From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Thu Sep 01 2005 - 17:40:07 GMT-3
If the requirement is to not allow you to be a transit AS and you are
neighbored to only one AS at this time....
Which is the best method to ensure you don't become a transit AS if
neither is specified?
1. only advertised routes with an empty path to the eBGP neighbor AS
(e.g. permit only ^$)
Logic: local AS routes do not have a path when advertised. It is the
receiving AS neighbor that appends the AS path to a prefix.
This way the prefixes will be empty in path for local AS originated
prefixes. No other learned prefixes would be advertised regardless.
In effect my AS is not advertising reachability to any other AS. So, it
cant be a transit AS.
2. set "no-export" community to learned prefixes from eBGP neighbors.
Send community to all iBGP neighbors
Makes sure eBGP neighbor AS' can reach you but not advertise
learned prefixes from your AS.
Any thoughts...
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