We have two office locations, A and B.
We have two ADSL2+ lines at both A and B, as well as a switch at both sites.
At site A, the ADSL2+ line is plugged into a system running pfSense 2.x, that's currently acting as a router/firewall for the computers at site A.
We have a single Ethernet cable linking site A to site B.
We'd like to use the ADSL2+ line at site B with the pfSense box as a redundant-failover dual-WAN. I can do this by using the Ethernet cable between the two to connect the ADSL2+ modem at site B back to the second WAN port on the pfsense box at site A. However, we also need to connect the switch at site B back to the pfSense box as well. Yet we only have one Ethernet cable.
What are some options that would let me connect the site B modem back to site A, and also connect the LAN at site B back to site A as well?
Would some kind of tagging work? Or are there other alternatives?