Packet Capturing

Jul 04, 2008 2 Replies
S

Hi all I want to do some 'sniffing' on my network due to users reporting speed issues on the LAN, I have PRTG installed but I am not seeing anything unusual in the graphs to indicate high utilisation on the LAN I have downloaded and installed Ethereal. On my system of course in a switched network, I am seeing traffic over the wire, but it is only traffic originating or destined for my IP and of course broadcast traffic I remember there was a way on a Cisco switch to set a port that basically acts as a conduit for all traffic that passes over the fabric I want to set a system up to capture all data packets over the network for analysis, if someone could tell me the best way to do this it would be appreciated



Scott


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P

Hi Scott,

You are looking for "Port Monitor mode". Its called different things on different platforms but essentually that's what it is. Look under your device specific documenation.

Cheers.....................pk.

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N

The following is an example of Switch Port Analyzer (SPAN) on a Cisco 2950T:

e.g.:

monitor session 1 source interface Fa0/1 monitor session 1 destination interface Fa0/16 encapsulation dot1q

In this case I chose an inter-VLAN routing trunk port (Fa0/1) as the SPAN source, and the Fa0/16 port as the SPAN destination. I used "encapsulation dot1q" to preserve the 802.1Q headers, but that's optional.

As the other responder stated, you should consult the documentation for your specific platform.

Best Regards, News Reader

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