Hi,
In my nested esxi homelab I'm running vcenter, vcloud director and vshield manager all appliances and all version 5.5. I created a vcloud environment following the 'vmware vcloud director 5.1 evaluation guide'. I created a internal network (virtual wire) with two Linux hosts connected to it. Tcpdump revealed that the destination host connected to the virtual wire does not send SYN_ACK back. The source host stays in SYN_SENT. Source and destination are on the same virtual wire. There is no asymmetric routing, no duplicate MAC's and no private VLAN involved. Ping works fine.