What term does OSPF use to refer to a router that has interfaces in more than one area?

The term used by OSPF (Open Shortest Path First) to refer to a router that has interfaces in more than one area is Area Border Router. An Area Border Router functions as a bridge between different OSPF areas and is responsible for exchanging routing information between them. This is crucial for maintaining the efficiency and scalability of OSPF, as it helps manage the traffic and routing tables that span multiple areas.

The Area Border Router plays a significant role in summarizing routing information from one area before sending it to another, thereby reducing the amount of routing information that needs to be exchanged. This capability helps in managing the overall OSPF domain, improving network performance and stability.

Other terms, such as Designated Router, primarily refer to a router elected to represent a multi-access network segment, which focuses on managing neighborship and routing updates within that segment rather than inter-area communication. Routing Device is a generic term that does not specifically apply to the OSPF context, and Backbone Router refers to routers that connect to the OSPF backbone area (Area 0) but does not necessarily indicate interfaces in more than one area.