It is possible to log neighbor state changes to a UNIX syslog server. This is extremely useful for most syslog-based monitoring systems because it gives early warning of problems with iBGP peers, and more especially external BGP neighbors. The logging is enabled by the following commands:
router bgp 109 bgp log-neighbor-changes
Note that, as of IOS Software Releases 12.1(4) and 12.0(12)ST, the default action is to log all BGP neighbor changes (see DDTS CSCdm59903). At time of writing, the default was not yet included in iOs Software Release 12.0s.
Also note that, as of CSCdr54231, BGP notification messages are included when bgp log-neighbor-changes is configured. Before CSCdr54231, the only way to see these messages was to enable debug ip bgp, which was a bit limiting for most ISPs! This alteration has been included in IOS Software Releases from 12.0(10)S3, 12.1(3), and 11.1(34)CC.
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