Open vSwitch can be configured to communicate with one or more external OpenFlow controllers. The IP address and TCP port of a target controller can be specified as follows:
ovs-vsctl set-controller <BRIDGE> tcp:$CONTROLLER_ADDRESS:$CONTROLLER_PORT
In order to assign multiple controllers to the Open vSwitch, you just need to specify all necessary controller addresses and ports in the same command:
ovs-vsctl set-controller <BRIDGE> tcp:$CONTROLLER_ADDRESS1:$CONTROLLER_PORT1 \ tcp:$CONTROLLER_ADDRESS2:$CONTROLLER_PORT2 \ tcp:$CONTROLLER_ADDRESS3:$CONTROLLER_PORT3 \ tcp:$CONTROLLER_ADDRESS4:$CONTROLLER_PORT4 ...
NOTE: Do not use separate commands for assigning multiple controllers, as the last command overwrites the previous controller configuration.