I am trying to test setting up this scenario using my router 493G (and will then invest in a CCR).
So doing a single vlan 120 (a subinterface, attached to bridge interface) and then setting up vlan interface IP address (to serve as gateway for vlan) and then adding necessary dhcp scope set to use vlan interface, works and I can get an Ip address and then a splash page thru external hosted page (login.html file, under hotspot directory, directing to external portal) and I can authenticate and all works.
So then I create another vlan 101 (under interfaces, attached to bridge and did my regular tagging on the bridge and the downstream physical interface on the router going to the switch below, just like I did for the first vlan). And this time, I did not assign this vlan interface any IP address since I will like to make it an isolated VLAN, to work off of a dhcp scope with interface set to bridge. Created the required dhcp scope etc for bridge as interface, but I dont get any IP address on my test laptop attached on an untagged vlan 101.
When the router was factory reset, I had all ports ( other than the uplink WAN port) in the same bridge and dhcp scope was on the bridge and that was working. After I now add a vlan interface and scope, I am not able to get IP address from vlan 101 (even if I make one bridge port as access, via PVID 101 and attach test laptop to it).
I have read this excellent post / article by @pcunite and I believe I am doing all I need to do correctly in terms of vlan tagging, so there is no end to end vlan tag missing.
If few folks in this old thread are able to achieve this, I am not sure what I could be doing wrong where I am not able to bind multiple vlan interfaces to obtain IP address form a common pool set up on the bridge. Unless ROS firmware no longer supports this feature, I am stumped.
Any guidance will be very much appreciated. Thanks all.