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

Question

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.

• A
  5% (1)
• B
  10% (2)
• C
  81% (17)
• D
  5% (1)

Explanation

In a large, single-area fully-meshed OSPF topology, the DR (Designated Router) and BDR (Backup Designated Router) are the central points that manage LSA flooding - all other routers (DROthers) send updates only to the DR/BDR, which then flood to the rest of the network. Placing these routers optimally (high bandwidth, central location, highest priority) minimizes unnecessary flooding and ensures efficient LSA distribution, which is why C is correct.

Why the distractors are wrong:

• A is incorrect because passive interfaces suppress OSPF hello packets entirely, removing those interfaces from OSPF participation - they don't control LSA flooding behavior among active routers.
• B is incorrect because OSPF does not use access control lists to filter LSAs between neighbors; ACLs cannot selectively block OSPF flooding within an area (redistribution filtering is a different concept).
• D is incorrect because splitting point-to-point links into separate areas would actually introduce inter-area LSA traffic (Type 3 Summary LSAs), increasing overhead rather than reducing it.

Memory tip: Think "DR = traffic cop" - just as placing a traffic cop at the busiest intersection reduces chaos, placing the DR/BDR at the optimal network hub reduces flooding chaos. If the cop is in the wrong spot, everyone still ends up shouting.

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