From: Guyler, Rik (rguyler@shp-dayton.org)
Date: Mon May 21 2007 - 23:15:55 ART
I've also seen this when a non-Cisco (or at least a non-CDP) device sits
between two Cisco devices operating at different duplex settings. The CDP
passes down from one Cisco device running at 100/full to the non-Cisco and
then to the other Cisco running at 10/half for eaxmple. Since CDP passes
through the non-Cisco box, it thinks the half-duplex connection is directly
attached to the full-duplex and reports this error (in error ;-).
A "true" duplex mismatch will result in a fair number of interface errors,
especially if there is a fair amount of traffic on the interface. Look
particularly close at the "late collisions" counter...that's usually a
no-brainer for a duplex mismatch.
Rik
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Daniel Kutchin
Sent: Sunday, May 20, 2007 7:17 AM
To: 'Cisco certification'
Subject: RE: Duplex mismatch error
Your Duplex mode Auto-negotiation failed (which is usually the case when
connecting FastEthernet and older Ethernet Ports)
You expected the duplex settings to be autonegotiated correctly. You are
probably following what the literature says:
- Speed and Duplex modes are autonegotiated independently
- Duplex mode signals from Ethernet ports are usually not understood by
FastEthernet ports; or are non-existent.
- In that case Duplex negotiation fails and Cisco FastEthernet ports default
to HALF-Duplex (HDX) mode.
I have encountered that in the field this is not so. When Cisco FastEthernet
and Ethernet Ports (capable of both FDX and HDX) are connected together in
autonegotiation mode, Ethernet Ports go to HDX and FastEthernet ports to
FDX!
So just select the Duplex settings manually and have your peace.
Daniel
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Rob
McDonald
Sent: Sonntag, 20. Mai 2007 08:38
To: Cisco certification
Subject: Duplex mismatch error
Hello group,
This is a dumb question but I can't get rid of it. I thought this is very
simple to deal with :(
I'm seeing the following error on my switch:
%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet0/16 (not
half duplex), with BB1 Ethernet1/0 (half duplex).
BB1's Ethernet 1/0 is half duplex (Default mode)
3560's Switch port is set to Duplex auto.
I do have full connectivity. Can someone please take a look at it.
Thanks,
Rob
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