regular expression _154$ and ^154$

Requirement : Part of the acquisition agreement between AS 300 and AS 200 includes stipulations on what traffic AS 300 will provide transit for.

This agreement states that AS 300 will not provide transit for traffic coming from AS 60 and its customers, that is destined for AS 154. Configure AS 300 to reflect this policy

Configuration: router bgp 300 neighbor 204.12.1.154 route-map STOP_TRANSIT_TO_AS_154 out ! ip as-path access-list 5 permit _154$ ! route-map STOP_TRANSIT_TO_AS_154 deny 20 match as-path 5 ! route-map STOP_TRANSIT_TO_AS_154 permit 30

In the configuration above ,can we configure regular expression _154$ as ^154$ ?

Reply to
zillah
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The ^ is the beginning of an AS PATH.

The _ is a space.

So, the _154$ means anything originating FROM AS 154, but having passed through ANOTHER AS.

If it were ^154$, it would only cover stuff that originated from AS 154 AND was directly connected to your AS.

Jonathan

Reply to
Jonathan

Thanks Jonathan, sory for my late reply, but as you know there is no email notification.

Reply to
zillah

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