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Routing & Switching · Intermediate

Area Border Router (ABR)

An OSPF router with interfaces in area 0 and at least one other area, which summarizes routes between them.

Definition

An ABR maintains a separate LSDB for each attached area and generates Type 3 summary LSAs and Type 4 ASBR summary LSAs. It is the only place inter-area summarization (area range) can be configured. ABRs also convert Type 7 to Type 5 for NSSAs (the ABR with the highest RID).

Example

area 1 range 10.1.0.0 255.255.0.0 on the ABR

Exam tip

OSPF inter-area summarization can only be done on an ABR; external summarization only on an ASBR.

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