Route server: Route-server.ip.att.net

Fri Nov 4 20:46:03 UTC 2011

Did you do a show ip route for 12.122.83.91?  It's probably a loopback of
the nearest BGP peer it may not be the actual next hop interface IP
though.  Not sure about the blocked hops, but I can think of a few
explanations.  Overall the point of that router is to provide a view of the
route table and not the physical hops from one point to another.  Since
actual customer traffic wouldn't flow through the route server the first
few hops are probably irrelevant.

2011/11/4 Michael Sabino <michael.rocco.sabino at gmail.com>

> Hi,
>
> Could you give me the relevant configs explaining why when I traceroute to
> 12.83.43.9 on route-server.ip.att.net, the first hop is "
> j6300.cbbtier3.att.net (12.0.1.202)". However, when I type "show ip route
> 12.83.43.9", the RIB shows, "* 12.122.83.91, from 12.122.83.91, 7w0d ago".
>
> I asked someone who is knowledgeable about the matter, and he seems to
> think that you can change the interface which sends back ICMP unreachables,
> but I don't know how to do this on my own simulated equipment.
>
> Also, I have noticed that when I traceroute to any ip address on the
> internet from my home connection, the last hop that's in common with all
> traceroutes is 12.83.43.9. This is a hop after several hops which seem to
> be filtered. What is the purpose of this IP?
>
> Are there any publically available documentation that would help me
> understand the process of aggregating multiple DSLAMs, etc on my at&t
> u-verse connection?
>
> I am a CCNA/CCNP student in college and this would help me understand WANs
> better.
>
>
> Thanks
>
> Michael R. Sabino
> michael.rocco.sabino at gmail.com
>
>