Which of the following are the advantages of electing DR/BDR in the MA network? (Multiple choice)

Question

Options

• AFacilitate synchronization of link status
• BNo multicast packets needed to maintain neighbor status
• COSPF neighbors can be established as long as TCP is reachable
• DReduce duplicate traffic

• A
  82% (36)
• B
  7% (3)
• C
  11% (5)

Explanation

Electing a DR/BDR on a Multi-Access (MA) network like Ethernet solves two core OSPF scalability problems. Without DR/BDR, every router would need to form full adjacencies with every other router, causing each LSA to be flooded redundantly - the DR acts as a central redistribution point, synchronizing link-state information (A) and eliminating duplicate LSA floods (D) by having all routers report to the DR, which then distributes updates once to everyone.

Why B is wrong: OSPF still uses multicast Hellos (224.0.0.5) to maintain neighbor state even with DR/BDR - the election doesn't remove multicast, it refines how it's used (adding 224.0.0.6 for DR/BDR-specific traffic).

Why C is wrong: OSPF runs directly over IP (protocol 89), not TCP. Reachability via TCP is irrelevant; OSPF adjacency depends on IP connectivity and Hello parameter matching, not transport-layer sessions.

Memory tip: Picture the DR as a neighborhood bulletin board - instead of every resident posting flyers on every other neighbor's door (duplicate traffic, hard to sync), everyone posts once to the board (DR), which keeps one authoritative copy and notifies all. Sync + no duplicates = DR's job.

No community discussion yet for this question.