Technosophy

Practical computer tips, with a smattering of digital philosophy

Wireless networking slow, flaky, or crashing your router? Have an Intel 5300, 5100, 6205, 6300 wireless chipset? Disable 802.11n!

Has your Intel-based laptop’s wireless connection been bizarrely slow, buggy, or unstable since you can remember? Have you found that connecting to certain wireless routers can cause the routers themselves to crash?  If any of the above applies, you might want to try disabling your wireless card’s 802.11n functionality – even if you don’t ever connect to n-capable access points.

A large number of people in the Linux community have been reporting significant instability with many bgn-capable Intel wireless chips, and have found that disabling 802.11n usually outright fixes the problems. (See here, here, and here for ubuntu bug discussions on this subject.

Nor apparently, are the Linux folks alone: Windows users have been reporting similar instability with the 6300 chipset, most of which can also apparently be resolved by disabling 802.11n.

To do this on Linux, simply create a new .conf file in /etc/modprobe.d, with whatever name you like (as long as it ends with.conf, of course.  Mine’s iwlagn.conf, since iwlagn is the kernel module being modified), and add the line “options iwlagn 11n_disable=1″ to the file.  Save, remove and reinsert the kernel module (or just reboot) and voila!

sudo -s
cat "options iwlagn 11n_disable=1" > /etc/modprobe.d/iwlagn.conf
modprobe -rf iwlagn
modprobe -v iwlagn
exit

For what it’s worth, I can personally confirm the existence of huge out-of-the-box stability problems on both Windows 7 and Ubuntu, with both 802.11g routers (without N capabilities), and routers with support for 802.11n.  I can also attest that disabling 802.11n does indeed immediately resolve all of the stability issues I’ve encountered (even if I’m connecting to a 802.11g-only router), at least on the Linux side of things.  Unfortunately, I haven’t had a chance to try implementing this fix on Windows, but I can confirm that updating driver stacks doesn’t help at all.

I should also note that both of my test-cases involve Lenovo laptops (R400 and T420), and that many of the posts in the threads linked above  reference Lenovo machines.  Granted, machines from other manufacturers are clearly being affected by this issue as well, but Lenovos seem to be disproportionally affected, for whatever reason.

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