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Network bottleneck, help needed!

Discussion in 'Networks' started by nugget, Oct 5, 2007.

  1. nugget
    Honorary Member

    nugget Junior toady

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    Does anyone know of a tool to help uncover network bottlenecks?

    Our system is set up with all XP Pro clients, 1 Win2K3 server (DC and print server), 1 SuSE Linux Enterprise server (DHCP and file server) with a NAS attached to it. The servers are on the 1st floor of the building and most of the clients are on the 4th. The switch (1st floor) is connected to a glass fibre channel converter through to the 3rd floor to another switch and then to another converter to the 4th floor and from there to the patch panel and the rest of the network (all 3 switches are gigabit).

    The people on the 1st floor have a relatively fast connection to the data (they can open network shares and files very quickly) but the poor sods on the 4th floor take longer to open a share and forever to open any data file. As you can imagine this does not make it very easy for the people to work and no-one is happy with the situation seeing as it was supposed to turn out just the opposite (faster connections and better performance).:cry:


    Any help would be appreciated.
     
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  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Not really enough info unfortunately! :ohmy

    If the switches have logs or SNMP performance monitoring that's where I'd look first.

    There are two classic problems that I assume you have eliminated:
    1) switch ports haven't been set to full-duplex
    2) the switches don't like the converters.

    Why the extra hop on the 3rd floor? Normaly I'd expect the 4th to be directly connected to the 1st. Some high-speed switches don't like being daisy-chained like this.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  3. greenbrucelee
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    greenbrucelee Zettabyte Poster

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    This is a long shot and maybe not worth saying, but have you checked all the cabling is still intact i.e plenum etc going through the different floors.

    But I would be more inclined to say there has to be a switch problem somewhere.
     
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  4. Spice_Weasel

    Spice_Weasel Kilobyte Poster

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    More information would be helpful - what kind of switches are used? What sort of information can you get from the switches? Is this a new problem, or has it always been like this? Are the uplinks multiple fibres that are trunked/aggregated or are the uplinks single fibres?

    Since 1st floor computers have good access while the 4th floor is slow, test connect speed between hosts on the 4th floor, that can help narrow down the problem to the 1st-3rd-4th link. My first thought would be a possible issue between the switches and the converters, I have seen cases of converters running at 1 gig on the optical link between the converters, but only at 100 meg on the copper ethernet connecting to the switch.

    Spice_Weasel
     
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  5. nugget
    Honorary Member

    nugget Junior toady

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    We were originally only on the 4th floor until recently (needed more space). The opportunity came up to take over the 3rd floor from the company that had the 3rd and 1st floors. They had a large network setup connecting both floors directly. We were too late to get the 3rd floor so we have temporarily moved into the 1st floor until the 3rd becomes available again (10 months or so).

    In preparation for this we put in a fiber channel connection to the 3rd floor (from the 4th) and from that switch directly to the 1st floor.
     
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  6. BosonMichael
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    BosonMichael Yottabyte Poster

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    GBL, he says he's got fibre between floors.

    Without sniffing packets, here's the low-tech troubleshooting method... if the 1st and 3rd floors are sending/receiving data OK, have you tried shutting off EVERYTHING on the 4th floor except one computer (or removing all cables from the switch except one computer) and testing the speed with only that computer? Of course, this might not be an option during the day... and at night, the problem may go away if it's related to a computer running during the day, or too much bandwidth going through the switch.

    On that train of thought... perhaps you've got someone monopolizing the bandwidth on the 4th floor... shutting off all the computers except one would help you figure that out.

    Are you sure you've got the ports at each end of the 3rd-4th floor link configured correctly?
     
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  7. nugget
    Honorary Member

    nugget Junior toady

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    The problem has been solved now. :biggrin

    Thanks for the tip Harry.

    I checked all the relevant switches (as I've done before) and everything is okay. I then thought I'd check the media converters (were quite hidden from view) and after reading the manual figured out that they were set to half duplex speed.

    To say that I'm embarrassed about this is an understatement.:oops:

    I'm a big boy and I'll take it on the chin, but I guess that's what you get when you trust a so called IT professional to know what he's doing. It's the last time I'll be doing that.:x
     
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  8. Phoenix
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    Phoenix 53656e696f7220 4d6f64

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    Actually I hope people always trust us to know what we are doing :)
    It helps when you actually DO know what your doing though
     
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  9. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    I'm glad it is working now. And I'm chuffed that I was so close to the right answer without seeing the kit! :biggrin

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+

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