This is the default load balancing mechanism for both vSS and vDS. With this mechanism, every virtual switch port to which a vNIC/VMkernel interface connects to is associated with an uplink (vmnic/dvUplink) in a round-robin fashion. Once associated, the corresponding uplinks are always used for traffic unless there is an uplink failure, a VMotion, or a power cycle of a VM.

The following diagram depicts the round-robin distribution of ports - where-in port 1 and 3 are assigned to uplink-A and ports 2 and 3 to uplink B :