Cisco asr top talkers

I got a request from a friend to describe the Netflow top talkers feature.
Netflow is a Cisco proprietary protocol that is used to see which
protocols are used in your network and how much traffic they are generating.

Netflow uses a tuple of source IP, destination IP, source port number,
destination port number and protocol number to define a session.

Based on
this we can use the top talkers feature to see which IPs are generating
most traffic in our network.

To demonstrate this I have setup a really simple network with two routers
R1 and R2. They are running OSPF simply so that I can source traffic from
different loopbacks from R1.

This is the routing table of R2:

R2#sh ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/11] via 12.12.12.1, 00:11:41, FastEthernet0/0 111.0.0.0/32 is subnetted, 1 subnets O 111.111.111.111 [110/11] via 12.12.12.1, 00:11:01, FastEthernet0/0 11.0.0.0/32 is subnetted, 1 subnets O 11.11.11.11 [110/11] via 12.12.12.1, 00:11:11, FastEthernet0/0

So now we will activate Netflow on R2 and also configure the top talkers feature.

R2(con

wireshark show top talkers

show flow top talkers