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Zorluk: OrtaOSPFv2 Network Types and DR/BDR Selection

A network administrator is connecting multiple routers to a shared multiaccess Ethernet segment running OSPFv2. Place the parameter criteria used to determine the Designated Router (DR) election winner in order of evaluation precedence, starting with the parameter evaluated first down to the final fallback tie-breaker.

  1. 1Highest OSPF interface priority value (non-zero)
  2. 2Manually configured OSPF Router ID
  3. 3Highest IPv4 address on an active loopback interface
  4. 4Highest IPv4 address on an active physical interface

Cevap

The correct order of precedence for OSPFv2 DR election is: (1) Highest OSPF interface priority value, (2) Manually configured OSPF Router ID, (3) Highest IPv4 address on an active loopback interface, and (4) Highest IPv4 address on an active physical interface.
The DR/BDR election process evaluates interface priority first, where the highest non-zero priority wins. If priorities are tied, OSPF breaks the tie using the Router ID. The Router ID selection itself follows a strict hierarchy: explicit configuration first, followed by the highest active loopback IP address, and finally the highest active physical interface IP address.

Adım Adım Çözüm

1
Evaluate OSPF interface priority
Highest priority (1-255) wins. A priority of 0 excludes the router from becoming DR/BDR.
Interface priority is the primary metric defined by OSPF for DR/BDR election.
2
Evaluate explicit Router ID if priorities tie
Router with the highest router-id command value wins.
If interface priorities are equal, OSPF uses the Router ID as a tie-breaker, preferring manually defined IDs.
3
Evaluate loopback interfaces if no explicit Router ID exists
Router with the highest IP address on an active loopback interface wins.
Loopback interfaces provide stability and automatically take precedence over physical interfaces for Router ID selection.
4
Evaluate physical interfaces if no loopback or explicit Router ID exists
Router with the highest IP address on an active physical interface wins.
Physical interface IP addresses serve as the absolute fallback for Router ID determination.

Anahtar Kavram

OSPFv2 DR/BDR Election Precedence Criteria
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Konular

OSPFv2 Network Types and DR/BDR Selection

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