Recently, I was faced with an interesting virtual networking problem: how to allow a large virtualization environment to be failed over to a recovery data center and thoroughly tested, without impacting the production network. As is often the case, my quest for an elegant solution took me down the rabbit hole and led to consideration of several new virtualization networking technologies. In the end, I didn't achieve exactly what I set out to, but I did catch a glimpse of what the future might hold.
In this case, a large VMware vSphere-based virtualization infrastructure had been configured to fail over to a duplicate secondary data center elsewhere on the same campus, the entirety automated through the use of VMware's Site Recovery Manager (SRM).
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Since both data centers had visibility to the same mutually redundant core route switches and associated layer two (L2) networks, an actual failover would be relatively seamless from a networking perspective, involving none of the dynamic routing or, worse, re-addressing that might be required in a typical geographic site failover. If the production data center were to become unavailable for whatever reason, SRM could simply bring the virtual machines back up at the secondary data center in virtual networks configured identically to those in the primary data center, and life would continue without any real changes to the network.