Laser Link bringing down network

[nip]

Can anyone shed any light on this problem, possibly someone has had something similar happen? Last year I had a laser link installed to allow a seperate building access to the network. This was working fine until a couple of weeks ago when all the workstations on the network hung, and rebooting the server had no effect. Thinking it was a switch failure due to the hot weather (server and switches are kept in a small cupboard, gets v. hot in summer months, but at least I was finally able to persuade them to get me an air conditioner unit!) i was troubleshooting along those lines when I realised that all would work well until I plugged in the patch cable running (via a POE injector) to the laser unit, carrying out a continuous ping to the router from the server whilst plugging unit in and out confirmed it was dropping the connection when plugged in. As far as I am aware, the laser unit doesn't use an IP address as its just a medium to transfer data (as is a normal cat5 cable), I've even terminated the link into a different patch panel with no difference. Just can't understand why this would affect the link to the router, they're not even on the same segment of the network, anyone think of something else I can try?

[Geoff]

network loop at the far end of the link?

[DaveJ2717uk]

Or as we were told once ("the building must have moved with the heat") causing loss of link. Still laugh about that....

[bizzel]

Just a thought. What would happen if an eagle-eyed student managed to bring in a laser pointer and hit one of the units?

[kmount]

They'd get a marksman at Bisley!

[ICTNUT]

Can you tell us what units you are using??

We have a number of LaserBit links and have never had issues with these from the point I installed them no matter what the weather.

We have had kids try to break the beams but they never manage to cause any issues.

[srochford]

We have a number of LaserBit links and have never had issues with these from the point I installed them no matter what the weather.

We have had kids try to break the beams but they never manage to cause any issues.

Ours were generally reliable except in fog (which London gets too much of in early mornings in the autumn) and on one occasion when snow blew directly onto the front of the unit.

Dare I ask how kids were trying to break the beams? Are they near ground level?

[nip]

Thanks for the replies, chaps. These are 100Mbps Laserbit units. I've tried disconnecting the far end, and even tested the POE injector from the other building in the main building with the same results, I admit the symptoms seem to suggest a loopback issue, but i've isolated it to just that link so it must be either a faulty cable, or the laserbit unit itself. I'm going to try and bypass the cable next week during half term to see if this works, if not, it must be the laserbit unit itself causing the problem, would you agree?
As for pupils sabotaging the system, it does raise an interesting point doesn't it, were a special school so while I have doubts about our kids doing this, you should never say never, as the saying goes!

[Geoff]

We have had kids try to break the beams but they never manage to cause any issues.

Heh, I have an image of a kid jumping up, hand outstretched, only to have it burst into flames as soon as he makes contact with the laser beam.

[bizzel]

On a serious note, I'd suggest that either the cable or unit has failed. How are they powered and can you reset them?

[nip]

They're power over ethernet (using 3Com injectors), and I didn't see a reset button on the laser unit although I was wobbling about on my rickety set of ladders and not really looking, I'll see what I can find again today when I bypass the cabling.