TRACEROUTE WORKS RANDOMLY

[nicolasvibert]

Hello,

I was wondering if someone had encountered an issue like mine:

A 7200 router with "sh ip int brief" has all interfaces up/up, a ping to 10.2.16.86 working well (any other address in its ARP table gives the same result), with sh ip route 10.2.16.86 indicating the following :

Know via connected, distance 0, metric 0 ; directly connected, via Fast Ethernet 6/0.

But the output of traceroute 10.2.16.86 is as follow :

1 10.2.16.86 8ms 8ms *

And the same occurs with any IP address in its ARP table.

Has anyone seen something like this?

Thank you in advance,

Nicolas

[thisisshanky]

The * means you have successfully trace routed to your destination. You get this in one hop, because its directly attached to the ethernet port.

[Steve Fuller]

Hi Nicolas,

The * means the probe has timed out. This is not a problem when executing a trace route to an IOS device as the behaviour is caused by the ICMP Unreachable Rate limiting that IOS has to protect against certain Denial of Service attacks.

This is explained in more detail in the document "Using the traceroute Command on Operating Systems" (http://www.cisco.com/en/US/tech/tk364/technologies_tech_note09186a00801ae32a.shtml). See the section on ICMP Unreachables Rate Limitation.

Regards

Steve