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.
Network Topology
You are connected to R1. Configure single-area OSPFv2 on R1 and R2 so that they become fully adjacent. The link between them is 10.0.0.0/30, with R1 using G0/0 and R2 using G0/1. The current configuration has mismatched hello/dead timers: R1's G0/0 uses hello 10 and dead 40, while R2's G0/1 uses hello 30 and dead 120. Also, the 'passive-interface loopback0' command is missing on R1. Ensure OSPF is enabled in area 0, use router-id 1.1.1.1 on R1 and 2.2.2.2 on R2, and correct the timer mismatch.
R1#show running-config | section router ospf
router ospf 1
router-id 1.1.1.1
network 10.0.0.0 0.0.0.3 area 0
network 10.0.0.1 0.0.0.0 area 0
!
R1#show ip ospf interface g0/0
GigabitEthernet0/0 is up, line protocol is up
Internet Address 10.0.0.1/30, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 1.1.1.1, Interface address 10.0.0.1
Backup Designated router (ID) 0.0.0.0, Interface address 0.0.0.0
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:03
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
R1#show ip ospf neighbor
R1#
R2#show running-config | section router ospf
router ospf 1
router-id 2.2.2.2
network 10.0.0.0 0.0.0.3 area 0
!
R2#show ip ospf interface g0/1
GigabitEthernet0/1 is up, line protocol is up
Internet Address 10.0.0.2/30, Area 0
Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State BDR, Priority 1
Designated Router (ID) 1.1.1.1, Interface address 10.0.0.1
Backup Designated router (ID) 2.2.2.2, Interface address 10.0.0.2
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
Hello due in 00:00:12
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
A
On R2, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.
This is correct because R2's G0/1 has hello/dead timers of 30/120, while R1's G0/0 uses 10/40. Changing R2's timers to match resolves the mismatch. Additionally, R1's loopback0 should be made passive to prevent OSPF hellos from being sent out, as there is no neighbor on that interface.
B
On R1, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under G0/0. On R2, configure 'passive-interface loopback0' under router ospf.
Why wrong: This is incorrect because changing R1's timers to match R2's non-default timers is not the standard approach; the default timers (10/40) are more common and should be used. Also, R2 does not have a loopback0 interface mentioned in the scenario; the passive-interface command should be applied on R1's loopback0.
C
On R1, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/0. On R2, configure 'passive-interface loopback0' under router ospf.
Why wrong: This is incorrect because R1's G0/0 already has the correct timers (10/40); no change is needed there. The timer mismatch is on R2's G0/1. Also, R2 does not have a loopback0 interface; the passive-interface command should be on R1.
D
On R2, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.
Why wrong: This is incorrect because R2's G0/1 already has timers of 30/120; changing them to the same values does not fix the mismatch. The timers need to be changed to match R1's default timers (10/40).
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
On R2, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.
The adjacency fails because R2's G0/1 has hello/dead timers of 30/120, while R1's G0/0 uses 10/40. To fix, on R2 under interface G0/1, use 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40'. Additionally, R1's loopback0 is advertised via a /32 network statement but should be made passive to prevent OSPF hellos from being sent out (where no neighbor exists). On R1, configure 'passive-interface loopback0' under router ospf. After both changes, adjacency forms.
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.
✓
On R2, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.
Why this is correct
This is correct because R2's G0/1 has hello/dead timers of 30/120, while R1's G0/0 uses 10/40. Changing R2's timers to match resolves the mismatch. Additionally, R1's loopback0 should be made passive to prevent OSPF hellos from being sent out, as there is no neighbor on that interface.
On R1, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under G0/0. On R2, configure 'passive-interface loopback0' under router ospf.
Why it's wrong here
This is incorrect because changing R1's timers to match R2's non-default timers is not the standard approach; the default timers (10/40) are more common and should be used. Also, R2 does not have a loopback0 interface mentioned in the scenario; the passive-interface command should be applied on R1's loopback0.
✗
On R1, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/0. On R2, configure 'passive-interface loopback0' under router ospf.
Why it's wrong here
This is incorrect because R1's G0/0 already has the correct timers (10/40); no change is needed there. The timer mismatch is on R2's G0/1. Also, R2 does not have a loopback0 interface; the passive-interface command should be on R1.
✗
On R2, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.
Why it's wrong here
This is incorrect because R2's G0/1 already has timers of 30/120; changing them to the same values does not fix the mismatch. The timers need to be changed to match R1's default timers (10/40).
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.
✓On R2, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.Correct answer▾
Why this is correct
This is correct because R2's G0/1 has hello/dead timers of 30/120, while R1's G0/0 uses 10/40. Changing R2's timers to match resolves the mismatch. Additionally, R1's loopback0 should be made passive to prevent OSPF hellos from being sent out, as there is no neighbor on that interface.
✗On R1, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under G0/0. On R2, configure 'passive-interface loopback0' under router ospf.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the passive-interface command is applied on the wrong router (R2 instead of R1) and the timers are changed on R1 instead of R2.
Why candidates choose this
Candidates might think that adjusting the router with the default timers to match the non-default ones is acceptable, or they may confuse which router has the loopback interface.
✗On R1, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/0. On R2, configure 'passive-interface loopback0' under router ospf.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the timer change is applied to the wrong interface (R1's G0/0 already has correct timers) and the passive-interface is applied to the wrong router.
Why candidates choose this
Candidates may assume both routers need timer configuration or misidentify which router has the loopback interface.
✗On R2, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the timer values are not changed; they remain mismatched with R1's timers.
Why candidates choose this
Candidates might think that setting timers to the same values on both sides is sufficient, but they must match the other router's timers. Here, R2's timers are already 30/120, so no change is made, and the mismatch persists.
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
This is incorrect because changing R1's timers to match R2's non-default timers is not the standard approach; the default timers (10/40) are more common and should be used. Also, R2 does not have a loopback0 interface mentioned in the scenario; the passive-interface command should be applied on R1's loopback0.
Scenario analysis trap
This is incorrect because changing R1's timers to match R2's non-default timers is not the standard approach; the default timers (10/40) are more common and should be used. Also, R2 does not have a loopback0 interface mentioned in the scenario; the passive-interface command should be applied on R1's loopback0.
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: On R2, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under G0/1. On R1, configure 'passive-interface loopback0' under router ospf. — The adjacency fails because R2's G0/1 has hello/dead timers of 30/120, while R1's G0/0 uses 10/40. To fix, on R2 under interface G0/1, use 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40'. Additionally, R1's loopback0 is advertised via a /32 network statement but should be made passive to prevent OSPF hellos from being sent out (where no neighbor exists). On R1, configure 'passive-interface loopback0' under router ospf. After both changes, adjacency forms.
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.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.