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tcp/udp ports - how to find out?

Hi,

I have a 2600 router with two interfaces. Is there an easy way to find out what conversations take place from one int to another, and what ports are used? I tried this making an access-list 'permit tcp any any log' and 'permit udp any any log' but this gave me no answer on the ports used. I could use an analyser but can it be done with the router?

Erik

1 REPLY

Re: tcp/udp ports - how to find out?

It can be done with the router, however; this has a considerable impact on the routers performance.

How to do it:

1: turn off Fast switching through the interface command: no ip route-cache

2: switch on debugging: debug ip packets

Tips to reduce the impact on router-CPU:

- use an access-list to debug particular traffic

- redirect console output to a telnet session

Under heavy traffic, debugging on packet level will definitely cause the router to reboot. Be aware of this. Using a sniffer is the method of choice!

Regards,

Leo

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