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New Member

how to mirror an interface on router or switch

i m network engineer in an ISP. i want to keep track of the internet traffic of each ip and different applications used by that ip, for that i choose etherreal software. from a etherreal forum someone told me to mirror a router or switch interface.can u please tell me that command and the procedure of doing that, please.


Re: how to mirror an interface on router or switch


You cannot mirror the traffic on a router, it has to be on a L2/L3 switch. What you can do is that you can monitor the routers interface plugged inot the switch port and can see what traffic is goint in or out of that interface using ethereal.

On an IOS switch to the following:

conf t

monitor session 1 source interface fa 0/x (you router port ) both <-- both rx and tx traffic, you can set either rx or TX also.

monitor session 1 destination interface fa 0/x <-- Interface where you PC is connected with ethereal on it.

On a CAT OS switch

Set span 6/1 6/2 where 6/1 is source and 6/2 is destination interface.

Please see the link it will come handy.


-amit singh

New Member

Re: how to mirror an interface on router or switch


If you want to keep track ONLY of IP traffic the Netflow could be a better choise.

Check out this link:

//Mikhail Galiulin