In OSPF, the Area Border Router (ABR) generates Type-4 Summary LSAs to advertise the location of an Autonomous System Boundary Router (ASBR) to other areas. This LSA informs routers in different areas how to reach the ASBR for external routes. ASBR generates Type-5 LSAs for external routes, but ABR summarizes them with Type-4. Not all routers or stub routers do this. Exact extract: This article describes the basic steps to configure FortiGates in an OSPF scenario where the FortiGates will be ABR and ASBR OSPF routers across 3 areas. Router3 is the Autonomous System Border Router (ASBR). It routes all traffic to the ISP BGP router for internet access. It redistributes routes from BGP and ... Type 4 LSAs exist to let the area know the router-id of the ASBR, so the routers can look at the type 5 route, find advertising-router, and map
... An ASBR summary LSA is generated by an ABR and describes the location of an ASBR (Autonomous System Boundary Router) that connects to an external network. The FortiGate in the middle shall be a ABR between the two areas. But I don't want R2 in area 0.0.0.0 to have every /32 route for every VPN client. So I tried ...