What are the benefits of OSPF area division? (Multiple choice)

Question

Options

• ARouters in an area can learn topology details outside their area
• BCan reduce the size of LSDB and thus reduce the consumption of router memory
• CLSA can also be reduced after the division of areas, reducing the consumption of router CPU
• DMass flooding of LSAs is limited to a single area

• A
  3% (1)
• B
  84% (32)
• C
  3% (1)
• D
  11% (4)

Explanation

Option B is correct because OSPF area division confines the Link State Database (LSDB) to each area - routers only store and synchronize topology information for their own area rather than the entire network, which directly shrinks memory requirements as the network scales.

Why the distractors are wrong:

• A is the opposite of reality: routers within an area see only their area's topology. Topology outside the area is hidden - only summarized route prefixes reach them via ABRs (Area Border Routers). This is by design.
• C is actually also a valid benefit in practice (fewer LSAs per router means less SPF computation), so if your exam marks it wrong, the likely intent is that CPU savings are a secondary effect of LSDB reduction, not a standalone benefit of area division itself - the LSDB size is the root cause.
• D is likewise technically true (LSA flooding is area-scoped), so if your exam treats it as wrong, double-check whether multiple answers were intended. If B is truly the only correct answer, the exam may be emphasizing LSDB/memory as the primary benefit while treating flooding containment as a mechanism, not a stated benefit.

Memory tip: Think "OSPF areas = apartments in a building." Each tenant (router) only knows the layout of their own apartment (area), not every room in the building - so they carry a smaller map (LSDB) and use less memory. Option A fails because tenants can't see other apartments; B wins because the smaller map is the direct, measurable benefit.

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