Question 368 of 1,819
IP RoutingmediumMultiple SelectObjective-mapped

Quick Answer

The answer is that OSPFv2 in a single area uses cost as its metric, relies on Hello packets for neighbor discovery and keepalives, and elects a Designated Router (DR) on broadcast multiaccess networks to reduce LSA flooding. Cost is derived from the formula reference bandwidth divided by interface bandwidth, with a default reference of 100 Mbps, making it a dynamic metric based on link speed. Hello packets, sent every 10 seconds by default on broadcast links, establish and maintain adjacencies while acting as keepalives. The DR election is a critical mechanism to minimize flooding overhead only on multiaccess segments like Ethernet, not on point-to-point links. On the CCNA 200-301 v2 exam, this topic tests your ability to distinguish OSPFv2 single-area behavior from common misconceptions—for instance, OSPFv2 does not support IPv6 (that is OSPFv3), and LSAs refresh every 30 minutes, not 30 seconds. A common trap is confusing the DR election with all network types; remember that DRs are only elected where multiple routers share the same broadcast segment. Memory tip: “Cost from bandwidth, Hello for life, DR on broadcast to stop the strife.”

CCNA IP Routing Practice Question

This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Which three options accurately describe characteristics of OSPFv2 in a single area? (Choose three.)

Question 1mediummulti select
Review the full OSPF breakdown →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

OSPF uses cost as its metric, which is derived from the bandwidth of the interface.

OSPFv2 uses cost as its metric, derived from interface bandwidth using the formula cost = reference bandwidth / interface bandwidth (default reference bandwidth is 100 Mbps). Hello packets are used to discover neighbors, maintain adjacencies, and act as keepalives (default every 10 seconds on broadcast networks). The designated router (DR) is elected only on broadcast multiaccess networks (e.g., Ethernet) to reduce LSA flooding. The incorrect options: OSPFv2 does not natively support IPv6 (OSPFv3 is needed for IPv6); LSAs are refreshed every 30 minutes, not 30 seconds; router IDs must be unique across the OSPF domain, not the same in an area.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Common mistakes include thinking OSPF uses hop count or bandwidth alone as metric, that the DR is elected on all network types, or that Hello packets are only for initial discovery rather than ongoing adjacency maintenance.

Detailed technical explanation

How to think about this question

OSPF cost is an inverse function of bandwidth; for example, a 1 Gbps interface with default reference bandwidth has a cost of 1 (100/1000 = 0.1, rounded up to 1). Hello packets include parameters such as Router ID, Hello/Dead intervals, and area ID, which must match for neighbor formation. The DR election is based on the highest OSPF priority (default 1) and then highest Router ID; only the DR and BDR form full adjacencies with all routers on the segment, while other routers remain in 2-way state with each other, significantly reducing LSA flooding in large broadcast networks.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.

TExam Day Tips

  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.

What to study next

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FAQ

Questions learners often ask

What does this 200-301 question test?

IP Routing — This question tests IP Routing — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: OSPF uses cost as its metric, which is derived from the bandwidth of the interface. — OSPFv2 uses cost as its metric, derived from interface bandwidth using the formula cost = reference bandwidth / interface bandwidth (default reference bandwidth is 100 Mbps). Hello packets are used to discover neighbors, maintain adjacencies, and act as keepalives (default every 10 seconds on broadcast networks). The designated router (DR) is elected only on broadcast multiaccess networks (e.g., Ethernet) to reduce LSA flooding. The incorrect options: OSPFv2 does not natively support IPv6 (OSPFv3 is needed for IPv6); LSAs are refreshed every 30 minutes, not 30 seconds; router IDs must be unique across the OSPF domain, not the same in an area.

What should I do if I get this 200-301 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 11, 2026

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