The answer is that there is no problem; split horizon is enabled, which is a normal and expected configuration. This is correct because split horizon is a fundamental loop prevention mechanism in EIGRP that prevents a route learned on an interface from being advertised back out that same interface, thereby avoiding routing loops. In the context of the Cisco CCNP ENARSI 300-410 exam, this command tests your ability to interpret the show ip eigrp interfaces detail output and recognize that split horizon being enabled is the default and desirable state, not a misconfiguration. A common trap is assuming that split horizon must be disabled for certain hub-and-spoke topologies, but the exam expects you to know it remains enabled unless explicitly changed for specific designs like DMVPN. Memory tip: think of split horizon as a "one-way mirror" — it reflects routes in, but never lets them go back out the same door.
300-410 EIGRP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of eigrp troubleshooting. 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 interfaces detail Gi0/0
EIGRP-IPv4 Interfaces for AS(100)
Interface: GigabitEthernet0/0
Peers: 1
Xmit Queue Un/Reliable: 0/0
Mean SRTT: 12
Pacing Time Un/Reliable: 0/10
Multicast Flow Timer: 50
Pending Routes: 0
Hello interval: 5
Hold time: 15
Split horizon: Enabled
Next multicast: 0.0.0.0
Next broadcast: 0.0.0.0
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Split horizon is enabled, which is a normal and expected configuration.
The detail output shows split horizon is enabled on the interface. Split horizon is a loop prevention mechanism that prevents routes from being advertised out the interface they were learned on. This is normal and expected. There is no problem.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Split horizon is enabled, which is a normal and expected configuration.
Why this is correct
Split horizon is enabled by default on EIGRP interfaces and helps prevent routing loops.
Split horizon is disabled, which could cause routing loops.
Why it's wrong here
The output shows 'Split horizon: Enabled', not disabled.
✗
The hold time of 15 seconds is too short and may cause instability.
Why it's wrong here
15 seconds is the default hold time for EIGRP on LAN interfaces.
✗
The interface has no peers, indicating a problem.
Why it's wrong here
The output shows 'Peers: 1', so there is one peer.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
The output shows 'Split horizon: Enabled', not disabled.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Split horizon is enabled, which is a normal and expected configuration. — The detail output shows split horizon is enabled on the interface. Split horizon is a loop prevention mechanism that prevents routes from being advertised out the interface they were learned on. This is normal and expected. There is no problem.
What should I do if I get this 300-410 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer runs the following command on Router R1:
R1# show ip eigrp interfaces
EIGRP-IPv4 Interfaces for AS(100)
Xmit Queue Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes
Gi0/0 1 0/0 12 0/10 50 0
Gi0/1 1 0/0 15 0/10 50 0
Gi0/2 1 0/0 18 0/10 50 0
Gi0/3 1 0/0 20 0/10 50 0
Gi0/4 0 0/0 0 0/10 50 0
Based on this output, which statement is correct?
medium
✓ A.Interface Gi0/4 has no EIGRP neighbor, which may indicate a configuration issue or lack of connectivity.
B.All interfaces have at least one EIGRP neighbor.
C.The mean SRTT on Gi0/2 is 18 ms, which is too high and indicates a problem.
D.The pending routes count of 0 on all interfaces indicates a routing loop.
Why A: The show ip eigrp interfaces command shows EIGRP-enabled interfaces and their statistics. Gi0/4 has 0 peers, meaning no EIGRP neighbor is formed on that interface. The other interfaces have 1 peer each, indicating a neighbor relationship.
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Question Discussion
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