easyMultiple ChoiceObjective-mapped
300-410 Practice Question: Which EIGRP packet type is used to acknowledge…
Which EIGRP packet type is used to acknowledge receipt of a reliable packet?
⚠ Common exam trap
Cisco often tests the distinction between packet types that are sent reliably versus unreliably, and the trap here is that candidates confuse the Reply packet (which is a response to a Query) with an acknowledgment, when in fact Reply packets are data-carrying reliable packets that themselves require an Ack.
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
D is correct because the EIGRP Ack (Acknowledgement) packet is a special packet used exclusively to confirm the reliable delivery of EIGRP packets such as Update, Query, and Reply. Ack packets are sent as unicast to the source router and contain no data, serving only as a delivery confirmation. This mechanism ensures that EIGRP's Reliable Transport Protocol (RTP) can guarantee ordered and guaranteed delivery of critical routing information.
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 are used for neighbor discovery and keepalive, not for acknowledgment.
- ✗
Update
Why it's wrong here
Update packets carry routing information and are sent reliably, but they are not used for acknowledgment.
- ✗
Reply
Why it's wrong here
Reply packets are sent in response to Query packets, not as general acknowledgments.
- ✓
Ack
Why this is correct
Correct. The Ack packet is an empty packet used to confirm receipt of reliable packets.
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
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