Switching, Catalyst 2000

[BoduHuseynu]

I have multiple logs of my switch duplex mismatch and discovered its connected access port with voice Vlan and phone port is connected to the PC. is there anything I can fix this issue?

[Richard Burts]

It might be helpful if you would post a few of the log messages.  Also please post the configuration of the switch port/interface and the output of show interface for the port/interface. It might also be helpful if you post the output of ipconfig (or similar command depending on OS of the PC).

[BoduHuseynu]

 
05:24:37.981: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:25:37.812: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:26:37.550: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:27:37.252: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:28:38.139: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:29:37.750: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:30:37.480: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:31:37.291: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:32:02.353: %SW_MATM-4-MACFLAP_NOTIF: Host e4f0.0421.4331 in vlan 10 is flapping between port Gi1/0/6 and port Gi1/0/37
Nov 27 05:32:37.912: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:33:37.764: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:34:37.442: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:35:37.934: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:36:37.682: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:37:00.486: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/9, changed state to down
Nov 27 05:37:01.493: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/9, changed state to down
Nov 27 05:37:28.887: %SW_MATM-4-MACFLAP_NOTIF: Host e4f0.0421.4331 in vlan 10 is flapping between port Gi1/0/13 and port Gi1/0/37
Nov 27 05:37:37.489: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:38:38.128: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:39:37.963: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:40:37.665: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:41:37.419: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:42:37.237: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:43:01.708: %SW_MATM-4-MACFLAP_NOTIF: Host e4f0.0421.4331 in vlan 10 is flapping between port Gi1/0/13 and port Gi1/0/6
Nov 27 05:43:38.030: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).
Nov 27 05:43:47.904: %SW_MATM-4-MACFLAP_NOTIF: Host e4f0.0421.4331 in vlan 10 is flapping between port Gi1/0/13 and port Gi1/0/37
Nov 27 05:44:37.847: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/21 (not half duplex), with T290015658D00E2 WAN PORT (half duplex).

[Leo Laohoo]

What is the config for port Gi 1/0/21?

[Richard Burts]

Note that the log messages are generated by cdp. So it is more an informational message than what the switch considers a disabling problem. Traffic still flows over the interface, but is less than optimum performance. If we get the output of show interface I would expect to see two way traffic (output frames and input frames but lots of runts/incomplete frames).

The configuration of G1/0/21 is in the file attached to his response. It is straightforward: access port, access vlan 30, voice vlan 20. Nothing specified about duplex in the parts of the config included, so duplex negotiation is implied - but apparently not working.

Pretty clearly the issue is that the switch port is operating full duplex but the connected device is half duplex. I am a bit puzzled that if negotiation failed the switch did not operate as half duplex. But that appears to be the case. The solution would be to configure the switch port for half duplex. 

[Leo Laohoo]

I suspect the downstream client has manually configured speed and duplex setting (but not half duplex).

[MHM Cisco World]

 WAN PORT <<- WAN port you connect Phone and PC ??
anyway 
disable autonego
hardcode the speed and duplex 

it seem that phone not support autonego and SW select 100/half.