Which two options are reasons for designing a large OSPF network with multiple areas connected to the backbone? (Choose two)

Question

Options

• AReduce the number of routes within an area
• BRoute tagging capability
• CSimplify logical topology
• DEnhance failure detection
• EReduce SPF algorithm runs

Explanation

A (Reduce the number of routes within an area) and E (Reduce SPF algorithm runs) are the correct answers. Multi-area OSPF keeps each area's Link State Database (LSDB) smaller by confining detailed topology information locally - Area Border Routers (ABRs) summarize inter-area routes, so routers don't carry the full network's route table. Additionally, when a link flaps, only routers within that area must rerun the Dijkstra SPF calculation; routers in other areas receive only a summary LSA update, avoiding a costly full recalculation.

Why the distractors are wrong:

• B (Route tagging) - Tagging is used during route redistribution between protocols, not a benefit of multi-area OSPF design.
• C (Simplify logical topology) - Multiple areas actually increase complexity (ABRs, backbone area requirement, virtual links); single-area is simpler to manage.
• D (Enhance failure detection) - Hello/Dead timers and BFD operate the same regardless of area count; areas don't change how OSPF detects failures.

Memory tip: Think "A-rea = less routes, E-fficiency = less SPF work." Both benefits come from containment - containing topology detail and containing the blast radius of topology changes to a single area.

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