Debug IP Packets

up2thetimeup2thetime Member Posts: 154
in CCNP
Hey guys,

Needed some help with the debug ip packet command...

I have some traffic that flows through RouterA (ie. a ping from one end of the network will go through RouterA to reach the destination).

When I enable debug ip packet on RouterA, it does not show the packet being forwarded (it does not show that ICMP packets are flowing through RouterA even though the Ping is successful). However when I do a trace from one end of the network to the other, the debug generates the expected logs.

Any ideas?

Thanks!
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Comments

  • vinbuckvinbuck Member Posts: 785 ■■■■□□□□□□
    try debug ip icmp instead. If you are diagnosing a routing issue, you might try debug ip routing and debug ip packet together.
    Cisco was my first networking love, but my "other" router is a Mikrotik...
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  • networker050184networker050184 Mod Posts: 11,962 Mod
    Debug ip packet only gets traffic punted to the CPU. Tracerouote traffic has an expired TTL which causes this to be punted to the CPU for processing which is why you see that. Transit ICMP traffic will be CEF switched like normal traffic and you won't see anything.

    You can disable CEF and you should be able to see the transit traffic at that point. Keep in mind this isn't something you want to do in production though.
    An expert is a man who has made all the mistakes which can be made.
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  • up2thetimeup2thetime Member Posts: 154
    Hmm... i disabled cef, but RouterA still doesn't show the forwarding....

    I did a show ip cef to confirm cef was turned off....

    Edit:

    Sorry, i didn't give it a few minutes.

    It seems to be working. Looks like it took a few minutes to kick in after cef was disabled.

    Thanks for the information!!
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