Yeah...prepending isn't a big deal...but when someone prepends their own AS 70+ times, I wonder WTF they're thinking. On Thu, 23 Oct 2008, James Baker wrote:
bgp path prepend?
-----Original Message----- From: Jon Lewis [mailto:jlewis@lewis.org] Sent: Thursday, 23 October 2008 3:40 p.m. To: nanog@nanog.org Subject: What's with all the long aspaths?
Is there something silly going around? I doubt I'm the only one noticing these being triggered by our generous maxas-limit setting.
Oct 9 23:01:46: %BGP-6-ASPATH: ... 27754 27754 27754 ... Oct 17 11:10:40: %BGP-6-ASPATH: ... 43413 43413 43413 ... Oct 22 06:34:09: %BGP-6-ASPATH: ... 38230 38230 38230 ...
Anyone have theories as to what these networks are trying to accomplish?
---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
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---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
Jon Lewis wrote:
Yeah...prepending isn't a big deal...but when someone prepends their own AS 70+ times, I wonder WTF they're thinking.
I'm sure they get the attention of NOCs around the world as messages like this show up on consoles Oct 22 04:34:05 MDT: %BGP-6-BIGCHUNK: Big chunk pool request (306) for aspath. Replenishing with malloc This time I couldn't be bothered to dig too deeply into who was the cause.
On Wed, 22 Oct 2008, Mike Lewinski wrote:
I'm sure they get the attention of NOCs around the world as messages like this show up on consoles
Oct 22 04:34:05 MDT: %BGP-6-BIGCHUNK: Big chunk pool request (306) for aspath. Replenishing with malloc
You might consider something like bgp maxas-limit 75 to exchange that log message for the less scarey Oct 22 06:34:09: %BGP-6-ASPATH: Long AS path ... As an added bonus, you ignore their route while they're playing such games. ---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
Jon Lewis <jlewis@lewis.org> writes:
You might consider something like bgp maxas-limit 75 to exchange that log message for the less scarey Oct 22 06:34:09: %BGP-6-ASPATH: Long AS path ...
As an added bonus, you ignore their route while they're playing such games.
Which is exactly what they want. What you *really* want to do is: router bgp foo neighbor bar route-map prepend-this-you-fool in ip as-path access-list 66 permit _blah_blah_blah_blah_blah_blah_blah_blah_blah_ route-map prepend-this-you-fool permit 10 match as-path 66 set local-preference 1000 -r
I'm sure they get the attention of NOCs around the world as messages
Sounds like some automated scripts that didn't do any sanity checking. Process pulls the current BGP table, checks for the longest path, and then prepends the AS that many times to guarantee everyone takes the other path. But if two ISPs are doing this, well, the paths get longer and longer. I just checked our table for those ASs mentioned in your log, they look short now. Guess they caught it. Chuck -----Original Message----- From: Jon Lewis [mailto:jlewis@lewis.org] Sent: Wednesday, October 22, 2008 11:17 PM To: Mike Lewinski Cc: nanog@nanog.org Subject: Re: What's with all the long aspaths? On Wed, 22 Oct 2008, Mike Lewinski wrote: like
this show up on consoles
Oct 22 04:34:05 MDT: %BGP-6-BIGCHUNK: Big chunk pool request (306) for
aspath. Replenishing with malloc
You might consider something like bgp maxas-limit 75 to exchange that log message for the less scarey Oct 22 06:34:09: %BGP-6-ASPATH: Long AS path ... As an added bonus, you ignore their route while they're playing such games. ---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
Not using that prepended route is exactly what the point of the prepend is, so that's not "punishment". It may, in fact, be exactly what they're trying to get you to do.
-----Original Message----- From: Jon Lewis [mailto:jlewis@lewis.org] Sent: Wednesday, October 22, 2008 8:17 PM To: Mike Lewinski Cc: nanog@nanog.org Subject: Re: What's with all the long aspaths?
On Wed, 22 Oct 2008, Mike Lewinski wrote:
I'm sure they get the attention of NOCs around the world as messages like this show up on consoles
Oct 22 04:34:05 MDT: %BGP-6-BIGCHUNK: Big chunk pool request (306) for aspath. Replenishing with malloc
You might consider something like bgp maxas-limit 75 to exchange that log message for the less scarey Oct 22 06:34:09: %BGP-6-ASPATH: Long AS path ...
As an added bonus, you ignore their route while they're playing such games.
---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
Except when their primary path goes away and relatively few networks install the prepended route. It's all conjecture, but I like the 'in effort to defeat local pref' option. On Thu, Oct 23, 2008 at 10:53 AM, Tomas L. Byrnes <tomb@byrneit.net> wrote:
Not using that prepended route is exactly what the point of the prepend is, so that's not "punishment".
It may, in fact, be exactly what they're trying to get you to do.
-----Original Message----- From: Jon Lewis [mailto:jlewis@lewis.org] Sent: Wednesday, October 22, 2008 8:17 PM To: Mike Lewinski Cc: nanog@nanog.org Subject: Re: What's with all the long aspaths?
On Wed, 22 Oct 2008, Mike Lewinski wrote:
I'm sure they get the attention of NOCs around the world as messages like this show up on consoles
Oct 22 04:34:05 MDT: %BGP-6-BIGCHUNK: Big chunk pool request (306) for aspath. Replenishing with malloc
You might consider something like bgp maxas-limit 75 to exchange that log message for the less scarey Oct 22 06:34:09: %BGP-6-ASPATH: Long AS path ...
As an added bonus, you ignore their route while they're playing such games.
---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
participants (6)
-
Church, Charles -
Jason Iannone -
Jon Lewis -
Mike Lewinski -
Robert E. Seastrom -
Tomas L. Byrnes