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New Member

Cat 2950 port monitoring problems.

I have a WS-C2950-24 running c2950-iq412-mz.121-9.EA1.bin software. I've configured a monitor session with these commands:

monitor session 1 destination interface F0/2

monitor session 1 source interface F 0/8

This works partially in that data from F 0/8 does get spanned to port F 0/2, but the packets are unreadable by the Sniffer I have plugged in to F0/2. The Sniffer

decodes them as WelFleet layer 2 packets. There is no layer 3 decode at all, and I know these are IP, TCPIP, FTP packets because all tthose protocols work just fine through the switch.

Is there a problem with the code on this switch concerning port monitoring?

5 REPLIES
Cisco Employee

Re: Cat 2950 port monitoring problems.

Never heard of any such bug. What sniffer application do you use? Can you try ethereal?

www.ethereal.com

Bronze

Re: Cat 2950 port monitoring problems.

For whatever reason, SPAN'd packets on 2950's include VLAN tags. Some sniffers get confused by this.

New Member

Re: Cat 2950 port monitoring problems.

I'll check this out with a newer version of the Sniffer software. Is there a way to stop the switch from tagging the packets? I will never use trunking with this switch and don't need vlan tagging.

Bronze

Re: Cat 2950 port monitoring problems.

This has come up in the past and someone from Cisco said that a future software release was going to make this configurable. As far as I know, this hasn't happened yet.

You may want to open a case with TAC and try to get a bug ID assigned to this issue. The more people that complain, the faster it will hopefully get resolved.

New Member

Re: Cat 2950 port monitoring problems.

If you are referring to the Catalyst 2950T maybe my experience with IOS bugs is also related to your problem and this suggestion could help...

Just like your experience I'm using version IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(9)EA1,in my switch and theres so many problem I encountered such as, buffer failures, switch not allowing packet to pass through it appears hang up though it is not and theres to trace in logs but the drops are very highly unusual...

I upgrade the CAT2950T IOS to version listed below and it solved many problem.

switch IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(13)EA1b,

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