Enable netflow statistics on a Cisco router

Introduction

OptiView XG is NOT a NetFlow collector, but it is possible to querry a Cisco routers for network flow based statistics.  The data (top-n) will be available under Device Details or in Application Infrastrcture Tests.  In order to do so, the router first must be configured correctly.

 

Solution
This example has been tested with a CISCO router model 1911 running IOS version 15.  For more information about the commands used in this script, contact you CISCO partner.  
At this time, we consider that SNMP read-only access to the router has already been established and the community has sufficient view rights.

 

1: Enter Global Configuration Mode

Add the following commands to the global configuration section of the router: 

Note: the flow export destination address is not important, but you must enable flow exports in order to populate the flow top-talker list. 

• conf t
• ip flow-cache timeout active 1
• ip flow-cache timeout inactive 14
• ip flow-export source GigabitEthernet0/1
• ip flow-export version 9
• ip flow-export destination 127.0.0.1 2055
• ip flow-top-talkers
• top 100
• sort-by bytes
• cache-timeout 300000
• exit
• wr mem

 

2: Enter Interface Configuration Mode

Note: This is a general applicable but not the only way for enabling NetFlow exports per interface.  Please read your Cisco documentation for more information on how to configure NetFlow.

Add the following command to the interface configuration section of all interfaces carrying traffic.  There are at least two interfaces that carry traffic, one facing the network, one facing the site.  These may be physical interfaces or virtual interfaces like sub-interfaces, dialers or tunnels.  

• conf t
• interface <interface name>
• ip flow egress
• exit
• wr mem

3: Debug

• Use the IOS command sh ip flow export and check if any flows are exported
• Use the IOS command sh ip flow top-talkersand check if the top-talker list is populated