RT-AX86U doesn't switch back to DFS channel

[Qbcd]

So I use a DFS channel with my RT-AX86U. Every few months, the router switches to a non-DFS channel, I guess it detected radar. But then it doesn't switch back, and I have to manually switch it back (by resetting it) after noticing the lower quality of the non-DFS channel, which where I am is quite noticeable due to interference.

What's the issue here? Shouldn't the router automatically switch back to its original DFS channel after some time? Any thoughts on what may be happening and how to fix it?

Thanks. Any input is appreciated (unless you want to tell me not to use a DFS channel).

 

[AndreiV]

the router switches to a non-DFS channel, I guess it detected radar.

So it switched channel to prevent you interfering with radar , should it switch back so you can do the same thing again?

 

[Volfi]

Same happens for me. I live in city center, nearest airport 70km away, no chance for weather radar detection. But when there is false positive and router migrates from channel 120 to 48 or so, no chance it will go back without restart

 

[Qbcd]

So it switched channel to prevent you interfering with radar , should it switch back so you can do the same thing again?

Typically, routers will switch back after a few hours or at a certain time of day. And of course it won't switch back if it's still detecting radar. I've tried waiting 2 days and it didn't switch.

Same happens for me. I live in city center, nearest airport 70km away, no chance for weather radar detection. But when there is false positive and router migrates from channel 120 to 48 or so, no chance it will go back without restart

I suspect mine are false positives too, because it only happens once every 3 months and I am about 15 mi from an airport, but not under any flight paths. Also, when it happens and I check the log and it's not mentioned that radar was detected or a channel was switched. So I don't know why it does it, maybe it is a totally separate glitch.

 

[bbunge]

Try Auto Channel with DFS checked with bandwidth set to 20, 40, 80, 160. Trust your router to choose what is best. Mine runs at 80 MHz most of the time until an AX client connects and then it goes to 160 MHz.

 

[thiggins]

There is nothing in the DFS rules that says the router must move back to the channel it vacated after a radar event. It all depends on the algorithm design. It's a feature, not a bug.

 

[Tvlz]

You could try Channelhog

ChannelHog - Monitor And Force Maximum 5GHz Bandwidth

v1.1.1 Updated - 28th June 2022 ChannelHog - Monitor and force maximum 5GHz bandwidth About; Tired of badly configured neighbours and DFS cutting your wireless bandwidth in half? Then this is the script for you! ChannelHog will monitor your current 5GHz channel bandwidth on a daily basis...

www.snbforums.com

 

[OzarkEdge]

So I use a DFS channel with my RT-AX86U. Every few months, the router switches to a non-DFS channel, I guess it detected radar. But then it doesn't switch back, and I have to manually switch it back (by resetting it) after noticing the lower quality of the non-DFS channel, which where I am is quite noticeable due to interference.

What's the issue here? Shouldn't the router automatically switch back to its original DFS channel after some time? Any thoughts on what may be happening and how to fix it?

Thanks. Any input is appreciated (unless you want to tell me not to use a DFS channel).

Have you tried channels 36-64 at 160 MHz bw... only half of those are DFS. I wonder if the router still scans all DFS channels.

OE

 

[Qbcd]

Try Auto Channel with DFS checked with bandwidth set to 20, 40, 80, 160. Trust your router to choose what is best. Mine runs at 80 MHz most of the time until an AX client connects and then it goes to 160 MHz.

Hm, I don't have the option to check DFS, if I select Auto I'm sure it will default to non-DFS. I have stock firmware, don't really want to change. And I have it set to 80/40/20, don't need 160 yet.

Have you tried channels 36-64 at 160 MHz bw... only half of those are DFS. I wonder if the router still scans all DFS channels.

OE

Hm no, I'm using channel 100. I definitely don't want to use the non-DFS ones because there's lots of interference there. And I don't want to use the sub-100 DFS channels because where I live those have a much lower legal power limit, which hurts my AI Mesh. Also, I use 80MHz. But I'm sure it scans all DFS channels, I don't think the channel used is the problem.

There is nothing in the DFS rules that says the router must move back to the channel it vacated after a radar event. It all depends on the algorithm design. It's a feature, not a bug.

I understand that, but you'd think a router like the RT-AX86U would have that feature... Does it actually not have it? I thought mine was buggy in some way or I set up something wrong.

 

[ColinTaylor]

FYI: I experience the same issue with my RT-AX86U and use the following script (on Merlin's firmware) to restart the WiFi subsystem if the channel has moved. Unfortunately a full WiFi restart is required to get the channel to change back to the original as merely doing a down/up on the 5GHz interface isn't sufficient. That does of course mean that all WiFi devices are momentarily disconnected, and if you're in the UK/EU it might take 10 minutes before the 5GHz band becomes available.

channel_check.sh

#!/bin/sh

logger -t "channel_check" "Checking..."

ifname="$(nvram get wl1_ifname)"
targchanspec="$(nvram get wl1_chanspec)"
targchan=${targchanspec%/*}
currchanspec="$(wl -i $ifname chanspec | awk '{print $1}')"
currchan=${currchanspec%/*}

if [ "$targchan" != "0" ] && [ "$currchan" != "$targchan" ]; then
    logger -t "channel_check" "Channel has changed from ${targchan} to ${currchan}. Restarting WiFi."
    service restart_wireless
fi

logger -t "channel_check" "Done."

Then run it periodically from cron by putting something like this in services-start.

/usr/sbin/cru a Radar "30 */2 * * * /jffs/scripts/channel_check.sh"