1. A multi-tenant datacenter, comprising: a plurality of physical client systems in a first datacenter each physical client system having a set of physical infrastructure resources; and a first cloud computing environment established in the first datacenter, and coupled to the physical client systems by OSI Layer 2, prior to an OSI Layer 3 connection, as the physical connection of a data channel for the transfer of data frames, each frame having a plurality of OSI Layer 2 tags permitting at least two client systems to have overlapping VLANs and or overlapping IP address ranges, the first cloud computing environment thereby virtually extending the physical infrastructure resources of each physical client system, wherein the OSI Layer 2 tags are selected from the group consisting of Segment ID Tags and Global VLAN Tags.