OSPF is a dynamic link-state routing protocol replacing the distance vector routing protocol, RIP. Though, OSPF has important advantages over RIP. OSPF offers faster convergence and scales to much larger network implementations. The OSPF defines five types of OSPF network:
Point-to-point– When tow routers interconnected over a common link without any other router is called a point-to-point network. The figure below illustrates the point-to-point link.
Broadcast multiaccess– When multiple routers are interconnected over an Ethernet network known as OSPF Broadcast multi-access network. It contains multiple devices on the same shared media, which are sharing data.
Ethernet LANs are the most common example of broadcast multi-access networks. There are different hosts, printers, routers, and other devices that are all members of the same network. The figure below illustrates the broadcast multi-access network.
Nonbroadcast multiaccess (NBMA)– When Multiple routers interconnected in a nonbroadcast network known as Nonbroadcast multi-access (NBMA), such as Frame Relay which does not allow broadcast. The figure below illustrates the NBMA.
Point-to-multipoint– This network contains a router connected with multiple sites. Usually, this is a hub-and-spoke topology over an NBMA network. The figure below illustrates the point-to-multipoint network.
Virtual links – Special OSPF network is used to interconnect remote OSPF areas to the backbone area. The figure below illustrates the special virtual links. In the figure, area 10 cannot connect directly to the area0. A special OSPF area must be configured to connect area 10 to area 0. The router R1 and R2 area1 is a special OSPF virtual link for interconnecting area 10 and area 0