Wierd network problem

[LeMarchand]

Hi, I did search to see if anyone had had a similar problem but didn't find anything...

Anyway, one of my schools has a wireless network consisting of 6 3 Com APs (which replaced 6 older APs) installed by PC World as part of a deal where the school bought 200+ laptops (1/child) so the chances of getting any support from them is pretty slim. (I know, the choice was made before my time - I certainly wouldn't have recommended PCW).

Anyway, most of the time the network is fine. However, every so often it cuts out. All APs are showing as on etc, but only get picked up intermittently. The problem normally lasts for an hour or two and then cures itself. I don't think that this is a network problem as such, as I can normally pick up various nearby domestic signals, and these go out at the same time. The problem seems to be limited to the actual building as I can go outside and pick up neighbouring signals (and often our own). The building is mainly brick and steel with a large glass roof.

The outages may be time related (so far they have happened between 10 and 12 in the morning) or possibly weather-related (possibly when the sun comes out after a dull spell). Nearby we have a number of houses on one side, and a small quay and various light industrial units on the other. The units include a garage, Plumb Base and a welding place.

So, has anyone got any ideas as to what could be causing the outages?

[tech_guy]

Have you tried using NetStumbler to see what other wireless networks are in your vicinity?

[LeMarchand]

Yeah - either doesn't pick anything up until I go out of the building or shows 1 or 2 APs (could be the schools, could be private) normally grey but occasionally flashing green for a few seconds.

In fact I tend to leave NetStumbler running when the problem occurs as as soon as it starts lighting up, I know it's safe to tell the teachers the network is back up.

[SYNACK]

Could be large scale rf interference, I had a client location that was near to a manufacturing facility. One of the machines nearby must have been badly wired and so spiked a huge amount of interference which killed the WiFi but only intermittently. Probably when they turned it on. The solution at that site was to go to 11a but you might want to get some gear to scan the frequencies. Someone was talking about it on here earlier but I can't recall what it was called.

You could also try using this to narrow it down:
uanr.com - 802.11b/g Wifi Spectrum Scans

[ozzy]

"and a welding place"
Arc welding equiptment does cause interferance to wireless gear, maybe they are using a bit if equiptment that does big welds!!(joining pipes etc) there is also a type of welding for plastics that uses RF.

[fatnhairy]

had issues with 3com WAPS where they go AWOL. Solved by putting timer switches on power injectors to turn them off for 15 mins at 5am every morning.

Also, worth getting a wireless survey of site done. we use airmagnet and its excellent

[LeMarchand]

Cheers, everyone!

I guess that I feel a bit better now that I have confirmation that it could be outside interference. I'll check whether they're using a/b/g next time I'm in. As the welding place is one of the networks I can pick up, I might just pop in and ask if they get problems too.

I've tried rebooting the APs and injectors to no avail. They're mounted quite high up, necessitating the use of a stool/metre rule. Unfortunately the old geezers wandering around last time I was doing that were from Health & Safety .