Which OSPF networks types are compatible and allow communication through the two peering devices?

Question

Options

• Abroadcast to nonbroadcast
• Bpoint-to-multipoint to nonbroadcast
• Cbroadcast to point-to-point
• Dpoint-to-multipoint to broadcast

• A
  74% (17)
• B
  13% (3)
• C
  4% (1)
• D
  9% (2)

Explanation

OSPF Network Type Compatibility

Broadcast and nonbroadcast network types are compatible because they share the same DR/BDR election process and neighbor discovery mechanisms - the key difference is simply that broadcast performs automatic neighbor discovery while nonbroadcast requires manually configured neighbors; this shared DR/BDR framework allows the two types to form adjacencies and exchange routing information successfully.

Why the distractors are wrong:

• B (point-to-multipoint to nonbroadcast) - These are incompatible because point-to-multipoint does not elect a DR/BDR, while nonbroadcast does, causing a Hello parameter mismatch
• C (broadcast to point-to-point) - Point-to-point does not participate in DR/BDR elections and uses different Hello/Dead timers (10/40 vs 30/120), making these incompatible
• D (point-to-multipoint to broadcast) - Point-to-multipoint skips DR/BDR election entirely, making it incompatible with broadcast which requires it

Memory Tip: Think of compatible pairs as "same DR/BDR behavior, different discovery method." Broadcast and nonbroadcast both elect a DR/BDR - that shared characteristic is what makes them the compatible pair. If one side skips the DR/BDR election, compatibility breaks.

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