I know this should be fairly basic thing to do but for some reason I fail to wrap my head around it and decide how to do it easiest way.
Basically I have a physical port igb1 used for my server so it has been assigned in interfaces without VLANs and have own DHCP etc normally. But now I have a need for more subnets and I have run out of ports on my OPNSense so I need to tranform this existing interface into a VLAN so I can then get the existing network and a new one from the same port and then in VLAN aware switch handle rest.
But what is the most effective way of transforming this existing network into a VLAN network. What I mean by that is that I would like to keep the existing DHCP static mappings and the same ip subnet on the existing network so minimal changes done to it.
Just assign the logical name in Interfaces > Assignments to a VLAN interface and all address configuration, DHCP, firewall rules ... will follow.
That's why this extra level of abstraction exists ;)
Of course it was that simple :) I thought too complicated. Thank you kind person for your help!
I probably shouldn't admit how long it took to dawn on me that the assignments / device column contains drop-down menus. I somehow got it in my head that once an assignment is made, the only way to change it would be to delete and create a new assignment. In fairness, I think the section at the bottom that says "No devices available for assignment" should really be something like "No unassigned interfaces" ;)