traceroute results differs between a Win PC and a Cisco router

[dahirton]

I'm experiencing a pretty weird packet behaviour when issuing a traceroute from two different devices: a Windows PC and a Cisco router.

When tracing from a PC in the LAN, I can see the router's ethernet interface (used as the destination address) responding as the last hop for the trace.

When I do the same thing using an extended trace from the router where my default gateway is setup and issuing the source address as the router's ethernet address, the remote end responds me back with the serial ip address of the destination router as the last hop. this is usually what uses to happedn when we extended trace from LAN-to-LAN in Cisco routers and I'd like to know why it differs from a PC in the LAN.

Thanks, Dahirton.

[tstevens]

Don't entirely understand your description, but do realize that cisco routers use UDP to a high "bogus" port number, while windows machines use ICMP (ping) to accomplish traceroute.

[dahirton]

Hi Stevens, thanks for your initial feedback anyway. I'll try to lay out what I'm trying to understand. I have the following picture:

PC ---- Router1 ----Wan---- Router2

When I do tracert from PC using Windows towards the ethernet address of Router2, I got a response from that specific ip address, as being the last hop for my tracert command. When issuing a extended traceroute from Router1, using as source address Router1's ethernet ip address and destination Router2' ethernet ip address, thr remote end give me as the last hop for my tracerouter command, the ip associated with the Wan link (serial port) and not effectively the ethernet address which I'm trying to reach. So I'm wondering why do wenhaqve two different behaviors within this scenario. I did some debug in the remote end router and could realize that in addition to the UDP packet, the windows PC send some regular echo request packets and receives replies as well. Hope it's more clear now.

Thanks.

[dahirton]

I still wanna have a more precise explanation over this subject - if there's one!

Although it seems quite obvious I can't understand why such packets behaves in two different ways.

Thanks,