%CDP-4-DUPLEX_MISMATCH (IP-phone)

Unanswered Question
Jun 16th, 2010

Hi! I'm getting this error on an access switch.

%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet0/9 (not half duplex), with SEP00141C8Dxxxx Port 1 (half duplex).

Why is the phone port 1 half duplex? Shouldn't the phones be configured as auto-negotiation as default?

Could it be a cabling issue?

Will it affect the throughput / performance on that port?

This is happening with some of my other phones + switches.

I have this problem too.
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Ganesh Hariharan Wed, 06/16/2010 - 08:49

Hi! I'm getting this error on an access switch.

%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet0/9 (not half duplex), with SEP00141C8Dxxxx Port 1 (half duplex).

Why is the phone port 1 half duplex? Shouldn't the phones be configured as auto-negotiation as default?

Could it be a cabling issue?

Will it affect the throughput / performance on that port?

This is happening with some of my other phones + switches.

Hi,

Have you checked from switch side is auto negotion is configured with the port where ip phone is configured.

HTH


Ganesh.H

brunstadnett Thu, 06/17/2010 - 00:28

Hi!

There is nothing configured on the switch-port therefore it should be auto, because the default is auto negotiation.

Normally 100BaseTX is going full duplex and 100 Mbit/s, so why is the phone going down to half duplex?

Aaron Harrison Mon, 06/21/2010 - 00:59

Hi

First thing to check is whether the phone has been configured for half duplex - this is a setting configured from the phone itself (via the keypad). You can go into 'settings', then 'network configuration' and scroll down until you see the 'PC' and 'SW' port configurations.

If you are not near the phone you can browse to the phone IP with Internet Explorer and then click 'Network Configuration' on the left. Somewhere in that list should be the configured speed/duplex settings.

If it is configured for auto/auto, then I would check that there are not multiple devices on the affected switch port - for example someone may have inserted a hub or other intermediate device.

Aaron

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