[21283] in North American Network Operators' Group
Re: Strange BGP announcement.
daemon@ATHENA.MIT.EDU (George Matey)
Tue Nov 10 00:27:50 1998
Date: Mon, 09 Nov 1998 11:11:07 -0500
To: Brett Frankenberger <brettf@netcom.com>,
sgifford@alastair.tir.com (Scott Gifford)
From: George Matey <gmatey@BayNetworks.COM>
Cc: nanog@merit.edu
In-Reply-To: <199811091330.FAA04046@netcom12.netcom.com>
At 07:30 AM 11/9/98 -0600, Brett Frankenberger wrote:
>:: Scott Gifford writes ::
>>
>> > > > Bays don't crash (at least not in the general case ... for example,
>> > > > mine stayed up this time and the last time this happened), but
they do
>> > > > send a NOTIFY and bring down the BGP session, as required by the
RFC.
>> > > > (I believe gated does this also.)
>>
>> In case any Bay Networks users didn't already know this, reasonably new
>> version of the system software have a switch to turn off this behavior:
>>
>> 1:TN]$g wfBgpPeerEntry.41.*
>> wfBgpPeerEntry.wfBgpPeerASLoopDetect.157.130.101.182.157.130.101.181 = 2
>> wfBgpPeerEntry.wfBgpPeerASLoopDetect.204.70.16.38.204.70.16.37 = 1
>> wfBgpPeerEntry.wfBgpPeerASLoopDetect.204.70.100.66.204.70.100.65 = 1
>> wfBgpPeerEntry.wfBgpPeerASLoopDetect.209.54.51.230.209.54.51.229 = 2
>> wfBgpPeerEntry.wfBgpPeerASLoopDetect.209.54.101.238.209.54.101.237 = 2
>>
>> [1:TN]$set
wfBgpPeerEntry.wfBgpPeerASLoopDetect.204.70.100.66.204.70.100.65 2
>> (41) (interface)
>> [1:TN]$commit
>>
>> Set this flag to '2' for each interface to keep your router from tearing
>> down BGP sessions when it finds a loop. Don't forget to commit
>> afterwards, and then to do a "save config config" so it will take after
>> you reboot.
>
>This wasn't a loop. This was a malformed AS path. The length of the
>entire AS Path attribute was 14 bytes, and the length of the first AS
>Sequence segment was 7 AS's, even though there wasn't room to fit that
>many in 14 bytes. (7AS's * 2 bytes each + 2 bytes for the segment
>header, gives a minimum of 16 bytes needed.)
>
>Does this attribute also disable detection of malformed AS Paths?
No.
--
George
>
> - Brett (brettf@netcom.com)
>
>---------------------------------------------------------------------------
---
> ... Coming soon to a | Brett
Frankenberger
>.sig near you ... a Humorous Quote ... | brettf@netcom.com
>
>
