OSPF routers of different types control the traffic that goes in and out of areas. The OSPF routers are categorized based on the function they perform in the routing domain.

There are four different types of OSPF routers:

Redistribution in multiarea OSPF occurs when an ASBR connects different routing domains (e.g., EIGRP and OSPF) and configures them to exchange and advertise routing information between those routing domains.

A router can be classified as more than one router type. For example, if a router connects to area 0 and area 1, and in addition, maintains routing information for another, non-OSPF network, it falls under three different classifications: a backbone router, an ABR, and an ASBR.