VSAN 6.x
here is the post from Rawlinson Rivera
VMware Virtual SAN & vSphere HA Recommendations - VMware vSphere Blog - VMware Blogs
The post is explaining many scenarios, among those one of the objective is, what can happen when you don't use non-VSAN datastore as heartbeat. Chances of seeing split brain scenario in that case is high if you don't set proper Isolation Addresses. Now that in VSAN 6, when HA and VSAN are enabled together, HA will be using VSAN network instead of Management network. In-Short use VSAN network default gateway as isolation address, and not management network default gateway.