@woozle 

I have been contemplating the purchase of an AXE75 but your post has postponed my decision.  As you are what I consider a very "savvy" contributor to the forum, then surely there must be a problem.  I only use AX55 routers here and device isolation works somewhat but not in all cases.  I have an outstanding issue with Tp-Link support where device isolation only works in the main router in an EasyMesh environment.  The satellite router does not "respect" the device isolation settings of the main router.  The same holds true when using an additional AX55 working in AP mode. Until this is fixed I have decided to use independent networks to isolate my devices.

  @jra11500 

Ok, today I spent a considerable amount of time to test this more thoroughly.

Here is what I was able to gather.

A device that is in the "Isolated Devices" list is not able to access the router itself or any other non-isolated device that is not connected via the same Wi-Fi AP. By Wi-Fi APs I mean the router's 2.4 GHz Wi-Fi, 5 GHz Wi-Fi and 6 GHz Wi-Fi.

However, a device that is in the "Isolated Devices" list is able to communicate with non-isolated devices that are connected to the same Wi-Fi AP as the isolated device!

For example, if the isolated device is connected to the 5 GHz Wi-Fi, then the isolated device can't communicate with non-isolated devices connected via Ethernet, 2.4 GHz Wi-Fi or 6 GHz Wi-Fi, but it can still communicate with non-isolated devices that are also connected to the router's 5 GHz Wi-Fi.

I also performed the same tests on my Archer AX53 V1 running firmware version 1.2.4 beta and it appeared to behave exactly like the Archer AXE75.

So, I am wondering whether other "AX" router models from TP-Link would show this behavior as well?

Could you perhaps test this on your AX55 router? (just in single router mode, without EasyMesh Satellites, to keep the network layout simple)

Or anyone else who cares to test it on their "AX" router?

I am also in the process of testing the Device Isolation feature on my Archer C64 1.13.3. It doesn't have the above issue, but somehow doesn't appear to work properly either.

  @woozle 

I just tested the issue on one of my AX55 routers that uses the 1.3.2 firmware.  Using a PC and a laptop, I put the laptop in the isolated devices list.  If both are connected to the 5G network of the router, the un-isolated PC can still ping the isolated laptop and also get into the laptop's shared file folders.  It does not work the other way around, i.e. the isolated laptop can not ping the un-isolated PC nor see its shared folders.

Now the strange part...  I reversed the roles, placing the PC in the isolated devices list and un-isolating the laptop.  The isolated PC can still ping and access files on the laptop while the laptop can not ping or access files on the PC.  I cleared the arp cache on both computers and the results are the same.  I can't reboot the router at the moment because the network is in use by other family members.

The PC is an iMac running Windows 10 and the laptop is an Hp running Windows 11 but that shouldn't make any difference.  I will continue testing and post any new results here.

Update:  The problem with pinging and file sharing in one direction only was due to the Windows file sharing settings on the PC.  Now both the PC and the laptop can see each other and share files as long as they are connected to the same Wi-Fi band and independently of whether one device is isolated and the other un-isolated.  This confirms your findings.

  @jra11500 

Thanks for your testing!

So, TP-Link really needs to have a good look at their implementation of "Device Isolation".   @Marvin_S @Sunshine

Currently, on these "AX" router models the only way to isolate one particular device from all other devices would be to reserve one SSID solely for that one device, which is not reasonable. (on a main router that could also be an "IoT" SSID, but as we know the IoT SSID is not being extended to EasyMesh Satellites)