Cisco Certified Network Associate (CCNA) Practice Exam 2026 - Free CCNA Practice Questions and Study Guide

Type 4 LSA, or Link-State Advertisement, is specifically generated by an Area Border Router (ABR) in OSPF (Open Shortest Path First) networking. The primary function of the ABR is to connect different OSPF areas and to manage the exchanges of routing information between these areas.

When an ABR advertises Type 4 LSAs, it signifies the existence of an Autonomous System Boundary Router (ASBR) that is connected to the OSPF domain. Type 4 LSAs point to the ASBR's location so that routers in other areas can know how to reach the external routes. This is crucial for ensuring that all routers within an OSPF topology have a consistent view of how to route packets to external networks.

In the context of OSPF, understanding the role of different router types – such as Designated Routers (DRs) and ASBRs – is essential. While a Designated Router is responsible for generating Type 2 LSAs for multi-access networks and representing the network to other OSPF routers, it does not handle Type 4 LSAs. Similarly, an ASBR is responsible for generating Type 5 LSAs, which represent external routing information. Therefore, the