Data Centers can be connected with Overly Transport Virtulaiztion OTV, FabricPath or MPLS, In addition QinQ can be used to connect two Data Centers. Below is a diagram shows you how two Data Centers connected via 1G and 10G Dark fiber. In this case QinQ is used to secure the different vlans by encapsulating inside a Metro vlan. QinQ uses two dot1q tags, the outer tag, which is the metro vlan used to transport the inner vlan​, it is like MPLS VPN with two labels, the IGP label

VMware NSX is a network virtualization solution from VMware to make Data Center network more flexible and agile, the same way VMware has revolutionized the virtualization of x86 servers with its ESXi hypervisor solution. NSX is one of the most important part of VMware's Software Defined Data Center (SDDC) strategy. One of the use case for VMware NSX is vMotion across a layer 3 IP network by building a layer 2 switched network with VXLAN tunnels between the ESXi hypervisors. N