@TechUnsupport 

Since the TP-Link is already capable of acting as a router it would make sense that it acts as a router (but only) for the guest network. Routing requests outside of the local subnet range to the gateway, and blocking traffic that is destined for the local/protected subnet. Depending on the setup of the software it would (even) allow for an entirely different IP range.

But anyway I repeat; If the separation is not functional in AP mode, then the switch that says "isolate" should not be there in AP mode.

@AdrianHi Some people still seem to be doubting that the M5 can now do guest network isolation in AP mode, at least in the right circumstances.

Here is my set up:

A NAS plus a few other devices are connected via wire to my non-TP-Link router modem that has its built-in Wifi disabled. A printer is connected to the TP-Link main Wifi network.

If I connect my laptop to the main wifi network, I can connect to all of these services. If I connect the laptop to my guest wifi, network it cannot reach any of these services, only the internet.

@AdrianHi You are actually right!

For me it only started working now with the nov 2020 update (1.5.1 Build 20201022 Rel. 66804).

All updates before (also where it was announced), I had checked and it did not work.

So glad that this feature is here now and working!

Great job of TP-Link to update and support this hardware still.

@AdrianHi Thank you for the good news! Just to double-confirm, in your setup your Deco is in AP mode, right? A question for you then - do you see that "Guest network isolation in AP mode" switch in your Settings? Or it just works now the way it should, without any new switch in UI? 

@SlavaS 

Yes AP mode and I do see a switch to choose to isolate the guest network.

@AdrianHi 

I have 3 M5 units in router mode but my guest network is NOT isolated from the main network, I don't have the option to isolate the guest network. If put the unit in AP mode the guest network doesn't have an internet connection at all and is still not isolated from the internal network while there is a switch. All devices are getting a ip adres in the same range, main or guest WiFi. 
 

Am I doing something wrong?

@Machielj 

If the M5 units are set and working in router mode, then they are providing the routing function for your internet connection. If you then switch to AP mode, what device on your network is providing the routing function because it will not be the M5? Unless you have another router or router/modem providing the routing function with the Deco in AP mode, you will not get an internet connection as you have found.

I still use my router + modem for the routing function and have wifi disabled on it so only the Deco's provide the wifi services.

The real question is why you are not seeing the option to have a guest network when the M5 is in router mode. Unfortunately, I've not worked with my Deco's in this mode so I don't remember what the menu options look like in this mode.