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Difficulty: EasyOSPFv2 Network Types and DR/BDR Selection

Match each OSPFv2 network configuration or interface state on the left with its correct DR/BDR election behavior and timer trait on the right.

  • Broadcast Network TypeElects a Designated Router (DR) and Backup Designated Router (BDR) with default Hello/Dead timers of 10s/40s.
  • Point-to-Point Network TypeForms neighbor adjacencies directly without electing a DR or BDR using default Hello/Dead timers of 10s/40s.
  • Interface OSPF Priority set to 0Renders the router interface completely ineligible to become a DR or BDR on a multiaccess network.

Answer

Broadcast Network Type pairs with electing a DR/BDR using 10s/40s timers; Point-to-Point Network Type pairs with forming direct adjacencies without DR/BDR election using 10s/40s timers; Interface OSPF Priority set to 0 pairs with rendering the router interface completely ineligible for DR/BDR election.
Each OSPF network type has specific rules regarding DR/BDR elections and default timers. Broadcast networks elect DR/BDRs and use 10s/40s timers. Point-to-Point networks bypass DR/BDR elections entirely while sharing the 10s/40s timer defaults. Setting interface priority to 0 explicitly revokes DR/BDR eligibility.

Step-by-Step Solution

1
Analyze OSPF Broadcast media characteristics.
Broadcast networks (like Ethernet) require DR and BDR election to reduce adjacencies on multiaccess segments, operating with 10s Hello and 40s Dead timers.
Broadcast multiaccess segments require a central Designated Router to handle LSA flooding.
2
Evaluate Point-to-Point OSPF network behavior.
Point-to-point links only connect two devices, so no DR/BDR election is needed, though 10s Hello and 40s Dead timers are still used.
DR/BDR election is unnecessary when only two routers share the link.
3
Determine the impact of setting OSPF interface priority to 0.
Setting the priority to 0 disqualifies the router interface from becoming DR or BDR.
Cisco IOS uses priority 0 specifically to keep lower-capacity routers in DROTHER state.

Key Concept

OSPFv2 Network Types and DR/BDR Selection Criteria
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Topics

OSPFv2 Network Types and DR/BDR Selection

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