Spotting “The Churn”
Two steps to ID the churn in your network
1 – Run “show ip route bgp | include , 00:00” once every 60 seconds for ~5 minutes. This will give you a list of routes that have changed within the past minute. If a route is changing every minute then there is a good chance it is churning.
Router#show ip route bgp | include , 00:00
B 2.6.4.0/22 [200/1] via 8.3.4.18, 00:00:32
B 3.8.6.0/23 [200/1] via 7.5.2.5, 00:00:58
Router#
Wait 60 seconds…
Router#show ip route bgp | include , 00:00
B 17.6.7.0/24 [200/1] via 7.5.2.12, 00:00:17
B 3.8.6.0/23 [200/1] via 7.5.2.5, 00:00:57
Router#
3.8.6.0/23 has changed twice in the last 2 minutes. It is possible that this prefix is churning.