352-001 Question #524: Real Exam Question with Answer & Explanation

The correct answer is C: Ensure DR and BDR routers are placed optimally in the topology.. In a large single-area fully-meshed OSPF topology, LSA flooding is controlled by the DR and BDR, so their optimal placement minimizes unnecessary replication across the segment.

Question

How can a network designer reduce the amount of LSA flooding occurring in a large, single area fully- meshed OSPF topology?

Options

AImplemented passive OSPF interfaces on the routers not participating on the DR/BDR election.
BUse access control lists to control outbound advertisements.
CEnsure DR and BDR routers are placed optimally in the topology.
DPlace all point-to-point links in their own dedicated areas.

Explanation

In a large single-area fully-meshed OSPF topology, LSA flooding is controlled by the DR and BDR, so their optimal placement minimizes unnecessary replication across the segment.

Common mistakes.

A. Passive interfaces suppress OSPF hellos entirely on that interface, preventing adjacency formation rather than controlling LSA flooding within an established topology.
B. ACLs cannot filter OSPF LSAs on a per-advertisement basis because OSPF uses multicast and the LSA database must be identical across all routers in an area to maintain convergence.
D. Moving point-to-point links into separate areas would reduce flooding through area segmentation, but this fundamentally changes the topology design rather than optimizing the existing single-area fully-meshed structure.

Concept tested. OSPF DR/BDR placement and LSA flood reduction

Reference. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13703-8.html

Community Discussion

No community discussion yet for this question.

Full 352-001 Practice