WNDR3700v1 cannot select 40MHz, Always Reverts to 20MHz

[theirongiant]

I moved to a new apartment, and running Ethernet cable from the living room to the office isn't really feasible yet. So, in a pinch, I'm using a WNDR3700 as a client bridge to an ASUS RT-N66U that is about 30 feet away. It's working well, but not optimally.

For whatever reason, DD-WRT didn't support Bonjour/multicast packets across a client bridge. This led me to switch to Gargoyle. The setup was a breeze; Gargoyle found my network and joined it correctly on the first try. It's nice to have AirPlay streaming and AirDrop working!

The WNDR3700v1 is joined to a 5GHz network on the ASUS RT-N66U with WPA2 encryption, Channel 36, Width Auto (20/40), and Extension Channel Auto. The signal strength is 65% according to Gargoyle, and there are only 4 other 5GHz networks nearby (instead of 20+ @ 2.4GHz).

The WNDR3700v1 has a fresh installation of Gargoyle 1.5.10.

The only problem I'm having is with the Channel Width setting on the WNDR3700: it just won't "stick." I change it to 40Mhz, press "Save Changes," and in about 30 seconds it's done. but now I see that it has reverted back to 20MHz.

Is there a bug or "feature" in the Gargoyle software that's causing this? Is it specific to my router?

Thanks!

[BashfulBladder]

First, I would recommend trying to find empty channel space.

If those 4 other 5GHz networks are on the same channel or overlap your double-wide, OpenWrt's 'good neighbor policy' might have come into effect. In a nutshell, the chip vendors asked OpenSource firmware to detect competing wifi signals & change to HT20. They never asked the manufacturers (who buy their chips) to do the same, so they don't.

If there is no free channel space (and 5 HT40 APs will do that for the non-DFS channels; if you live in a metropolitan US area, you probably are subject to DFS), as I recall there is something called the noscan option, but it will be done on the command line. Google: openwrt noscan

[theirongiant]

Thank you. I forgot to mention that the Radio Mode is "N-A" not N-G-B. And the 5GHz light is blinking on the WNDR3700 (as expected).

I edited /etc/config/wireless with the following changes:

Code: Select all

option noscan '1'

I rebooted the router and went back to the wifi config page. The channel was still 36, and channel mode 20MHz. I set Channel 157, 40MHz (+below), and saved changes. Now the channel is set back to 36, but 40MHz stayed active.

I copied some files between this computer and the NAS (Ethernet) which is attached to the ASUS base station. The fastest transfer I got was 8.4MB/sec, which roughly translates to 65-70Mbps.

Is there a command that will show me the speed at which the wifi is connected? ifconfig doesn't have this info.

Also, there are two radios on this device. Is Gargoyle not capable of configuring them separately? Or is this locked out because I'm in client bridge mode?

I rebooted again, and it reverted back to 20MHz.

Thanks again.

First, I would recommend trying to find empty channel space.

If those 4 other 5GHz networks are on the same channel or overlap your double-wide, OpenWrt's 'good neighbor policy' might have come into effect. In a nutshell, the chip vendors asked OpenSource firmware to detect competing wifi signals & change to HT20. They never asked the manufacturers (who buy their chips) to do the same, so they don't.

If there is no free channel space (and 5 HT40 APs will do that for the non-DFS channels; if you live in a metropolitan US area, you probably are subject to DFS), as I recall there is something called the noscan option, but it will be done on the command line. Google: openwrt noscan

[BashfulBladder]

> Is there a command that will show me the speed at which the wifi is connected? ifconfig doesn't have this info.
iw dev wlan1 station dump (you may have to adjust wlan1 from iwconfig)

look at the tx bitrate. For example, idling I currently have: tx bitrate: 108.0 MBit/s MCS 5 40Mhz

even though iwlist reports a max MCS rate of 15 on the 5GHz band.

> Also, there are two radios on this device. Is Gargoyle not capable of configuring them separately? Or is this locked out because I'm in client bridge mode?

Well, Gargoyle lets you change the channels & encryption on each band. Perhaps you are looking for more advanced configuration - which the web UI does not currently support. As I don't use a wireless bridge, I have no idea if that impacts the scene.

> I rebooted again, and it reverted back to 20MHz.
First of all, after you change the settings you have to execute /sbin/wifi for the settings to take effect. See http://wiki.openwrt.org/doc/uci/wireless (near the bottom; instructions are for 2.4GHz band) Saving on the webpage does that, but I don't know if it clobbers the noscan setting.

If 'uci show wireless' shows the noscan setting, I don't know why it would not be preserved after rebooting. You could try adding the 'uci set whatever.thing.and.such.noscan=1' or however the line goes to /etc/rc.local which gets executed after a reboot. But if the noscan setting is still keeping you from HT40 speeds, I don't have any great ath9k insights for you.

[theirongiant]

I started a large file transfer and then took this snapshot. The TX / RX values were changing constantly.

Station 08:60:6e:bb:9c:dc (on wlan1)
inactive time: 0 ms
rx bytes: 69786254
rx packets: 53568
tx bytes: 4604379
tx packets: 53383
tx retries: 1666
tx failed: 0
signal: -66 [-68, -67] dBm
signal avg: -66 [-67, -69] dBm
tx bitrate: 180.0 MBit/s MCS 12 40Mhz short GI
rx bitrate: 162.0 MBit/s MCS 12 40Mhz
authorized: yes
authenticated: yes
preamble: long
WMM/WME: yes
MFP: no
TDLS peer: no

Click to enlarge Screenshot