switch port collisions

Unanswered Question
Jun 18th, 2008


If you have a lot of switch port access collisions (2950 switch) does this mean you have speed and duplex mismatch?

Thanks for your help.


I have this problem too.
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Mark Yeates Wed, 06/18/2008 - 17:44


Collisions are very common in a half duplex environment, and not possible when a connection is full duplex. It is possible that you have a speed/duplex mismatch. If necessary hard code your interfaces to your desired settings ie 100-full and see if that corrects the issue.


lazon Wed, 06/18/2008 - 18:08

Hello mark,

Thank's a lot for your response, so your saying that if it's a half duplex environment, I have to hardcode the switch port to 10-half duplex. Thank's again.


Mark Yeates Wed, 06/18/2008 - 18:50

You will want to set your devices to the best settings possible based on their capabilities. If possible you will at least want the highest speed, and full duplex settings. The errors that you are seeing is because they are running half duplex. For best results you will need full duplex, and the highest speed that the interfaces are capable of.

hennigan Wed, 06/18/2008 - 22:23

A speed mismatch will keep the link from coming up at all.

Collisions are normal in a half-duplex environment.

What is on the other end of the link? If it is only capable of half-duplex, then collisions are to be expected.

If the other end is full-duplex and showing incrementing runts, then you have a mismatch. As a rule either BOTH sides should be set to autonegotiate, or BOTH should have speed-duplex hard-configured, usually to the highest common speed and full-duplex if both are capable.

Bottom line -- determine the capabilities of the other end of the link, tweak as needed.

lazon Thu, 06/19/2008 - 14:02

Thanks again for your response guy's, I really appreciate the explanation. At least I have a better understanding on what causes collisions to accumulate in a switch environment. Thanks.



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