352-011 · Question #97
Company ABC grew organically and now their single-area OSPF network has an unacceptably slow convergence time after a topology change. To address the slow convergence time, they want to introduce a…
The correct answer is A. Routing is suboptimal. Route summarization at ABRs reduces LSA flooding and shrinks the LSDB, which is exactly what speeds up convergence - but the trade-off is suboptimal routing: summary prefixes hide the granular topology, so routers may select a longer path to a specific destination when a…
Question
Company ABC grew organically and now their single-area OSPF network has an unacceptably slow convergence time after a topology change. To address the slow convergence time, they want to introduce a multiarea OSPF design and implement address summarization at the area border routers, which option should be their main concern about this redesign?
Options
- ARouting is suboptimal
- BSPF calculation takes longer
- COperations complexity is increased
- DMore memory is needed across the routers on the network
How the community answered
(43 responses)- A67% (29)
- B5% (2)
- C12% (5)
- D16% (7)
Explanation
Route summarization at ABRs reduces LSA flooding and shrinks the LSDB, which is exactly what speeds up convergence - but the trade-off is suboptimal routing: summary prefixes hide the granular topology, so routers may select a longer path to a specific destination when a shorter one exists but is obscured by the aggregate. B is wrong because multi-area OSPF makes SPF faster, not slower - each area runs SPF independently on a smaller topology, which is a core benefit of the redesign. C is wrong because while operational complexity does increase slightly, it is not the primary concern specific to address summarization - it's a general multi-area trade-off, not a summarization side effect. D is wrong because multi-area OSPF reduces memory requirements; routers only store their own area's LSDB rather than the entire network's.
Memory tip: Think "Summary = Sacrifice precision for speed." Summarization buys you convergence performance by hiding detail, and hidden detail means routers can't always find the true best path - suboptimal routing is the price you pay.
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