IPv6 Training (Cisco) Using the “bgp log-neighbor-changes” Command

The “bgp log-neighbor-changes" command

By Charles Ross CCNP #CSCO10444244

Network administrators (like you) use the Cisco IOS “Router” configuration command named “bgp log-neighbor-changes” on BGP routers; to enable (allow) those routers to log their BGP neighbor(s) resets.

Another way of explaining it is; a network administrator will type (use) the “bgp log-neighbor-changes” “Router” configuration command on a BGP router, if he or she wants that particular router to be able to log its BGP neighbors (Peers) status changes, the status changes are up, down, and reset.

As you may have already started to figure out; the “bgp log-neighbor-changes” “Router” configuration command, is mainly used for troubleshooting purposes. It can be used to identify network connectivity problems and also measure network stability.

And, unlike the BGP “debug” commands, the “bgp log-neighbor-changes” “Router” configuration command does not cause a significant performance impact to a network which is a very good thing.

Now, if a UNIX syslog facility is enabled on the BGP network; the BGP log messages will be sent to the UNIX host that is running the syslog daemon, so the BGP messages can be stored and archived on the Unix host disk. But, if a UNIX syslog facility is not enabled on the BGP network, then the status change BGP messages are retained inside the internal buffer of the particular BGP router, and are not stored to disk.

Network administrators (like you) can set the size of the internal buffer, which is dependent upon the available RAM, by using the logging buffered command. Now, if the “bgp log-neighbor-changes” “Router” configuration command is not enabled on a BGP router, that router will not log (track) its BGP neighbors (Peers) up and down status change messages, but it will log (track) its BGP neighbors (Peers) reset status change messages; and the two IOS commands that can be used to view those reset status change messages are show ip bgp neighbors and show bgp ipv6 neighbors.

Here is the correct syntax for the “bgp log-neighbor-changes” command:

router(config-router)# bgp log-neighbor-changes

And, if you want to disable the logging of changes in BGP neighbor adjacencies on a particular router; all you need to do is type the word “no” in front of the command like you see in the example below:

router(config-router)#no bgp log-neighbor-changes

I hope this article was very informative and helped you quickly understand the usage of the “bgp log-neighbor-changes” command. If you need to learn more about the command; I suggest you visit my website, were you’ll find the latest information regarding Cisco IPv6 Design and Implementation Techniques.

To your success,

Charles Ross

CCNP #CSCO10444244