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 in a VRF-Lite configuration?
⚠ Common exam trap
The trap is confusing which EIGRP packets are reliable — candidates may pick Update or Query because they know those use RTP, forgetting that ACK is the packet that actually confirms receipt.
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
EIGRP uses Reliable Transport Protocol (RTP) for Update, Query, and Reply packets, and the ACK packet is the mechanism that confirms receipt of those reliable packets. In a VRF-Lite configuration the same RTP behavior applies per-VRF, so an ACK is still the packet type that acknowledges an Update. Hello packets are unreliable and are not acknowledged, which is why ACK is the correct answer.
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 sent unreliably and carry no sequence or acknowledgement fields, so they cannot confirm receipt of an update. They serve neighbour discovery and keepalive maintenance in VRF-Lite. Acknowledgement is the packet type that confirms receipt during reliable transport.
- ✗
Update
Why it's wrong here
An Update packet carries routing information and is itself the payload that requires reliable delivery, not the mechanism that confirms receipt. In EIGRP’s reliable transport, the recipient must send an explicit ACK packet (a Hello with no data) to acknowledge the Update; the Update packet cannot serve as its own acknowledgement because reliable transport demands a separate, non-data-bearing confirmation. This option is tempting because Update packets are the primary means of propagating route changes, and in a non-reliable context they would be the correct choice for distributing VRF-Lite prefixes.
- ✓
ACK
Why this is correct
The ACK packet confirms receipt of EIGRP updates during reliable transport, operating within VRF-Lite exactly as in non-VRF deployments. It satisfies the stem by providing the acknowledgement mechanism that guarantees delivery of update, query, and reply packets.
- ✗
Query
Why it's wrong here
Query packets request route information for a destination from neighbours; they are sent reliably but their purpose is route discovery, not confirming receipt. The Acknowledgement packet performs that confirmation during reliable transport, including within VRF-Lite instances.
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
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