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New Member

SPAN problem

We are using a Catalyst 2950T to capture the traffic of our network. We set up monitor session from a source port to a destination port, where a laptop runs tcpdump. What we observed was that the tcpdump started seeing only broadcast traffic after a couple of days. Then we had to restart the switch in order to see normal (ingress/egress) traffic again. We tried to disable/enable the session, but no avail. We also tried a same set up on a Cat4006 switch (CatOS), same issue.

Does anyone know that Catalyst switch may have some limited resources for the SPAN session, and after certain number of packets, it just stops working? Is there any way to fix/workaround this issue besides restarting the switch?




Re: SPAN problem

The Catalyst 2950 Switches can have only one SPAN session active at a time and can monitor only source ports. These switches cannot monitor VLANs.

There are no know issues with the performance of the switch. But Cisco lists some conditions of the selection of destination ports. Make sure you comply to them....

New Member

Re: SPAN problem


We're having the same problem here with our Catalyst 4507R. This is a constant problem! We monitor a really busy port and after a certain amount of time we only receive multicast and broadcast. The only solution is to reload the switch. This is not so easy for us since it's our main distribution switch.

- Removing and re-adding the monitor session settings doesn't help.

- Shutting down the interface doesn't help.

Did any body else ever see this type of issue?

Re: SPAN problem

Sounds like a bug, it should not stop span after a while. You should open a TAC case.

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