In OSPF, the AS border router can be an Internal Router or an ABR, but it must belong to the backbone area.

Question

Options

• ATRUE
• BFALSE

• A
  27% (7)
• B
  73% (19)

Explanation

B is correct because the statement's claim that an ASBR must belong to the backbone area (Area 0) is false - an ASBR can reside in any OSPF area, including non-backbone areas, as long as it redistributes external routes into the OSPF domain. The first half of the statement is actually valid: an ASBR can simultaneously be an Internal Router (if it has all interfaces in one non-backbone area) or an ABR (if it connects multiple areas), but neither role forces it into Area 0.

Why A (TRUE) is wrong: Accepting the statement as true would incorrectly restrict ASBR placement to Area 0, which no OSPF RFC requires. A router in Area 2, for example, can redistribute EIGRP routes into OSPF and function as an ASBR without any backbone membership.

Memory tip: Think of the roles by their names - an ABR (Area Border Router) must touch the backbone because its job is to connect areas. An ASBR (AS Border Router) touches an external AS - its job has nothing to do with area boundaries, so backbone membership is irrelevant. If you mix up ABR and ASBR requirements on an exam, remember: ABR = backbone required, ASBR = backbone optional.

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