Losing network connectivity

[CAaronL]

Hello Kubuntu community,

I was so impressed with Kubuntu Raring, that I just had to live on the bleeding edge and try out 13.10 (Saucy). It's fun to see it evolve into a stable version, and overall, I haven't had any major issues, but there is one recurring issue that is more than a little annoying. I am hoping that someone more experienced with (K)ubuntu/Linux than I am might be able to recommend a fix.

As long as I just leave the computer running, Kubuntu Saucy works just as it should. I regularly (apt-get) update and upgrade, and as long as I'm leaving the distro actively running, there are no problems. Whenever I restart the computer for any reason, however, I lose network connectivity. I have a hard line running to the ethernet port on my PC's motherboard, and after a reboot, it's as if the network cable is unplugged. DNS lookups fail to resolve, and my LAN is completely unreachable from my Kubuntu PC.

I have learned that I can always get the network connection back, by doing the following:


* Reboot Kubuntu Saucy into "recovery mode."

* Choose "enable networking"
(in recovery mode, there is never a problem enabling
and getting the network connection working)

* Choose the "repair broken packages" (dpkg) option.

* Choose the "resume normal boot" option.

Kubuntu proceeds to boot normally, and all my network problems are fixed. I have gone through this process dozens of times now, and although I can always get my Kubuntu PC's network connection working again, it's kind of a pain to go through all this every time I have to restart the computer for any reason.

Anyone else having this issue, or have a guess about what exactly might be going on?

I would really love it if someone did figure this out.

Thanks!

[oshunluvr]

You could try configuring your lan manually. Based on my historical experience, it's likely a network manager problem. I've always just removed it from my desktop computers and configured everything without it. With 13.04, I didn't bother purging it as usual I just edited /etc/network/interfaces and put my name server in /etc/resolvconf/resolve.conf.d/tail

[GreyGeek]

By chance is your NetworkManager have the checkbox "Enable Wireless" checked?
If it does, even if you don't connect to a wireless lan, I've found that my wireless chip driver (ath9k) will drop the DNS address, even though the NetworkManager shows no indication of such and shows everything as just hunky dory. If I stop and restart my ath9k and eth0 connections I get connectivity again ... for a while. My dropping the DNS stopped when I unchecked "Enable wireless" and rebooted. Every time the ath9k driver is updated I retest it. So far, no joy. For me, it doesn't matter because my wife's Kubuntu (running on her Acer Aspire One 0D521 Netbook) picks up the wireless router and runs just fine.

[CAaronL]

Thanks for the advice.

What ended up working for me was to completely uninstall (apt-get purge) network-manager, reboot, and then reinstall it. Next time I booted up, I was online without any issues.

I wouldn't have even have known to target the network manager as causing the issue, so thank you for focusing me in on that.

[marco07]

Folks, I came here through a search. Here is my dilemma:
I have no idea how i lost my wireless connection and network manager nolonger sees my Lan's workgroup. I am suspecting perhaps a latest upgrdae may have caused it. It used to work well and i alway had automatic connection right after a boot-up. But lately, not that auto connect does not work, but also i can not reconnect through a fresh reconfiguration either through system settings or through network manager's icon on the system tray. Every time it trys to connect as shown by the icon, but evantually stalls. On one occation, after several trys, it connected, but it was so slow (1 to 3 bits/s) connection that I had to interrupt and retry with no success.
I followed above uggestions with no success. Rgarding the last suggestion (apt-get purge & apt-get reinstall network manger), I could not do that since without wireless I have no connection to the internet.
Any other ideas and suggetions to try befor I proceed with download & re-install of the new ISO.
Thanks in advance!
P.S. I must add that I have both Ubuntu 13.04 & Kubuntu 13.04 installed on separate partitions on the same hard drive without any similar issues.

[molecule-eye]

With some of the latest updates, my wifi isn't properly working in Saucy. It detects wifi networks but either won't connect to them or (more often) does but the internet is so slow it's unusuable (pages often don't load at all). Wired networking works just fine. I haven't tried any of the suggestions here but I will and get back. Either it's the network manager (I've tried both applets--the old and new) or the kernel update--I hope it's the former!

[SteveRiley]

It helps to know your hardware...sometimes wireless problems can be fixed by altering the module/driver configuration. Please copy/pasta the output of:

sudo lshw -C network

[GreyGeek]

You're in good hands with Steve!

I think I've finally narrowed down my intermitent Internet connection to one cause: the ath9k driver for my my AR9462 Wireless Network Adapter. If I blacklist it, "modprobe -r ath9k" it, and then "depmod -a", it never loads and my eth0 connection is rock solid. Modprobe ath9k back in and even if I uncheck "Enable Wireless", my eth0 connection repeatedly fails. If I enable wireless and make wlan0 the active connection the first thing I notice is that I often have to repeat the wlan0 connection attempt until it finally recieves an IP address. When it does succeed the rate often flucuates between 1Mb/s and 54Mb/s, with various stops inbetween, but eventually settles on 1Mb/s. When the rate is 1Mb/s the connection breaks and I must restart the network-manager service to reconnect.
With only a wlan0 connection my internet connection is essentailly unusable.

But, I have the luxury of being only 2 feet from my wifi router so I am always connected by eth0, and with ath0k missing from the list of kernel modules my connection is as fast and stable as Windstream allows..

[SteveRiley]

I think I've finally narrowed down my intermitent Internet connection to one cause: the ath9k driver for my my AR9462 Wireless Network Adapter. If I blacklist it, "modprobe -r ath9k" it, and then "depmod -a", it never loads and my eth0 connection is rock solid. Modprobe ath9k back in and even if I uncheck "Enable Wireless", my eth0 connection repeatedly fails.

That is totally baffling. The mere presence of the module for your wireless interface causes your wired interface to flake out. That is some goofy horkage.

What kind of wired interface do you have, and what's the driver for it?

[GreyGeek]

0d:00.0 Network controller: Qualcomm Atheros AR9462 Wireless Network Adapter (rev 01)
0e:00.0 Ethernet controller: Qualcomm Atheros AR8151 v2.0 Gigabit Ethernet (rev c0)

The eth driver is the atl1c. It has no properties to modify. (When I say rock solid I am excluding the playing of YouTube videos, which can diconnect my internet on occasions and force me to redo "sudo service network-service network-manager" as well. When that happens here are the only log notifications:

[27066.960543] ICMPv6 checksum failed [2001:4978:000f:0580:0000:0000:0000:0001 > 2001:4978:000f:0580:0000:0000:0000:0002]
[62098.822442] ICMPv6 checksum failed [2001:4978:000f:0580:0000:0000:0000:0001 > 2001:4978:000f:0580:0000:0000:0000:0002]
[65278.145779] ICMPv6 checksum failed [2001:4978:000f:0580:0000:0000:0000:0001 > 2001:4978:000f:0580:0000:0000:0000:0002]
[77649.324241] ADDRCONF(NETDEV_UP): eth0: link is not ready

but mostly this one:

[78236.979498] ADDRCONF(NETDEV_UP): eth0: link is not ready
[78237.357741] atl1c 0000:0e:00.0: irq 46 for MSI/MSI-X
[78237.357921] atl1c 0000:0e:00.0: atl1c: eth0 NIC Link is Up<100 Mbps Full Duplex>
[78247.483855] eth0: no IPv6 routers present

Really wierd. For the AR9462 chip in this Acer V3-771G the ath9k driver is worthless. It never used to be this way. When I first installed 12.04 both the wifi and eth0 were rock solid stable, but I was close to the router and connected with a cat5 cable. Re-installing 12.04.3 didn't help the wifi situation. A year ago we sold our home and moved to an apartment to avoid a lot of home maintenance chores (my wife didn't want me on the roof anymore). Here at our apt I am, conveniently, within a couple feet from the wifi router so I just plug a short cat5 into the back of it and connect with eth0. I never take this 17.3" laptop anywhere so wifi isn't important. Strangely, my wife's three year old Acer Aspire D520 notebook also uses the ath9k driver and her little box is rock solid with the wifi connection , which is all she uses. She is running 12.04 as well.

[SteveRiley]

Jerry, would you please add the following kernel boot parameter to /etc/default/grub, run update-grub, reboot, and then see if your problems go away:

ipv6.disable=1

[GreyGeek]

I saw those IPV6 lines reported by dmesg as well, but decided against doing that because I have tunnel that uses aiccu, which gives me IPV6 capability (sans DNS) via an sixxs tunnel. Half of my Internet traffic now comes over my sixxs connection! However, I did uninstall aiccu to see if the absence of the tunnel and sixxs made any difference on the stability of ath9k. It did not. (Aiccu is not a kernel mod and is not loaded via modprobe. It resides in system memory.)

I will do that out of curiosity, however, to see if it disables aiccu as well.

[GreyGeek]

That setting did nothing. My wireless disconnected within seconds after NetworkManager gave me a 48Mb connection.

Unsuprisingly, it did not affect my sixxs tunnel.