What are the design concerns when spanning a VLAN across a WAN?
First, a little background: I have an MPLS WAN with 4 offices, a main data center and a tier 2 data center. Both data centers have a full-rate DS3 that is approximately 80% utilized. Average latency between those two data centers is less than 30ms. We have an HSRP pair of Cisco 3845s at each location. And now, my question: Due to some recent DR design choices, it has come to question whether or not we can extend a VLAN across that MPLS WAN. Microsoft Exchange 2007 (and perhaps other versions) requires that each server in an Active/Passive cluster be on the same subnet. Apparently, the main reason is that they share a virtual IP address and, in the event of a server or WAN failure, the other server can assume the virtual IP until the issue is resolved. I realize that the routers we have are capable of bridging the traffic between both sites. In fact, there was a question recently asking basically the same question, but for different reasons. What I’m looking for are answers that outline
