AS path weirdness

Mon Mar 23 07:40:38 UTC 2009

On 21 Mar 2009, at 02:48, 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.

This has been observed when a vendor runs 32-bit AS aware code on part  
of their edge, and non-32-bit AS aware code on a different part of  
their edge.

> 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?
> 91.207.218.0/23|29222 6830 (65490) 3356 35320 3.21 23456

There's some history with this prefix.

http://www.andyd.net/media/talks/asn4_breaks_network.pdf [from nanog45]

Andy