Points to Remember

• Open Shortest Path First (OSPF) ensures interoperability between routing devices manufactured by diverse vendors.

• Link State Advertisement (LSA) is an OSPF packet containing source, destination, and routing information, which is advertised to all OSPF routers in a hierarchical area.

• A designated router (DR) reduces the number of adjacencies formed in a broadcast network.

• A backup designated router (BDR) acts as a standby for the DR on broadcast networks by collecting routing information updated from the adjacent OSPF routers and takes the role of a DR when the DR goes down.

• Multi-access/broadcast networks are physical networks that support interconnection of more than two routers that can communicate directly.

• A single area (SA) is a logical subdivision of the greater OSPF domain, grouping routers that run OSPF with identical topological databases.

• A Totally Stubby Area (TSA) is a type of a nonstandard OSPF area that is used when few networks with limited connectivity are connected to the remaining network.

• Four types of OSPF routers are Internal Router (IR), Area Border Router (ABR), Backbone Router (BR), and Autonomous System Boundary Router (ASBR).

• The priority value is the primary parameter used in DR and BDR elections in an OSPF routing process.

• In a loading state, the information exchange between the OSPF routers that have formed adjacency is finalized.

• To prevent routing loops and sub-optimal routing in the network, configure redistribution into OSPF and between OSPF and another IGP.