This 200-301 practice question tests your understanding of ip routing. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Exhibit
R1# show ip ospf database summary
OSPF Router with ID (192.168.1.1) (Process ID 1)
Summary Net Link States (Area 0)
LS age: 312
Options: (No TOS-capability, DC)
LS Type: Summary Links(Network)
Link State ID: 10.1.0.0 (summary Network Number)
Advertising Router: 10.1.1.1
LS Seq Number: 8000000A
Checksum: 0x1F3A
Length: 28
Network Mask: /16
MTID: 0 Metric: 1000
LS age: 467
Options: (No TOS-capability, DC)
LS Type: Summary Links(Network)
Link State ID: 10.2.0.0 (summary Network Number)
Advertising Router: 10.1.1.1
LS Seq Number: 80000005
Checksum: 0xA5C1
Length: 28
Network Mask: /16
MTID: 0 Metric: 10
LS age: 285
Options: (No TOS-capability, DC)
LS Type: Summary Links(Network)
Link State ID: 10.3.0.0 (summary Network Number)
Advertising Router: 10.1.1.1
LS Seq Number: 80000007
Checksum: 0x7F2B
Length: 28
Network Mask: /16
MTID: 0 Metric: 20
Refer to the exhibit. A network engineer notices that traffic from R1 to the 10.1.0.0/16 network is taking a longer path than expected despite OSPF being the only routing protocol. The engineer examines the OSPF LSDB on R1 to investigate. Based on the output, what is the most likely cause of the suboptimal routing?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
R1# show ip ospf database summary
OSPF Router with ID (192.168.1.1) (Process ID 1)
Summary Net Link States (Area 0)
LS age: 312
Options: (No TOS-capability, DC)
LS Type: Summary Links(Network)
Link State ID: 10.1.0.0 (summary Network Number)
Advertising Router: 10.1.1.1
LS Seq Number: 8000000A
Checksum: 0x1F3A
Length: 28
Network Mask: /16
MTID: 0 Metric: 1000
LS age: 467
Options: (No TOS-capability, DC)
LS Type: Summary Links(Network)
Link State ID: 10.2.0.0 (summary Network Number)
Advertising Router: 10.1.1.1
LS Seq Number: 80000005
Checksum: 0xA5C1
Length: 28
Network Mask: /16
MTID: 0 Metric: 10
LS age: 285
Options: (No TOS-capability, DC)
LS Type: Summary Links(Network)
Link State ID: 10.3.0.0 (summary Network Number)
Advertising Router: 10.1.1.1
LS Seq Number: 80000007
Checksum: 0x7F2B
Length: 28
Network Mask: /16
MTID: 0 Metric: 20
A
The reference bandwidth has been misconfigured on R1, causing the OSPF cost calculation to be inflated for some links.
Why wrong: A misconfigured reference bandwidth would affect the metric of all LSAs originated by or received on R1, but other summary LSAs from the same ABR show normal metrics. Additionally, reference bandwidth changes only impact local interface costs, not the metric carried in an LSA originated by another router.
B
The ABR is filtering the 10.1.0.0/16 route from Area 1 into Area 0, causing the router to recalculate the metric higher.
Why wrong: Route filtering with a distribute-list or prefix-list prevents the LSA from being advertised; it does not modify the metric. A filtered route would not appear in the LSDB at all, not appear with an inflated metric.
C
The ABR is configured with the 'area 1 range 10.1.0.0 255.255.0.0 cost 1000' command.
The ABR (10.1.1.1) is advertising a Type 3 summary LSA for 10.1.0.0/16 with a metric of 1000. This matches the behavior of the 'area range' command with the 'cost' keyword, which overrides the default metric calculation for inter-area summaries and injects the specified cost. The other LSAs from the same ABR use normal metrics, confirming the summary-specific configuration.
D
The metric-type for OSPF external routes has been set to type 2, causing the metric to be inflated to 1000 for the 10.1.0.0/16 prefix.
Why wrong: External routes are advertised in Type 5 LSAs (or Type 7 in NSSA), not Type 3 summary LSAs. The metric type (E1 vs E2) does not apply to inter-area summary routes. The exhibit clearly shows 'Summary Net Link States' (Type 3), so external route metric type is irrelevant.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ABR is configured with the 'area 1 range 10.1.0.0 255.255.0.0 cost 1000' command.
The exhibit shows three Type 3 summary LSAs from the same ABR (10.1.1.1). Two of them have metrics 10 and 20, which are consistent with normal OSPF intra-area path costs. The LSA for 10.1.0.0/16 has metric 1000, an abnormally high value. This indicates that the ABR is injecting this summary with a manually configured cost, typically done with the 'area <id> range <network> <mask> cost <value>' command. Global reference bandwidth changes would affect all metrics equally, and route filtering does not alter metric values. External route metric types are unrelated to Type 3 inter-area summaries.
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 reference bandwidth has been misconfigured on R1, causing the OSPF cost calculation to be inflated for some links.
Why it's wrong here
A misconfigured reference bandwidth would affect the metric of all LSAs originated by or received on R1, but other summary LSAs from the same ABR show normal metrics. Additionally, reference bandwidth changes only impact local interface costs, not the metric carried in an LSA originated by another router.
✗
The ABR is filtering the 10.1.0.0/16 route from Area 1 into Area 0, causing the router to recalculate the metric higher.
Why it's wrong here
Route filtering with a distribute-list or prefix-list prevents the LSA from being advertised; it does not modify the metric. A filtered route would not appear in the LSDB at all, not appear with an inflated metric.
✓
The ABR is configured with the 'area 1 range 10.1.0.0 255.255.0.0 cost 1000' command.
Why this is correct
The ABR (10.1.1.1) is advertising a Type 3 summary LSA for 10.1.0.0/16 with a metric of 1000. This matches the behavior of the 'area range' command with the 'cost' keyword, which overrides the default metric calculation for inter-area summaries and injects the specified cost. The other LSAs from the same ABR use normal metrics, confirming the summary-specific configuration.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The metric-type for OSPF external routes has been set to type 2, causing the metric to be inflated to 1000 for the 10.1.0.0/16 prefix.
Why it's wrong here
External routes are advertised in Type 5 LSAs (or Type 7 in NSSA), not Type 3 summary LSAs. The metric type (E1 vs E2) does not apply to inter-area summary routes. The exhibit clearly shows 'Summary Net Link States' (Type 3), so external route metric type is irrelevant.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The ABR is configured with the 'area 1 range 10.1.0.0 255.255.0.0 cost 1000' command.Correct answer▾
Why this is correct
The ABR (10.1.1.1) is advertising a Type 3 summary LSA for 10.1.0.0/16 with a metric of 1000. This matches the behavior of the 'area range' command with the 'cost' keyword, which overrides the default metric calculation for inter-area summaries and injects the specified cost. The other LSAs from the same ABR use normal metrics, confirming the summary-specific configuration.
✗The reference bandwidth has been misconfigured on R1, causing the OSPF cost calculation to be inflated for some links.Wrong answer — click to see why▾
Why this is wrong here
Candidates may attribute arbitrary high metrics to a bandwidth calculation error, without noticing that only one LSA is affected.
✗The ABR is filtering the 10.1.0.0/16 route from Area 1 into Area 0, causing the router to recalculate the metric higher.Wrong answer — click to see why▾
Why this is wrong here
A misunderstanding that filtering can somehow alter the metric rather than block the advertisement completely.
✗The metric-type for OSPF external routes has been set to type 2, causing the metric to be inflated to 1000 for the 10.1.0.0/16 prefix.Wrong answer — click to see why▾
Why this is wrong here
Confusion between external and inter-area route types leads candidates to think that metric-type manipulation could affect an internal summary LSA.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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
A misconfigured reference bandwidth would affect the metric of all LSAs originated by or received on R1, but other summary LSAs from the same ABR show normal metrics. Additionally, reference bandwidth changes only impact local interface costs, not the metric carried in an LSA originated by another router.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
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 200-301 OSPF questions on adjacency and route selection.
IP Routing — This question tests IP Routing — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The ABR is configured with the 'area 1 range 10.1.0.0 255.255.0.0 cost 1000' command. — The exhibit shows three Type 3 summary LSAs from the same ABR (10.1.1.1). Two of them have metrics 10 and 20, which are consistent with normal OSPF intra-area path costs. The LSA for 10.1.0.0/16 has metric 1000, an abnormally high value. This indicates that the ABR is injecting this summary with a manually configured cost, typically done with the 'area <id> range <network> <mask> cost <value>' command. Global reference bandwidth changes would affect all metrics equally, and route filtering does not alter metric values. External route metric types are unrelated to Type 3 inter-area summaries.
What should I do if I get this 200-301 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 200-301 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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