Anyone else seeing "(invalid or corrupt AS path) 3 bytes E01100" ?

Joe Provo nanog-post at rsuc.gweep.net
Thu Aug 20 05:02:11 CDT 2009


On Tue, Aug 18, 2009 at 09:37:22AM +0200, Ivan Pepelnjak wrote:
> > Anybody have a handy route-map that will deny anything with a 
> > as-path longer than say 15-20? ;-)
> 
> http://wiki.nil.com/Filter_excessively_prepended_BGP_paths

It will still be a while before we see unbroken 4byte AS behavior 
(that whole 'fix the teardown on a anyone sneezing' problem). But
like with stale bogon filters, I expect folks inclined to use this
to drop it in and forget about it.  So it would be wise to adjust 
the recommended filter to anticipate a 2byteAS view allowing multiple 
instances of AS-TRANS; there's likely a more elegant approach, but 
the quick step of explicitly allowing _(23465_)+ before you deny
_([0-9]+)_\1_\1_\1_\1_

Cheers,

Joe


-- 
             RSUC / GweepNet / Spunk / FnB / Usenix / SAGE




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