mediumMultiple Choice
300-410 Practice Question: Which EIGRP packet type is used to confirm…
Which EIGRP packet type is used to confirm receipt of an update during reliable transport?
⚠ Common exam trap
Many candidates confuse the purpose of Hello packets (which are also small and frequent) with ACK packets, forgetting that Hellos are used for neighbor discovery and keepalive, not for reliable transport acknowledgment.
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
✓
ACK
C is correct because EIGRP uses a reliable transport protocol (RTP) to ensure delivery of certain packets like Updates, Queries, and Replies. The ACK packet is a lightweight, unreliable packet sent to explicitly acknowledge receipt of a reliable packet, confirming that the update was received without needing a full retransmission.
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
Why it's wrong here
Hello packets serve neighbour discovery and keepalive functions, not reliable transport confirmation. EIGRP uses a reliable transport protocol (RTP) that requires an ACK packet to acknowledge receipt of an update; a Hello packet lacks the sequence-number acknowledgment field needed for this. It is tempting because Hello packets are the most frequently exchanged EIGRP packet type, but they would be correct only for detecting neighbour loss or maintaining adjacency, not for confirming a specific update.
- ✗
Update
Why it's wrong here
Update packets carry routing information; they are the payload being acknowledged, not the acknowledgement itself. It is tempting because updates are the reliably transported messages, and an Update would be correct when advertising a new route or changed metric to neighbours.
- ✓
ACK
Why this is correct
EIGRP uses the ACK packet to confirm receipt of updates, queries, and replies during reliable transport, satisfying the reliable delivery requirement. Unlike Hello packets, which are unreliable and need no acknowledgement, ACKs carry no data and are sent as unicast to the originating router, confirming that specific update was received.
- ✗
Query
Why it's wrong here
Query packets request specific route information from neighbours when a route is lost; they do not acknowledge received updates. It is tempting because queries also participate in EIGRP's reliable transport, and a Query would be correct when the router needs to find an alternative path.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.