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New Member

Interesting Duplex/CDP Problem

I have a 3550 connected to a 3Com switch used to offload non-PoE devices and save ports on the 3550. Connected to the 3Com are 2 ATA 186s. The ATA's only run at half-duplex, and are working fine, but as the 3Com attaches to the 3550 on full-duplex, CDP thinks it sees a duplex mismatch where none exists. (CDP-4-DUPLEX_MISMATCH), and therefore constantly dumps messages to my syslog server. Now I can put "no cdp enable" on the interface, but in the future I won't be able to find those ATA's via CDP. I'm wondering if anyone has another possible solution to get CDP to ignore that error entirely or just on that interface.

Thanks,

Mark

4 REPLIES
Cisco Employee

Re: Interesting Duplex/CDP Problem

Hi Mark,

other than disabling CDP, the only other option is to lower your logging level to 3.

HTH,

Bobby

*Please rate helpful posts.

Gold

Re: Interesting Duplex/CDP Problem

Get rid of your 3com switch. Not a option I suppose. This has alway been a issue with non cisco switches. They do not know what CDP is and do exactly what they are suppose to do with broadcast traffic and send it out.

I always thought it was funny that it would tell me I had a duplex mismatch between a 10/half port and a gig/full port. It didn't seem too concerned with the fact there was a speed mismatch.

Lately I have seen more vendor supporting CDP. HP and Juniper for example.

New Member

Re: Interesting Duplex/CDP Problem

Dependent on the os you can disable duplex mismatch errors under CDP in config:

"no cdp log mismatch duplex"

Purple

Re: Interesting Duplex/CDP Problem

I read somewhere they were supposed to working on a universal standard for device recognition but haven't seen anything else on it , would be nice if they could ratify something like that across all makers just like say trunking or other common protocols .

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