As shown in the figure, in the MA network, if R1 must be DR, R2 must be BDR, and R3, R4, and R5 do not participate in the election, then the maximum dr-priority of R1 is (___), the dr-priority of R2…

Question

Options

• A3
• B
• C
• D

• A
  83% (24)
• B
  7% (2)
• C
  10% (3)

Explanation

In OSPF DR/BDR elections on a Multi-Access (MA) network, routers with a dr-priority of 0 are excluded from the election entirely, so R3, R4, and R5 must each be set to 0. The DR is the router with the highest non-zero priority, and the BDR holds the second-highest priority - meaning R2's priority must be strictly less than R1's. Based on the figure (which shows R1 configured with a priority of 4), the maximum dr-priority R2 can hold while still serving as BDR rather than becoming DR is 3 - one below R1's value - which is why option A is correct.

The distractors do not apply here because no value equal to or greater than R1's priority would allow R2 to remain BDR (it would instead tie for or win the DR role), and any value of 0 for R2 would remove it from the election altogether. R3, R4, and R5 cannot have any value other than 0 if they are to be kept out of the election process.

Memory tip: Think of it as a strict ranking - DR owns the top spot, BDR owns the next spot, and zeros sit out. To lock in the roles, each priority must be uniquely ordered: R1 > R2 > 0, with non-participants always set to exactly 0.

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