Monday, November 29, 2010

Lightning TIP Viewing Traffic as it Crosses a Router

Do you have a need to see the packets crossing your router? If you do then you can use the debug ip packet detail command to see this traffic. The problem is it's typically so much traffic it's not useful.This is where an access list can help.

access-list 101 permit ip host 192.168.0.1 host 192.168.0.2
access-list 101 permit ip host 192.168.0.2 host 192.168.0.1

Now reuse the earlier debug with the access-list.

Router#debug ip packet detail 101

If you tweak your logging settings just right you should be able to capture the packet detail to syslog or to the console in real time giving you insight into the specific traffic you might be looking for.

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