High number of output erros on switch ports

Posted on 2006-05-24
Last Modified: 2010-03-19

I have been investigating a network performance issue we seem to have at the moment. Running a Ping from a router to several servers on the same LAN connected via a Catalyst Switch returns about 98% success for 1000 Ping request. I would expect this to be 100% right?

Looking at the switch interfaces I can see that 3 ports have a high number of output errors reported. Resetting the counters they start rising again straight away.

Iam onto somthing here? if so what is the best way to fix the high output errors on these ports.

All other counters on the interfaces seem normal, not queue drops etc

Thanks all,

Question by:dgandy321123
    LVL 79

    Accepted Solution

    Yes, I believe that you are onto something here.
    Any errors on a switchport are cause for concern.
    Is there any indication of type of errors? CRC? Frame?
    How about collisions?
    #1 problem on switchports and poor performance = duplex mismatch
    Switchport set to "auto", server set to 100/full-duple = guaranteed duplex mismatch
    Switchport set to 100/full, server set to auto = duplex mismatch
    switchport set to auto, server set to auto = OK
    switchport set to 100/full, server set to 100/full = duplex mismatch

    Although...... I would expect input errors vs output errors . . .

    Author Comment

    On further inspection the ports with the issue are set to half duplex 100mb - the others are full duplex,  they are OK.

    The output errors also match the same number as late collisions on the interfaces with errors.

    What do you suggest?
    LVL 79

    Expert Comment

    What are these ports connected to? Most modern server nics are full-duplex capable.
    Suggest you set the server NIC to auto and the switchports to auto and let them re-negotiate the duplex settings.
    Late collisions suggest a duplex mismatch. Switchport set to 100/half, server set to 100/full

    Author Comment

    I will need to get someone to find out what is connected to these ports. If I ping out internet proxy which is not connected to one these of these ports with output errors, but still on the same switch I still see about 2% drops when pinging the proxy.

    Would the errors on the 3 offending switch ports cause issues on all other ports on that switch?

    I let you know how we go with changing the port settings after we find out what is connect to the 3 offending ports

    Author Comment

    Thanks lrmoore,

    Upon further investigation the problem was this:

    Switch Port 0/9 - Auto-duplex, Auto-speed
    Peribit - Local Full Duplex, 100Mb
    Peribit - Remote Full Duplex 100Mb
    Router interface FastEthernet2/0 Auto-duplex, Auto-speed

    Changing the router and switch port to 100Mb Full has fixed the issue and output errors are no more and the performance through that router and through the switch has improved!


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