easyMultiple Choice
300-410 Practice Question: Which OSPF packet type is used to send link-state…
Which OSPF packet type is used to send link-state advertisements (LSAs) and is acknowledged by the receiver?
⚠ Common exam trap
The trap is confusing the packet types—candidates may pick Hello or DBD because they are more familiar, but the key is that LSUs carry LSAs and are acknowledged, while Hello and DBD serve different purposes in neighbor discovery and database synchronization.
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
✓
Link State Update (type 4)
OSPF Link State Update (LSU) packets, type 4, are used to send link-state advertisements (LSAs) to neighboring routers. The receiver acknowledges receipt of LSUs with Link State Acknowledgment (LSAck) packets, ensuring reliable flooding of LSAs. This reliable flooding mechanism is fundamental to OSPF's link-state database synchronization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Hello (type 1)
Why it's wrong here
Hello packets perform neighbour discovery and dead-interval keepalive on the interface, carrying no LSAs and requiring no acknowledgement. They are tempting because they establish and maintain adjacencies, which is their actual purpose; they would be the answer if the question asked which packet forms OSPF neighbour relationships.
- ✗
Database Description (type 2)
Why it's wrong here
Database Description packets exchange LSA headers during adjacency formation to build the link-state database summary; they are not the acknowledged carrier of full LSAs. They are tempting because they do describe database contents, and would be correct if the question asked how routers compare databases before synchronisation.
- ✗
Link State Request (type 3)
Why it's wrong here
Link State Request packets ask a neighbour for specific LSAs missing from the local database; they request rather than carry LSAs and are not acknowledged. They are tempting because they directly concern LSA retrieval, and would be correct if the question asked which packet solicits a particular LSA during database synchronisation.
- ✓
Link State Update (type 4)
Why this is correct
Link State Update packets carry LSAs to neighbouring routers, and each LSU transmission is acknowledged by the receiver using Link State Acknowledgment packets. This reliable flooding mechanism distinguishes type 4 from Link State Request and Database Description packets.
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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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 300-410 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 300-410 exam.