I am trying to develop a conceptual design. A company has at least two data centers with each being mutihomed to the Internet through different providers using BGP in a active/backup role. If the company wants to go active/active to the Internet how would they backhaul the iBGP traffic between the set of CE routers? The only ways I could think of would be to set up WAN links on the CE routers, cost prohibitive or the other would be to create a tunnel between the sets of CE routers. Does this make sense or are there other potential solutions?