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I'm puzzled. Connections go from router to router. How does it help to say routerb-x-y-z-routerc.blah.net when routerc will show up as the next hop in the traceroute?

I think it will help when routerc fails to show up as the next hop :)

No.

Actually yes. At first I had the same thought that you did, but knowing which router the packet was supposed to have come from makes it easy to tell from the output of a traceroute weather the routing changed in the middle. Having to use IP addresses to figure this out is much more work. On the other hand, I do question the idea of trying to cram all this info into the the interface names in the DNS.

Traceroute gives you the incoming interface on a router. For a given incoming interface on a router there are multiple next hop routers (and multiple outgoing interfaces).

Knowing that the outgoing interface that a packet came from on the previous hop router is not worth adding to the DNS.

If this is a point-to-point link, as you seem to be assuming, then it should be subnetted as a /30 and you can thus subtract or add 1 to the IP address as appropriate to find the previous hop's outgoing interface, if that information is important to you.

If it is a multiple-access link, then there is no chance of the incoming interface being specific to a particular previous hop anyway, so this scheme falls apart.

--jhawk