CCIE Pursuit Blog

March 20, 2008

Cisco IOS Hints and Tips: Filtering Gotcha With ‘neighbor local-as’

Cisco IOS Hints and Trickshas a nice post concerning one of the possible “gotchas” of using the neighbor local-as command (without the no-prepend option):

Local-AS has to be matched by incoming filter-list
 
In a previous post I’ve described how you can use neighbor local-as feature to fix AS-number mismatch between adjacent autonomous systems. However, without additional options, the local-as is inserted in the AS-path of incoming BGP updates before any inbound filters. Your inbound filters thus have to match the local-as as well.

—Read The Rest Here—

Cisco Command Reference:

neighbor local-as

To customize the AS_PATH attribute for routes received from an external Border Gateway Protocol (eBGP) neighbor, use the neighbor local-as command in address family or router configuration mode. To disable AS_PATH attribute customization, use the no form of this command.

neighbor ip-address local-as as-number [no-prepend [replace-as [dual-as]]]

no neighbor ip-address local-as as-number

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