Quick Answer
The answer is that the neighbor has advertised three prefixes to R1, as indicated directly by the “Prefixes: 3” field in the output. This field, found under the detailed neighbor information from the show ip eigrp neighbors detail command, explicitly counts the number of routes that the neighbor has sent and that R1 has accepted into its topology table. On the ENCOR 350-401 exam, this command tests your ability to interpret EIGRP neighbor state and route exchange details, often appearing in questions that ask you to verify neighbor relationships or troubleshoot missing routes. A common trap is confusing the “Prefixes” count with the total number of routes in the routing table or with the sequence number; remember that “Prefixes” here refers only to routes learned from that specific neighbor. For a quick memory tip, think of “Prefixes” as the neighbor’s “gift count”—it tells you exactly how many routes that neighbor has shared with you.
This 350-401 practice question tests your understanding of eigrp. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer runs the following command on Router R1:
R1# show ip eigrp neighbors detail
EIGRP-IPv4 Neighbors for AS(100) H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.2 Gi0/0 13 00:12:34 12 100 0 45 Version 2.0/2.0, Retrans: 0, Retry: 0, Maxseq: 0 Prefixes: 3 Topology ids: 0 Authentication: None Topology: base (0x0)
Based on this output, what can be concluded?
The neighbor is using EIGRP version 1.
Why wrong: The version is shown as 2.0/2.0.
The neighbor has advertised 3 prefixes to R1.
The 'Prefixes: 3' field indicates the number of prefixes learned from this neighbor.
There is a high number of retransmissions indicating packet loss.
Why wrong: Retransmissions are 0.
The neighbor is using MD5 authentication.
Why wrong: Authentication is None.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The neighbor has advertised 3 prefixes to R1.
The output shows 'Prefixes: 3' under the neighbor details, which indicates that the neighbor has advertised exactly three prefixes to R1. This is a direct interpretation of the 'show ip eigrp neighbors detail' command, where the 'Prefixes' field lists the number of routes learned from that neighbor.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The neighbor is using EIGRP version 1.
Why it's wrong here
The version is shown as 2.0/2.0.
The neighbor has advertised 3 prefixes to R1.
Why this is correct
The 'Prefixes: 3' field indicates the number of prefixes learned from this neighbor.
Related concept
Read the scenario before looking for a memorised answer.
There is a high number of retransmissions indicating packet loss.
Why it's wrong here
Retransmissions are 0.
The neighbor is using MD5 authentication.
Why it's wrong here
Authentication is None.
Common exam traps
Cisco often tests the ability to read the 'show ip eigrp neighbors detail' output carefully, where candidates may confuse the 'Prefixes' field with the number of interfaces or ignore the 'Retrans' and 'Authentication' fields, leading them to select incorrect options based on assumptions rather than the explicit data shown.
Trap categories for this question
Command / output trap
The version is shown as 2.0/2.0.
Detailed technical explanation
The 'show ip eigrp neighbors detail' command provides granular information about each EIGRP neighbor, including the software version, retransmission count, and number of prefixes learned. In EIGRP, the 'Prefixes' count reflects the number of routes received from that neighbor after the initial exchange and any subsequent updates, which is critical for troubleshooting routing inconsistencies or missing routes in complex topologies.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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FAQ
EIGRP — This question tests EIGRP — Read the scenario before looking for a memorised answer..
The correct answer is: The neighbor has advertised 3 prefixes to R1. — The output shows 'Prefixes: 3' under the neighbor details, which indicates that the neighbor has advertised exactly three prefixes to R1. This is a direct interpretation of the 'show ip eigrp neighbors detail' command, where the 'Prefixes' field lists the number of routes learned from that neighbor.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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