Re : Accurate monitoring of IN / OUT Traffic

Hi Sumit,

You have referred the correct link. That explains how to use the commands on the interface. In the router supports "egress" we always recommend ip flow egress enabled on all the router. Also, multiple netflow commands on the same interface will give double counted information. There should not be any other NetFlow commands like 'ip route-cache flow' or 'ip flow ingress' on the interface. Also, please make sure that "ip flow egress" is applied on all active interfaces. 

A brief on each NetFlow enabling command is below:

ip route-cache flow:
Used in older IOS - New IOS do not support this command.
Captures IN traffic of the interface its applied on. ie. Does INGRESS NetFlow accounting
Has to be applied only on the main interface. Sub-interfaces will automatically be enabled with INGRESS NetFlow accounting.

ip flow ingress:
Used in new IOS
Captures IN traffic of the interface its applied on. ie. Does INGRESS NetFlow accounting
Has to be applied on each L3 interface including sub-interface to enable INGRESS NetFlow accounting.

ip flow egress:
Used in new IOS
Captures the OUT traffic for the interface its applied on. ie. Does EGRESS NetFlow accounting
Has to be applied on each L3 interface including sub-interface to enable EGRESS NetFlow accounting.

Regrading the version of NetFlow commands:
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

Thanks and Regards
Praveen Manohar
NetFlow Analyzer TAC.