+---------------------+           +-------+  +------+
  | +--+  +-------+---+ |           |Transit|--|Top of|==Physical
  | |VM|--|       |   | | +------+ /|Router |  | Rack |==Servers
  | +--+  |Virtual|NIC|---|Top of|/ +-------+\/+------+
  | +--+  |Switch |   | | | Rack |\ +-------+/\+------+
  | |VM|--|       |   | | +------+ \|Transit|  |Uplink|   WAN
  | +--+  +-------+---+ |           |Router |--|      |=========>
  +---------------------+           +-------+  +------+
         Hypervisor

              ()===================================()
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