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Duplex mismatch with cisco phone 7940

vladrac-ccna
Level 5
Level 5

Hello,

Not sure if this is a bug or something else.

I'm receiving the following msg on the syslog, but both phone and switch are correctly set to AUTO negotiate the duplex and speed.

Dec 21 11:37:01.107 EST: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet3/3 (not full duplex), with SEP001360C3E06D Port 1 (full duplex).

After a interface recycle (shut/no shut) it stop.

Any ideas?

Vlad

3 Replies 3

gogasca
Level 10
Level 10

Which Switch platform and IOS running?

Could you please post your switch port config?

Thanks

interface FastEthernet3/1

switchport access vlan 10

switchport mode access

switchport voice vlan 20

switchport port-security maximum 3

switchport port-security

switchport port-security aging time 1

switchport port-security aging type inactivity

load-interval 60

qos vlan-based

no snmp trap link-status

tx-queue 3

priority high

end

on the phone:

PC Port Disabled NO

SW Port Configuration AUTO

PC Port Configuration AUTO

Have you tried to just set fixed speed and duplex on the switch port? Unfortunately, duplex negotiation is not 100% reliable.