- A
The wildcard mask should be 255.255.255.0.
Why wrong: EIGRP uses wildcard masks, not subnet masks.
- B
The network address should be the classful network 10.0.0.0.
Why wrong: EIGRP allows subnet-specific network statements.
- C
The configuration is correct as shown.
The network command with a wildcard mask is valid for EIGRP.
- D
The AS number 400 is invalid; EIGRP AS numbers must be between 1 and 65535.
Why wrong: EIGRP AS numbers can be from 1 to 65535; 400 is valid.
Quick Answer
The answer is that the configuration is correct as shown. The EIGRP network command with wildcard mask syntax uses a 32-bit inverse mask, and 0.0.0.255 correctly matches only the first 24 bits of the 10.1.1.0 subnet, enabling EIGRP on that specific interface. While many candidates mistakenly believe the network address must be a classful boundary, EIGRP actually allows any subnet address paired with the appropriate wildcard mask, making this a valid and precise configuration. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding that EIGRP’s network command does not require a classful network; the wildcard mask defines the exact range of interfaces to advertise. A common trap is confusing the wildcard mask with a subnet mask or assuming the network statement must be the major network. Remember the memory tip: “Wildcard zeros match, ones ignore”—so 0.0.0.255 means the first three octets must match exactly, which is perfectly fine for a /24 subnet.
300-410 EIGRP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of eigrp troubleshooting. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Given the following configuration snippet on Router R5:
router eigrp 400 network 10.1.1.0 0.0.0.255
What is wrong with this configuration?
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
The configuration is correct as shown.
The network command in EIGRP uses a wildcard mask, but the mask 0.0.0.255 is correct for a /24 prefix. However, the network address 10.1.1.0 is a subnet, which is valid. There is no error; the configuration is correct.
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.
- ✗
The wildcard mask should be 255.255.255.0.
Why it's wrong here
EIGRP uses wildcard masks, not subnet masks.
- ✗
The network address should be the classful network 10.0.0.0.
Why it's wrong here
EIGRP allows subnet-specific network statements.
- ✓
The configuration is correct as shown.
Why this is correct
The network command with a wildcard mask is valid for EIGRP.
Related concept
CIDR notation defines the prefix length.
- ✗
The AS number 400 is invalid; EIGRP AS numbers must be between 1 and 65535.
Why it's wrong here
EIGRP AS numbers can be from 1 to 65535; 400 is valid.
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.
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.
What to study next
Got this wrong? Here's your next step.
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.
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EIGRP Troubleshooting — study guide chapter
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FAQ
Questions learners often ask
What does this 300-410 question test?
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: The configuration is correct as shown. — The network command in EIGRP uses a wildcard mask, but the mask 0.0.0.255 is correct for a /24 prefix. However, the network address 10.1.1.0 is a subnet, which is valid. There is no error; the configuration is correct.
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.
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Last reviewed: Jun 18, 2026
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