The answer is the OSPF passive-interface command applied to GigabitEthernet0/0, which prevents hello packets from being sent. When an interface is configured as passive under OSPF, the router stops transmitting hello packets on that link, and because OSPF adjacency formation depends entirely on the bidirectional exchange of these hellos, the neighbor relationship stalls in the INIT or DOWN state. This is a classic CCNA 200-301 v2 troubleshooting scenario: the exam often presents a show ip ospf interface output that explicitly reads “No Hellos (Passive interface)” to test your ability to identify why an adjacency fails even when the neighbor is correctly configured. A common trap is assuming the problem is a mismatched network type or area ID, but the passive interface flag is a direct and unambiguous indicator. For a quick memory tip, remember “Passive means no packets, no adjacency—if hellos are silent, the neighbor stays silent too.”
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. 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.
Exhibit
R1# show ip ospf interface GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up
Internet Address 192.168.1.1/24, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State PASSIVE, Priority 1
No designated router on this network
No backup designated router on this network
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
No Hellos (Passive interface)
Adjacent neighbor count is 0
Refer to the exhibit. A network administrator is troubleshooting an OSPF adjacency on R1's GigabitEthernet0/0 interface connected directly to R2. R2 is powered on and shows correct OSPF configuration, but the adjacency is stuck in the INIT or DOWN state. Based on the output, what is the most likely cause of the failure?
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 interface GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up
Internet Address 192.168.1.1/24, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State PASSIVE, Priority 1
No designated router on this network
No backup designated router on this network
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
No Hellos (Passive interface)
Adjacent neighbor count is 0
A
The OSPF network type on R1's GigabitEthernet0/0 does not match the network type on R2.
Why wrong: The output shows Network Type BROADCAST, which is the default for Ethernet interfaces. There is no evidence of a mismatch; the passive-interface command is the actual problem.
B
The OSPF hello and dead timers on R1 do not match those configured on R2.
Why wrong: The timers shown (Hello 10, Dead 40) are the default values and would match R2 if it also uses defaults. More importantly, the passive state means no hellos are transmitted, so timer mismatch is not the cause.
C
The GigabitEthernet0/0 interface on R1 has been assigned to a different OSPF area than R2's connected interface.
Why wrong: The output shows Area 0 for R1's interface. There is no indication of an area mismatch; R2 could also be in Area 0. The passive state prevents any hello exchange necessary to detect an area mismatch.
D
The OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent.
The line 'No Hellos (Passive interface)' in the output directly indicates that the interface has been configured as passive, which suppresses all OSPF hello messages and blocks adjacency formation.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent.
The command output explicitly shows 'No Hellos (Passive interface)', confirming that the passive-interface command has been applied to GigabitEthernet0/0. With this configuration, OSPF does not send or receive hello packets on the interface, preventing any adjacency from forming with the directly connected neighbor R2.
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 OSPF network type on R1's GigabitEthernet0/0 does not match the network type on R2.
Why it's wrong here
The output shows Network Type BROADCAST, which is the default for Ethernet interfaces. There is no evidence of a mismatch; the passive-interface command is the actual problem.
✗
The OSPF hello and dead timers on R1 do not match those configured on R2.
Why it's wrong here
The timers shown (Hello 10, Dead 40) are the default values and would match R2 if it also uses defaults. More importantly, the passive state means no hellos are transmitted, so timer mismatch is not the cause.
✗
The GigabitEthernet0/0 interface on R1 has been assigned to a different OSPF area than R2's connected interface.
Why it's wrong here
The output shows Area 0 for R1's interface. There is no indication of an area mismatch; R2 could also be in Area 0. The passive state prevents any hello exchange necessary to detect an area mismatch.
✓
The OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent.
Why this is correct
The line 'No Hellos (Passive interface)' in the output directly indicates that the interface has been configured as passive, which suppresses all OSPF hello messages and blocks adjacency formation.
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 OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent.Correct answer▾
Why this is correct
The line 'No Hellos (Passive interface)' in the output directly indicates that the interface has been configured as passive, which suppresses all OSPF hello messages and blocks adjacency formation.
✗The OSPF network type on R1's GigabitEthernet0/0 does not match the network type on R2.Wrong answer — click to see why▾
Why this is wrong here
Candidates may think network type mismatch when they see no adjacency, but the exhibit does not indicate a mismatch and explicitly shows the passive state.
✗The OSPF hello and dead timers on R1 do not match those configured on R2.Wrong answer — click to see why▾
Why this is wrong here
Timer mismatch is a classic troubleshooting trap, but the 'No Hellos (Passive interface)' message overrides any timer considerations.
✗The GigabitEthernet0/0 interface on R1 has been assigned to a different OSPF area than R2's connected interface.Wrong answer — click to see why▾
Why this is wrong here
Candidates may guess area mismatch as a cause, but the exhibit provides no evidence of it, while the passive-interface message is a direct cause.
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
The output shows Network Type BROADCAST, which is the default for Ethernet interfaces. There is no evidence of a mismatch; the passive-interface command is the actual problem.
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 OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent. — The command output explicitly shows 'No Hellos (Passive interface)', confirming that the passive-interface command has been applied to GigabitEthernet0/0. With this configuration, OSPF does not send or receive hello packets on the interface, preventing any adjacency from forming with the directly connected neighbor R2.
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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