Source IP Address in traceroute

Unanswered Question
Feb 6th, 2009
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I have a Windows PC connected to a LAN segment. The same LAN segment contains a WAN router with a serial interface.

I issue a traceroute from the Windows PC to a device reachable through the WAN. I'd expect the WAN router to respond that the first hop is the IP address on the LAN interface. Instead, the router indicates the first hop in the IP address on the WAN interface. What would cause the router to respond to the traceroute with the IP address of an interface other than the one used to reach the client?

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Richard Burts Fri, 02/06/2009 - 13:40
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That is a strange result. Perhaps if we had some additional information we could find an explanation for the behavior. Can you provide us with the IP of your PC, the IP of the router LAN, the IP of the router WAN, and the output of your traceroute?

Is it possible that the router has any kind of bridging environment that would pass the traceroute through the LAN interface? Is it possible that the router has some IP unnumbered configuration that would make ambiguous the relationship of LAN address and WAN address?




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