Enable netflow statistics on a Cisco router

Introduction

OptiView XG is NOT a NetFlow collector, but it is possible to have OptiView poll a Cisco router for IP flow based network statistics. The results (top-n) are available on the OptiView under Device Details or in Application Infrastrcture Tests. In order to do this, routers in your network must be configured correctly.

 

 

Solution

This configuration example has been tested with a CISCO router model 1911 running IOS version 15. For more information about the commands used in this script, read the router's IOS specific manual. We consider SNMP read-only access to the router already being properly configured and the community has sufficient view rights on the relevant MIBs.

Global Configuration Mode

You must enable flow exports in order to get the top counter tables populated.

Enter Global Configuration Mode on the router and add the following commands to the configuration. Substitute <SourceInterface> and <DestinationAddress> with the appropriate values.

conf t
ip flow-cache timeout active 1
ip flow-cache timeout inactive 14
ip flow-export source <SourceInterface>
ip flow-export version 9
ip flow-export destination <DestinationAddress> 2055
ip flow-top-talkers 
top 100
sort-by bytes
cache-timeout 300000
exit
exit
ip flow-top-applications
top 100 
sort-by bytes 
cache-timeout 300000 
exit 
wr mem

Interface Configuration Mode

This is a common yet not unique way to enable NetFlow exports for interfaces. Please read your router's IOS specific manual for more information on how to configure NetFlow on a per interface basis.

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 and one facing the site. These can be physical or virtual interfaces like sub -, dialer - and tunnel interfaces.

conf t
interface <InterfaceName>
ip flow egress
exit 
wr mem

Debug

Still in priviledges mode, use the following commands to verify flow exports and population of the top counters

sh ip flow export
sh ip flow top-talkers
sh ip flow top-applications