SPAN monitor session limits in 3750 stack

Unanswered Question
Feb 24th, 2009


I have a customer that needs to span several ports and VLANs to several different locations on their 3750, in such a manner that they really need three monitoring sessions.

They currently have sessions 2 active, which I believe is the maximum a 3750 will support. They are as follows:

monitor session 1 source interface Gi1/0/1 - 2

monitor session 1 destination interface Gi1/0/9

monitor session 2 source interface Gi1/0/3

monitor session 2 destination interface Gi1/0/14

They need a third one added, which if possible to add would be:

monitor session 3 source vlan 2

monitor session 3 destination interface gi1/0/10

Because they can not add a third independent session, they've purchased a second 3750 and a stackwise cable, and asked me to setup a stack for them in order to gain additional SPAN abilities (they also need additional port density).

I suspect that stacking these switches will not allow for additional monitoring sessions, but I am curious if anyone has experience with this and knows for sure?

If not, I had thought about not stacking the switches, but instead just trunking between them, and doing RSPAN from the 2nd switch. My concern with this would be that I am unable to setup any additional sessions on the first switch, which unless I'm mistaken would be needed for the RSPAN VLAN.

I suspect there is an easier way to accomplish what they wish to do. I would be very grateful for any feedback or suggestions any of you might have.



I have this problem too.
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