Already found that in researching for a solution. Sadly the customer cannot afford the devices that L2TPv3 runs on. Any other solutions?

Do the sites really *need* L2 adjacency? Maybe now is the time to talk to this customer about L3 separation between sites. Things get alot more easy and affordable when we can use good old fashion IP routing. ;)

-Brad

How would I go about designing a failover network using RIP? If I keep multiple vlans at each site, what equipment would be needed to route the traffic between sites over a fiber connection (from service provider), plus provide a backup (over DSL) in the event that the fiber connection went down?

may be you can try opensource solution, openvpn bridging tunnel (http://openvpn.net/bridge.html)

I actually stopped trying to carry layer 2 functionality over redundant links and just used my point to point connection with routers, then tied the same routers together over a GRE tunnel and setup EIGRP to route the networks on both sides. So now, Vlan 1-4 exist on both sides, only with different IP schemes.

That is the correct solution. Once traffic gets to destination via GRE, it will naturally take again the correct VLAN due to the addressing.