- 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.
Question 700 of 2,152
EIGRP Network Command: Correct Wildcard Mask Usage
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?
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.
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.
Option C is correct because the configuration uses a valid EIGRP AS number (400) and a correct wildcard mask (0.0.0.255) to match the 10.1.1.0/24 subnet. In EIGRP, the network command uses a wildcard mask to specify the exact interfaces to advertise, and 0.0.0.255 is the proper inverse of the subnet mask 255.255.255.0.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
Read the scenario before looking for a memorised answer.
- ✗
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: answer the scenario, not the keyword
Cisco often tests the distinction between wildcard masks and subnet masks, leading candidates to incorrectly assume that a subnet mask (like 255.255.255.0) should be used in the EIGRP network command instead of the correct wildcard mask.
Detailed technical explanation
How to think about this question
EIGRP uses the network command with a wildcard mask to enable the protocol on interfaces whose IP address falls within the specified range; the wildcard mask is the inverse of the subnet mask (e.g., 0.0.0.255 for /24). This allows precise control over which interfaces participate in EIGRP, avoiding the broader classful behavior seen in older routing protocols like RIPv1. In real-world scenarios, using a specific wildcard mask prevents accidental adjacency formation on unintended interfaces, especially in complex topologies with multiple subnets.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
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.
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The configuration is correct as shown. — Option C is correct because the configuration uses a valid EIGRP AS number (400) and a correct wildcard mask (0.0.0.255) to match the 10.1.1.0/24 subnet. In EIGRP, the network command uses a wildcard mask to specify the exact interfaces to advertise, and 0.0.0.255 is the proper inverse of the subnet mask 255.255.255.0.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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