An OSPF installation consists of one or more areas. An OSPF area is typically divided into logical areas linked by Area Border Routers. A group of contiguous networks form an area. An Area Border Router (ABR) links one or more areas to the OSPF network backbone (area ID 0). See “Area border router (ABR)”.

OSPF is an interior routing protocol. It includes a backbone AS, and possibly additional ASes. The DR and BDR are elected from potential routers with the highest priorities. The DR handles much of the administration to lower the network traffic required. New routers are discovered through hello packets sent from the DR using the multicast address of 224.0.0.5. If the DR goes offline at any time, the BDR has a complete table of routes that is uses when it takes over as the DR router.

OSPF does not use UDP or TCP, but is encapsulated directly in IP datagrams as protocol 89. This is in contrast to RIP, or BGP. OSPF handles its own error detection and correction functions.

The OSPF protocol, when running on IPv4, can operate securely between routers, optionally using a variety of authentication methods to allow only trusted routers to participate in routing. OSPFv3, running on IPv6, no longer supports protocol-internal authentication. Instead, it relies on IPv6 protocol security (IPsec).

Other important parts of how OSPF works includes: