Wireless Access

We've got a requirement to deploy multiple virtual controllers in a 'large campus' topology with stretched L2 networks using VXLAN.

Is there any guidance on whether the VRRP used by ArubaOS Clustering requires multicast support to work? Are there options to explicitly support unicast?

In my experience, do not stretch clusters across sprawling physical switching infrastructures.  Cluster members rely on having sub 50 millisecond response times between each other to maintain a cluster membership.  Extending that across sprawling physical infrastructures that creates latency will lead to cluster reconvergence.

Thanks and noted

For interest's sake, is multicast support required for Cluster VRRP?

A cluster VRRP is not required.  It is only useful for COA (Change of Authorization).  Besides that a VRRP is not required for a cluster.