Debug Packet !

Unanswered Question
Mar 6th, 2009

Hi, i have been trying to use debug Packet command on cli ( with terminal monitor on). But i am not able to see any result ? why is that so. I can see various other debug results but i couldnt see a single line shown after debug packet. Is this command not working anymore or is there any other issue ??

I have this problem too.
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adamclarkuk_2 Fri, 03/06/2009 - 02:10


This command does work but will only show packets that are process switch and not cef switched. If you ping an IP address on the router and debug for that, you will see output.


Adding a log entry to line on the ACL attached to the interface will force the packet to be punted to the CPU and also show up in the output.


illusion_rox Fri, 03/06/2009 - 02:40

I have disabled cef switching but still i am not able to see any output :(

adamclarkuk_2 Fri, 03/06/2009 - 02:44

Added an ACL to your interface with a log against the entry you want to see

example below :-

access-list 100 permit ip host host log

access-list 100 permit ip host host log

access-list 100 permit ip any any

interface FastEthernet0/0

ip address

ip access-group 101 in

Router#debug ip packet 100

cnscisco Sat, 08/10/2013 - 00:38


Just wanted to say thanks much. Adding the access list (with the log option) on the appropriate interface, did it for me. It produced the results I wanted. Before I was not able to see the expected output from packets to  the far end device, after the acl I could see activity to the destinations of interest.

Where would we be without this forum and others like it?

glen.grant Fri, 03/06/2009 - 07:31

On the interface you are trying to debug do a "no ip route-cache " .

adamclarkuk_2 Fri, 03/06/2009 - 07:41

Hi Glen

Not sure how that will help as the log entry forces the packet to be process switched as can be observed with the command

show interface x/x stats

I have not been able to get any output from debug packet but the command 'debug ip packet detail' should give you all the info you need.


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