CME phones are stuck at registering

[umeshplamthottam]

Hi All,

Hope that everyone is fine.

I have ran into an issue today, that my CME phones are stuck at registering for 30 Minutes and once our onsite team removed and reconnected the Gig cable phones started registering.

this is also happened earlier as well.

When they reconnect the cable phones will start working.

while I am analyzing the logs I found one error there.

.Feb 1 16:21:33.754 UTC: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet0/2 (not half duplex), with switchHostname GigabitEthernet1/0/35 (half duplex).
.Feb 1 16:21:33.958 UTC: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up
.Feb 1 16:21:34.666 UTC: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet0/2 (not half duplex), with switchHostname GigabitEthernet1/0/35 (half duplex).

Is this duplex mismatch can lead to unregister phones from CME and prevent them from further registering.

 Please advice.

[M02@rt37 · Accepted solution]

Hello @umeshplamthottam 

Duplex mismatch can potentially cause network issues, including problems with device registration, and it might be related to the trouble you are experiencing with your CME phones.

A duplex mismatch occurs when two devices connected to the same Ethernet segment have different duplex settings (one is operating in full duplex mode, and the other is in half duplex mode). This can lead to communication problems, packet loss, and network instability.

In your logs, the messages %CDP-4-DUPLEX_MISMATCH indicate that a duplex mismatch was discovered on the interface GigabitEthernet0/2, where your CME phone is likely connected. This interface is connecting to another device with hostname "switchHostname" on GigabitEthernet1/0/35, and there's a mismatch in the duplex settings.

You should ensure that both side of the conection are configured with the same duplex settings (either both set to full duplex or both set to half duplex). You can manually configure the duplex settings on both the CME phone interface and the corresponding switch interface to avoid the mismatch.

interface GigabitEthernet0/2
duplex full
speed auto # or specify the speed setting if needed

After these changes, monitor the logs to see if the duplex mismatch messages persist. Thanks.

[Roger Kallberg]

IMO if not absolutely necessary to set duplex to a specific value, it is for the most better to set it to auto negotiation on both sides. Also if duplex is set to a specific value it is advised to also set the speed to a specific value and not have that set to auto negotiate. Mixing set values with auto negotiation is a bad practice that is best to avoid.