352-001 · Question #439
Which two options are reasons for designing a large OSPF network with multiple areas connected to the backbone? (Choose 2)
The correct answer is A. Reduce the number of routes within an area. E. Reduces SPF algorithm runs. Dividing a large OSPF network into multiple areas reduces both the size of the link-state database within each area and the frequency of SPF recalculations, improving scalability and stability.
Question
Which two options are reasons for designing a large OSPF network with multiple areas connected to the backbone? (Choose 2)
Options
- AReduce the number of routes within an area.
- BRoute tagging capability.
- CEnhance failure detection.
- DSimplify logical topology.
- EReduces SPF algorithm runs.
How the community answered
(51 responses)- A94% (48)
- B4% (2)
- C2% (1)
Why each option
Dividing a large OSPF network into multiple areas reduces both the size of the link-state database within each area and the frequency of SPF recalculations, improving scalability and stability.
Area boundaries allow summarization so that routers inside an area only maintain LSAs for their own area, directly reducing the routing table and LSDB size within each area.
Route tagging is used during redistribution to mark external routes, and it is not a reason to design multiple OSPF areas.
Multi-area OSPF does not inherently enhance failure detection - Hello/Dead timers and BFD govern detection speed regardless of area design.
Adding multiple areas and an ABR hierarchy increases logical complexity rather than simplifying it.
SPF is computed per area, so a topology change in one area does not trigger an SPF recalculation in other areas, lowering CPU overhead across the network.
Concept tested: OSPF multi-area design benefits and scalability
Source: https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/7039-1.html
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