- A
Area ID
Correct: OSPF neighbors must be in the same area, and the Area ID is checked during adjacency formation.
- B
Router ID
Why wrong: Incorrect: Router ID must be unique per router, but it does not need to match between neighbors.
- C
MTU mismatch
Correct: MTU mismatch prevents OSPF adjacency from forming fully; routers get stuck in EXSTART/EXCHANGE state if MTU values do not match.
- D
Hello and dead intervals
Correct: Hello and dead intervals must match between OSPF neighbors; otherwise, they will not form an adjacency.
- E
Authentication settings
Why wrong: Incorrect: While authentication settings must match if configured, they are optional and not a required factor for all OSPF adjacencies.
Question 78 of 514
OSPF Neighbor Adjacency Requirements — Area, Timers, and Authentication | JNCIA-Junos Explained
This JNCIA-JUNOS practice question tests your understanding of networking fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. A key principle to apply: oSPF adjacency requirements. 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.
Which THREE factors influence OSPF neighbor adjacency formation? (Choose three.)
Quick Answer
The answer is that Area ID, timers, and authentication settings are three critical factors that influence OSPF neighbor adjacency formation. This is correct because OSPF routers must agree on the same Area ID, as it defines the logical segment of the OSPF domain and is carried in Hello packets; a mismatch causes routers to believe they are in different areas, blocking adjacency. Additionally, Hello and Dead timers must match exactly, and authentication settings—such as simple password or MD5—must be identical, or Hello packets will be rejected. On the JNCIA-Junos exam, this concept tests your understanding of OSPF’s neighbor discovery process, often appearing as a multiple-select question where common traps include forgetting that the Router ID does not need to match or that network types must be compatible but are not a direct adjacency requirement. A useful memory tip is “A-T-A”: Area, Timers, Authentication—three pillars that must align for OSPF neighbors to say hello.
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
✓
Area ID
OSPF neighbor adjacency formation requires that both routers agree on several parameters. Among these are the Area ID (must match), Hello and dead intervals (must match), and MTU (must match). If any of these differ, the adjacency will not form. Router ID must be unique per router but not identical between neighbors. Authentication settings are optional and, if configured, must also match.
Key principle: OSPF adjacency requirements
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Area ID
- ✗
Router ID
Why it's wrong here
Incorrect: Router ID must be unique per router, but it does not need to match between neighbors.
- ✓
MTU mismatch
- ✓
Hello and dead intervals
- ✗
Authentication settings
Why it's wrong here
Incorrect: While authentication settings must match if configured, they are optional and not a required factor for all OSPF adjacencies.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often overlook MTU mismatch as a factor because the adjacency may appear to start but gets stuck in EXSTART/EXCHANGE state if the MTU values differ. Also, they may mistakenly think Router ID must match between neighbors.
Detailed technical explanation
How to think about this question
OSPF Hello packets carry the Area ID, Hello interval, Dead interval, and authentication data (if configured). These parameters must match on both sides for the neighbor state to progress beyond 2-Way. The Dead interval is typically four times the Hello interval, and any mismatch causes the neighbor to be stuck in INIT or EXSTART state. In JUNOS, you can verify these with 'show ospf neighbor detail' and 'show ospf interface'.
KKey Concepts to Remember
- OSPF adjacency requirements
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
OSPF adjacency requirements
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.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
What to study next
Got this wrong? Here's your next step.
Review oSPF adjacency requirements, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
- →
Networking Fundamentals — study guide chapter
Learn the concepts, then practise the questions
- →
Networking Fundamentals practice questions
Targeted practice on this topic area only
- →
All JNCIA-JUNOS questions
514 questions across all exam domains
- →
Juniper Networks Certified Associate Junos JNCIA-Junos study guide
Full concept coverage aligned to exam objectives
- →
JNCIA-JUNOS practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related JNCIA-JUNOS practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
User Interfaces practice questions
Practise JNCIA-JUNOS questions linked to User Interfaces.
Junos Configuration Basics practice questions
Practise JNCIA-JUNOS questions linked to Junos Configuration Basics.
Operational Monitoring and Maintenance practice questions
Practise JNCIA-JUNOS questions linked to Operational Monitoring and Maintenance.
Routing Fundamentals practice questions
Practise JNCIA-JUNOS questions linked to Routing Fundamentals.
Networking Fundamentals practice questions
Practise JNCIA-JUNOS questions linked to Networking Fundamentals.
Junos OS Fundamentals practice questions
Practise JNCIA-JUNOS questions linked to Junos OS Fundamentals.
JNCIA-JUNOS fundamentals practice questions
Practise JNCIA-JUNOS questions linked to JNCIA-JUNOS fundamentals.
JNCIA-JUNOS scenario practice questions
Practise JNCIA-JUNOS questions linked to JNCIA-JUNOS scenario.
JNCIA-JUNOS troubleshooting practice questions
Practise JNCIA-JUNOS questions linked to JNCIA-JUNOS troubleshooting.
Practice this exam
Start a free JNCIA-JUNOS practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
Networking Fundamentals — This question tests Networking Fundamentals — OSPF adjacency requirements.
What is the correct answer to this question?
The correct answer is: Area ID — OSPF neighbor adjacency formation requires that both routers agree on several parameters. Among these are the Area ID (must match), Hello and dead intervals (must match), and MTU (must match). If any of these differ, the adjacency will not form. Router ID must be unique per router but not identical between neighbors. Authentication settings are optional and, if configured, must also match.
What should I do if I get this JNCIA-JUNOS question wrong?
Review oSPF adjacency requirements, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
What is the key concept behind this question?
OSPF adjacency requirements
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 →
Keep practising
More JNCIA-JUNOS practice questions
- A junior engineer needs to collect a snapshot of the current system state, including routing tables, interfaces, and con…
- A network engineer is troubleshooting a connectivity issue and wants to see the active routes in the routing table. Whic…
- You are the network engineer for a mid-sized enterprise with a Juniper MX router running Junos. The router has two uplin…
- Which TWO attributes are used by Junos to select the active route among multiple routes to the same destination?
- What is the default preference of a direct route in Junos?
- A router has two routes to the same destination: one with preference 10 and metric 5, and another with preference 15 and…
Last reviewed: Jun 24, 2026
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks 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 JNCIA-JUNOS 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.