Dual Channel Broadcast?

[RMerlin]

Wasn't using a Browser. noticed old SSID in Windows 8 "Networks" panel as wired connection linked to AC66.

Anyhow, I've downloaded your "RT-AC66U_3.0.0.4_354.27-BETA1" build, might as well move to this firmware if I'm going through the process again.

But, unless I missed something, the recommended method for clearing NVRAM still hasn't been given? And can this process cause problems if done wrong or out of order with the config reset?

I apologize for seemingly beating this thread issue to death with all the cautious questions but experimenting with this sort of thing isn't trivial for me and I don't want to find myself in more trouble.

Thanks to all who have offered help.

The method used does not matter. What matters most is that you do it AFTER flashing, otherwise you will end up with the default values of the old firmware instead of those from the new firmware. There is no need to reset before flashing, since the new firmware is compatible (unlike if you had been flashing Tomato or DD-WRT).

Simplest method IMHO: Flash the router. When it's done flashing note down your important settings, then press and hold the reset button for about 5 seconds. Release it. Give it 2-3 minutes to reboot, then reconfigure everything manually.

 

[rljames]

Guess I was just confused AGAIN, I thought another Poster was suggesting that "Reset" and "NVRAM clearing" were two separate things... I'll go with your advice and simply use the "reset button press" method after flashing.

Anyhow, I think I've done everything recommended to get my system current and correctly updated. I'm now using latest RMerlin firmware ("RT-AC66U_3.0.0.4_354.27-BETA1"), I've "reset" to factory defaults post flashing and reconfigured without reloading any saved config file.

So back to the original issue - AC66 dropping dual channel broadcast.

This morning, after yesterday update of the AC66 firmware and leaving the both radios off overnight, I restarted wireless and noticed that 2.4GHz was broadcasting on channels 1+5 as it should. However, after about 10 minutes it dropped back to channel 1 only. So *something* is causing the fallback.

 

[RMerlin]

Guess I was just confused AGAIN, I thought another Poster was suggesting that "Reset" and "NVRAM clearing" were two separate things... I'll go with your advice and simply use the "reset button press" method after flashing.

Anyhow, I think I've done everything recommended to get my system current and correctly updated. I'm now using latest RMerlin firmware ("RT-AC66U_3.0.0.4_354.27-BETA1"), I've "reset" to factory defaults post flashing and reconfigured without reloading any saved config file.

So back to the original issue - AC66 dropping dual channel broadcast.

This morning, after yesterday update of the AC66 firmware and leaving the both radios off overnight, I restarted wireless and noticed that 2.4GHz was broadcasting on channels 1+5 as it should. However, after about 10 minutes it dropped back to channel 1 only. So *something* is causing the fallback.

Most likely interference. The 2.4 GHz band is overcrowded - 40 MHz channel width will always be problematic, unless you were in a location without any 2.4 GHz interference. That does not only mean just without neighbor routers, but also without a 2.4 GHz-based cordless phone, without a microwave oven (they also emit frequencies in that range), without Bluetooth, etc...

There is just too much interference in the 2.4 GHz band, and out of 12 channels 40 MHz channel width end up overlapping no less than 5 channels.

 

[njweb]

Unless I am missing something, I just use the Asus UI to do a 'factory reset' after installing a new firmware revision.
I realize this clears the SSID's and passwords, in case the other procedures do not clear them.
Aside from that possible downside to my approach, I assume this does clear NVRAM right?

 

[rljames]

There is just too much interference in the 2.4 GHz band, and out of 12 channels 40 MHz channel width end up overlapping no less than 5 channels.

So what is the purpose of providing/using the 40MHz only channel width option? Shouldn't this setting force the use of dual channels?

And alternatively, the 20/40MHz option allow for "auto" fallback if interference is present?

As I mentioned previously, prior Netgear WNDR3700 held broadcast very steady, in the exact same environment, at dual channel.

 

[RMerlin]

So what is the purpose of providing/using the 40MHz only channel width option? Shouldn't this setting force the use of dual channels?

And alternatively, the 20/40MHz option allow for "auto" fallback if interference is present?

As I mentioned previously, prior Netgear WNDR3700 held broadcast very steady, in the exact same environment, at dual channel.

No idea. This is handled internally by the closed-source driver.

Interference tolerance is something that can be adjusted - it's possible that Asus uses different tolerance values perhaps. Again, I can only speculate since this is all closed source. I know it can at least be partly controlled by the userspace "wl" tool:

admin@Stargate:/usr/lib# wl interference help
interference
        Get/Set interference mitigation mode. Choices are:
        0 = none
        1 = non wlan
        2 = wlan manual
        3 = wlan automatic
        4 = wlan automatic with noise reduction

The "Interference Management" option Asus aded to the webui at some point (unsure if the option still exists in 270) changes that setting. I guess you could try disabling it:

wl -i eth1 interference 0

See if it makes any difference. Otherwise, set it to 3 or 4, and try again to see if it makes any difference.

Note that this change won't survive reboots.

 

[rljames]

I believe that interference can cause dual channel "fallback" but that doesn't explain why the "40MHz" only bandwidth option is following some detection level algorithm. Again, seems to me that the "detection" behavior should be reserved for the "20/40MHz" setting. Otherwise the two options are redundant.

And I think there may be more to the issue than misrepresented config settings. Once the bandwidth does switch to single channel only, from what I can see it never returns to the "40MHz" option requested dual channel mode. A router 30 second power removal and then reboot appears consistent in returning to dual channel so the AC66 seems to *think*, at that point at least, the interference level required for dual channel is acceptable.

As for interference sources - I have several wireless clients managed by the AC66, a typical cordless phone and microwave (neither generally in use) but nothing extraordinary. And as I said, no significant networks in the area,

Using Putty Telnet to my AC66 "wl" reports;
admin@RT-AC66U:/tmp/home/root# wl interference
Non-wireless LAN Interference mitigation is enabled. (mode 1)

I'm confused by the "non-wireless" detail?

And if I set "mode = 0" it appears to be reset to "1" if the Channel changes.