific Labels
For the nonaggregate label case, by definition, the router does not need to examine the underlying IP
packet to determine where to route the packet. In order to cause the IP flows to populate the cache, the
flow hardware mpls-vpn ip vrf-id configuration command must be entered. This causes the specific
label flow traffic to be stripped of its label and recirculated to the reserved VPN VLAN prior to being
forwarded to the exit interface. This introduces more delay in forwarding the traffic than would
otherwise be experienced.
Configuring MPLS VPN Netflow Capture and Export
To ensure that you have enabled the capturing and export of NetFlow data for all of the traffic that you
want to analyze, regardless of the MPLS aggregate label it is using, you should configure the
ip flow ingress command on the MPLS interface and configure the flow hardware mpls-vpn ip vrf-id
command for each VPN VRF on the router in global configuration mode.
Note
The steps required to configure NetFlow data export (NDE) for data in the NetFlow cache are provided
in the “How to Configure NDE for VRF Interfaces for an MPLS VPN” section on page 6.
Cisco IOS NetFlow Configuration Guide
5
NDE for VRF Interfaces
How to Configure NDE for VRF Interfaces for an MPLS VPN
VRF Name as the Source Interface in the NetFlow Cache
For traffic received for an MPLS VPN on an MPLS interface, the source interface for the traffic in the
NetFlow cache is listed as the VPN name, not the physical interface on which the traffic was received.
For example, traffic being received on FastEthernet0/0 on PE2 in Figure 2 will be displayed in the
NetFlow cache on the router as being received over VPN Red, not interface FastEthernet0/0.
How to Configure NDE for VRF Interfaces for an MPLS VPN
Perform this task to configure the NDE for VRF Interfaces feature on an MPLS VPN. This configuration
is appropriate for the router named PE1 in Figure 3. Repeat this task on router PE2 but remember to
change the interface references to the appropriate interfaces for PE2.
Note
This task does not include the commands to configure open shortest path first (OSPF) and border
gateway protocol (BGP) that are required to activate the MPLS VPN between routers PE1 and PE2. See
the “Configuration Examples for NDE for VRF Interfaces” section on page 11 for the complete
configurations for all of the devices in the example network in Figure 3.
Figure 3
Example Network with One MPLS VPN
VRF Red
rd 100:1
rt 100:1
VPN v4 route distribution between PE routers
Performed by multi-protocol BGP
VRF Red
rd 100:1
rt 100:1
OSPF
172.16.1.2/24
FE1/1
10.1.0.2/24
FE0/0
Hosts
CE1
G5/2
10.1.0.1/24
FE0/1
172.16.1.1/24
Lo0 172.20.1.2/32
P1
FE0/0
172.16.2.2/24
PE2
10.2.0.1/24
FE0/1
FE0/1
10.2.0.2/24
Lo0 172.20.1.3/32 Lo0 172.20.1.4/32
CE2
Hosts
Lo0 10.2.2.2/32
230538
Lo0 10.1.1.1/32
PE1
172.16.2.1/24
FE0/0
eBGP or other
routing protocol
iBGP peers
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip vrf vrf-id
4.
rd route-distinguisher
5.
route-target {import | export | both} route-target-ext-community
6.
interface type number
7.
ip address ip-address mask
8.
exit
9.
mpls label protocol {ldp | tdp}
Cisco IOS NetFlow Configuration Guide
6
eBGP or other
routing protocol
NDE for VRF Interfaces
How to Configure NDE for VRF Interfaces for an MPLS VPN
10. mpls ldp router-id type number
11. interface type number
12. ip address ip-address mask
13. mpls ip
14. ip flow ingress
15. interface type number
16. ip vrf forwarding vrf-id
17. ip address ip-address mask
18. exit
19. mls nde sender
20. mls flow ip {interface-destination-source | interface-full}
21. ip flow-export version 9
22. ip flow-export destination {ip-address | hostname} udp-port
23. flow hardware mpls-vpn ip vrf-id
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ip vrf vrf-id
Defines a VPN routing and forwarding (VRF) instance and
enters VRF configuration mode.
Example:
Router(config)# ip vrf red
Step 4
rd route-distinguisher
Creates a routing and forwarding table for a Virtual Private
Network (VPN) routing/forwarding instance (VRF).
Example:
Router(config)# rd 200:2
Step 5
route-target {import | export | both}
route-target-ext-community
Creates a route-target extended community for a VPN VRF.
Example:
Router(config)# route-target both 200:20
Step 6
interface type number
Specifies the interface type and number to configure and
enters interface configuration mode.
Example:
Router(config)# interface loopback 0
Cisco IOS NetFlow Configuration Guide
7
NDE for VRF Interfaces
How to Configure NDE for VRF Interfaces for an MPLS VPN
Step 7
Command or Action
Purpose
ip address ip-address mask
Configure an IP address on the interface.
Example:
Router(config-if)# ip address 172.20.1.2
255.255.255.0
Step 8
Exits interface configuration mode and returns to global
configuration mode.
exit
Example:
Router(config-if)# exit
Step 9
mpls label {ldp | tdp}
Specifies the MPLS label distribution protocol.
Example:
Router(config)# mpls label protocol ldp
Step 10
mpls ldp router-id type number
Specifies a preferred interface for determining the Label
Distribution Protocol (LDP) router ID.
Example:
Router(config)# mpls ldp router-id loopback0
Step 11
interface type number
Specifies the interface type and number to configure and
enters interface configuration mode.
Example:
Router(config-if)# interface fastethernet1/1
Step 12
ip address ip-address mask
Configures an IP address on the interface.
Example:
Router(config-if)# ip address 172.16.1.2
255.255.255.0
Step 13
mpls ip
Enables MPLS forwarding of IPv4 packets along normally
routed paths for a particular interface.
Example:
Router(config-if)# mpls ip
Step 14
ip flow ingress
Enables NetFlow on the interface to capture traffic that is
being received by the interface.
Example:
Router(config-if)# ip flow ingress
Step 15
interface type number
Specifies the interface type and number to configure and
enters interface configuration mode.
Example:
Router(config)# interface GigabitEthernet5/2
Step 16
ip vrf forwarding vrf-id
Example:
Router(config-if)# ip vrf forwarding red
Cisco IOS NetFlow Configuration Guide
8
Associates a VPN VRF with an interface or subinterface.
NDE for VRF Interfaces
How to Configure NDE for VRF Interfaces for an MPLS VPN
Step 17
Command or Action
Purpose
ip address ip-address mask
Configure an IP address on the interface.
Example:
Router(config-if)# ip address 10.1.0.1
255.255.255.0
Step 18
Exits interface configuration mode and returns to global
configuration mode.
exit
Example:
Router(config-if)# exit
Step 19
mls nde sender
Enables NetFlow on the PFC.
Example:
Router(config)# mls nde sender
Step 20
mls flow ip {interface-destination-source |
interface-full}
Specifies the NetFlow flow mask for IP traffic.
Example:
Router(config)# mls flow ip
interface-destination-source
Step 21
ip flow-export version 9
Configures NetFlow data export to use the version 9 export
format.
Example:
Router(config)# ip flow-export version 9
Step 22
ip flow-export destination {ip-address |
hostname} udp-port
Example:
Configures the IP address or hostname of the workstation to
which you want to send the NetFlow information and the
number of the UDP port on which the workstation is
listening for this input.
Router(config)# ip flow-export destination
172.16.2.6 99
Step 23
flow hardware mpls-vpn ip vrf-id
Enables the NDE for VRF Interfaces feature for the VRF.
Example:
Router(config)# flow hardware mpls-vpn ip red
Examples
The following output of the show mls nde command displays the NDE configuration and statistics.
PE1# show mls nde
Netflow Data Export enabled
Exporting flows to 172.16.2.6 (99)
Exporting flows from 172.16.1.2 (51203)
Version: 9
Layer2 flow creation is disabled
Layer2 flow export is disabled
Include Filter not configured
Exclude Filter not configured
Total Netflow Data Export Packets are:
4 packets, 0 no packets, 19 records
Total Netflow Data Export Send Errors:
Cisco IOS NetFlow Configuration Guide
9
NDE for VRF Interfaces
How to Configure NDE for VRF Interfaces for an MPLS VPN
IPWRITE_NO_FIB = 0
IPWRITE_ADJ_FAILED = 0
IPWRITE_PROCESS = 0
IPWRITE_ENQUEUE_FAILED = 0
IPWRITE_IPC_FAILED = 0
IPWRITE_OUTPUT_FAILED = 0
IPWRITE_MTU_FAILED = 0
IPWRITE_ENCAPFIX_FAILED = 0
Netflow Aggregation Disabled
PE1#
The following output of the show mls netflow ip module command displays the Netflow entries in the
PFC. The first row of output shows traffic on VPN red.
Note
Module 5 is the active supervisor 720 on this Cisco 7600 series router.
Router# show mls netflow ip module 5
Displaying Netflow entries in module 5
DstIP
SrcIP
Prot:SrcPort:DstPort Src i/f
:AdjPtr
----------------------------------------------------------------------------Pkts
Bytes
Age
LastSeen Attributes
--------------------------------------------------10.1.1.1
10.2.0.2
0
:0
:0
vpn:red
:0x0
504
398020
1
23:20:48
L3 - Dynamic
224.0.0.5
172.16.1.1
89 :0
:0
Fa1/1
:0x0
1
84
7
23:20:42
L2 - Dynamic
0.0.0.0
0.0.0.0
0
:0
:0
-:0x0
2238
1582910
33
23:20:48
L3 - Dynamic
224.0.0.2
172.16.1.1
udp :646
:646
Fa1/1
:0x0
5
310
21
23:20:46
L2 - Dynamic
172.16.2.6
172.16.1.2
0
:0
:0
Fa1/1
:0x0
1
140
22
23:20:27
L2 - Dynamic
Router#
The following output of the show ip cache flow command displays the data in the NetFlow cache. The
last line of data in the output shows that the source interface for this traffic is VPN Red.
PE1# show ip cache flow
------------------------------------------------------------------------------MSFC:
IP packet size distribution (3139 total packets):
1-32
64
96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .685 .309 .000 .000 .000 .000 .003 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
2 active, 4094 inactive, 56 added
20904 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 33992 bytes
0 active, 1024 inactive, 4 added, 4 added to flow
0 alloc failures, 0 force free
1 chunk, 2 chunks added
last clearing of statistics never
Cisco IOS NetFlow Configuration Guide
10
NDE for VRF Interfaces
Configuration Examples for NDE for VRF Interfaces
Protocol
-------TCP-BGP
TCP-other
UDP-other
IP-other
Total:
SrcIf
Fa1/1
Fa1/1
Total
Flows
10
6
28
6
50
SrcIPaddress
172.16.1.1
172.16.1.1
Flows
/Sec
0.0
0.0
0.0
0.0
0.0
Packets Bytes
/Flow /Pkt
1
49
2
49
74
63
153
80
60
68
DstIf
Null
Null
Packets Active(Sec) Idle(Sec)
/Sec
/Flow
/Flow
0.0
0.0
15.3
0.0
4.5
15.5
0.1
320.5
12.7
0.0
1488.3
1.7
0.2
358.6
12.2
DstIPaddress
224.0.0.2
224.0.0.5
Pr SrcP DstP
11 0286 0286
59 0000 0000
Pkts
74
33
------------------------------------------------------------------------------PFC:
Displaying Hardware entries in Module 5
SrcIf
SrcIPaddress
DstIPaddress
Fa1/1
172.20.1.2
172.20.1.3
Fa1/1
172.20.1.3
172.20.1.2
Fa1/1
172.16.1.2
172.16.2.6
Fa1/1
172.16.1.1
224.0.0.2
-0.0.0.0
0.0.0.0
vpn:red
10.2.0.2
10.1.1.1
.
.
.
PE1#
Pr
0
0
0
udp
0
0
SrcP
0
0
0
646
0
0
Dss
0
0
0
64
0
0
Configuration Examples for NDE for VRF Interfaces
The following configuration example shows how to configure a simple network topology with the NDE
for VRF Interfaces feature configured on two PE routers.
This section contains the following example configurations:
•
Configurations for the Example Network with One MPLS VPN: Example, page 11
•
Configuring the NDE for VRF Interfaces Feature on a VRF: Example, page 15
Configurations for the Example Network with One MPLS VPN: Example
This section contains the configurations for all of the devices in Figure 3. The NDE for VRF Interfaces
feature is configured on routers PE1 and PE2.
CE1
!
hostname CE1
!
ip cef
!
interface Loopback0
no shutdown
ip address 10.1.1.1 255.255.255.255
!
interface FastEthernet0/0
no shutdown
ip address 10.1.0.2 255.255.255.0
!
Cisco IOS NetFlow Configuration Guide
11
NDE for VRF Interfaces
Configuration Examples for NDE for VRF Interfaces
ip default-network 0.0.0.0
ip route 0.0.0.0 0.0.0.0 10.1.0.1
!
end
PE1
!
hostname PE1
!
ip cef distributed
!
mls nde sender
mls flow ip interface-destination-source
ip flow-export destination 172.16.2.6 99
ip flow-export version 9
!
ip vrf red
rd 200:2
route-target export 200:20
route-target import 200:20
!
flow hardware mpls-vpn ip red
!
multilink bundle-name authenticated
mpls label protocol ldp
!
interface Loopback0
ip address 172.20.1.2 255.255.255.255
!
interface gigabitEthernet5/2
no shutdown
ip vrf forwarding red
ip address 10.1.0.1 255.255.255.0
!
interface FastEthernet1/1
no shutdown
interface FastEthernet1/1
ip address 172.16.1.2 255.255.255.0
ip flow ingress
mpls ip
!
router ospf 100
router-id 172.20.1.2
log-adjacency-changes
network 172.16.0.0 0.0.255.255 area 0
network 172.20.1.2 0.0.0.0 area 0
!
router bgp 200
no synchronization
bgp log-neighbor-changes
network 172.0.0.0 mask 255.0.0.0
neighbor as200 peer-group
neighbor as200 remote-as 200
neighbor as200 description as200
neighbor as200 update-source Loopback0
neighbor as200 route-reflector-client
neighbor 172.20.1.4 remote-as 200
neighbor 172.20.1.4 description iBGP with r4
neighbor 172.20.1.4 update-source Loopback0
no auto-summary
!
address-family vpnv4
Cisco IOS NetFlow Configuration Guide
12
NDE for VRF Interfaces
Configuration Examples for NDE for VRF Interfaces
neighbor 172.20.1.4 activate
neighbor 172.20.1.4 send-community both
exit-address-family
!
address-family ipv4 vrf red
no synchronization
network 10.1.0.0 mask 255.255.255.0
network 10.1.1.1 mask 255.255.255.255
exit-address-family
!
ip route 172.0.0.0 255.0.0.0 Null0
ip route vrf red 10.1.1.1 255.255.255.255 10.1.0.2
!
mpls ldp router-id Loopback0
!
end
P1
!
hostname P1
!
ip cef
!
no ip domain lookup
!
mpls label protocol ldp
!
interface Loopback0
no shutdown
ip address 172.20.1.3 255.255.255.255
!
interface FastEthernet0/0
no shutdown
ip address 172.16.2.1 255.255.255.0
mpls ip
!
interface FastEthernet0/1
no shutdown
ip address 172.16.1.1 255.255.255.0
mpls ip
!
router ospf 100
router-id 172.20.1.3
log-adjacency-changes
network 172.16.0.0 0.0.255.255 area 0
network 172.20.1.3 0.0.0.0 area 0
!
mpls ldp router-id Loopback0
!
end
PE2
!
hostname PE2
!
ip cef distributed
!
mls nde sender
mls flow ip interface-destination-source
ip flow-export destination 172.16.2.6 99
ip flow-export version 9
!
Cisco IOS NetFlow Configuration Guide
13
NDE for VRF Interfaces
Configuration Examples for NDE for VRF Interfaces
ip vrf red
rd 200:2
route-target export 200:20
route-target import 200:20
!
flow hardware mpls-vpn ip red
!
multilink bundle-name authenticated
mpls label protocol ldp
!
interface Loopback0
no shutdown
ip address 172.20.1.4 255.255.255.255
!
interface FastEthernet0/0
no shutdown
ip address 172.16.2.2 255.255.255.0
mpls ip
ip flow ingress
!
interface FastEthernet0/1
no shutdown
ip vrf forwarding red
ip address 10.2.0.1 255.255.255.0
!
router ospf 100
router-id 172.20.1.4
log-adjacency-changes
network 172.16.0.0 0.0.255.255 area 0
network 172.20.1.4 0.0.0.0 area 0
!
router bgp 200
no synchronization
bgp log-neighbor-changes
network 172.0.0.0 mask 255.0.0.0
neighbor as200 peer-group
neighbor as200 remote-as 200
neighbor as200 description as200
neighbor as200 update-source Loopback0
neighbor as200 route-reflector-client
neighbor 172.20.1.2 remote-as 200
neighbor 172.20.1.2 description iBGP with r2
neighbor 172.20.1.2 update-source Loopback0
no auto-summary
!
address-family vpnv4
neighbor 172.20.1.2 activate
neighbor 172.20.1.2 send-community both
exit-address-family
!
address-family ipv4 vrf red
no synchronization
network 10.2.0.0 mask 255.255.255.0
network 10.2.2.2 mask 255.255.255.255
exit-address-family
!
ip route 172.0.0.0 255.0.0.0 Null0
ip route vrf red 10.2.2.2 255.255.255.255 10.2.0.2
!
mpls ldp router-id Loopback0
!
end
Cisco IOS NetFlow Configuration Guide
14
NDE for VRF Interfaces
Where to Go Next
CE2
!
hostname CE2
!
ip cef
!
interface Loopback0
no shutdown
ip address 10.2.2.2 255.255.255.255
!
interface FastEthernet0/1
no shutdown
ip address 10.2.0.2 255.255.255.0
!
ip default-network 0.0.0.0
ip route 0.0.0.0 0.0.0.0 10.2.0.1
!
end
Configuring the NDE for VRF Interfaces Feature on a VRF: Example
This example configuration shows how to configure the NDE for VRF Interfaces feature for a VRF.
When you enable NetFlow on interface GigabitEthernet2/3 with the ip flow ingress command, the
NetFlow cache will contain information for traffic for VPN vpn1.
PE1
!
ip vrf vpn1
rd 100:1
route-target export 100:1
route-target import 100:1
!
mls flow ip interface-full
!
interface GigabitEthernet2/3
ip vrf forwarding vpn1
ip address 10.0.0.1 255.0.0.0
ip flow ingress
!
interface GigabitEthernet2/7
ip vrf forwarding vpn1
ip address 172.16.20.1 255.255.255.0
!
ip flow-export version 9
ip flow-export destination 192.168.10.2 20000
end
Where to Go Next
•
See the Configuring NetFlow and NDE chapter of the Cisco 7600 Series Cisco IOS Software
Configuration Guide, for more information on configuring NetFlow features on Cisco 7600 series
routers.
Cisco IOS NetFlow Configuration Guide
15
NDE for VRF Interfaces
Additional References
•
See the Configuring PFC3BXL and PFC3B Mode Multiprotocol Label Switching (MPLS) chapter
of the Cisco 7600 Series Cisco IOS Software Configuration Guide, for more information on
configuring MPLS features on Cisco 7600 series routers.
Additional References
The following sections provide references related to the NDE for VRF Interfaces feature.
Related Documents
Related Topic
Document Title
NetFlow commands, complete command syntax,
command mode, defaults, command history, usage
guidelines, and examples.
Cisco IOS NetFlow Command Reference
Information for configuring NetFlow, MPLS, and other Cisco 7600 Series Cisco IOS Software Configuration Guide
features on Cisco 7600 series routers.
Standards
Standard
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIB
MIBs Link
No new or modified MIBS are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFC
Title
No new or modified RFCs are supported by this
feature, and support for existing RFCs has not been
modified by this feature.
—
Cisco IOS NetFlow Configuration Guide
16
NDE for VRF Interfaces
Feature Information for NDE for VRF Interfaces
Technical Assistance
Description
Link
The Cisco Support website provides extensive online http://www.cisco.com/techsupport
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies. Access to most tools
on the Cisco Support website requires a Cisco.com user
ID and password. If you have a valid service contract
but do not have a user ID or password, you can register
on Cisco.com.
Feature Information for NDE for VRF Interfaces
Table 1 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a
specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support.
Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images
support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 1
Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for NDE for VRF Interfaces
Feature Name
Releases
Feature Information
NDE for VRF Interfaces
12.2(33)SRB
15.0(1)S
The NDE support for VRF interfaces features enables
capturing and exporting NetFlow flow information from VRF
interfaces.
In 12.2(33)SRB, this feature was introduced on the Cisco
7600 series routers.
The following sections provide information about this
feature:
•
Information About NDE for VRF Interfaces, page 2
•
How to Configure NDE for VRF Interfaces for an MPLS
VPN, page 6
The following commands were introduced or modified by
this feature: flow hardware mpls-vpn ip, show ip cache
flow, show ip cache flow aggregation, show mls netflow ip.
Cisco IOS NetFlow Configuration Guide
17
NDE for VRF Interfaces
Feature Information for NDE for VRF Interfaces
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks
can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word
partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental.
© 2005–2010 Cisco Systems, Inc. All rights reserved.
Cisco IOS NetFlow Configuration Guide
18