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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?

Cheers, Victor

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This is exactly what VLANs are made for. But if for some reason you don't want to use VLANs, you can also use a VPN. – David Schwartz Jan 25 '13 at 22:45
Hi - Hmm, so VLAN tagging would work fine in this case? What about if we're using the ADSL2+ modems in bridge mode, and PPPoE authentication from the pfSense box? We have a Linksys SRW2048 at Site A, and a dumb, non-managed switch at the other. We'd probably need to replace the switch at Site B - would getting the same brand/model help? (The Linksys webview interface is somewhat frustrating - Internet Explorer only, so I'm happy with changing brands, if that's not going to cause problems). – victorhooi Jan 26 '13 at 1:41
@DavidSchwartz Also - can you put your comment as an answer below please? =) – victorhooi Jan 26 '13 at 1:41

You can split one ethernet cable (for 100Mbps).

X - not connected pin!

on 1 line RJ45 use white-orange - orange - white-green - X - X - green - X - X (side A and B)

on 2 line RJ45 use white-blue - blue - white-brown - X - X - brown - X - X (side A and B)

Pin position

Or you can use this method

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