Fighting with computers

Computers are not always friendly.

Saturday, August 12, 2006

Weird Wireless

I'm visiting a friend who has a new house and a new wireless setup from Telef├│nica. He needed some help from his company IT department to get the thing working. On arrival he tells me that he can use the wifi connection and it works, but at the same time the computer says it is not connected.

I suspected that odd behaviuor could be due to the common WinXP/manufacturer driver schizophrenia where both the system and the wifi card manufacturer's software are trying to manage the card settings. I tried to disable the WinXP handling of the card but then I was getting disconnected. So I tried the wifi card's software: Hmmm, cool! Network scanning shows a beautiful sonar-like display where you can the different networks on your neighbourhood, names, MAC addresses, channels and ... surprise: There are two different AP using the same ESSID nearby on different channels. This is probably because a neighbour has a similar setup as my friend's.

Ok, time to change the ESSID to something different, like my friends first name. However, I cannot log on the wireless router web interface. I do not know the admin password and it is not provided together with the user documentation. What it is provided is a windows software that does the configuration of the wifi router. A couple of attempts gets the ESSID changed to unique name (unless in this neighbourhood).

Now I should be able to get my laptop and my wife's working at my friend's but it is a no go. My laptop just cannot see that network name even if am ten inches away from the router. It does not seem like a signal problem as my friend's laptop is working ok. I started my trusty Ubuntu and I can see the network and I can received the beacons using ethereal with the card on monitor mode but I cannot log on the network. The problem becomes apparent when I try to select the channel: iwconfig eth1 channel 12 gives me an error. So the problem is that channel 12 is not allowed in this country and both Ubuntu and WinXP are avoinding it. Time to change to a new channel.

Once the channel has been set to a valid channel everything goes ok with any of our systems. Please note that setting your ESSID to a unique name in your neighbourhood is a key point to get a trouble-free wireless experience. If you use the default ESSID of your router you are calling for trouble. You can or cannot be lucky, but if you are unlucky the problem is that you'll have intermitent connectivity.


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