bad wireless card or software problem?
 

A few weeks ago I switched from fiber to cable. My router switched as well. The only settings that are really different is the address mask. The router is 10.0.0.1 instead of 192.168.1.1, and the new DHCP pool is from 10.0.0.4 to 10.0.0.253. The problem is, that since then I haven't been able to get my wireless card in one machine to work. The rest are fine. Now I know what you are thinking. Obviously, it has something to do with the router. The problem is. I don't see anything wrong with it.

Indecently the one machine is a laptop which seems to work everywhere else. However, in the past month or so. download speeds have drastically decreased. For example a file that should be a 10 minute download comes up as 19 hours.

here's what I have tried so far. without changing anything the laptop see's the network and when I ask it to connect, it does. ifconfig shows that it is assigned a valid IP. When I log at the log files in the router it shows the dhcp request but don't show record or my machine connecting or having ever connected to the network.
Occasionally I can ping the router, with horrible latency. bit even that is rare.
I have an external usb card. Works, as long as I bring down the other device with ifconfig, but still very slow. Speedtest.net rates it at 3.49 mbps down 4.05 up. My computer connected to the router gets 52.9 mbps down and 10.7 up.

to me it kinda sounds like a software problem, but I'm not really sure what to check. Any suggestions?

Also, this is probably just a coincidence but a couple weeks before I started noticing slow speeds I switched from Gentoo to Ubuntu.
I don't see what that would change anything, but I just figured I'd mention it.

some of these may help

lspci
http://paste.ubuntu.com/5613603/

lsusb (the RTL8187 is the usb card that still works slowly)
http://paste.ubuntu.com/5613604/

Just off the top of my head (ie before starting to think) I would first try running a live Ubuntu or some other distro from a USB stick or SD card. With a totally clean environment does the wireless network still show problems? You've tried a different wireless card I gather so it sort of rules out hardware issues. Are they still there when connected with an ethernet cable? What about network copies between local machines?

Other than that it's difficult to see what could cause slowness other than a poor quality wireless link or a slow responding web server stuffed with ads.

Ken

Assuming that the router contains the wireless radio, changing routers changed the receiver sensitivity, transmitter power, antenna pattern and possibly the connection frequency used by your wireless network. All of these can affect the reliability of the connection. If you are using encrypted wireless, a noisy connection causes major problems for wpa_supplicant as it tries to authenticate with the router. You will need to use the wireless tools for your system to figure out what is going on. Wpa_supplicant can be run manually with debugging enabled to see if it is having trouble staying connected. If you have the old router, try the same experiment and see if the output differs. You might also try running without encryption as a test (but don't leave it that way!). Since the hookup works, albeit slowly, the chances are that nothing is "broken", but that the ensemble of your equipment is not playing nicely together. On my system, I had to upgrade a wireless adapter from what came with the machine due to similar problems.

Never mind, I missed the part about the other wireless connections being OK.

Thanks guys,

Trying a live CD does sound like a quick way to find out.

Rod3775, you're comments are similar to what I was thinking based on all of this. It just seems strange that it would

a. go from working perfectly to basically not working at all on one network with a new router.
b. simultaneously become extremely impaired on all other networks
c. Transfer enough information to get DHCP info, but not enough that the router even knows its there

perhaps it's not a hardware issue but it seems lower lever than applications or modules.

I'll look in to diagnosing the wpa_supplicant and let you know what I figure out.