RT-AX86U takes too long to broadcast 5GHz after reboot

[Khadanja]

I've moved from RT-AC68U to RT-AX86U about 6-7 months ago. When I set it first time, it was ok but now I'm noticing that the 5GHz SSID takes too long to come up on devices, 2GHz comes straightaway. Is this normal? I could be wrong but I don't think it was taking this long before when I first set it up. Can others who have same model please test & let me know? Thanks

 

[bennor]

Is this normal?

Might be. What firmware are you running? If Asus-Merlin firmware what addon's (like YazFi) are you running?

On a RT-AX86U Pro running 3004.388.8 and YazFi, the 5Ghz comes online a few minutes later than the 2Ghz does either at power on boot or reboot. Been like that for a while, using different firmware's.

 

[NetNewb124]

You're most likely using DFS channels and it's the radar clearance? It can take up to 10 mins.

 

[bennor]

You're most likely using DFS channels and it's the radar clearance? It can take up to 10 mins.

That could be a possible likely cause or contributing factor. Easy to miss it that it's enabled (assuming its supported in one's country), if one isn't thinking about it or specifically looking for it. Example:

SmallNetBuilder's Wi-Fi Dynamic Frequency Selection (DFS) FAQ - SmallNetBuilder

What is Dynamic Frequency Selection (DFS) and why should you care? Here's the straight poop.

www.smallnetbuilder.com

[Wireless Router] What is DFS (Dynamic Frequency Selection) and how does it work on ASUS router? | Official Support | ASUS Global

 

[Unisoft]

Using channels 100 or above? DFS has radar detection and takes 10 mins after reboot for it to come up.
Apart from looking in wireless settings for 5ghz network at the channel number configured, as a test set to channel 48 and reboot and see if it comes up quickly after a reboot.
That's the trade-off - less congested channels, but longer time to be available after a reboot vs ones that everyone else may pick in a busy AP area but are quick to come up after a reboot.

Now on my TP Link extender (business) and Devolo Powerline extender, 100-112 comes up very quickly but after channel 112 it also takes 10 mins for radar detection. Not sure why Asus and TPLink and Devolo differ on those channels.

 

[bennor]

Using channels 100 or above? DFS has radar detection and takes 10 mins after reboot for it to come up.
Apart from looking in wireless settings for 5ghz network at the channel number configured, as a test set to channel 48 and reboot and see if it comes up quickly after a reboot.

If DFS is enabled its going to likely be a delay no matter what channel is used. Have DFS/160 MHz enabled with the channel set to 36 and still see a multi minute long delay in the 5Ghz WiFi coming up every time the router is rebooted or a firewall reload is triggered. Even going to certain pages in the GUI, like the Adaptive QoS page, triggers a delay in 5Ghz WiFi coming back up. Thought the issue was caused by YazFi at the time and had some discussion on it here.

 

[RMerlin]

Using channels 100 or above? DFS has radar detection and takes 10 mins after reboot for it to come up.

DFS scanning takes a minute, not ten.

 

[ColinTaylor]

DFS scanning takes a minute, not ten.

In Europe it takes at least 10 minutes if channels 120 to 128 (weather radar) are to be used. Other DFS channels are only one minute.

 

[RMerlin]

In Europe it takes at least 10 minutes if channels 120 to 128 (weather radar) are to be used. Other DFS channels are only one minute.

Ouch. I can't imagine using that personally, it's almost as if they support these channels "just for the bulletpoint".

They really need the 6 GHz bands to get open in more countries.

 

[jerry6]

DFS scanning takes a minute, not ten.

Is this model specific ? I use channel 149 and have never noticed a delay connecting

 

[ColinTaylor]

Is this model specific ? I use channel 149 and have never noticed a delay connecting

149 to 165 are not DFS channels in Canadaland.

 

[jerry6]

149 to 165 are not DFS channels in Canadaland.

Thanks I/m not to clear on these dfs channels in Kanukistan I'll look it up and play with dif chennels see if I get a delay .
Thanks
you were right had a 1 minute delay using channel 130 , never to old to learn something new

 

[Tech9]

I/m not to clear on these dfs channels in Kanukistan

Look here for reference:

List of WLAN channels - Wikipedia

en.wikipedia.org

 

[Khadanja]

Thanks everyone, removed tick from Enable 160 MHz & it's lot quicker now.

 

[Unisoft]

DFS scanning takes a minute, not ten.

In UK it most certainly does and as I described in my original post. I know, I use it on three AX86U in different geographical locations and other manufacturer gear. I do have 160 enabled as well though.

 

[Unisoft]

In Europe it takes at least 10 minutes if channels 120 to 128 (weather radar) are to be used. Other DFS channels are only one minute.

In UK, That's not correct on RT-AX86U. If you have 160mhz enabled, DFS channels 100 upwards take 10 minutes after reboot.
On other manufacturers kit, channel 100-112 only take one minute, but DFS channels above 112 take 10 minutes also.

 

[Unisoft]

If DFS is enabled its going to likely be a delay no matter what channel is used. Have DFS/160 MHz enabled with the channel set to 36 and still see a multi minute long delay in the 5Ghz WiFi coming up every time the router is rebooted or a firewall reload is triggered. Even going to certain pages in the GUI, like the Adaptive QoS page, triggers a delay in 5Ghz WiFi coming back up. Thought the issue was caused by YazFi at the time and had some discussion on it here.

Again, not in the UK. Channels 36-48 are fine even with 160mhz and come up within a minute after reboot for this channel range. If you have 160mhz enabled and using DFS channels 100 upwards, it takes 10 minutes after reboot.
This is on the RT-AX86U anyway, it is possible other Asus models could be different, I accept and of course other countries may have different regulations that Asus have to adhere to.

 

[ColinTaylor]

In UK, That's not correct on RT-AX86U. If you have 160mhz enabled, DFS channels 100 upwards take 10 minutes after reboot.

That's exactly the point I was trying to make. Obviously I wasn't clear enough.

160MHz bandwidth on the RT-AX86U is either channels 36 to 64, or 100 to 128. So in the latter case regardless of which primary channel you choose between 100 and 128 it will always include 120 to 128 (weather radar).

In the OP he never said whether he was using 160MHz or not. So he could have used 80MHz and channels 100 to 112 and only have waited 1 minute as he wouldn't be using the weather radar channels. Alternatively, he could use any of the channels from 36 to 64 and only wait 1 minute even when using 160MHz.