In a DvR domain, the Controller nodes are the central nodes on which Layer 3 is configured. They own all the Layer 3 configuration and push the configuration information to the Leaf nodes within the SPB network.
A DvR domain can have one or more controllers for redundancy and you must configure every Layer 2 VSN (VLAN) and Layer 3 VSN within the domain, on the Controller(s). A node that you configure as a DvR Controller is considered the controller for all the Layer 2 and Layer 3 VSNs configured on that node. A Controller is configured with its own subnet IP address for every DvR enabled Layer 2 VSN within the domain.
All Layer 2 VSNs on a DvR Controller need not be DvR enabled. A controller can be configured with individual Layer 2 VSNs that are DvR disabled.
The Layer 3 configuration data that is pushed to the Leaf nodes include the Layer 3 IP subnet information for all Layer 2 VSNs within the DvR domain. It also includes the IP routes learned or redistributed by the Controllers from networks outside the SPB network, into the DvR Domain. Controllers also send information on whether Multicast is enabled on a specific DvR enabled Layer 2 VSN, and the version of IGMP. DvR Controllers inject a default route into the DvR domain for external route reachability. Use route policies to inject specific routes into a DvR domain or inject host routes into OSPF or BGP.
A Controller can only belong to one DvR domain, based on the domain ID that you configure on the node.
DvR Controllers include all DvR Leaf functions, thus a Leaf node free deployment is a valid network deployment. Especially if you use DvR in Campus deployments to replace VRRP or RSMLT, a Controller-only deployment, as Fabric Attach server nodes, is a valid deployment option.