In vSphere 5.x, it is possible to use static routes to allow migration with vMotion across subnets, although this is not officially supported. vSphere 6.0 introduces TCP/IPv4 and multiple netstack instances. vMotion uses TCP/IPv4 to acquire a netstack instance and default gateway to support vMotion across subnets, and this configuration must be used instead of static routing.
yes, Vmware supports vMotion and HA cross subnet from6.0.
Useful Kb while deploying this:-
Deploying vCenter High Availability with network addresses in separate subnets
Thanks,
Karanveer