slow file download from new 3com switch

Posted on 2005-04-09
Last Modified: 2011-10-03
We have replace some older planet switches with newer 4200 series 3com switches. There  are 250 workstations and 24 switches roughly half 3 com half planet switches.

when downloading a 50MB file from the server it takes 10 seconds from a planet switch and 100 seconds from a 3 com switch.

All connections are full duplex and 100Mb as far as I know.

Could there be bandwith throttling or something on the new switches that the old switches don't have?
Question by:s_fawcett
    LVL 11

    Expert Comment

    It should not take 100 seconds on 3COM 4200, can you see their configuration ? Is it showing connection at 100 Mbit/sec full duplex (check port LED on the switch) ? Try to connect 2 PC's on the new switches and measure download speed ...
    LVL 5

    Expert Comment

    How many switches between the server and the workstation?  There may be no problem with your switches - they *could* just be deployed in a piss-poor manner.  Don't forget if you are daisychainging switches your bandwidth is aggregate:  the slowest link determines the highest speed.

    Author Comment

    from server to 1Gb switch 3com 3812.  output 80Mb/s

    Igb fibre link to planet switch   output (100Mb ports) measured at 80 Mb/s

    IGb copper link to the 4200 series 3com output  (100Mb ports) briefly at 80 Mb  but falls to a steady 5Mb/s.

    This is using a speed check utility on a laptop (100Mb card)  which is used at various points in the server room.

    In short not more than 2 switches away from the server.

    LVL 5

    Expert Comment

    hrm, so based on what you said above, linearly the layout is:

    [server]---[3com 3812]---[planet switch]---[3com 4200]---[workstation]

    If all your switches are managed, I would query the stp configuration.   Unless you are specifying your root bridge, you may be passing packets to the edge of your switch fabric rather than taking a direct path.  This is only one suggestion.

    I would also try spanning the port on the 4200 where you drop to 5Mb/s, and placing a sniffer (Ethereal) on that port.
    LVL 23

    Accepted Solution

    "The default state for 10/100/1000 Mbps ports is auto-negotiation
    enabled, where the speed, duplex and flow control modes are
    negotiated. Alternatively, auto-negotiation can be disabled and the
    speed, duplex and flow control setting can be manually configured."

    Page 16 of the manual.  I would suggest the manual configuration,
    get it off autoconfiguration, that sounds like your problem....

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