Anyone notice strange announcements for

Jack Bates jbates at
Mon Jan 12 21:09:40 UTC 2009

Florian Weimer wrote:
> I think this is over the line.  You can't put other people's IDs into
> routing data on production networks.  (Well, technically you can,
> obviously, but you shouldn't.)

Actually, the placement of the ASN is exactly what they need to do the 
test, as it is treated as a routing loop and discarded. This allows for 
fancy reachability tests while a portion of the network cannot see the 
route in question.

Of course, people track their ASN usage these days and get red alarms 
when their ASN shows up in ways unexpected. I'm not completely sure why 
the ASN matters, except it's probably just a bonus service to route 
hijacking detection (since ASN hijacking doesn't exactly serve a purpose 
except to limit the route being advertised and perhaps leave someone 
complaining to the wrong person if the hijacker is doing bad things).


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