Virtual links are configured between any backbone routers that share a link to a nonbackbone area and function as if they were direct links. Hello protocol to acquire neighbors , which are routers with interfaces to a common network. The router sends hello packets to its neighbors and receives their hello packets. In addition to helping acquire neighbors, hello packets also act as keep-alives to let routers know that other routers are still functional. Among other things, the designated router is responsible for generating LSAs for the entire multiaccess network.
Designated routers allow a reduction in network traffic and in the size of the topological database.
When the link-state databases of two neighboring routers are synchronized, the routers are said to be adjacent . On multiaccess networks, the designated router determines which routers should become adjacent. Topological databases are synchronized between pairs of adjacent routers. Adjacencies control the distribution of routing-protocol packets, which are sent and received only on adjacencies. Each router periodically sends an LSA to provide information on a router's adjacencies or to inform others when a router's state changes.