prcheck - cisco as-path lists generation
- Date: Wed, 5 Jan 94 12:42:44 +0100
I would like to comment the following:
I run the prcheck for the AS137 (level 7) and as the last job it has generated
the as-path access list. The out-bound filter lists contain line:
ip as-path access-list 1 permit .* 137$.
This will not work! Why?
The border router usually derives the local routes (of proper AS) from
internal routing protocols (IGRP for example) and thus they are not taged
with AS i.e the field "path" does not contain any AS number. So, having
access list defined in such a manner the router will announce no network to
its neighbours (we alrady experienced this type of error).
The correct line should be:
ip as-path access-list 1 permit ^$
i.e permit all local networks.