We are currently experiencing an issue with our 2866ax where WiFi clients (phones, tablets, laptops) on all SSIDs periodically (happens every few days) get disconnected and cannot reconnect. The error on android clients is "Couldn't get IP address". The issue is resolved by either enabling/disabling the WiFi on the router or rebooting the router.

Other info:

• It mainly appears to be affecting 5G WiFi - re-connecting to 2.4G will often work whilst 5G does not.

• It is happening to devices in the same room (within 2-3 metres) of the router with good signal.

• We have configured 2.4 & 5G channels optimally already. There is very limited interference on all 5G channels in any case.

• When it occurs, it affects multiple devices and device types (android phone, android tablet, windows laptop).

• Router firmware is up-to-date (version 4.4.3.2) as is client firmware/OS.

• We are using multiple SSIDs (x4) on both 2.4G and 5G.

• We are using multiple subnets, which each have an IP pool of 100 and we have <30 devices in total connected at any given time.

I have looked at the syslog entries for WLAN whilst this issue is occuring and it does not appear to reveal anything useful, though I'm not expert on this.

We have raised with Draytek support, but they have been pretty useless so far unfortunately. They initially they just provided a link to a guide on WLAN performance (https://www.draytek.co.uk/support/guides/wlan-performance?return=17665011) which was pretty useless as it's not a performance issue. They have since offered to join a call to screenshare, but then failed to show up.

Hence I'm raising it here to see if anyone else has experienced similar issues?

Hi,

Have you checked to see if the 5G wireless channel is changing/jumping?

When the 5G’s broadcast channel is within a certain range, that is not permitted (without a licence), the Vigor router will change the wireless channel to a legal one automatically and continue operating.

This jump might be confusing your devices, and causing them to ignore the new channel.

Consequently, rebooting the router or disabling/enabling the 5G wireless will force the router to return to the illegal channel again, which may take a few days to jump again to a legal channel.

This would most likely happen if you have manually set the 5G channel but could still happen if it is set to auto as well.

Note, you will not be able to tell which channel the router has jumped to by simply looking at the wireless settings on the router, the settings will stay as they were configured, but the router will change the actual broadcast channel it’s using - to a legal one.

The router does this because it is periodically scanning the local airwaves to check that it isn’t broadcasting against a nearby licensed user’s broadcast channel. Effectively saying “you can use this illegal channel until I spot someone else, legally, using it and then I’ll change channel!”

Using a wireless scanning tool or checking the channel reported by a device - if one can still connect, is the only way you’ll know exactly what channel the router’s 5G wireless has jumped to.

Thanks for your reply HodgesanDY, which is far more useful than anything Draytek support have offered.

I've now set the 2866ax to channel 40 for 5G, which is in the legal (license free) band and will see how that goes. It would be useful if there was an explanation or warning on the router when setting a non-legal channel (in a licensed band).

It's worth noting we also have a VigorAP 906 and a VigorAP 960c that were both set to channels outside the license free band, but we've had no issues on those, only the 2866ax. I've now set those to use channels in the legal band.

I've also now set the 5G SSIDs to be different than the 2.4G ones (suffixed with 5G) as one of the issues appears to be that when the 5G WLAN stops working on the 2866ax, then clients don't seem to failover to the 2.4G SSID. It means having multiple SSIDs on the clients, but hopefully that will result in them connecting to the 2.4G SSID if the 5G SSID won't connect.

Yep I've got a 2866ax at home and I have trouble with Android devices. Thanks for the answer to prevent the channel hopping, my 2.4 was set to auto, I had missed that.
My problems are more severe though I have the one tablet, (amazon fire) that if it connects to the Wi-fi will cause the entire Wi-fi network to drop and no other clients can connect. Draytek support have not offered a fix. I have installed a Ap900 specifically for this tablet to connect to, which works fine

And I've just realised that having given my 5GHz and 2.4GHz SSIDs the same name so that the clients choose which to connect to , has also created a fair amount of hopping back and forth. This seems to affect the Android deivice more, perhaps as they are more mobile.
I've just renamed my 2.4GHz SSID a different name and things seems to have improived

I have a new 2865ax which is showing a similar issue with the 5Ghz WiFi.
Wired connections and a couple of 2.4Ghz only clients seem to be fine.
Periodically the devices connected to 5Ghz ( iPhones, iPads, Windows Laptops and some smart appliances ) loses their IP address and spin trying to reconnect.
Since the 5Ghz WiFi is available and preferred, the devices usually don't connect to the 2.4Ghz. The devices seem to default to IP addresses in the range 169.254.x.x indicating a DHCP issue.
My temporary workaround has been to disable the 5Ghz WiFi so everything is stable on 2.4Ghz while I log a message with support.