CDP Duplex Mismatch Message and extra info

[francescovestri]

Hello,

I am receiving a logging message from a switch  of this type:

(SW_3750_1)%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet5/1 (not half duplex), with SEP111122223333 Port1  (half duplex). (SW_3750_2)

While I receognize this as a common duplex mismatch message, my question is, what is the hostname at the end of the line about (SW_3750_2)?

It is certainly not the Switch I am sitting on (SW_3750_1), where the log messages are showing. And it is not what is connected to the port, which is obviouly a Cisco Phone.

show cdp neighbor shows the Cisco Phone connected to the port. I am wondering if it's a switch connected behind the phone?

Many thanks,

Francesco

[Mark Malone]

Hi can you post the show cdp neighbour off that switch sw-3750-1

Is there something else connected in between a HUB ?

[francescovestri]

Hi,

I cant copy and paste the output because it is on a separate machine with no internet access.

There are several phones connected to the switch. All of these switches have the following flags active:

P (Phone), H for Host and M for 2 mac relay feature.

Port 5/1 instead, the one that is also showing the SW_3750_2 only has the P and H flags.

Let me point out that SW_3750_2 is nowhere in my network diagram, it might be a rogue switch that has been plugged (or not documented).

Other official switches do appear on the show cdp neighbor on their individual ports.

This SW_3750_2 does not show in the show cdp neigh, on port 5/2 there is only the above Cisco Phone.

Francesco

[pwwiddicombe]

maybe at one time there was a DNS entry for the SW_3750_2 entry; it has since changed and the phone now has that IP address ?  sh cdp neigh detail  might give some more information.

The issue is probably that the port was set to full duplex on the switch; which messes up with autoconfig on the phone.