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New Member

CDP-4-DUPLEX_MISMATCH:

I'm getting the following message on my front end router.

It references an IP address of a router that is elsewhere in the facility on the same subnet.

%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet0/1 (not half duplex), with <IP of Remote Router> FastEthe.

I know the hub that the remote router is connected to is not Full Duplex.

What should I do?

Thanks,

Scott<-

2 REPLIES

Re: CDP-4-DUPLEX_MISMATCH:

This error message is caused by receiving a CDP advertisement from another router which has it's port configured in different duplex mode which is considered abnormal.

Depending on the infrastructure between routers it might or not mean a real problem, but it's suspicious.

Use sh int command to check if there are any errors (collisions, CRC, deferred packets, runts) on router interfaces. If there are some errors you should set manually the interface duplex and speed to correct value. It might help to set it manually even if it's autodetected correctly (I've noticed such a case today morning).

If you are sure the duplex is set correctly and there are no errors you can just ignore the messages or disable CDP on the interfaces.

Regards,

Milan

New Member

Re: CDP-4-DUPLEX_MISMATCH:

Thanks Milan!

I'll go and set the ports. I think they are all Auto.

Cheers!

Scott<-

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