This 200-301 practice question tests your understanding of ip routing. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 route 172.16.0.0
Routing entry for 172.16.0.0/16
Known via "ospf 1", distance 110, metric 20, type inter area
Redistributing via ospf 1
Last update from 10.1.1.2 on GigabitEthernet0/0, 00:02:15 ago
Routing Descriptor Blocks:
* 10.1.1.2, from 10.2.2.2, 00:02:15 ago, via GigabitEthernet0/0
Route metric is 20, traffic share count is 1
Refer to the exhibit. A network engineer is verifying OSPF routing on R1. All routers in the topology are expected to reside in OSPF area 0, and the network 172.16.0.0/16 should be advertised from R2 within the same area. The engineer issues the show ip route 172.16.0.0 command on R1 and sees the output in the exhibit. The engineer expected to see an intra-area route (O) instead of an inter-area route (O IA). What is the most likely cause of this discrepancy?
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 route 172.16.0.0
Routing entry for 172.16.0.0/16
Known via "ospf 1", distance 110, metric 20, type inter area
Redistributing via ospf 1
Last update from 10.1.1.2 on GigabitEthernet0/0, 00:02:15 ago
Routing Descriptor Blocks:
* 10.1.1.2, from 10.2.2.2, 00:02:15 ago, via GigabitEthernet0/0
Route metric is 20, traffic share count is 1
A
R1 has a mismatched OSPF process ID compared to the ABR.
Why wrong: OSPF process IDs are locally significant and do not need to match between routers for neighborship or route installation. A mismatch would not affect the area classification of routes.
B
The network type on GigabitEthernet0/0 is configured as non-broadcast, preventing full adjacency.
Why wrong: A non-broadcast network type could prevent neighbor formation, but the route is present in the routing table, indicating adjacency is established. Even if adjacency exists, the network type does not alter whether a route is intra-area or inter-area.
C
The metric for the route is too high, causing OSPF to treat it as an inter-area route.
Why wrong: OSPF classifies routes based on the LSA type (Type-1 for intra-area, Type-3 for inter-area), not on the metric value. A high metric would still result in an O route if the network is in the same area.
D
The destination network 172.16.0.0/16 is located in a different OSPF area.
The routing table entry shows 'type inter area'. This indicates the prefix is being learned via an OSPF Type-3 summary LSA, which is only generated when the network is in a different area than the local router. Therefore, the network is indeed in a different area, contradicting the assumption that R1 and the destination are both in area 0.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The destination network 172.16.0.0/16 is located in a different OSPF area.
The exhibit explicitly lists the route type as 'inter area' for 172.16.0.0/16. In OSPF, an inter-area (IA) route means the destination network resides in a different OSPF area than the local router. Since all routers are expected to be in area 0, the presence of an IA route indicates the 172.16.0.0/16 network is actually located in a different area, causing the ABR to generate a Type-3 summary LSA.
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.
✗
R1 has a mismatched OSPF process ID compared to the ABR.
Why it's wrong here
OSPF process IDs are locally significant and do not need to match between routers for neighborship or route installation. A mismatch would not affect the area classification of routes.
✗
The network type on GigabitEthernet0/0 is configured as non-broadcast, preventing full adjacency.
Why it's wrong here
A non-broadcast network type could prevent neighbor formation, but the route is present in the routing table, indicating adjacency is established. Even if adjacency exists, the network type does not alter whether a route is intra-area or inter-area.
✗
The metric for the route is too high, causing OSPF to treat it as an inter-area route.
Why it's wrong here
OSPF classifies routes based on the LSA type (Type-1 for intra-area, Type-3 for inter-area), not on the metric value. A high metric would still result in an O route if the network is in the same area.
✓
The destination network 172.16.0.0/16 is located in a different OSPF area.
Why this is correct
The routing table entry shows 'type inter area'. This indicates the prefix is being learned via an OSPF Type-3 summary LSA, which is only generated when the network is in a different area than the local router. Therefore, the network is indeed in a different area, contradicting the assumption that R1 and the destination are both in area 0.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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 destination network 172.16.0.0/16 is located in a different OSPF area.Correct answer▾
Why this is correct
The routing table entry shows 'type inter area'. This indicates the prefix is being learned via an OSPF Type-3 summary LSA, which is only generated when the network is in a different area than the local router. Therefore, the network is indeed in a different area, contradicting the assumption that R1 and the destination are both in area 0.
✗R1 has a mismatched OSPF process ID compared to the ABR.Wrong answer — click to see why▾
Why this is wrong here
Candidates mistakenly assume that OSPF process IDs must match globally for proper LSA exchange, but they are only locally significant.
✗The network type on GigabitEthernet0/0 is configured as non-broadcast, preventing full adjacency.Wrong answer — click to see why▾
Why this is wrong here
Candidates may think that the network type influences the OSPF LSA type, but it only affects neighbor discovery and DR/BDR election, not the area origin of LSAs.
✗The metric for the route is too high, causing OSPF to treat it as an inter-area route.Wrong answer — click to see why▾
Why this is wrong here
Candidates sometimes confuse the metric influence with the route type, thinking that OSPF converts routes when the cost exceeds a threshold.
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.
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 destination network 172.16.0.0/16 is located in a different OSPF area. — The exhibit explicitly lists the route type as 'inter area' for 172.16.0.0/16. In OSPF, an inter-area (IA) route means the destination network resides in a different OSPF area than the local router. Since all routers are expected to be in area 0, the presence of an IA route indicates the 172.16.0.0/16 network is actually located in a different area, causing the ABR to generate a Type-3 summary LSA.
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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