Getting Started with Configuring NetFlow and NetFlow Data Export

Table Of Contents

Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export

Contents

Prerequisites for Configuring NetFlow and NetFlow Data Export

Restrictions for Configuring NetFlow and NetFlow Data Export

NetFlow Data Capture

NetFlow Data Export

Information About Configuring NetFlow and NetFlow Data Export

NetFlow Data Capture

NetFlow Flows: Key Fields

NetFlow Data Export Using the Version 9 Export Format

How to Configure NetFlow and NetFlow Data Export

Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format

Verify that NetFlow is Operational and View NetFlow Statistics

Verifying that NetFlow Data Export is Operational

Configuration Examples for Configuring NetFlow and NetFlow Data Export

Configuring Egress NetFlow Accounting: Example

Configuring NetFlow Subinterface Support: Example

Configuring NetFlow Multiple Export Destinations: Example

Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format

Configure NetFlow for Analyzing PPPoE Session Traffic

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Glossary

Feature Information for Configuring NetFlow and NetFlow Data Export

Getting Started with Configuring Cisco IOS NetFlow and NetFlow Data Export

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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 the "Configuring NetFlow and NetFlow Data Export" module.

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.

Module History

This module was first published on February 5th, 2006, and last updated on September 5th, 2006.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all features. To find information about feature support and configuration, use the "Feature Information for Configuring NetFlow and NetFlow Data Export" section.

Contents

•Prerequisites for Configuring NetFlow and NetFlow Data Export

•Restrictions for Configuring NetFlow and NetFlow Data Export

•Information About Configuring NetFlow and NetFlow Data Export

•How to Configure NetFlow and NetFlow Data Export

•Configuration Examples for Configuring NetFlow and NetFlow Data Export

•Additional References

•Glossary

•Feature Information for Configuring NetFlow and NetFlow Data Export

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.

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Note In Cisco IOS 12.2S releases, egress NetFlow captures either IPv4 or MPLS packets as they leave the router.

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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

•NetFlow Flows: Key Fields

•NetFlow Data Export Using the Version 9 Export Format

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.

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 (required)

•Verify that NetFlow is Operational and View NetFlow Statistics (optional)

•Verifying that NetFlow Data Export is Operational (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

1. enable

2. configure terminal

3. ip flow-export destination {{ip-address | hostname} udp-port}

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

	Command or Action	Purpose
Step 1	enable Example: Router> enable	(Required) Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	(Required) Enters global configuration mode.
Step 3	ip flow-export destination {{ip-address | hostname} udp-port} Example: Router(config)# ip flow-export destination 172.16.10.2 99	(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. Note The workstation is running an application such as NetFlow Collection Engine (NFC) that is used to analyze the exported data.
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 Example: Router(config)# ip flow-export version 9	(Optional) Enables the export of information in NetFlow cache entries. •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.
Step 6	interface interface-type interface-number Example: Router(config)# interface ethernet 0/0	(Required) Specifies the interface that you want to enable NetFlow on and enters interface configuration mode.
Step 7	ip flow {ingress | egress} Example: Router(config-if)# ip flow ingress or Example: Router(config-if)# ip flow 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.
Step 8	exit Example: Router(config-if)# exit	(Optional) Exits interface configuration mode and returns to global configuration mode. Note 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 Example: Router(config-if)# end	(Required) Exits the current configuration mode and returns to privileged EXEC mode.

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

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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)

--------         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         SrcIPaddress    DstIf         DstIPaddress    Pr SrcP DstP  Pkts

Et0/0         192.168.67.6    Et1/0.1       172.16.10.200   01 0000 0C01    51 

Et0/0         10.10.18.1      Null          172.16.11.5     11 0043 0043    51 

Et0/0         10.10.18.1      Null          172.16.11.5     11 0045 0045    51 

Et0/0         10.234.53.1     Et1/0.1       172.16.10.2     01 0000 0800    51 

Et0/0         10.10.19.1      Null          172.16.11.6     11 0044 0044    51 

Et0/0         10.10.19.1      Null          172.16.11.6     11 00A2 00A2    51 

Et0/0         192.168.87.200  Et1/0.1       172.16.10.2     06 0014 0014    50 

Et0/0         192.168.87.200  Et1/0.1       172.16.10.2     06 0015 0015    52 

.

.

.

Et0/0         172.16.1.84     Et1/0.1       172.16.10.19    06 0087 0087    50 

Et0/0         172.16.1.84     Et1/0.1       172.16.10.19    06 0050 0050    51 

Et0/0         172.16.1.85     Et1/0.1       172.16.10.20    06 0089 0089    49 

Et0/0         172.16.1.85     Et1/0.1       172.16.10.20    06 0050 0050    50 

Et0/0         10.251.10.1     Et1/0.1       172.16.10.2     01 0000 0800    51 

Et0/0         10.162.37.71    Null          172.16.11.3     06 027C 027C    49 

Router#

Step 3 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

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          SrcIPaddress    DstIf          DstIPaddress    Pr TOS Flgs  Pkts

Port Msk AS                    Port Msk AS    NextHop              B/Pk  Active

Et0/0          192.168.67.6    Et1/0.1        172.16.10.200   01 00  10     799 

0000 /0  0                     0C01 /0  0     0.0.0.0                28  1258.1

Et0/0          10.10.18.1      Null           172.16.11.5     11 00  10     799 

0043 /0  0                     0043 /0  0     0.0.0.0                28  1258.0

Et0/0          10.10.18.1      Null           172.16.11.5     11 00  10     799 

0045 /0  0                     0045 /0  0     0.0.0.0                28  1258.0

Et0/0          10.234.53.1     Et1/0.1        172.16.10.2     01 00  10     799 

0000 /0  0                     0800 /0  0     0.0.0.0                28  1258.1

Et0/0          10.10.19.1      Null           172.16.11.6     11 00  10     799 

0044 /0  0                     0044 /0  0     0.0.0.0                28  1258.1

.

.

.

Et0/0          172.16.1.84     Et1/0.1        172.16.10.19    06 00  00     799 

0087 /0  0                     0087 /0  0     0.0.0.0                40  1258.1

Et0/0          172.16.1.84     Et1/0.1        172.16.10.19    06 00  00     799 

0050 /0  0                     0050 /0  0     0.0.0.0                40  1258.0

Et0/0          172.16.1.85     Et1/0.1        172.16.10.20    06 00  00     798 

0089 /0  0                     0089 /0  0     0.0.0.0                40  1256.5

Et0/0          172.16.1.85     Et1/0.1        172.16.10.20    06 00  00     799 

0050 /0  0                     0050 /0  0     0.0.0.0                40  1258.0

Et0/0          10.251.10.1     Et1/0.1        172.16.10.2     01 00  10     799 

0000 /0  0                     0800 /0  0     0.0.0.0              1500  1258.1

Et0/0          10.162.37.71    Null           172.16.11.3     06 00  00     798 

027C /0  0                     027C /0  0     0.0.0.0                40  1256.4

Router#

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

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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

•Configuring NetFlow Subinterface Support: Example

•Configuring NetFlow Multiple Export Destinations: Example

•Configure NetFlow and NetFlow Data Export Using the Version 9 Export Format

•Configure NetFlow for Analyzing PPPoE Session Traffic

Configuring Egress NetFlow Accounting: Example

The following example shows how to configure Egress NetFlow Accounting:

configure terminal

!

interface ethernet 0/0

 ip flow egress

!

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

•NetFlow SubInterface Support for egress (transmitted) traffic on a subinterface

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

!

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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.

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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.

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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

!

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 Cisco IOS NetFlow Configuration Guide 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 MPLS-aware NetFlow	"Configuring MPLS-aware NetFlow"
Tasks for configuring MPLS egress NetFlow accounting	"Configuring MPLS Egress NetFlow Accounting"
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 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 CNS NetFlow Collection Engine	"Cisco CNS NetFlow Collection Engine User's Guide, 5.0"

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 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.	http://www.cisco.com/techsupport

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.

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Note Refer to the Cisco Dictionary of Internetworking Terms and Acronyms for terms not included in this glossary.

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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" 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.

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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.

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Table 1 Feature Information for Configuring NetFlow and NetFlow Data Export 

Feature Name	Releases	Feature Configuration Information
Egress NetFlow Accounting	12.3(11)T	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" module. 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" module. 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	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" module. 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	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" module. The following commands were modified by this feature: debug ip flow export, export, ip flow-export, and show ip flow export.

Copyright © 2006 Cisco Systems, Inc. All rights reserved
This module first published February 5th, 2006. Last updated September 5th, 2006