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Weird Traceroutes (Traceroutes go past IP being tracerouted)

I have a 2651 router with some ISL trunks. I noticed the other day when doing a traceroute to one of the IPs, it hits the IP and then continues on.

Ips are added to the interface, are advertised via OSPF. Not all the IPS on this dvice are seeing this weird problem.

I am running IOS version 12.2.17a

CEF is enabled

Here is an example from a UNIX server./

traceroute to 207.xx.xx.6 (207.34.112.6), 30 hops max, 38 byte packets

1 207.xx.xx.1 0.627 ms 0.667 ms 0.491 ms

2 207.xx.xx.229 11.819 ms 5.573 ms 3.002 ms

3 207.xx.xx.6 11.942 ms 12.339 ms 12.528 ms

4 * * *

Pings to the IP work perfectly fine. to the IP I am tracerouting to.

I have been racking my brain for almost 3 days.

Also if I traceroute 207.xx.xx.2 I get there in the 3 hops I am supposed to. The range above is a /24

Could the CEF tables be corrupt?

If anyone can shed some light I would certainly appreciate it as I am lost and stuck.

Jim

1 REPLY

Re: Weird Traceroutes (Traceroutes go past IP being tracerouted)

Hi,

have you tested a MS Windows traceroute to the same target?

Or Cisco trace?

Each trecroute implementation can be using different packets (sometimes MS tracert works while UNIX not, e.g.).

So I'd try to involve a protocol analyzer, capture traceroute packets and see what's going on.

There might be also some NAT or something similar involved.

Are you administering the target device?

Regards,

Milan

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