Log Neighbor Changes

Load isis.cfg

#IOS-XE
config replace flash:isis.cfg

#IOS-XR
configure
load bootflash:isis.cfg
commit replace
y

Configure R1 so that when Gi2.12 is manually shut down, the following log message appears:

Configure R2 so that when Gi2.12 on R1 is shut down, no log message appears at all.

Answer

#R1
router isis
 log-adjacency-changes all

#R2
router isis
 no log-adjacency-changes

Explanation

By default, log-adjacency-changes is enabled. However, this only logs adjacency changes that are detected through the ISIS Hello. If the interface goes down, the adjacency is lost based on the interface, not the missing Hellos, so no log is generated. If we use the all keyword, it will log all adjacency changes, even those caused by non-Hello events.

On R2, we will lose the R1 neighbor based on lost Hellos. The default setting on this version of IOS-XE appears to be log-adjacency-changes. So if we disable this, R2 will not see any log messages when any neighbors are lost.