The output of a certain router is shown in the figure. According to the information analysis in the figure, which one of the following descriptions is correct?

Question

Options

• AThe reason why there is no DR and BDR in the figure may be that the dr-priority of the peer router is set to 0
• BIf the local router has a new routing table that needs to synchronize and does not receive the Hello packet from the other party within 6 seconds shown in the figure, the state will become Down
• CThe time interval of Hello packets used by this adjacency is 5 seconds
• DThe network type used by the router must not be broadcast

• A
  7% (3)
• B
  5% (2)
• C
  2% (1)
• D
  85% (35)

Explanation

Option D is correct because DR/BDR elections only occur on Broadcast and NBMA network types - the figure's output showing no DR or BDR means the network type cannot be broadcast (it is most likely Point-to-Point or Point-to-Multipoint, which skip DR/BDR entirely).

Why the distractors fail:

• A is wrong because setting one peer's DR priority to 0 only prevents that router from being elected DR/BDR - the local router could still be elected. You would need both routers at priority 0 to suppress DR/BDR entirely, so this alone cannot explain the absence of DR/BDR.
• B is wrong on two counts: the Dead interval (not 6 seconds) governs the Down transition, and the trigger is expiry of the Dead timer without receiving a Hello - not whether the router has routing data pending synchronization. These are independent mechanisms.
• C is wrong because the value shown in the figure is not the Hello interval, or the stated value of 5 seconds does not match what is displayed. Default Hello intervals for non-broadcast types are 10 s (Point-to-Point) or 30 s (NBMA).

Memory tip: Link the concepts together - "No DR/BDR = Not Broadcast." DR and BDR are broadcast-network features; their absence is your strongest signal that the network type is something else (Point-to-Point being the most common exam scenario).

No community discussion yet for this question.