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  1. #1
    Super Moderator BATcher's Avatar
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    Original situation: router -> ethernet switch -> three PCs
    For two PCs, PINGing the router gave figures of the usual 1-3 ms, but one PC (connected using a two-metre patch cable!) gave variable figures in the mid hundreds of milliseconds.

    Next situation: as above, but directly connect the offending PC to one of the router ports, obtaining same extremely long PING times.

    Can anyone suggest a possible solution other than replacing the ethernet patch cable (next task when next I go there)? Could a dodgy ethernet card/socket on the PC give these results? Anything else I should look for? On the offending PC I could connect to the internet using IE without any obvious problem, although the user did say that "occasionally she did have problems"...

    Thanks!
    BATcher

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  2. #2
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    [quote name='BATcher' post='768904' date='02-Apr-2009 12:57']Original situation: router -> ethernet switch -> three PCs
    For two PCs, PINGing the router gave figures of the usual 1-3 ms, but one PC (connected using a two-metre patch cable!) gave variable figures in the mid hundreds of milliseconds.

    Next situation: as above, but directly connect the offending PC to one of the router ports, obtaining same extremely long PING times.

    Can anyone suggest a possible solution other than replacing the ethernet patch cable (next task when next I go there)? Could a dodgy ethernet card/socket on the PC give these results? Anything else I should look for? On the offending PC I could connect to the internet using IE without any obvious problem, although the user did say that "occasionally she did have problems"...

    Thanks![/quote]

    How could you "directly connect the offending PC" to the router WITHOUT using a patch cable? Have you tried swapping the problem PC and one of the other ones to each other's "original" router port? Does Device Manager show any problems with the NIC in the problem PC?

  3. #3
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    My usual approach to any problem of this sort is to divide the problem down until I can trap it in a sufficiently small area and replace or repair it.

    In this case the possible sources of this problem are
    • The CPU/Memory/Motherboard hardware on the problem PC
    • The NIC on the problem PC
    • The operating system and drivers on the problem PC
    • The NIC and TCP/IP configuration parameters on the problem PC
    • The network cable
    • The switch port hardware
    • The configuration of the switch port
    Things you could do to try and isolate which of these is the cause.
    • Boot the problem PC from a Knoppix CD and try ping from there.
      • If this works then you have a problem with your Windows operating system or configuration
    • Connect the PC to a switch port and network cable that have worked effectively from another PC
      • If this works then you have a problem with a cable or switch port

  4. #4
    Super Moderator BATcher's Avatar
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    [quote name='JJDetroit' post='769327' date='06-Apr-2009 12:45']How could you "directly connect the offending PC" to the router WITHOUT using a patch cable?[/quote]
    Err, wireless?
    BATcher

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  5. #5
    Super Moderator BATcher's Avatar
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    [quote name='StuartR' post='769337' date='06-Apr-2009 13:53'][/quote]
    Thanks, Stuart!
    I'd be very interested to know what TCP parameters could cause since a huge (but variable) increase in the expected PING time! I think I'm back to asking whether there is a cheap but effective hardware device that can tell you whether ethernet packets are being dropped or retries attempted. I don't suppose there would be anything about this in either of the relevant Event Logs.

    I think we can easily eliminate router ports as the problem, so it's probably patch cable, NIC or driver(s).

    I'm not sure when next I'm going there, because I have to write a complicated backup BATch file first...
    BATcher

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  6. #6
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    [quote name='BATcher' post='769357' date='06-Apr-2009 09:40'][/quote]

    If you want to try software analysis have a look at Download details: Microsoft Network Monitor 3.2.

    Joe
    Joe

  7. #7
    Super Moderator BATcher's Avatar
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    [quote name='joeperez' post='769365' date='06-Apr-2009 16:09']If you want to try software analysis have a look at Download details: Microsoft Network Monitor 3.2.[/quote]
    Thanks, Joe - someone has also suggested WireShark. Hope it's not a matter of needing to know what the answer is before you can ask the questions!
    BATcher

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  8. #8
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    [quote name='BATcher' post='769357' date='06-Apr-2009 15:40']I'd be very interested to know what TCP parameters could cause since a huge (but variable) increase in the expected PING time![/quote]
    More likely to be datalink layer parameters, such as setting half duplex on the NIC and full duplex on the router port, but I suspect that really silly settings of some TCP parameters could cause packets to get lost.

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