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Difficulty: MediumOSPFv2 Network Types and DR/BDR Selection

Match each OSPFv2 network type on the left to its correct DR/BDR election requirement and default Hello timer on the right.

  • Broadcast MultiaccessElects DR/BDR; default Hello timer is 10 seconds
  • Point-to-PointDoes NOT elect DR/BDR; default Hello timer is 10 seconds
  • Point-to-MultipointDoes NOT elect DR/BDR; default Hello timer is 30 seconds

Answer

Broadcast Multiaccess matches with 'Elects DR/BDR; default Hello timer is 10 seconds'. Point-to-Point matches with 'Does NOT elect DR/BDR; default Hello timer is 10 seconds'. Point-to-Multipoint matches with 'Does NOT elect DR/BDR; default Hello timer is 30 seconds'.
Broadcast Multiaccess networks use a 10-second Hello timer and perform DR/BDR elections to manage multiaccess adjacencies. Point-to-Point networks use a 10-second Hello timer but suppress DR/BDR elections because only two endpoints exist. Point-to-Multipoint networks suppress DR/BDR elections and operate with a 30-second Hello timer.

Step-by-Step Solution

1
Determine DR/BDR election requirements for each OSPFv2 network type.
DR/BDR elections only occur on multiaccess media (Broadcast and Non-Broadcast Multiaccess). Point-to-Point and Point-to-Multipoint types bypass DR/BDR elections.
DR/BDR selection prevents unnecessary adjacency overhead on multiaccess networks.
2
Recall default OSPFv2 Hello timers for each network type.
Broadcast and Point-to-Point network types default to 10-second Hello timers. Non-Broadcast and Point-to-Multipoint default to 30-second Hello timers.
OSPF timer defaults depend on whether the underlying physical medium is considered high-speed broadcast/point-to-point or slower non-broadcast media.
3
Match the attributes of each network type.
Broadcast Multiaccess -> DR/BDR elected, 10s Hello. Point-to-Point -> No DR/BDR, 10s Hello. Point-to-Multipoint -> No DR/BDR, 30s Hello.
Combines the DR/BDR requirement with the appropriate interface default Hello timer.

Key Concept

OSPFv2 Network Types, DR/BDR Selection, and Default Timers
Estimated Time:1m 30s
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Topics

OSPFv2 Network Types and DR/BDR Selection

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