AS path question.

Greg Whynott Greg.Whynott at oicr.on.ca
Wed Nov 10 14:39:31 CST 2010


thanks all,  this makes sense now.    and i just showed the internet how ignorant I am…


i have my maxas-limit set to 10 based on an article I was reading.  perhaps I should up that a bit.

what sort of problems are associated to overly long AS paths?   is it more of a system resource control setting?

-g



On Nov 10, 2010, at 3:31 PM, Nick Olsen wrote:

They are prepending routes.
Looks like both 43022 are prepending, As well as 47359...Multiple times... They do this to make that route look "bad" so it comes in other transit they have.

Nick Olsen
Network Operations
(855) FLSPEED  x106

[http://www.flhsi.com/files/emaillogo.jpg]


________________________________
From: "Greg Whynott" <Greg.Whynott at oicr.on.ca<mailto:Greg.Whynott at oicr.on.ca>>
Sent: Wednesday, November 10, 2010 3:23 PM
To: "nanog at nanog.org<mailto:nanog at nanog.org> list" <nanog at nanog.org<mailto:nanog at nanog.org>>
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 MAXAS-LIMIT



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,
greg






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Gregory Whynott
Network Operations

Ontario Institute for Cancer Research
MaRS Centre, South Tower
101 College Street, Suite 800
Toronto, Ontario, Canada M5G 0A3
Tel: 647-294-2813
www.oicr.on.ca<http://www.oicr.on.ca/>







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