Area Border Router

Definition of Area Border Router

An Area Border Router (ABR) is a networking device that connects and controls the data flow between two or more Open Shortest Path First (OSPF) areas within a network. The ABR maintains a separate link-state database for each area it connects and performs route summarization to optimize communication between the areas. Thus, ABRs play a crucial role in simplifying and improving the efficiency of large networks using the OSPF protocol.


The phonetic pronunciation of the keyword “Area Border Router” is:- Area: ˈɛəriə- Border: ˈbɔrdər- Router: ˈruːtərCombined, it would be: ˈɛəriə ˈbɔrdər ˈruːtər

Key Takeaways

  1. Area Border Routers (ABRs) connect an OSPF area to the backbone, enabling communication between different areas. They maintain both intra-area and inter-area routing information.
  2. ABRs run the OSPF protocol and summarize routes at the border, contributing to a smaller routing table and improved network scalability.
  3. By filtering and redistributing routes, ABRs provide better control over routing information, manage traffic, and enhance network stability and performance.

Importance of Area Border Router

The term Area Border Router (ABR) is important in the world of technology, particularly in the context of computer networks and routing, as it plays a crucial role in ensuring efficient and scalable routing within large networks.

ABRs are essential components of OSPF (Open Shortest Path First) networks, where they function as gateways between different OSPF areas, connecting them and responsible for sharing routing information.

By separating large networks into smaller hierarchical areas, ABRs help control routing overhead and improve network stability, leading to faster convergence times and more efficient use of resources, critical for achieving optimal performance and reliability in large-scale network environments.


An Area Border Router (ABR) serves a vital purpose within a network by streamlining communication and enhancing efficiency. As networks grow in size and complexity, they are often divided into smaller segments called areas for ease of management and to reduce the amount of information exchanged between routers.

These areas, particularly in large networks, enable better control over data traffic, prevent congestion, and improve overall performance. ABRs come into play by acting as intermediaries that connect these areas, allowing for seamless communication and streamlined flow of information across the entire network.

ABRs are responsible for ensuring that routers have knowledge of their surrounding areas, a crucial feature in enabling inter-area communication. They maintain and share up-to-date routing information by aggregating and filtering data from numerous sources, including internal routers within its area and other ABRs.

This consolidated information allows routers to optimize their routing tables and to make more informed decisions when faced with multiple potential paths for data transmission. In essence, an Area Border Router’s primary role is to facilitate communication between different areas within a network and to ensure the efficient flow of data, ultimately enabling the entire network to function effectively.

Examples of Area Border Router

Internet Service Providers (ISPs): In the context of ISPs, Area Border Routers play a crucial role by connecting different OSPF areas. An ISP often has multiple OSPF areas that need to be connected to provide seamless internet connectivity to its customers. Using ABRs, ISPs can efficiently manage their OSPF routing preferences and exchange routing information between areas to maintain proper communication.

Enterprise Networks: In large organizations with geographically diverse branches and campuses, it is common to have multiple OSPF areas for efficient management of network resources. The Area Border Routers in such scenarios connect the different OSPF areas within the organization, ensuring smooth data transfers between them. By using ABRs in their enterprise networks, companies can effectively route network traffic between various locations and ensure stable interconnectivity.

Data Center Interconnects: In modern data centers, the use of redundant connections between different data centers or between various areas within the same data center is essential for maintaining high availability and disaster recovery capabilities. In such environments, Area Border Routers can be used to connect virtual OSPF areas or physical locations, facilitating the exchange of routing information between these locations. This allows for better management of resources, improved routing efficiency, and minimized downtime.

Area Border Router FAQ

1. What is an Area Border Router (ABR)?

An Area Border Router (ABR) is a router that connects and manages communication between two or more OSPF (Open Shortest Path First) areas in a large-scale network. It is responsible for summarizing routing information and sharing it with other ABRs, making the routing process more efficient and scalable.

2. Why are Area Border Routers important?

Area Border Routers play a crucial role in the OSPF protocol by reducing routing traffic and enabling networks to be partitioned into smaller manageable areas. This improves the overall performance of the network and helps prevent routing loops in complex systems.

3. How does an ABR function?

An ABR maintains a separate link-state database for each area it is connected to. It advertises summary LSAs (Link-State Advertisements) into both backbone and non-backbone areas, allowing routers within those areas to learn about routes outside their area. In the OSPF backbone area, ABRs exchange routing information with other ABRs, ensuring the network remains up-to-date and synchronized.

4. What is OSPF, and how is it related to ABRs?

OSPF (Open Shortest Path First) is a widely used Interior Gateway Protocol (IGP) that is designed to manage routing within large-scale networks. ABRs play a crucial role in OSPF by facilitating communication between different OSPF areas, making it a more scalable routing solution compared to flat routing protocols.

5. What are the common types of OSPF areas, and how do ABRs support them?

OSPF supports several types of areas, including Backbone Area (Area 0), Standard Area, Stub Area, Totally Stubby Area, and Not-So-Stubby Area (NSSA). ABRs help organize and manage OSPF routing information by exchanging summary LSAs between these OSPF areas, enabling routers to establish optimal paths for data transmission across a complex network.

Related Technology Terms

  • Open Shortest Path First (OSPF)
  • Border Gateway Protocol (BGP)
  • Routing Information Protocol (RIP)
  • Interior Gateway Protocol (IGP)
  • Autonomous System Boundary Router (ASBR)

Sources for More Information


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