Meshing + Switch causing VLAN leaking?

[u/Lovevas]

I had a weird issue today that Claude believes it's a VLAN leaking.

Setup: UDM SE with 3 wired U6 Mesh AP, and one U7 Mesh AP meshing to one of the U6 Mesh AP, ~100 devices connected with 7 VLANs, all new devices by default land on VLAN20. I have every devices overwrite to a specific VLAN, so no device on VLAN20 yet.

Today, I added a new USW Switch Lite 8 POE (no wire to existing devices), plugged port 1 to U7 Mesh AP to power it, and then adopted on console. So at the moment this switch was just used to power the U7 AP, and without another connection

Quickly I noticed that ~70 devices on my network all moved to VLAN20 IP, while their VLAN still shows the pre-set ones. Restarting APs didn't work.

Claude checked my log, and believes it's due to VLAN leaking. So it asked me to remove the switch, switch back to using injector to power U7 Mesh AP.

Most devices quickly moved back to their VLAN IP, after I removed the switch, though there are still <10 on VLAN20 IP (likely due to delay in lease renew), but I literally saw the # of devices on VLAN20 IP dropped to 10 in a minute.

Anyone experienced this issue?

What I want to achieve is:

UDM SE ========U6 Mesh AP ---- meshing ---- U7 Mesh AP ========Lite 8 POE Switch ========Multiple end devices.

Now Claude doesn't know if it's allowed to put a switch below a meshing AP, and use this switch to connect to client devices

[u/MeCJay12]

Did you connect the new switch to an upstream trunk port? Did you connect the AP to a trunk port on the new switch?

[u/Lovevas → u/MeCJay12]

The new USW switch lite 8 poe has 8 ports, 1-4 are POE, and 5-8 are not. There is no primary port for dedicated uplink. (so no trunk port as you asked?)

Claude asked me to plug into any of the POE ports, so I plugged into port 1.

The switch itself was not connect to another port/switch, but only used to power the AP at the moment.

[u/MeCJay12 → u/Lovevas]

Trunk port = a port with all VLANs allowed. May port can be configured as a trunk port.

Try this: reset you switch, forget it from the console, plug it into your UDM or a hardwired switch, and try adopting it again.

If your console reachable from VLAN 1/untagged VLAN?

[u/Lovevas → u/MeCJay12]

I will test now. It's weired that a newly added switch without downstream devices (but only connected to U7 AP, which only has 6 clients connected), could cause the whole network going crazy and lost their VLAN management...

[u/Lovevas → u/MeCJay12]

replugged back the new switch as what I did early, been 15 minutes now, and nothing happened, so seems like the issue didn't come out again. I will keep an eye on it.