Question 360 of 2,152
Route SummarizationhardMultiple SelectObjective-mapped

Quick Answer

The correct answer identifies that the 'area range' command can be configured only on ABRs, not on ASBRs, and that it creates a single Type 3 LSA for the summary prefix while suppressing the individual Type 3 LSAs for the component networks. This behavior is fundamental to OSPF inter-area route summarization because the ABR acts as the boundary between areas, summarizing routes from one area into another by generating a single summary LSA with a cost equal to the highest cost among the component routes, not the lowest. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how OSPF controls LSA flooding and routing table size between areas, and a common trap is confusing the 'area range' command with the 'summary-address' command, which is used on ASBRs for redistributed routes. A helpful memory tip is: "ABR uses area range for Type 3 summaries; ASBR uses summary-address for external routes."

300-410 Route Summarization Practice Question

This 300-410 practice question tests your understanding of route summarization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

An engineer is troubleshooting an OSPF network where route summarization is configured on an ABR. Which TWO statements correctly describe the behavior of OSPF inter-area route summarization using the 'area range' command? (Choose TWO.)

Question 1hardmulti select
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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

The 'area range' command creates a single Type 3 LSA for the summary prefix and suppresses the advertisement of individual Type 3 LSAs for the component networks.

The 'area range' command on an ABR summarizes routes from one area into another. It creates a single Type 3 LSA for the summary prefix, suppresses the individual Type 3 LSAs for the component networks, and does not affect Type 1 or Type 2 LSAs within the area. The summary LSA is advertised with a cost equal to the highest cost among the component routes, not the lowest. The command does not automatically summarize redistributed routes; that requires the 'summary-address' command under the OSPF process.

Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • The 'area range' command creates a single Type 3 LSA for the summary prefix and suppresses the advertisement of individual Type 3 LSAs for the component networks.

    Why this is correct

    Correct. The ABR generates one Type 3 LSA for the range and does not advertise the individual Type 3 LSAs for the more specific routes.

    Related concept

    OSPF neighbours must agree on key parameters.

  • The cost of the summary LSA is set to the lowest cost among the component routes within the range.

    Why it's wrong here

    Incorrect. The cost of the summary LSA is the highest (maximum) cost among the component routes, not the lowest.

  • The 'area range' command also summarizes external routes redistributed into OSPF from other protocols.

    Why it's wrong here

    Incorrect. External routes are summarized using the 'summary-address' command under the OSPF process, not the 'area range' command.

  • The summary route is advertised with a metric type of E1 or E2, depending on the original external metric type.

    Why it's wrong here

    Incorrect. The 'area range' command applies to inter-area routes (Type 3 LSAs), not external routes. External metric types apply to Type 5/7 LSAs.

  • The 'area range' command can be configured only on ABRs and not on ASBRs.

    Why this is correct

    Correct. The 'area range' command is used on ABRs to summarize routes between OSPF areas. ASBRs use 'summary-address' for external route summarization.

    Related concept

    OSPF neighbours must agree on key parameters.

Common exam traps

Common exam trap: OSPF can fail even when IP connectivity looks correct

OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.

Trap categories for this question

  • Command / output trap

    Incorrect. External routes are summarized using the 'summary-address' command under the OSPF process, not the 'area range' command.

Detailed technical explanation

How to think about this question

OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.

KKey Concepts to Remember

  • OSPF neighbours must agree on key parameters.
  • Router ID selection can affect neighbour relationships and LSDB output.
  • OSPF cost influences the preferred path.
  • A route can appear in OSPF information but not become the installed route.

TExam Day Tips

  • Check area mismatch first when OSPF adjacency fails.
  • Review passive interfaces when a network is advertised but no neighbour forms.
  • Use show ip ospf neighbor and show ip route clues carefully.

Key takeaway

OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

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

Got this wrong? Here's your next step.

Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 300-410 question test?

Route Summarization — This question tests Route Summarization — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: The 'area range' command creates a single Type 3 LSA for the summary prefix and suppresses the advertisement of individual Type 3 LSAs for the component networks. — The 'area range' command on an ABR summarizes routes from one area into another. It creates a single Type 3 LSA for the summary prefix, suppresses the individual Type 3 LSAs for the component networks, and does not affect Type 1 or Type 2 LSAs within the area. The summary LSA is advertised with a cost equal to the highest cost among the component routes, not the lowest. The command does not automatically summarize redistributed routes; that requires the 'summary-address' command under the OSPF process.

What should I do if I get this 300-410 question wrong?

Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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Same concept, more angles

2 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. Which TWO configuration steps are required to implement manual route summarization in OSPF on an ABR? (Choose TWO.)

medium
  • A.Configure the 'area area-id range network mask' command under router OSPF configuration.
  • B.Ensure the summary address is a supernet of the networks being summarized.
  • C.Use the 'summary-address network mask' command under router OSPF configuration.
  • D.Apply the 'ip summary-address ospf' command under the interface connecting to the backbone.
  • E.Configure a 'network' statement that matches the summary address.

Why A: In OSPF, manual summarization on an ABR is done using the 'area range' command under router configuration mode, which summarizes routes from one area into another. The summary address must be within the range of networks in the area. The 'summary-address' command is used for external routes on ASBRs, not for inter-area summarization. 'network' commands define interfaces, not summarization. 'default-information originate' is for default routes.

Variation 2. In OSPF, what is the default metric for a Type 3 summary LSA generated by an ABR using the 'area range' command?

easy
  • A.The lowest metric among the summarized routes.
  • B.The highest metric among the summarized routes.
  • C.The sum of all metrics.
  • D.The metric is set to 1 by default.

Why A: The default metric for a Type 3 summary LSA is the lowest metric among the component routes being summarized.

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Last reviewed: Jun 18, 2026

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