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Thread: Unstable wifi connection after 14.04 upgrade

  1. #1
    Join Date
    Feb 2014
    Beans
    29

    Unstable wifi connection after 14.04 upgrade

    Hello,

    After I upgraded my PC to Ubuntu 14.04, the connection has been really unstable. The connection frequently drops, fails to connect, or is very slow. This does not occur in Windows 8. The result's to varunendra's scirpt that I have seen people using on this forum are attached. Does anybody have any idea how I can fix this, or at the very least diagnose the problem?

    I also temporarily put the result of the script on pastebin in case you don't want to download the attached archive

    http://pastebin.com/KCV5R16Z

    Thanks in advance.
    Attached Files Attached Files

  2. #2
    Join Date
    Aug 2011
    Location
    Berlin, Germany
    Beans
    7,929
    Distro
    Ubuntu Mate 20.04 Focal Fossa

    Re: Unstable wifi connection after 14.04 upgrade

    Hi,

    deactivate the N-mode of the driver (bug):
    Code:
    echo "options iwlwifi 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf
    sudo modprobe -rfv iwlwifi
    sudo modprobe -v iwlwifi
    Additionally you can deactivate the power management of the card:
    Code:
    sudo iwconfig wlan0 power off

  3. #3
    Join Date
    Feb 2014
    Beans
    29

    Re: Unstable wifi connection after 14.04 upgrade

    Thanks!! I'm getting "modprobe: FATAL: Module iwlwifi is in use." when I run "sudo modprobe -rfv iwlwifi" but the other three commands seem to have improved things. Can you (or anyone reading this) please explain to me what exactly those commands did? What is the N-mode of the card?

  4. #4
    Join Date
    Aug 2011
    Location
    Berlin, Germany
    Beans
    7,929
    Distro
    Ubuntu Mate 20.04 Focal Fossa

    Re: Unstable wifi connection after 14.04 upgrade

    There are different modes your router provides (or could provide depending on the model): a, b, c, g and n. Here, the N-mode of the driver is buggy. You can check the router manual

  5. #5
    Join Date
    Apr 2014
    Beans
    6

    Re: Unstable wifi connection after 14.04 upgrade

    I even tried newer kernels (3.15.0-031500rc3) but the issue persists.
    Disabling N mode "fixed" the issue for now.

  6. #6
    Join Date
    Apr 2014
    Beans
    6

    Re: Unstable wifi connection after 14.04 upgrade

    I take it back...disabling N mode does not fix the issue.
    Looking at iwconfig, I have extremely high Invalid misc packet count. Right now, it is over 3,000, and my uptime is 5 minutes. After a few hours of browsing, it is well over 600,000.

  7. #7
    Join Date
    May 2007
    Beans
    17

    Re: Unstable wifi connection after 14.04 upgrade

    Disabling N mode worked for me.

    Code:
    radu@sasuke:~$ iwconfig
    wlan0     IEEE 802.11abg  ESSID:"FOO"  
              Mode:Managed  Frequency:2.462 GHz  Access Point: 28:BE:9B:05:7E:68   
              Bit Rate=54 Mb/s   Tx-Power=15 dBm   
              Retry  long limit:7   RTS thr:off   Fragment thr:off
              Power Management:off
              Link Quality=50/70  Signal level=-60 dBm  
              Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
              Tx excessive retries:0  Invalid misc:1093   Missed beacon:0
    
    radu@sasuke:~$ uptime
     23:56:59 up  3:13,  2 users,  load average: 0,29, 0,46, 0,47
    I hope they will fix the 802.11n mode, as it's really annoying to use a slower speed.

  8. #8
    Join Date
    Feb 2007
    Location
    Norman, OK
    Beans
    52
    Distro
    Ubuntu Development Release

    Re: Unstable wifi connection after 14.04 upgrade

    This issue still persists with the latest beta of Ubuntu 14.10... You'd think that would be resolved; such a basic functionality of an OS. Hate to having to boot into Windows just to get persistent wifi connectivity.

  9. #9
    Join Date
    Oct 2013
    Beans
    37

    Re: Unstable wifi connection after 14.04 upgrade

    This did not work for me, I may need additional help here. Sometimes I don't even get a list of available WiFis.
    Code:
    wlan0     IEEE 802.11g  ESSID:off/any  
              Mode:Managed  Frequency:2.437 GHz  Access Point: Not-Associated   
              Bit Rate:1 Mb/s   Sensitivity=-200 dBm  
              RTS thr=2346 B   Fragment thr=2346 B   
              Power Management:off
              Link Quality:0  Signal level:0  Noise level:0
              Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
              Tx excessive retries:0  Invalid misc:0   Missed beacon:0
    
    
    lo        no wireless extensions.
    
    
    eth0      no wireless extensions.
    
    
    usb0      no wireless extensions.

  10. #10
    Join Date
    Aug 2011
    Location
    Berlin, Germany
    Beans
    7,929
    Distro
    Ubuntu Mate 20.04 Focal Fossa

    Re: Unstable wifi connection after 14.04 upgrade

    Change the mtu value to 1500 instead of "Automatic" in the network manager profile

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