During an INE Volume II lab I discovered a great way to filter the debug output from a router. The Debug Condition Interface command allows you to only show the debug output from a specific interface.
There are other conditions you can filter on as well including application, mac-address, vlan and there are a number of voice related commands which I am not interested in at this time.
For this example I had to configure OSPF to use unicast and not multicast, I then had to verify this was working, so I considered using an access list, and then discovered the debug condition command.
To filter the debug output to only interface fa0/1 use the following command
Rack6R5#debug condition interface fa0/1 Condition 1 set
To then filter this even more we are going to filter to only ospf hello’s
Rack6R5#debug ip ospf hello OSPF hello events debugging is on
The output from this is now a very filtered view of exaclty what I want to see
Rack6R5# *Mar 1 00:59:01.573: OSPF: Rcv hello from 220.127.116.11 area 45 from FastEthernet0/1 18.104.22.168 *Mar 1 00:59:01.573: OSPF: End of hello processing