Hi all 
Kindly, help me with this dilemma..
I have 3 hosts in a DRS/DPM/HA cluster (ESXi 5.1) with a vDS connecting them and a vCenter appliance (5.1) hosted on the cluster and managing it...I tested something weird in my lab.. I powered off the vCenter appliance for 24+ to simulate if my vCenter goes down for that long duration without recovery due to any disaster..I began to test somethings during this duration.. and I was surprised that after nearly 24-25 hrs the vDS went down and I couldn't contact the other hosts from any of them..and when I powered up the vCenter the vDS is still down and I restored it from a backup of configuration.
I tested that twice till now after that incidence and I got the same effect after the same duration...
Thanks so much..