The DvR backbone is automatically established among the DvR Controllers from all DvR domains. Every Controller node has an edge gateway to its DvR domain, to the DvR backbone and all other non-DvR domains within the network.
Controllers exchange host route information such that any host can be reached in a shortcut switched manner, irrespective of its location. For these host route information exchanges, controllers use an automatically assigned backbone I-SID. Local subnets to the Controllers are automatically injected into the DvR host route exchanges.
To redistribute DvR host routes into OSPF or BGP, you can configure route policies. These host routes are not injected into IS-IS.