[112848] in North American Network Operators' Group
Re: AS path weirdness
daemon@ATHENA.MIT.EDU (James Aldridge)
Sun Mar 22 08:25:04 2009
To: NANOG list <nanog@nanog.org>
In-Reply-To: <49C4558C.8050306@packetnexus.com>
Date: Sun, 22 Mar 2009 12:09:34 +0000
From: James Aldridge <jhma@mcvax.org>
X-SA-Exim-Mail-From: jhma@mcvax.org
Errors-To: nanog-bounces@nanog.org
Jason Lewis wrote:
> I'm not entirely sure what I'm looking at. The reserved AS, 65490
> appears in parentheses and I've never seen that in MRT formatted data
> and not sure why it's happening.
That would be a single-element AS_SET, I guess.
> I'm also not clear on why I see 23456 *and* a 32 bit AS in the path. Is
> anyone else seeing this or is it something wacky at RRC04?
That's certainly not limited to rrc04. From one of our routers at the AMS-IX
I see the following (JunOS 9.2, so 32-bit AS numbers are in "ASPLAIN" format
and AS_TRANS is spelt out):
A Destination P Prf Metric 1 Metric 2 Next hop AS path
* 91.201.176.0/22 B 170 100 0 >195.69.144.110 3356 21219 196638 I
B 170 100 10 >193.0.0.147 12859 21219 196638 I
B 170 100 50 >195.69.144.200 12859 21219 196638 I
B 170 100 100 >195.69.144.35 12859 21219 196638 I
B 170 100 >195.69.144.178 6320 3327 21219 196638 I
B 170 100 0 >195.69.145.47 8218 3257 3356 21219 196638 I
B 170 100 >195.69.144.50 1103 3549 3327 21219 196638 I
B 170 100 >195.69.144.34 1103 3257 3356 21219 196638 I
B 170 100 0 >195.69.145.144 1273 3549 3327 21219 196638 I
B 170 100 100 >195.69.144.89 286 3549 3549 3327 21219 196638 I
* 91.207.218.0/23 B 170 100 0 >195.69.144.110 3356 13249 6886 196629 I
B 170 100 0 >193.0.0.147 3356 13249 6886 196629 I
B 170 100 50 >195.69.144.200 12859 35320 196629 AS_TRANS ?
B 170 100 100 >195.69.144.35 12859 35320 196629 AS_TRANS ?
B 170 100 >195.69.144.178 6320 2914 35320 196629 AS_TRANS ?
B 170 100 0 >195.69.145.144 1273 2914 35320 196629 AS_TRANS ?
B 170 100 100 >195.69.144.89 286 2914 35320 196629 AS_TRANS ?
B 170 100 0 >195.69.145.47 8218 3257 3356 13249 6886 196629 I
B 170 100 >195.69.144.50 1103 3549 3356 13249 6886 196629 I
B 170 100 >195.69.144.34 1103 3257 3356 13249 6886 196629 I
* 195.88.52.0/23 B 170 100 0 >195.69.144.110 3356 13249 28761 196665 I
B 170 100 0 >193.0.0.147 3356 13249 28761 196665 I
B 170 100 50 >195.69.144.200 12859 13249 28761 196665 I
B 170 100 100 >195.69.144.35 12859 13249 28761 196665 I
B 170 100 0 >195.69.145.144 1273 3356 13249 28761 196665 I
B 170 100 100 >195.69.144.89 286 3356 13249 28761 196665 I
B 170 100 0 >195.69.145.47 8218 3257 3356 13249 28761 196665 I
B 170 100 >195.69.144.50 1103 3549 3356 13249 28761 196665 I
B 170 100 >195.69.144.34 1103 3257 3356 13249 28761 196665 I
* 195.128.231.0/24 B 170 100 0 >195.69.144.110 3356 13249 6886 196629 35748 I
B 170 100 10 >193.0.0.147 12859 35320 196629 AS_TRANS 35748 I
B 170 100 50 >195.69.144.200 12859 35320 196629 AS_TRANS 35748 I
B 170 100 100 >195.69.144.35 12859 35320 196629 AS_TRANS 35748 I
B 170 100 >195.69.144.178 6320 2914 35320 196629 AS_TRANS 35748 I
B 170 100 0 >195.69.145.144 1273 2914 35320 196629 AS_TRANS 35748 I
B 170 100 100 >195.69.144.89 286 2914 35320 196629 AS_TRANS 35748 I
B 170 100 0 >195.69.145.47 8218 3257 2914 35320 196629 AS_TRANS 35748 I
B 170 100 >195.69.144.50 1103 3257 2914 35320 196629 AS_TRANS 35748 I
B 170 100 >195.69.144.34 1103 3257 2914 35320 196629 AS_TRANS 35748 I
AS_TRANS and a 32-bit ASN only seem to appear together in the paths through
35320 so it looks as though something odd is going on there.
James
