[SOLVED] wifi won't do 802.11n

[Rich]

I recently upgraded an old Netgear router/access point that only did 802.11a/b/g with a newer model that also does 802.11n and ac.
I made the necessary changes to access the newer router using my Dell Latitude E6430 (Ultimate-N Centronics 6300 wifi). The driver is the Intel iwlwifi firmware. The OS is Debian 8 (Jessie).
The laptop accesses the router just fine, but won't use any speed higher than 54 Mbps. iwlist scan identifies 20+ wifi systems in my neighborhood, including both the 'n' and the 'ac' systems in the new router, but shows maximum speeds of 54 Mbps for all of them. Similarly, wavemon shows wlan0 running a/b/g but no n, and a maximum speed of 54.
The laptop is a dual boot machine. When I boot to Windows 7 Pro, I find that it will run 130 Mbps, and probably would go faster if I moved closer to the router.
Can someone point out a cure?
... Rich

[squeeze]

Can someone point out a cure?

GIYF.

I was having this exact issue recently and fixed it by re-setting the wireless security to use WPA2 and AES. It's strange but my windows 7 Home Premium dual boot could cope with my previous wireless settings which were WPA/WPA2-PSK with TKIP algorithm, but Ubuntu Maverick would just not work at a higher speed than 54Mbps until I reset as described. I'm now getting 150Mbps.

Source: https://ubuntuforums.org/showthread.php?t=1727762

[Rich]

Thanks for the reply, squeeze.
The Netgear documentation warned about a problem with mode n and security levels, so I've set them on the router to "WPA2-PSK [AES]".
I don't see a comparable setting I can make on the laptop. In /etc/network/interfaces, I have:
wpa-psk xxxxxxxxxxxxxxx
Is something like "wpa-aes" valid?

[squeeze]

Sometimes i really wonder what prevents people from using a search engine

[Rich]

A mild poke, but not a just one. In fact, I've done a great deal of searching and reading about this during the past few days.

A search for wpa-aes doesn't turn up anything, and it's not in the man pages (or other documentation) for interfaces, wpa_supplicant, wireless, etc. In fact I've seen posts that say that AES is a default for WPA/WPA2.

As for the wpa-aes comment, I'm definitely fishing here. Since I haven't found a fix, I'll toss around most any idea in hopes that it will lead to a fix.

The only nearly relevant information I've come up with in searching had to do with the same problem occurring for Atheros wireless chipsets. The cure for those drivers doesn't apply to the iwlwifi driver used in the Intel system in this laptop.

[TonyT]

Using Network Manager? Try edit connections and delete the current connection to your wlan. Then rescan and connect again.

[Rich]

Piecing together bits from several sources, I've found this solution. As root:

Code: Select all

rmmod iwladm  //a dependency of iwlwifi that must be removed first
rmmod iwlwifi
vi /etc/modprobe.d/iwlwifi.conf
  (add:  option iwlwifi 11n_disable=8)
modprobe iwlwifi
/etc/init.d/networking restart

11n_disable=8 sets this option to "enable agg TX (UINT)". I have only a fuzzy idea what this means, but it appears to work.

At my usual operating position, I am now getting up to 130 Mbps from the 2.4 GHz radio and 270 Mbps from the 5 gig radio.