Examkin

Question

Difficulty: MediumOSPFv2 Network Types and DR/BDR Selection

A network administrator configures the command `ip ospf network point-to-point` on interface GigabitEthernet0/1 of router R1, which connects directly to router R2 over an Ethernet segment in OSPFv2 Area 0. Which operational change occurs on this interface as a result of this configuration?

  1. OSPF suppresses Designated Router (DR) and Backup Designated Router (BDR) elections on the interface while maintaining the default 10-second Hello timer.Answer
  2. B
    OSPF automatically changes the interface priority to 0, preventing R1 from participating in the DR/BDR election process.
  3. C
    OSPF alters the default Hello and Dead timers to 30 seconds and 120 seconds respectively, requiring manual timer adjustments on R2.
  4. D
    OSPF converts the underlying Ethernet segment into separate collision domains, blocking multicast Hello packets from reaching R2.

Answer

OSPF suppresses Designated Router (DR) and Backup Designated Router (BDR) elections on the interface while maintaining the default 10-second Hello timer.
On point-to-point OSPF networks, DR and BDR elections are completely suppressed because only two routers reside on the link. The default Hello and Dead timers for point-to-point network types on Ethernet media remain 10 seconds and 40 seconds, respectively.

Step-by-Step Solution

1
Analyze default OSPF behavior on Ethernet interfaces.
Ethernet interfaces default to the OSPF Broadcast network type, which requires DR/BDR election and uses Hello/Dead timers of 10s/40s.
Broadcast multiaccess networks elect a DR and BDR to reduce adjacency overhead on shared segments.
2
Evaluate the effect of the `ip ospf network point-to-point` command.
Changing the network type to point-to-point informs OSPF that only two routers exist on the link, rendering DR/BDR elections unnecessary.
Point-to-point OSPF network types do not elect a DR or BDR and establish FULL neighbor adjacencies directly between the two endpoints.
3
Verify timer changes associated with the Point-to-Point network type.
Point-to-Point interfaces retain the standard 10-second Hello and 40-second Dead timer defaults.
Only Non-Broadcast (NBMA) and Point-to-Multipoint network types change default timers to 30s/120s.

Key Concept

OSPFv2 Network Types and DR/BDR Election Behavior
Rate this question

Topics

OSPFv2 Network Types and DR/BDR Selection

More questions from this topic