Correction on Traceroute Mal-formed packets

From: John McLaren (
Date: Thu Mar 06 2003 - 12:45:31 EST

Thanks to Casey's direction, I have done some further tests.

The new tests have shown that it is NOT the format of the traceroute UDP
packet at fault, but rather that it is any udp packet with a TTL of 1.
Evidently the router responds incorrectly to ANY UDP Packet with a TTL of 1
- it sends an ICMP Port Unreachable rather than a Time Exceeded. Naturally,
this confuses the traceroute routine - but the problem is with the Cisco 2621.

Thanks for your input Casey.


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