11-03-2006 12:55 PM - edited 03-05-2019 12:36 PM
Hi,
I have inherited a 3550 trunked to a MAN with an extended vlan access port crossed over to a 2950 vlan 1 access port.
With both sides hardset to 100/full, the 2950 runs in 100/half causing the 3550 to see collisions and log %CDP-4-DUPLEX_MISMATCH.
When I set the port on the 3550 to auto speed/duplex, both sides came up at 100/full and the errors stopped.
Can someone explain this?
Thanks, Steve
c3550#show run int fas 0/2
Building configuration...
Current configuration : 206 bytes
!
interface FastEthernet0/2
description cross-over to c2950 fas0/1
switchport access vlan 2054
switchport mode access
switchport nonegotiate
no ip address
duplex full
speed 100
spanning-tree portfast
spanning-tree bpdufilter enable
end
c2950#show run int fas 0/1
Building configuration...
Current configuration : 157 bytes
!
interface FastEthernet0/1
description cross-over to c3550 fas0/2
switchport mode access
switchport nonegotiate
no ip address
duplex full
speed 100
end
11-03-2006 01:30 PM
Hi Steve ,
The %CDP-4-DUPLEX_MISMATCH messages may be generated repeatedly when Cisco Discovery Protocol (CDP) has discovered a mismatch of duplex configuration between CDP neighbors.
This message occurs when a duplex mismatch is detected between CDP neighbors. It can also occur when switches are separated by a non-Cisco switch or hub. If CDP version 2 reports the link as a half-duplex when a port or interface on a CDP-enabled device has been configured or auto negotiated to full-duplex, the alternate device may not support CDP version 2. This causes the error to occur. It is a cosmetic issue.
CDP is useful for detecting errors as well as port and system statistics on neighboring Cisco devices. CDP is Cisco proprietary and works be sending packets to a well-known MAC address 01-00-0C-CC-CC-CC.
To resolve this issue, perform these steps:
To disable CDP version 2, issue the no cdp advertise-v2 command.
To check the CDP version running on the device, issue the show cdp command.
By default, Cisco switch ports and interfaces are set to Auto-negotiate.
**You must match the speed and duplex settings on both sides by setting both sides to Auto-negotiate or by hardcoding.
Note: This error message also occurs in Switches running CatOS system software.
Hope it helps you.
Thanks,
satish
11-03-2006 01:52 PM
Thanks, Satish,
Are you certain it's only cosmetic?
show interface Fast 0/2 on the 3550 was picking up about 1000 input errors/CRC per hour. Both sides were hard coded to 100/full.
The input errors/CRC's stopped after I configured Fast 0/2 to auto speed and duplex and leaving the corresponding port on the 2950
hard coded to 100/full. CDP also stopped complaining.
Both switches are connected by a cat5 cross-over cable with no third party gear in the path.
Thanks again, Steve
11-05-2006 06:58 AM
Hi Steve ,
The problem which you are facing may be a bug ? I searched for known issues ,but couldn't able to find it out.Open a TAC case with cisco to resolve the issue.
Thanks,
satish
11-03-2006 05:45 PM
I would check to see if someone hasn't stuck another switch or hub between the 2950 and the 3550 .
11-05-2006 06:18 AM
Hi,
Try the following command in 3550 switch side.
no power inline never
It is used during the bug on some IOS versions. Typicaly seen when the devices are hardset to 100 MB / full duplex and are running CDP-v2
Try this and let us know,
Rate if it does,
Rgs
11-08-2006 10:06 AM
c3550(config-if)#no power inline
Command rejected: Not a Inline Power supported port.
Thank you all: I will pursue this TAC
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