The NSX control cluster runs NSX Controller cluster. NSX control cluster is a management system for control plane functions for logical switching and routing. Controller nodes are deployed as three controllers for high availability. A failed control cluster does not impact any data plane traffic.

A controller cluster is a central point for logical switching and routing. A controller cluster is important for unicast and hybrid control plane modes, and it eliminates the need for multicast support from the physical network. NSX Controller supports ARP suppression. NSX Controllers use distributed system, a slicing mechanism that helps utilize all cluster nodes. Every cluster nodes are used as a master for another logical switching and routing. Best practice for high availability is to create separate DRS rules for controller cluster VMs:

A controller cluster holds three tables—MAC, ARP, and VXLAN Tunnel Endpoint (VTEP) table.

Control VM is the next component in the control plane part. Control VM is a virtual appliance, that is used with distributed logical routing when you want to use dynamic routing protocol as an Open Shortest Path First (OSPF) or Border Gateway Protocol (BGP). The second use case is software L2 bridging VXLAN to VLAN.

Distributed logical router (DLR) can work without control VM only with static routing.