vSphere 5 adds a multi–network adaptor feature that enables the user to utilize multiple network adaptors for vMotion.
In the screen shot below, you can see that there are multiple vMotion vmkernel ports, with 1 active vmnic, and 3 standby nics.
Test results, show that migration times can be dramatically reduced when using this feature.
The VMkernel will transparently load balance vMotion traffic over all of the vMotion-enabled vmknics to saturate all of the connections. In fact, even where there is a single vMotion, VMkernel uses all of the available network adaptors to spread the vMotion traffic