Decided to set up a new SSID for my IOT devices and put them in their own VLAN.

I have a Mikrotik RB5009 and have a couple of Grandstream GWN7665 access points which are connected on ether1 and ether2. I have two SSIDs configured (lets call them Home and HomeIOT) on the GWN7665. HomeIOT is tagged with VLAN20 within the SSID configuration. I am with 2degrees and have a static IP address.

I have added a VLAN interface to the bridge (called bridge_iot) and set that to VLAN 20. It is also added to the LAN interface list "group".

I added a bridge VLAN and set the bridge, ether1 and ether2 to be tagged.

VLAN filtering is enabled and the bridge is PVID 1.

I've added both IPV4 and IPV6 subnets and ip addresses. IPV4 is 192.168.20.0/24 subnet (the bridge_iot interface has IP 192.168.20.1 and has a DHCP server bound to it for the IPv4 subnet). Likewise I've added IPV6 address to the interface from the IPV6 pool (which is named 2degrees). I use different subnets for the Home SSID and default network (192.168.94.0/24)

Almost everything works perfectly. Connecting to the Home SSID I get IP addresses from the correct subnets (both IPv4 and IPv6). This works fine. The "weirdness" comes from connecting to the HomeIOT SSID. Again; I get IP addresses from the correct subnets (both IPv4 and IPv6). Here IPv4 works perfectly, however, IPv6 has some problems. Pings work fine (both locally and across the internet) and no dropped packets are seen. However; websites have problems loading. Running some curl tests, forcing IPv6 with -6 option, the page will return fine in about 4 out of 5 calls but then randomly just hang. Ive tried a whole heap of things I can think of with no improvement. At the moment I havent set any different firewall rules at all for either subnet (at the moment they can see each other and traverse subnets too) - actually things are pretty open right now.  I suspect MTU settings but have tried a few different sizes with no changes (at the moment everything is the default of 1500).

For now I've disabled IPv6 on the VLAN - not really needed for IOT devices. However; I'd like to set up some other VLANs (in the future) for some separation and would like IPv6 on those.

Anyone got any ideas I can try?