Wireless Networking Troubles (aka I want those three days back)

This is the story of a wireless networking problem I had at home, what it was, the clues I missed, and how I eventually solved it.

The Setup

My main router is an MN-700, and its wireless is somewhat secure via WEP. I do broadcast my SSID as it makes debugging issues easier (well that is the theory). I have a repeater upstairs, a WAP11, configured similarly.

Wireless clients are New Thinkpad (T40, built-in Philips 802.11b radio), Old Thinkpad (600E, Orinoco Gold PC card), Audiotron (via Linksys WET11 wireless bridge).

The Symptoms

New Thinkpad is my wife's, and it has occasional wireless issue with losing touch with the domain controllers, but this is only slightly annoying if it stops her printing. She never loses the net connection.

On Tuesday we were having some additional wiring installed (getting ready for my HD Tivo) so I took the opportunity in the morning to pull down the latest Windows patches, plus the Wireless Rollup Pack KB826942 which I thought might help, plus an updated driver. Then I left for work.

When I got back, things were in bad shape. New Thinkpad couldn't see the net wirelessly, or wired via the tap upstairs. The wiring dudes had disconnected some stuff which I reconnected, which got her wired tap alive again. However New Thinkpad still couldnt see the wireless net. Old Thinkpad was happy with it though.

I tried my usual tricks of messing with New Laptop for a few hours, but still no luck, so I used the awesome System Restore to reset it back to Monday's state. Still no wireless network: did that Windows Update somehow change the firmware in the wireless radio??

The Audiotron could also not see the wireless net, however this was not as urgent as the laptop issue.

For the next few evenings I would spend many hours downloading stuff from the (very poorly arranged) IBM support site and trying it, adjusting settings, switching from Windows Zero Config to the IBM wireless software then back, all to no avail. The best I got was the wireless net would work for about five minutes, then would go away. There was still a good signal, but no packets could pass and the IP address would go away as my DHCP server would be unavailable.

By Thursday night I was losing it. My wife was upset she was tied to a net tap, and annoyed that me, a supposed expert with Windows, couldn't fix it. In desperation I slapped in an MN-720 PC card, but although it had a signal, again it couldnt obtain an IP address. At 11pm I decided to reboot the wireless routers, just because I had tried everything else. I got to the WAP11 and was about to power cycle it when I noticed that it wasnt connected to the wired network. It had been unplugged to plug in New Thinkpad. A lightbulb went off in my brain somewhere. I cursed, then smiled wryly to myself.

The Diagnosis

I have two wireless transmitters, same SSID and WEP key. One of them had been accidentally disconnected from the wired network. New Laptop would turn on, find the working one, get its IP address etc, be happy, then within a few minutes or so discover the other transmitter. It would decide to switch to that one, then boom! That one wasn't connected to an actual network, so neither was the laptop any more.

Clues I missed

  • The fact that the Audiotron also had wireless problems should have made me realize it wasnt an issue with New Laptop.
  • The fact that System Restore did not put back the old working state should also have made me realize it wasnt an issue with New Laptop.
  • The fact that the IBM software listed two networks with my SSID should have alerted me to the fact that yes, I have two routers, maybe I should check them both.
  • The fact that Tuesday was not only the day I pulled new stuff from Windows Update, but was also the day of general wiring changes in the wired network

One thing that I dont understand is that Old Laptop still worked great. It didnt get fooled by the errant wireless repeater. That is still a mystery to me.