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Wireless Networks Thread, Networking between two buildings - issues! in Technical; ...
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    Networking between two buildings - issues!

    First post here - sorry if these questions are answered elsewhere, but I'm quie busy and haven't had time to search.

    Having had problems with network traffic I recently bought an Ethernet extender to cure the problem, but it hasn't worked.

    Let me explain. We have two buildings connected (over telegraph poles) by approx 80 metre length of external grade CAT5, which worked fine for some months. At some point over Christmas, the connection dropped out and there was massive (approx 30%) packet loss. We put in another length of cable with the same problems. I was hoping the Ethernet extender would boost the signal enough to cure the packet loss but it doesn’t seem to work. Plugging in to different sockets on the POE switch at the “near” end makes no difference.

    The strange thing is, if you plug a laptop directly into the “far” end of the cable, it works fine (though it handshakes down to 10MB). However, if you attach it to a hub/switch the connection is lost (computers won’t be issued IP addresses, and if you used fixed IP there’s no traffic back).

    I’m completely at a dead end regarding solutions – I can’t think of anything else to try. The likelihood of having two damaged pieces of cable is minimal, but I can’t run a third attempt without buying another drum – which would be good money after bad at this point. Suggestions would be welcome!

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    localzuk's Avatar
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    I've been discussing this sort of potential issue with copper between buildings here, should we wish to go that route.

    The issues you may be having could be due to grounding problems - ie. the grounding voltage in each building could be different, and therefore the signal on the cat5 cable is disappearing.

    As others have advised me repeatedly - fibre is the best option.

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    I'd thoughht along similar lines, however I can't understand why this problem only occurred after several months of error-free connection.

    Any ideas how much a fibre link would cost?

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    localzuk's Avatar
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    Quote Originally Posted by smurfomatic View Post
    I'd thoughht along similar lines, however I can't understand why this problem only occurred after several months of error-free connection.

    Any ideas how much a fibre link would cost?
    What switches exist at each end?

    For a 100m run of pre-terminated fibre, you'd be looking at around £350. Then you'd need either mini-gbic's or media converters for each end, which will come in at around £200 each.

    So, total of about £750 for that I'd say.
    Last edited by localzuk; 10th February 2011 at 11:15 AM.

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    You should be able to maintain 100mb across 80 meters no problem. however if you are using solid copper CAT5 over a catenery wire you will need to be very careful with any flexible loops etc as these can crack and breakdown with age.
    Multistrand is better for these runs.

    As long as the cable wiremaps ok and has been tested for losses and NEXT there is no reason it wouldnt give you Gigabit.

    If as you say it work fine with a laptop at the far end of the run, your problem is most likely excessive broadcasting from a node in the labs that are normally seen on the end of that uplink.

    A few minutes capture with any packet analyser should reveal the culprit.

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    Quote Originally Posted by m25man View Post
    If as you say it work fine with a laptop at the far end of the run, your problem is most likely excessive broadcasting from a node in the labs that are normally seen on the end of that uplink.
    From the sounds of it it doesn't work fine (link speed drops to 10Mb). Are there any possible sources of electrical interference near the cable run (ie is there anything that's been added nearby over Christmas?)? I'm assuming the extender doesn't make a difference? If there's electrical interference, the extender would also repeat/amplify any interference on the cable.

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    @localzuk - the "near" end is a HP Procurve 2600, and the far end has been tried with an old 10MB hub and a Belkin F5D7231 wireless point/switch.

    @m25man - haven't tried packet analysing, but as I've said nothing changed hardware-wise from the time it worked to when it stopped. This was why I'd assumed it was a faulty cable. It is solid core, but it would be strange to have the second cable break immediately on installation.

    @Willott - nothing has changed in the area. The cable spans across the poles with one telephone cable - the phone still works fine (in fact it rang while I was in the office today!)

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    PS £750 is a bit expensive considering it's really only one person that uses the connection at the far end. However, there's a networked printer in their office which others need access to, which is why a hub is needed...

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    localzuk's Avatar
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    Quote Originally Posted by smurfomatic View Post
    PS £750 is a bit expensive considering it's really only one person that uses the connection at the far end. However, there's a networked printer in their office which others need access to, which is why a hub is needed...
    It might seem expensive, but compare £750 to not being able to connect that person to the network, and those others not being able to print. Also consider the life span of the cable.

    Also, you could consider a wireless link. Get a couple of APs, a couple of external antennas and use them as a wireless bridge. You could probably do this for a couple of hundred quid.

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    Comms express do custom made pre terminated fibre - we've used them before for this sort of thing, have a look here Custom Multimode Preterminated Fibre Cable - should be about £180 for 80m of 4 core. you do need a good sized hole into the building though, as the end comes in a protective case for when you pull it. Also need to protect the exposed fibres after you install.

    Then i'd put in one of these at each end - NETGEAR ProSafe 24 Port Gigabit Smart Switch - Misco.co.uk 24 port gig switch and comes with a free gig fiber module!

    Total cost is about £480.

    Steve

  11. Thanks to steveg from:

    AngryTechnician (18th February 2011)

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    A wireless link is a possibility, we've used them on another building (which we eventually had to replace with a laser link as it had a lot higher traffic than what we're discussing here). I will try to get over there today and packet analyse to check if it's a faulty component along the way, though I doubt it.

    We have fibre in place between buildings on site, though this is underground and has been installed for many years, we've never had any problems. The issue comes down to budget - can we justify a few hundred pounds (even for the "cheaper" wireless link) on an installation for one person?

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    localzuk's Avatar
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    Quote Originally Posted by smurfomatic View Post
    A wireless link is a possibility, we've used them on another building (which we eventually had to replace with a laser link as it had a lot higher traffic than what we're discussing here). I will try to get over there today and packet analyse to check if it's a faulty component along the way, though I doubt it.

    We have fibre in place between buildings on site, though this is underground and has been installed for many years, we've never had any problems. The issue comes down to budget - can we justify a few hundred pounds (even for the "cheaper" wireless link) on an installation for one person?
    Compare it to the person's salary...

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    Compare it to the person's salary...
    Good point - as they probably get more than me, I'll ask them to pay for it!

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    There's no way to relocate this person into the main buidling?

    Ben

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    @plexer - unfortunately this is a link to the school's sports hall, and the person in question has an office there. There's no other office space anywhere nearby. It's also a long way outside my job description to just tell them to move!

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