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Exams200-101Questions#159
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200-101 · Question #159

200-101 Question #159: Real Exam Question with Answer & Explanation

The correct answer is A: Configure the priority value of the Fa0/0 interface of RouterB to a higher value than any other interface on the Ethernet network.. OSPF DR election is determined by interface priority (highest wins) and router ID (tiebreaker); setting competitors' priority to zero disqualifies them, while raising RouterB's priority or router ID ensures it wins.

Question

A network administrator is configuring the routers in the graphic for OSPF. The OSPF process has been started and the networks have been configured for Area 0 as shown in the diagram. The network administrator has several options for configuring RouterB to ensure that it will be preferred as the designated router (DR) for the 172.16.1.0 /24 LAN segment. What configuration tasks could be used to establish this preference? (Choose three.)

Options

  • AConfigure the priority value of the Fa0/0 interface of RouterB to a higher value than any other interface on the Ethernet network.
  • BChange the router ID of Router B by assigning the IP address 172.16.1.130/24 to the Fa0/0 interface of RouterB.
  • CConfigure a loopback interface on RouterB with an IP address higher than any IP address on the other routers.
  • DChange the priority value of the Fa0/0 interface of RouterB to zero.
  • EChange the priority values of the Fa0/0 interfaces of RouterA and RouterC to zero.
  • FNo further configuration is necessary.

Explanation

OSPF DR election is determined by interface priority (highest wins) and router ID (tiebreaker); setting competitors' priority to zero disqualifies them, while raising RouterB's priority or router ID ensures it wins.

Common mistakes.

  • B. Assigning 172.16.1.130 to the Fa0/0 interface changes the interface IP, but the router ID is chosen from the highest loopback or highest active interface - this does not guarantee RouterB gets a higher router ID than the other routers.
  • D. Setting RouterB's Fa0/0 priority to zero makes it ineligible to be elected as DR or BDR, which is the opposite of the goal.
  • F. Without additional configuration, there is no guarantee that RouterB will win the DR election over RouterA and RouterC, so further configuration is required.

Concept tested. OSPF designated router election priority and router ID

Reference. https://www.cisco.com/c/en/us/tech/ip/open-shortest-path-first-ospf/index.html

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A network administrator is configuring the routers in the graphic... | 200-101 Q#159 Answer | NerdExam