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Area border router

Area border router

(also ABR)

Area border router definition

In the Open Shortest Path First (OSPF) protocol, area border routers connect OSPF areas to the backbone network (also known as “area 0” or “0.0.0.0”). Area border routers serve to provide summaries of the sub networks throughout a given OSPF system.

As the name suggests, area border routers are placed on the borders of OSPF areas to serve as entry and exit points for information. Because an area border router belongs to both the areas it connects to and the backbone network, it maintains the necessary routing information for each area.

Other routers in OSPF

• Backbone routers (BR) have at least one interface in the backbone area.
• Internal routers (IR) are routers that have all their interfaces in a single OSPF area.
• Autonomous system boundary routers (ASBR) distribute routes received from external autonomous systems throughout the internal one. ASBRS employ more than one routing protocol.