OS10 Enterprise Edition User Guide Release 10.4.0E(R3)

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Router types

Router types are attributes of the OSPF process—multiple OSPF processes may run on the same router. A router connected to more than one area, receiving routing from a BGP process connected to another AS, acts as both an area border router and an autonomous system border router.

Each router has a unique ID, written in decimal format—A.B.C.D. You do not have to associate the router ID with a valid IP address. To make troubleshooting easier, ensure the router ID is identical to the router’s IP address.

OSPF routing destinations

Backbone router
A backbone router (BR) is part of the OSPF Backbone, Area 0, and includes all ABRs. The BR includes routers connected only to the backbone and another ABR, but are only part of Area 0—shown as Router I in the example.
Area border router
Within an AS, an area border router (ABR) connects one or more areas to the backbone. The ABR keeps a copy of the link-state database for every area it connects to. It may keep multiple copies of the link state database. An ABR summarizes learned information from one of its attached areas before it is sent to other connected areas. An ABR can connect to many areas in an AS and is considered a member of each area it connects to—shown as Router H in the example.
Autonomous system border router
The autonomous system border router (ASBR) connects to more than one AS and exchanges information with the routers in other ASs. The ASBR connects to a non-IGP such as BGP or uses static routes—shown as Router N in the example.
Internal router
The internal router (IR) has adjacencies with ONLY routers in the same area—shown as Routers E, F, I, K, and M in the example.

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