What does an Autonomous System Border Router (ASBR) do?

An Autonomous System Border Router (ASBR) plays a critical role in interconnecting different routing protocols. One of its primary functions is to connect an OSPF (Open Shortest Path First) network to other routing protocols, such as BGP (Border Gateway Protocol) or EIGRP (Enhanced Interior Gateway Routing Protocol). This capability is essential for integrating multiple routing environments, allowing routing information to be shared seamlessly between different autonomous systems, or independently managed networks.

In the context of OSPF, an ASBR can import external routes into OSPF and advertise them to internal OSPF routers, facilitating effective routing across diverse network topologies. This is crucial when an organization uses multiple routing protocols across different segments of its network, enabling communication and data transfer regardless of the routing protocol in use on either side of the ASBR.

This function is distinct from simply connecting internal routers or acting as a backup. For instance, internal routers in an OSPF environment are primarily responsible for exchanging routing information within the same OSPF area. Running OSPF exclusively is a limited view of what an ASBR does since its role inherently requires interaction with other protocols. Additionally, while having certain redundancy features might be a part of network design, an AS