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Wired Networks Thread, slow network connection suddenly in Technical; Originally Posted by twin--turbo If there are no apparent network loops and after a reset of the network gear then ...
  1. #16

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    Quote Originally Posted by twin--turbo View Post
    If there are no apparent network loops and after a reset of the network gear then next call is to disconnect each distribution switch in turn and see if the problem goes away, if you can pin the source of the issue to a particular switch you can then unplug each port until you find a rouge device. if no rouge devices are present then the switch may be faulty.

    We once had a PC who's ether port was faulty and causing massive amounts of broadcast data across the network.

    One other thing to consider, if the fiber converters are in an open area then someone may have been playing with the dip switches that are common on these devices. If there is a speed or duplex mismatch then you will have some dreadful performance.

    Rob
    Thanks - i will try this also. I do have a spare switch which could replace a faulty one. i have no idea what dip switches are but there not in an open area so i hope nobody has done anything to them! ill look into that aswell!

  2. #17

    twin--turbo's Avatar
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    DIP switches are small switches on devices, not common these days but still seen on media converters to configure speed/duplex etc.

    Rob

  3. Thanks to twin--turbo from:

    Clkj (5th July 2012)

  4. #18

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    Quick update - Ive found a temporary fix but i dont understand what ive done to fix the WHOLE network (I just thought it would fix the office computers)

    Basic map.jpg

    As you can see. I used the old copper connection to try and get the 2 office computers working and unconnected link 1 - thinking this would only get the office working along with the IT suite. But everything worked after disconnecting link 1 and connecting the old copper link. So from what i can work out the fibre is working.

    Could a dodgey cable on link 1 have caused this the whole network to stop - apart from the computers connected via switch 1? or do you think ive somehow disconnected a loop by taking out link 1? if i have i have no idea what loop - it must have something to do with old wireing.

    (all the yellow and red lines are parts of the network not working yesterday - the green ones were working)

    Thanks again for all your help.
    Last edited by Clkj; 6th July 2012 at 11:14 AM.

  5. #19

    SYNACK's Avatar
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    Quote Originally Posted by Clkj View Post
    Quick update - Ive found a temporary fix but i dont understand what ive done to fix the WHOLE network (I just thought it would fix the office computers)

    Basic map.jpg

    As you can see. I used the old copper connection to try and get the 2 office computers working and unconnected link 1 - thinking this would only get the office working along with the IT suite. But everything worked after disconnecting link 1 and connecting the old copper link. So from what i can work out the fibre is working.

    Could a dodgey cable on link 1 have caused this the whole network to stop - apart from the computers connected via switch 1? or do you think ive somehow disconnected a loop by taking out link 1? if i have i have no idea what loop - it must have something to do with old wireing.

    (all the yellow and red lines are parts of the network not working yesterday - the green ones were working)

    Thanks again for all your help.
    Could be a dodgey link but more likely you've inadvertently disconnected a loopback. If I was you I'd try to document exactly how all the different switches are connected together as a starting point to get to know the network better and understand it more.

  6. #20

    twin--turbo's Avatar
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    was the copper connected before?

    Rob

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    Quote Originally Posted by twin--turbo View Post
    was the copper connected before?

    Rob
    No it wasnt connected before. All i did today was unplug link 1 and plug in the copper connection to switch 1 and the whole network went back to normal.

    I agree with what you say. The person taking care of the network before me didnt document anything or keep any records of anything. When i started all they passed on to me was the administrator password. None of the teachers laptops or office computers are actually on the domain there just stand alone computers.

    Most of the network is on the way out. i have 3 new managed switches to replace 3 of the old netgear ones. a whole new set of desktops and laptops and liceses for Windows 7. (Currently on XP). So as of the summer holidays most of it will be started from scratch anyway. (and everyone will be on the domain!)

    Thanks for all your help.

  8. #22

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    It does look like a fibre fault or indeed a duplex mis-match. Personally I try and avoid media converters, as it's one more link in the chain to go wrong. Installing fibre modules, such as a Cisco GLC-MM-SX will give you a dedicated 1Gbps link over OM1, OM2 or OM3 fibre and allow you to manage it properly both ends. All major manufacturers adhere to this standard.

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    Quote Originally Posted by Michael View Post
    It does look like a fibre fault or indeed a duplex mis-match. Personally I try and avoid media converters, as it's one more link in the chain to go wrong. Installing fibre modules, such as a Cisco GLC-MM-SX will give you a dedicated 1Gbps link over OM1, OM2 or OM3 fibre and allow you to manage it properly both ends. All major manufacturers adhere to this standard.
    Yeah its looking likely to be the fibre. whole network went agian today apart from the 2 switches that are not connected via the fibre. I didnt have time to do alot of testing today but im planning on connecting all 4 switches together not through the fibre and seeing if it works. If we get back up and running then im assuming its the fibre. I also want to test if 2 computers can communicate on the switches that arnt connecting the the network (if that makes sense) to rule out problems with the switches.

    Working at 2 schools means i dont have alot of time when something like this goes wrong. I cant leave one school to go to the other as im on 2 seperate contracts for each. Meaning it just has to wait which isnt great.

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    It was one of the media converters by the way!

    Thanks for everyones help.

  11. #25

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    Did you only replace one?

    I'd recommend replacing both especially if you didn't get the exact same make/model as a replacement.

    Ben

  12. #26

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    I would ditch them altogether and replace with SFP's in a switch.

    TT

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    Quote Originally Posted by plexer View Post
    Did you only replace one?

    I'd recommend replacing both especially if you didn't get the exact same make/model as a replacement.

    Ben
    Yes i did get 2 new ones.

    Quote Originally Posted by twin--turbo View Post
    I would ditch them altogether and replace with SFP's in a switch.

    TT
    That is the plan for the future. Hopefully the very near future when i install the new switches over the summer. The new converters i got were only 20 each as a temporary measure to get it back on.

    Thanks

  14. #28

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    I was called to our sister school last year after a power cut, non of the network was working apart from near the core switch. The core was connected to access switches in far flung areas of the buildings via media converters. After backdooring the Cisco core ( they had no idea of the password ) I confirmed that it was happy, but could not see the Access switches. At the Access switches, backdoor again and confirmed they were happy. Reset all the media converters at both ends and it jumped back into life!..

    And at another of my clients sites, they have a media converter that stops passing trafic if you look at the wiring closet!

    Rob

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    Quote Originally Posted by twin--turbo View Post
    I was called to our sister school last year after a power cut, non of the network was working apart from near the core switch. The core was connected to access switches in far flung areas of the buildings via media converters. After backdooring the Cisco core ( they had no idea of the password ) I confirmed that it was happy, but could not see the Access switches. At the Access switches, backdoor again and confirmed they were happy. Reset all the media converters at both ends and it jumped back into life!..

    And at another of my clients sites, they have a media converter that stops passing trafic if you look at the wiring closet!

    Rob
    They sound so reliable! or not.

    It was strange because they still looked like they were talking to each other (Lights flashing as they should) but they just wasnt working.

  16. #30

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    TBH, I don't know why the old NM had not used SFP's everything supported them ( well to use cheap ones you have to force the Cisco stuff ).

    All the converters were showing link at 1G/FD. Just no traffic...

    Rob

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