Troubleshooting wireless
 

If anyone here knows about troubleshooting wireless cards, I'd appreciate some input/feedback.

I've detailed the problem here: [url]https://www.reddit.com/r/linuxquestions/comments/3y39d0/how_to_troubleshoot_wifi_connections/[/url]

It will be easier if I repost your original question :[quote]Long story short, since I got a bad power jack on the motherboard of my laptop fixed, the WiFi has been wonky at best and non-operational at worst.

Most networks, including ones on which it worked before, simply don't work (and it's not a password issue). There is at least one network which does work, but only for minutes at a time, and every time it disconnects, it asks me for the password again, and I have to say click "OK" each time (the password is saved and prefilled and of course hasn't changed in the last ten minutes). But on every other network I've tried it simply doesn't work.

I'm reasonably certain the wired ethernet works fine, at least it is currently with this network and cable.

I'm using LMDE/Cinnamon, and unfortunately I haven't found anywhere in the Cinnamon GUI that actually tells me what the error is (other than the utterly useless "Wireless is disconnected" a few seconds after trying to connect).

I'm familiar with the command line and sort of familiar with some parts of the underlying kernel and OS, but as far as troubleshooting WiFi goes, I'm lost, and any help is very much appreciated. I suppose it should be noted that I've had some issues connecting even in Windows (which I hadn't booted in years before trying to test this), but I'm still holding out hope there's some something I can fix on a software level that will get it working again.[/quote]Jacob

For thoroughness then, here's the sum of the discussion so far:

[quote=/u/trollblut]here is my wifi reset script, the hardware or driver is buggy and sometimes i have pings > 2000 ms, package losses or it simply won't connect.
[CODE]rfkill block wlan
sleep 0.1
echo 1 > /sys/bus/pci/devices/0000\:03\:00.0/remove
sleep 0.1
echo 1 > /sys/bus/pci/rescan
sleep 0.1
rfkill unblock wlan
sleep 0.1
ip link set down wlp3s0
sleep 0.1
ip link set up wlp3s0
sleep 0.1
systemctl restart wpa_supplicant@wlp3s0 # this step is distribution dependant[/CODE]short of purging the kernel module this script resets the hardware to pre-init level
for diagnosis purposes, do the following
[CODE]rfkill list # show hard/soft-switches that can disable the hardware
lspci # shows pci devices
lsusb # shows usb devices
ip link show # shows working network devices
ip link set dev $DEV up # activates a link in case it is down
iwlist $DEV scan # searches wifis in range (detailed), first test of the wifi-hardware
iwlist $DEV scan | grep ESSID # only shows the names of wifis in range[/CODE]from this point on, i'd recommend to use wpa_supplicant in non-daemon mode. disable your network manager, enter a console and do the following
[CODE]wpa_passphrase ESSID PASSWORD | grep -v '#' > wpa.conf
wpa_supplicant -i $DEV -c wpa.conf -d [/CODE]then you see the actual action going on. with either
dhcpcd $DEV
or
dhclient $DEV
you can request an ip via dhcp[/quote]

[quote=Dubslow]Okay some weird shit is going on. iwlist wlan0 scan either shows networks or it doesn't, and as far as I can tell, it's totally random whether it does or not.
The other commands show the following:
[CODE]bill@didact ~ $ ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
link/ether 54:04:a6:4c:ca:88 brd ff:ff:ff:ff:ff:ff
3: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DORMANT group default qlen 1000
link/ether e4:d5:3d:c5:a7:f5 brd ff:ff:ff:ff:ff:ff
bill@didact ~ $ sudo ip link set dev wlan0: up
bill@didact ~ $ ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
link/ether 54:04:a6:4c:ca:88 brd ff:ff:ff:ff:ff:ff
3: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DORMANT group default qlen 1000
link/ether e4:d5:3d:c5:a7:f5 brd ff:ff:ff:ff:ff:ff[/CODE][/quote]

I see several possibilities :

- When your laptop was repaired it could be that one of the antenna wires was not properly re-plugged on the WiFi adapter, this would lead to erratic connections. Can you open the laptop to check ? (Such a check is easy on Dell Latitudes for instance.)

- Did you try the WiFi with a live OS ? This would eliminate all software issues of your current installation.

- If it does not work with a live OS and you still have hardware warranty have the laptop repaired.

- If it works you could disable the WiFi in the BIOS, boot, remove all drivers and configuration files for your WiFi adapter. Enable the adapter in the BIOS again and see what that gives. But since you say you have the problem in Windows as well I don't think it will work.

Jacob

The first thought had occurred to me, though I'm rather useless when it comes to disassembling laptops.

I have not, though I suppose it's worth a try.

Hah! This thing is nearly four years old, far beyond warranty, and that's before I got it repaired by a third party technician :smile:

Hmm... probably couldn't hurt, at this rate...

I really appreciate you taking the time to ponder the question. Thanks!

When a scan does work, do you see a lot of networks? As wifi use increases, routers can end up fighting over available channels.

When it is working temporarily, do you have a strong signal?

Do you have other Wifi devices which work in the same environment?

[QUOTE=Dubslow;420159]The first thought had occurred to me, though I'm rather useless when it comes to disassembling laptops.

I have not, though I suppose it's worth a try.

Hah! This thing is nearly four years old, far beyond warranty, and that's before I got it repaired by a third party technician :smile:

Hmm... probably couldn't hurt, at this rate...

I really appreciate you taking the time to ponder the question. Thanks![/QUOTE]

I would consider taking it to the third party technician for him to check if he has knocked anything. Theoretically if it is something he has done accidentally you shouldn't have to pay.

[QUOTE=henryzz;420218]I would consider taking it to the third party technician for him to check if he has knocked anything. Theoretically if it is something he has done accidentally you shouldn't have to pay.[/QUOTE]

I would agree. Your symptoms sound like a badly connected (possibly badly seated) antenna.

If you take it back to the tech, watch closely what he does. Disassembling and then reassembling hardware (which then still works) is a valuable skill set, and it's not as difficult and scary as it might seem.

Although, sometimes, you need special tools (very small screwdrivers, hex/allan keys, etc) and/or know the "special places" to pull, push or twist, especially for laptops and cellphones....

Yes, as I noted yesterday on reddit, I've discovered that in my current location at least, it works totally fine when I'm within 5 feet of the router, but 10-12 feet away it doesn't work at all.

I did indeed watch him reassemble it when I picked it up from him the first time, though with a dubious retention rate -- and my set of screwdrivers is almost certainly insufficient regardless. I'll look into taking it back to him...

[QUOTE=Dubslow;420243]I'll look into taking it back to him...[/QUOTE]

Don't be benign.

Watch, learn, question.