- A
On R1, configure the interface MTU to 1500 and then clear the OSPF process using 'clear ip ospf process'.
This is correct because OSPF requires matching MTU values on a link. The incorrect MTU on R1 (1400) caused the adjacency to stall in EXSTART. Setting MTU to 1500 and clearing the OSPF process allows proper adjacency formation.
- B
On R1, configure the interface MTU to 1500 and then reload the router to apply the change.
Why wrong: This is incorrect because reloading the router is unnecessary and disruptive. The MTU change takes effect immediately, and the OSPF process can be reset with 'clear ip ospf process' without a full reload.
- C
On R1, configure the interface MTU to 1500 and then change the OSPF network type to point-to-point.
Why wrong: This is incorrect because changing the OSPF network type does not resolve an MTU mismatch. The adjacency is stuck due to MTU, not network type. Point-to-point networks still require matching MTU.
- D
On R1, configure the interface MTU to 1500 and then adjust the OSPF hello and dead timers to match R2.
Why wrong: This is incorrect because mismatched hello/dead timers cause adjacency to be stuck in INIT or 2-WAY state, not EXSTART. EXSTART state indicates MTU mismatch, not timer mismatch.
Quick Answer
The answer is to configure the interface MTU on R1 to 1500 and then clear the OSPF process using the command clear ip ospf process. This is correct because OSPF requires matching MTU values on a link to form a full adjacency; when R1’s MTU of 1400 does not match R2’s default of 1500, the Database Description (DBD) packets exceed the smaller MTU, causing the adjacency to stall in the EXSTART state. On the CCNA 200-301 v2 exam, this scenario tests your understanding of OSPF neighbor formation states and the critical role of MTU consistency—a common trap is thinking the interface will simply drop packets, but OSPF specifically gets stuck in EXSTART/EXCHANGE. Remember the memory tip: “MTU mismatch? EXSTART is the hitch.” Always verify with show ip ospf neighbor and correct the MTU on the smaller side, then reset the process to force a fresh negotiation.
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.
You are connected to R1 via console. R1 and R2 are connected via a serial link. OSPFv2 has been configured, but the adjacency is stuck in EXSTART state. You suspect a mismatched MTU. On R1, the interface MTU is currently set to 1400, while R2 uses the default MTU of 1500. You need to verify and fix the issue.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
On R1, configure the interface MTU to 1500 and then clear the OSPF process using 'clear ip ospf process'.
OSPF requires matching MTU values on a link. The incorrect MTU on R1 (1400) caused the adjacency to stall in EXSTART. Setting MTU to 1500 and clearing the OSPF process allows proper adjacency formation.
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, configure the interface MTU to 1500 and then clear the OSPF process using 'clear ip ospf process'.
Why this is correct
This is correct because OSPF requires matching MTU values on a link. The incorrect MTU on R1 (1400) caused the adjacency to stall in EXSTART. Setting MTU to 1500 and clearing the OSPF process allows proper adjacency formation.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
On R1, configure the interface MTU to 1500 and then reload the router to apply the change.
- ✗
On R1, configure the interface MTU to 1500 and then change the OSPF network type to point-to-point.
- ✗
On R1, configure the interface MTU to 1500 and then adjust the OSPF hello and dead timers to match R2.
Why it's wrong here
This is incorrect because mismatched hello/dead timers cause adjacency to be stuck in INIT or 2-WAY state, not EXSTART. EXSTART state indicates MTU mismatch, not timer 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, configure the interface MTU to 1500 and then clear the OSPF process using 'clear ip ospf process'.Correct answer▾
Why this is correct
This is correct because OSPF requires matching MTU values on a link. The incorrect MTU on R1 (1400) caused the adjacency to stall in EXSTART. Setting MTU to 1500 and clearing the OSPF process allows proper adjacency formation.
✗On R1, configure the interface MTU to 1500 and then reload the router to apply the change.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that a reload is not required to apply MTU changes; the interface MTU is applied immediately, and the OSPF process can be cleared to re-establish adjacencies.
Why candidates choose this
Candidates might think that a reload is needed to apply configuration changes, but in Cisco IOS, many interface parameters take effect immediately without reload.
✗On R1, configure the interface MTU to 1500 and then change the OSPF network type to point-to-point.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that OSPF network type does not affect MTU requirements; MTU must match regardless of network type.
Why candidates choose this
Candidates may confuse MTU issues with network type issues, as both can cause OSPF adjacency problems. However, EXSTART state specifically points to MTU mismatch.
✗On R1, configure the interface MTU to 1500 and then adjust the OSPF hello and dead timers to match R2.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that timer mismatches affect the INIT and 2-WAY states, while EXSTART is associated with MTU or database descriptor (DBD) packet issues.
Why candidates choose this
Candidates often confuse the symptoms of timer mismatches with MTU mismatches. Both can prevent full adjacency, but the stuck state differs.
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.
What to study next
Got this wrong? Here's your next step.
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.
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FAQ
Questions learners often ask
What does this 200-301 question test?
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, configure the interface MTU to 1500 and then clear the OSPF process using 'clear ip ospf process'. — OSPF requires matching MTU values on a link. The incorrect MTU on R1 (1400) caused the adjacency to stall in EXSTART. Setting MTU to 1500 and clearing the OSPF process allows proper adjacency formation.
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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Last reviewed: Jun 7, 2026
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.
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