No access point problem

pwabrahams · 02-17-2008, 08:59 PM

I have an Acer laptop with a built-in wireless card. Right now I'm at a friend's house, sending this post under Windows because I can't get Linux to make a wireless connection here. I've used this laptop at three different locations: home (WPA-PSK enabled), a motel, and my friend's house. The router in this case belongs to her landlord and so is inaccessible (in particular, I can't reset it).

I'm trying to make sense of these observations:

1. At all three locations, the laptop connects perfectly well under Windows. Under Linux, the signal strength is adequate even when I can't connect.

2. At home I usually get a connection, but not always. When I don't get it, resetting the router solves the problem. As I noted above, my home connection uses WPA-PSK security; my Linux system uses wpa_supplicant. When I don't get a connection, the symptom is that the access point has no association.

3. At the motel I was able to get a connection but I had to disable wpa_supplicant, which makes sense since the motel has an unsecured wireless router.

4. At my friend's house I can't get a connection at all (under Linux, that is) because the access point has no association. However, iwlist ath0 scan does show the router.

I've drawn certain conclusions:

1. Although resetting the router at home is sometimes necessary for Linux, it is never necessary for Windows. So it should be possible to get the Linux connection at home without resetting the router since the hardware side of the picture is functioning (the Windows success shows that).

2. The wireless connection is sensitive to the router state but not totally dependent on it since Windows works. The motel router was set in such a way that Linux worked but the landlord's router is not. Both motel router and landlord router are unsecured.

I've tried these things at my friend's house, without success:

Code:

iwconfig ath0 essid "router essid"
dhclient ath0
ifup ath0

For all of these I get "access point: not associated". I've also tried using Wireless Assistant, which worked at the motel but not here.

I'm running Kubuntu Gutsy Gibbon.

jolphil · 02-18-2008, 07:31 AM

Hello,
First off I am not a guru but I use Kubuntu as well as others and have stayed in a Holiday inn express"Bad joke"..I have found in my case that so far I have had limited success with WPA but can usually connect with unsecured and WEP..I would think if the AP is a problem you could as su
do a "iwlist ath0 scan" to determine the access points MAC number then a "iwconfig ath0 ap XXXXXX" to set it to the correct ap..Then do a "iwconfig ath0" to see if it worked..
Thats how I usually stumble around it...Have you tried "wifi-radar" ? that has worked sometimes too..
Overall if you read the forums like this one or specifically the ubuntu forums you will see wireless is a general problem, but there are some "How to's" that do help ..There does not seem to be a "magic bullet" to wireless..
Thats about all I can add but I feel the someone more knowledgeable will jump in and help..
Good Luck and PS: I know your area well as my grandson lives in south Deerfield..
jolphil

pwabrahams · 02-18-2008, 12:57 PM

I tried connecting to ath0 by specifying the access point, but that doesn't work either. The problem is that the router won't send a DHCPOFFER message. (For a successful connection to the router, I see such a message in the output of iwconfig.)

The router at the motel connects under Linux; the one here does not. Both are unsecured, and both connect under Windows. So I now assume that there's some difference between how Linux asks for a DHCP address and how Windows asks for a DHCP address. Furthermore, based on my experience at home, a router can be in either State A or State B. In State A, it will issue a DHCP address to Linux; in State B it won't. Resetting the router moves it to State A, but some random events can move it back to State B. The router here is apparently in State B, and I can't get at it to reset it. The one at the motel was in State A, so I got my Linux connection there.

So I suppose the solution is to find some way to jigger the DHCP request so that it looks like the one that Windows issues.
Or wait until I get home and use Windows in the meantime.

jolphil · 02-23-2008, 03:09 PM

Quote:

Furthermore, based on my experience at home, a router can be in either State A or State B. In State A, it will issue a DHCP address to Linux; in State B it won't. Resetting the router moves it to State A, but some random events can move it back to State B. The router here is apparently in State B, and I can't get at it to reset it. The one at the motel was in State A, so I got my Linux connection there.

Gee, I never heard of that..Can you help with the A or B thing? Routers can have lots of configuration settings but I never saw that listed anywhere unless you are referring to the standard
A,B,G, and now N standards..(I am Confused)
jolphil

pwabrahams · 02-23-2008, 04:14 PM

Those A and B states aren't any kind of official or standard states. State A is characterized by my laptop being able to connect under Linux; state B is characterized by it being unable to connect under Linux. Other than those characteristics, I have no idea what's going on in State A or State B. I wish I did.