Wifi not working + previous experience with kernel panic - Realtek 8821AE

**praseodym** · September 4th, 2014

Do you get an IP address?

Code:

ifconfig -a
arp -v

**francis3** · September 4th, 2014

I don't believe so.

ifconfig -a gave me

Code:

wlan0     Link encap:Ethernet  HWaddr 6c:71:d9:bc:14:19  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

arp -v gave me just one entry for the wired connection.

**praseodym** · September 4th, 2014

Unplug the cable and check

Code:

sudo dhclient wlan0
ifconfig wlan0
iwconfig wlan0

**francis3** · September 4th, 2014

sudo dhclient wlan0 gave me nothing

ifconfig wlan0

Code:

wlan0     Link encap:Ethernet  HWaddr 6c:71:d9:bc:14:19  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

iwconfig

Code:

wlan0     IEEE 802.11abgn  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm   
          Retry short limit:7   RTS thr=2347 B   Fragment thr:off
          Power Management:off

**varunendra** · September 5th, 2014

Just curious - is your router a dualband one? Are 2.4 GHz and 5 GHz both enabled? If yes, I thing you should try disabling 5 GHz mode and try 2.4 GHz only. The change may require a reboot on both the router and the laptop to take effect properly.

Additionally, try explicitly setting the country code for regdomain settings -

Code:

sudo sed -i 's/^REG.*=$/&CA/' /etc/default/crda
sudo iw reg set CA

**francis3** · September 6th, 2014

I don't think it's dualband. Here is the info on the modem router.

http://www.actiontec.com/191.html

**varunendra** · September 6th, 2014

Hmm.. indeed it doesn't look like it can do dualband, not sure why the driver is going crazy about the 2.4/5GHz modes.

Anyway, looking at the router's manual gave me some more ideas -

1) Make sure 'WMM' is disabled. Evidently it is often a cause of troubles, although those troubles are 'slow speeds', not connection failure altogether.
2) Try 20 MHz channel width if it is set to 40 MHz.

And did you set the Regdomain code to 'CA' as suggested? Make sure the region in the router is also set to 'Canada'.

**francis3** · September 7th, 2014

Ok. WMM has been disabled. I was able to connect briefly but then the signal dropped again when the modem was restarting after I disable WMM. Channel is now at 20 MHz.

And yes, I've set the Regdomain to CA.

**varunendra** · September 7th, 2014

Originally Posted by francis3

I was able to connect briefly but then the signal dropped again when the modem was restarting after I disable WMM.

Obviously it would disconnect when the modem is restarting, but could you connect again when it got up and ready again? After a system (laptop) reboot?

Sorry for asking the obvious, but my experience has taught me that it is sometimes the obvious that needs to be cross-checked first, and then sometimes there is nothing else to check next.

**francis3** · September 16th, 2014

Hi Varun,

The whole modem was changed and now the wifi works again. I haven't experienced any drop since. I am going to mark this as solved.

Thank you all so much for your help. =)