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. R1 has OSPF configured on GigabitEthernet0/0 with network 10.0.0.0 0.0.0.3 area 1, ip ospf hello-interval 10, and ip ospf dead-interval 40. R2 has OSPF configured on its GigabitEthernet0/0 with network 10.0.0.0 0.0.0.3 area 0, ip ospf hello-interval 5, and ip ospf dead-interval 20. Correct these mismatches so that R1 and R2 become OSPF neighbors.
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 1
!
R1#show ip ospf interface gigabitethernet 0/0
GigabitEthernet0/0 is up, line protocol is up
Internet Address 10.0.0.1/30, Area 1
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
oob-resync timeout 40
Hello due in 00:00:07
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
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 gigabitethernet 0/0
GigabitEthernet0/0 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 DR, Priority 1
Designated Router (ID) 2.2.2.2, Interface address 10.0.0.2
Backup Designated router (ID) 0.0.0.0, Interface address 0.0.0.0
Timer intervals configured, Hello 5, Dead 20, Wait 20, Retransmit 5
oob-resync timeout 20
Hello due in 00:00:04
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
A
On R1, change the network statement to area 0 and set ip ospf hello-interval 5 and ip ospf dead-interval 20 under the interface.
This corrects both mismatches: area is changed to 0 to match R2, and timers are set to hello 5/dead 20 to match R2's timers. OSPF requires identical area IDs and hello/dead intervals on a link for adjacency to form.
B
On R2, change the network statement to area 1 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.
Why wrong: This is incorrect because while it aligns the area and timers, it changes R2's configuration to match R1's original settings. However, the question asks to correct the issues, and changing R1 is the more straightforward approach as R1 is the router you are connected to. Also, area 1 is not the standard backbone area; area 0 is typically used for single-area OSPF.
C
On R1, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.
Why wrong: This is incorrect because while it fixes the area mismatch by setting area 0, it does not fix the timer mismatch. R1's timers remain at hello 10/dead 40, which do not match R2's hello 5/dead 20. OSPF requires timers to match for adjacency.
D
On R2, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.
Why wrong: This is incorrect because it changes R2's area to 0 (which is already correct) but changes R2's timers to hello 10/dead 40, which would then mismatch with R1's timers. The area is already correct on R2, so no change is needed there. The timer change would create a new mismatch.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
On R1, change the network statement to area 0 and set ip ospf hello-interval 5 and ip ospf dead-interval 20 under the interface.
The OSPF adjacency fails due to two mismatches. First, the area is mismatched: R1 uses area 1, R2 uses area 0 (both must be the same area, typically area 0). Second, the hello and dead timers are mismatched: R1 uses Hello 10/Dead 40, R2 uses Hello 5/Dead 20. To fix, on R1 change the network statement to area 0 and adjust timers to match R2 (or vice versa). The solution below changes R1's area to 0 and sets hello to 5 and dead to 20 to match 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.
✓
On R1, change the network statement to area 0 and set ip ospf hello-interval 5 and ip ospf dead-interval 20 under the interface.
Why this is correct
This corrects both mismatches: area is changed to 0 to match R2, and timers are set to hello 5/dead 20 to match R2's timers. OSPF requires identical area IDs and hello/dead intervals on a link for adjacency to form.
On R2, change the network statement to area 1 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.
Why it's wrong here
This is incorrect because while it aligns the area and timers, it changes R2's configuration to match R1's original settings. However, the question asks to correct the issues, and changing R1 is the more straightforward approach as R1 is the router you are connected to. Also, area 1 is not the standard backbone area; area 0 is typically used for single-area OSPF.
✗
On R1, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.
Why it's wrong here
This is incorrect because while it fixes the area mismatch by setting area 0, it does not fix the timer mismatch. R1's timers remain at hello 10/dead 40, which do not match R2's hello 5/dead 20. OSPF requires timers to match for adjacency.
✗
On R2, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.
Why it's wrong here
This is incorrect because it changes R2's area to 0 (which is already correct) but changes R2's timers to hello 10/dead 40, which would then mismatch with R1's timers. The area is already correct on R2, so no change is needed there. The timer change would create a new mismatch.
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 R1, change the network statement to area 0 and set ip ospf hello-interval 5 and ip ospf dead-interval 20 under the interface.Correct answer▾
Why this is correct
This corrects both mismatches: area is changed to 0 to match R2, and timers are set to hello 5/dead 20 to match R2's timers. OSPF requires identical area IDs and hello/dead intervals on a link for adjacency to form.
✗On R2, change the network statement to area 1 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the question implies you are connected to R1, so configuring R1 is the expected action. Additionally, using area 1 instead of area 0 is not recommended for a single-area design.
Why candidates choose this
Candidates might think that changing either router is acceptable, but the question context ("You are connected to R1") suggests R1 should be modified. Also, some may not realize that area 0 is the preferred area for single-area OSPF.
✗On R1, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the timers are not changed to match R2; they remain at the original values.
Why candidates choose this
Candidates might think that only the area needs to be corrected, overlooking the timer mismatch. They may also assume that the default timers (hello 10/dead 40) are standard and should be used.
✗On R2, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that R2's area is already 0, so changing it to area 0 is redundant. Changing R2's timers to match R1's original timers would still leave a mismatch because R1's timers are not changed.
Why candidates choose this
Candidates might think that both routers need to be modified, or that changing the router you are not connected to is acceptable. They may also incorrectly assume that the default timers (hello 10/dead 40) are the correct ones to use.
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: On R1, change the network statement to area 0 and set ip ospf hello-interval 5 and ip ospf dead-interval 20 under the interface. — The OSPF adjacency fails due to two mismatches. First, the area is mismatched: R1 uses area 1, R2 uses area 0 (both must be the same area, typically area 0). Second, the hello and dead timers are mismatched: R1 uses Hello 10/Dead 40, R2 uses Hello 5/Dead 20. To fix, on R1 change the network statement to area 0 and adjust timers to match R2 (or vice versa). The solution below changes R1's area to 0 and sets hello to 5 and dead to 20 to match 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.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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