late collisians

[01JPKK]

my working place is using cisco 2950 manageble switches.one of our switch is using for testing purposes by mobole network poerations devision.they have pluged several mobile equipments like nano BTS....etc using 6 ports of the switch.rest ports are occupied with normal PC users.transmission people always complans about late collisions they are haveing.but,ididnt noticed any high collisian rates. is it posibale to occour late collisians by moblile transmission equpments,which is connected to cisco manageble switches.what kind of changes should i do in cisco switch to allow transmitting testing without any errors.coz i have to give priroty for those testings.ple reply me.

[leonvd79]

Late collisions are usually the result of long cable runs. If the cable exceeds the 100m rule for ethernet or fastethernet over Cat. 5 UTP you are likely to experience this errors.

If your users complain about late collisions it means that it is reproducable. What you can do is to either monitor the traffic or use some kind of traffic generator on the end of the cable that you suspect of causing these problems.

Before you begin you could clear the counter of the interface, for instance: "clear counters Fa0/24". Start transmission and see if the counters, especially collissions and late collisions increase.

From there on you must decide what to do when the problem is defined. Start with the physical aspect of wiring checking cable runs from the switch to the patch panel, punchdown block and so on.

HTH

Leon

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[Richard Burts]

There is another situation which I think needs to be considered. Late collisions are sometimes a symptom of a duplex mismatch. If one device is configured for full duplex and the switch is configured (or negotiates) to half duplex, then the half duplex side is likely to see late collisions.

Check the switch interface for its settings and check the interface for the connected device. Do they negotiate speed or is one or both have speed set (this will impact negotiation of duplex)? Do both negotiate duplex or is one have duplex set?

HTH

Rick