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Difficulty: EasyOSPFv2 Network Types and DR/BDR Selection

Match each OSPFv2 network type or interface configuration setting to its corresponding DR/BDR election behavior.

  • Broadcast network typeElects a Designated Router (DR) and Backup Designated Router (BDR)
  • Point-to-Point network typeDoes not elect a DR or BDR despite forming adjacencies
  • OSPF interface priority set to 0Ineligibility for DR/BDR election, forcing the router to remain DROTHER

Answer

Broadcast network type matches with electing a DR and BDR. Point-to-Point network type matches with not electing a DR or BDR. An OSPF interface priority set to 0 matches with ineligibility for DR/BDR election.
Broadcast network types require a Designated Router (DR) and Backup Designated Router (BDR) to minimize adjacency traffic across shared multiaccess segments. Point-to-Point network types connect only two routers, so DR and BDR elections are omitted completely. Configuring an OSPF interface priority of 0 excludes that router from participating in elections, forcing its role to DROTHER.

Step-by-Step Solution

1
Identify the election requirement for multiaccess media.
Broadcast networks elect a DR and BDR to manage adjacencies.
Ethernet broadcast networks are multiaccess, requiring centralized LSA flooding via DR/BDR.
2
Identify the election requirement for point-to-point media.
Point-to-Point networks form full adjacencies directly between the two endpoints without electing a DR or BDR.
There are only two devices on a point-to-point link, so a DR/BDR role provides no architectural benefit.
3
Determine the effect of configuring priority 0.
Setting ip ospf priority 0 makes the interface ineligible to become a DR or BDR.
Priority 0 is specifically reserved in OSPF to ensure a router stays in the DROTHER state regardless of Router ID.

Key Concept

OSPF DR/BDR Election Mechanics and Interface Types
Estimated Time:45s
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Topics

OSPFv2 Network Types and DR/BDR Selection

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