AS path question.

Holmes,David A dholmes at
Wed Nov 10 15:35:49 CST 2010

Some use AS prepends, not for traffic engineering, as ISPs often
override AS prepends with private peering (communities/local pref
settings), but for the simple purpose of making advertised prefixes
stand out amongst a welter of BGP routes. 

-----Original Message-----
From: Greg Whynott [mailto:Greg.Whynott at] 
Sent: Wednesday, November 10, 2010 12:22 PM
To: nanog at list
Subject: AS path question.

Recently I adjusted the maxas-limit option on our router,    logs
started reporting routes being refused because the AS path is to long.
seems to work as expected.

when I looked at the logs I was a bit confused at what i was looking
at...   why is it there are multiple AS's in the path that appear to be
the same AS?  I expected an AS path comprised of mostly unique ASs.

instead of this:

476330: Nov 10 14:55:07.247 EDT: %BGP-6-ASPATH: Long AS path 549 26677
6939 21011 43022 43022 43022 43022 43022 47359 47359 47359 47359 47359
47359 47359 47359 received from isp router: More than configured

i expected it would look more like:

476330: Nov 10 14:55:07.247 EDT: %BGP-6-ASPATH: Long AS path 549 26677
6939 21011 43022  47359 received from ... .. .

thanks for your time again,


This message and any attachments may contain confidential and/or
privileged information for the sole use of the intended recipient. Any
review or distribution by anyone other than the person for whom it was
originally intended is strictly prohibited. If you have received this
message in error, please contact the sender and delete all copies.
Opinions, conclusions or other information contained in this message may
not be that of the organization.

More information about the NANOG mailing list