OSPF Router types

OSPF Router Types

• Internal Router
• Backbone Router
• Area Border Router (ABR)
• Autonomous System Boundary Router (ASBR)
• Designated Router (DR)
• Backup Designated Router (BDR)

In this part of our OSPF tutorial, when speaking of an OSPF router, we are speaking of the OSPF routing process running on a given routing device. OSPF routers serve in various roles depending upon where they are located and which areas they participate in.

Internal Routers

An internal router connects only to one OSPF area. All of its interfaces connect to the area in which it is located and does not connect to any other area.

If a router connects to more than one area, it will be one of the following types of routers.

Backbone Routers

Backbone routers have one or more interfaces in Area 0 (the backbone area).

Area Border Router (ABR)

A router that connects more than one area is called an area border router or ABR. Usually an ABR is used to connect non-backbone areas to the backbone. If OSPF virtual links are used an ABR will also be used to connect the area using the virtual link to another non-backbone area.

Autonomous System Boundary Router (ASBR)

If the router connects the OSPF Autonomous System to another Autonomous System, it is called an Autonomous System Boundary Router (ASBR).

OSPF elects two or more routers to manage the Link State Advertisments:

Designated Router (DR)

Every OSPF area will have a designated router and a backup designated router. The Designated Router (DR) is the router to which all other routers within an area send their Link State Advertisements. The Designated Router will keep track of all link state updates and make sure the LSAs are flooded to the rest of the network using Reliable Multicast transport.

Backup Designated Router (BDR)

The election process which determines the Designated Router will also elect a Backup Designated Router (BDR). The BDR takes over from the DR when the DR fails.