[Help] Configuring Open VPN to bridge same subnets/vlans over wan tunnel

  • Good afternoon!
    Here is my current scenario

    Site A: (HQ) -WAN IP and 7 subnets (vlans) - One primary firewall that acts as the gateway for all the different subnets. Each subnet is in it's own Vlan.

    Site B: Connected to HQ via MPLS fiber link - Layer two. Same subnets and vlans reaching here via trunk.

    The change I've been asked to accomplish is the following.

    Site A: (HQ) - No changes - Except to branch off from that WAN link with another, seperate WAN IP, on a netgate XG-7100 running PFsense, with the ability to have an interface in every vlan.

    Site B: Cut the MPLS link, and place a distinct WAN link here, routed through a Netgate SG-3100

    The goal - Create a tunnel between both sites over the wan, and pass through the same subnets.

    Management doesn't want to remake new networks for this site, and keep everything on the same local lan, just hooked up like a tunnel.

    My expectation of this, is that it would be a layer 3 tunnel, something like OpenVPN Client/Server with TAP interfaces in each of the subnets, on both sides.

    What are some ways I would go about it?

    Thanks, and if there's any confusion, don't hesitate to ask. I'll answer as best as I can.