CCNA Network Services and Security Practice Question
Which OSPF neighbor state indicates that the routers have already exchanged full link-state databases?
⚠ Common exam trap
A frequent exam trap is selecting the 2-WAY or EXSTART states as the answer because they represent important steps in OSPF neighbor formation. However, 2-WAY only confirms bidirectional hello packets without database exchange, and EXSTART is merely the negotiation phase for database synchronization. Choosing these states overlooks the fact that full link-state database exchange and adjacency completion only occur at the FULL state. Misunderstanding this can lead to incorrect assumptions about OSPF neighbor readiness and routing stability.
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
✓
FULL
FULL means the adjacency is complete and database synchronization has finished. States such as INIT, 2-WAY, EXSTART, and EXCHANGE all occur earlier in the process.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
2-WAY
Why it's wrong here
In OSPF, the 2-WAY state confirms that both routers have received each other's Hello packets and bidirectional communication is established, but this state does not imply adjacency or database synchronization. On broadcast networks, routers remain in 2-WAY with non-DR/BDR neighbors, and only routers that form full adjacencies proceed to database exchange.
When this WOULD be correct
In a different question asking about the state where routers have acknowledged each other as neighbors but have not yet completed the database exchange, the 2-WAY state would be the correct answer. For example, a question could ask which state indicates that routers are ready to proceed with database synchronization.
- ✗
EXSTART
Why it's wrong here
EXSTART is the first step of database exchange where routers negotiate roles using Database Description packets, determining which router will be the master and the initial sequence number. No routing information is exchanged in this state—only the master/slave relationship and DD packet sequence are established, so reaching EXSTART does not mean the databases have been compared.
When this WOULD be correct
In a question asking about the OSPF state during the database exchange process, specifically regarding the negotiation phase between routers, EXSTART would be the correct answer when identifying the state before the actual database synchronization occurs.
- ✓
FULL
Why this is correct
The FULL state is reached after the database description, LSR, LSU, and LSAck packets have completed a full exchange of link-state databases. In FULL, the neighbors have identical link-state information and are considered fully adjacent, enabling them to compute accurate SPF routes and participate in routing updates. Only FULL neighbors exchange routing information.
- ✗
INIT
Why it's wrong here
In the INIT state, a router has received a Hello packet from a neighbor, but the Hello packet does not contain the receiving router's Router ID, meaning the neighbor has not yet seen a Hello from this router. Thus communication is one-way only, and OSPF requires confirmation of bidirectional visibility (seeing each other's Router ID) before advancing to 2-WAY.
When this WOULD be correct
In a question asking about the initial state of OSPF neighbor relationships or the process of establishing OSPF adjacencies, INIT could be the correct answer when referring to the very first step of neighbor discovery.
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.
✓FULLCorrect answer▾
Why this is correct
The FULL state is reached after the database description, LSR, LSU, and LSAck packets have completed a full exchange of link-state databases. In FULL, the neighbors have identical link-state information and are considered fully adjacent, enabling them to compute accurate SPF routes and participate in routing updates. Only FULL neighbors exchange routing information.
✗2-WAYWrong answer — click to see why▾
Why this is wrong here
The 2-WAY state indicates that bidirectional communication has been established via Hello packets, but no link-state database exchange has occurred. Full database exchange only happens after the EXSTART and EXCHANGE states.
★ When this WOULD be the correct answer
In a different question asking about the state where routers have acknowledged each other as neighbors but have not yet completed the database exchange, the 2-WAY state would be the correct answer. For example, a question could ask which state indicates that routers are ready to proceed with database synchronization.
Why candidates choose this
Students might confuse 2-WAY with FULL because both indicate a form of adjacency, but 2-WAY is only a preliminary state before database exchange begins.
✗EXSTARTWrong answer — click to see why▾
Why this is wrong here
EXSTART is the state where master-slave relationship is negotiated and initial Database Description (DD) packets are exchanged, but the actual link-state database content has not yet been fully exchanged. Full exchange occurs in the EXCHANGE and LOADING states.
★ When this WOULD be the correct answer
In a question asking about the OSPF state during the database exchange process, specifically regarding the negotiation phase between routers, EXSTART would be the correct answer when identifying the state before the actual database synchronization occurs.
Why candidates choose this
The name 'EXSTART' might be misinterpreted as 'exchange start' implying full exchange, but it is only the beginning of the exchange process.
✗INITWrong answer — click to see why▾
Why this is wrong here
The INIT state means that a router has received a Hello packet from a neighbor but has not yet seen its own Router ID in the neighbor's Hello, indicating that bidirectional communication is not confirmed. No database exchange occurs in this state.
★ When this WOULD be the correct answer
In a question asking about the initial state of OSPF neighbor relationships or the process of establishing OSPF adjacencies, INIT could be the correct answer when referring to the very first step of neighbor discovery.
Why candidates choose this
INIT might be mistaken for the initial stage of database exchange, but it is actually the very first step in neighbor discovery, far before any database synchronization.
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?”
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.
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Key term
Intermediate System to Intermediate System
A routing protocol used within large enterprise networks to exchange routing information between routers, helping data find the best path across the network.
Key term
OSPF
OSPF is a link-state routing protocol used to find the best path for data packets to travel across IP networks, like a smart GPS that recalculates routes when traffic changes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.