Nowadays in datacenters, a physical server runs many virtual servers. With this solution, management and monitoring is easier. But when a physical server is overloaded or fails, it affects the virtual servers too. Load balancing can be the solution for the overloadings, by distributing the virtual machines between the other physical machines. The migration process saves the memory state-which can be determined as static- of the virtual machine and moves to the new host machine, but the network state –which can be determined as non-static- can be invalid , if the new host is on a different subnet, because the migrated machine gets a new IP address, but the living TCP connections are binded to the old IP address.Because of the subnet change, all connections will be lost, until the machine sets up them in the new environment.With Software Defined Networking, we can dynamically reconfigure the network as the migration starts, so the packets will be routed to the new destination, resulting in no connection loss.