What is the function of an Area Border Router (ABR)?

The function of an Area Border Router (ABR) is to sit between two areas within an OSPF (Open Shortest Path First) network. An ABR is responsible for connecting internal areas to the backbone area (Area 0) and facilitating the distribution of routing information between different OSPF areas. By doing so, it enables the efficient aggregation of routes, reduces routing overhead, and allows for a more scalable OSPF design by isolating area-specific routing information from the rest of the network.

When OSPF is deployed, it is common to subdivide the network into multiple areas to enhance performance and manageability. The ABR ensures that there’s a structured flow of routing updates and that routers in one area have a means of accessing information that may reside in other areas. This also helps in minimizing the amount of routing information that needs to be advertised across the entire network, as the ABR can summarize routes from the non-backbone areas before they are sent to the backbone area.

In contrast, the other options refer to different roles within OSPF. Connecting OSPF to external networks is a function of an ASBR (Autonomous System Boundary Router), while load balancing can be performed by routers through various mechanisms