Networking between two buildings - issues!

[smurfomatic]

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!

[localzuk]

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.

[smurfomatic]

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?

[localzuk]

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.

Edited February 10, 2011 by localzuk

[m25man]

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.

[Willott]

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.

[smurfomatic]

@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!)

[smurfomatic]

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...

[localzuk]

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.

[steveg]

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

[smurfomatic]

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?

[localzuk]

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...

[smurfomatic]

Compare it to the person's salary...

 

Good point - as they probably get more than me, I'll ask them to pay for it!

[plexer]

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

 

Ben

[smurfomatic]

@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!

[plexer]

I wasn't suggesting you marched in there and told them to pack their bags but that piece of information wasn't available at the time it was more of is there a non-technical solution to the problem

 

Ben

[m25man]

10mb - 100mb, they still use the same 4 wires so if it works at 10mb there is no reason why it shouldnt work at 100mb.

 

If you have a "10mb Hub" at the far end and a node and a printer there is still plenty of scope for anything to bring all of your hub ports down thus causing the packet loss across your link.

All broadcast traffic is going to want to transit your link anyway!

 

Also, if you have an Autonegotiating Switch at one end and a 10Mb dumb hub at the other the switch is likely to complain bitterly about whats going on at the far end.

I would definately be looking to terminate each end with matching equipment or at least something that can autonegotiate correctly!

 

As for replacing it with Wifi - use a 5Ghz Ubiqiti Nano M Link, they are unbeatable with true wire speed 200Mhz Full Duplex with enough change out of £750 to have a weekend break in Barcelona....

[pennywest]

We went down this route a couple of years ago and decided it was easer with less hassle to get them broadband internet access and then use logmein to connect to a dedicated computer terminal in the main building.

[smurfomatic]

@m25man - the laptop negotiates down to 10MB as well, the Belkin hub I used was 100MB (the only reason I used the 10MB hub was it's the first one that came to hand). The printer isn't connected tot he hub at the moment, when I'm testing it's just cable in - hub - cable out to laptop. This is one of the reasons I'm confused...it should work at 100 if it works at 10!

 

@pennywest - unfortunately the phone line goes through our switchboard, so the only way to give them broadband would be to pay for a dedicated line.

[sparker]

Presumably you have checked that the cables are ok with a cheapie cable tester - that done perhaps next step is to isolate the cable say by connecting a little switch at one end and a laptop at the other and doing some speed tests. At least you would know if the problem IS your cable and not some other network gremlin - sorry if that is too obvious but sometimes you can waste a lot of time on the wrong hypothesis. If it is both of the cables then I would say some environmetal issue is at play somewhere.

I spent 3 hours checking powerline connectors that we were using to connect 4 temp classrooms rooms that all looked to be working but didn't actually ping and finally discovered that some helpful person had connected both ends of an ethernet cable into a switch but only got there by testing each component

[smurfomatic]

I've gone back to basics and checked the cable - it's intact and traffic goes OK. Must be some kind of interference, but I'm blowed if I can find where it's coming from!

[localzuk]

I've gone back to basics and checked the cable - it's intact and traffic goes OK. Must be some kind of interference, but I'm blowed if I can find where it's coming from!

 

Have you tried STP cable instead of UTP?

[smurfomatic]

Haven't got any STP cable to try, as I've said earlier didn't want to spend a few hundred quid on another drum of cable only to find it's still causing problems. Plus of course our maintenance men will get fed up with re-doing the same job...

 

I think we're going to have to bite the bullet and put a wireless link in - time to ask the boss how much we have left in the budget, that's not going to be popular if it means other people aren't getting the new PCs they've been asking for...

[3s-gtech]

Nooooo - forget wireless! Fibre it, it's not that expensive. I haven't spent more than £35 on a mini GBIC in years and I only buy official HP ones - you can save a fortune on them, and it'll be a job done properly.

[localzuk]

Nooooo - forget wireless! Fibre it, it's not that expensive. I haven't spent more than £35 on a mini GBIC in years and I only buy official HP ones - you can save a fortune on them, and it'll be a job done properly.

 

Huh? How????