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Zorluk: OrtaOSPFv2 Network Types and DR/BDR Selection

An engineer executes the following command on router R1 to inspect an OSPFv2 interface connected to a multiaccess Ethernet segment:

text
R1# show ip ospf interface GigabitEthernet0/1
GigabitEthernet0/1 is up, line protocol is up
Internet Address 192.168.1.1/24, Area 0, Attached via Network Statement
Process ID 1, Router ID 10.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DROTHER, Priority 0
Designated Router (ID) 10.3.3.3, Interface address 192.168.1.3
Backup Designated router (ID) 10.2.2.2, Interface address 192.168.1.2

If the current Designated Router with Router ID 10.3.3.3 unexpectedly reboots and goes offline, which router state transition will occur on this segment?

  1. The router with Router ID 10.2.2.2 will automatically transition from Backup Designated Router to Designated Router.Cevap
  2. B
    Router R1 (10.1.1.1) will be promoted to Backup Designated Router because its interface is actively functioning in State DROTHER.
  3. C
    Router R1 (10.1.1.1) will immediately take over as Designated Router because its OSPF process ID is 1.
  4. D
    All routers on the segment will remain in the INIT state until a manual clear ip ospf process command is issued.

Cevap

The router currently serving as the Backup Designated Router (Router ID 10.2.2.2) will automatically be promoted to the Designated Router role.
In OSPF broadcast multiaccess networks, when the active Designated Router (DR) fails or goes offline, the existing Backup Designated Router (BDR) is immediately promoted to become the new DR. In this output, the BDR is identified by Router ID 10.2.2.2, so it will assume the DR role.

Adım Adım Çözüm

1
Analyze the current state of OSPF routers on the broadcast segment
Router ID 10.3.3.3 is the active Designated Router (DR), Router ID 10.2.2.2 is the Backup Designated Router (BDR), and Router R1 (10.1.1.1) has Priority 0 and is in State DROTHER.
Determines the current functional roles assigned across the multiaccess network.
2
Evaluate the effect of a DR failure
When the active DR fails, OSPF non-preemptive logic mandates that the existing BDR immediately becomes the new DR to minimize downtime.
Avoids holding a full re-election for the DR position when a designated backup already exists.
3
Determine eligibility for the new BDR role
Router R1 cannot become BDR because its configured OSPF interface priority is 0.
An OSPF interface priority of 0 explicitly disqualifies a router from participating in DR/BDR elections.

Anahtar Kavram

OSPFv2 DR/BDR State Transitions and Priority 0 Exclusion
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Konular

OSPFv2 Network Types and DR/BDR Selection

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