To make switch as Hub for a fiber link

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Nov 5th, 2009
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Here is my problem:

i have a lab setup as :

switch1----fiber trunk---switch2

i would like to sniff trunk link using a switch3 i.e i will connect sniffer to switch3

switch1---fiber---switch3----fiber--switch 2

how can i setup switch3 , so that trunk between switch1 &switch2 comes up and i can sniff it on switch3?

The switch3 is 3750. Can i do it without setting up any trunk ports on switch3? ..Can i use Bridging, l2tunnel , or local switching or L2TPv3 ?Is it possible to achieve this?

Thanks in advance

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mike_guy29 Thu, 11/05/2009 - 13:43
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Rather than putting an additional switch in the middle would it not be easier to configure a SPAN port on either switch one or switch two.

For example if I had no other SPAN sessions configured and wanted to monitor port Gig0/1 by copying traffic to Gig0/3 I would issue the following two commands:

(config)# monitor session 1 source interface Gig0/1

(config)# monitor session 1 destination interface Gig0/2

When you specify the source you can specify which traffic direction you want to capture. The default is both. There are some additional parameters that can also be set depending upon your requirements.



singhsaju Fri, 11/06/2009 - 06:43
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Thanks for reply Mike. I have already collected the sniffer output by using monitor session on switch 1 and switch 2.

To further troubleshoot a problem/ssue i now need to sniff trunk link traffic in between the switches.

iyde Fri, 11/06/2009 - 14:28
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Still you could do a SPAN of the trunk port of each switch to your sniffer and in that way see the traffic on the trunk.

HTH, Ingolf


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