350-401 REST APIs and Data Models Practice Question
This 350-401 practice question tests your understanding of rest apis and data models. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
An engineer is using the Cisco IOS-XE RESTCONF API to create a new loopback interface. The following JSON payload is sent in a POST request to '/restconf/data/ietf-interfaces:interfaces':
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
POST /restconf/data/ietf-interfaces:interfaces
To create a new resource, the POST method is used. The URL should point to the collection of interfaces. The payload includes the 'ietf-interfaces:interface' list. The correct URL is '/restconf/data/ietf-interfaces:interfaces'.
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.
✓
POST /restconf/data/ietf-interfaces:interfaces
Why this is correct
POST is used to create a new resource under the interfaces collection.
PUT is used to replace or create a specific resource, not a collection.
✗
PATCH /restconf/data/ietf-interfaces:interfaces
Why it's wrong here
PATCH is used for partial updates.
✗
POST /restconf/data/ietf-interfaces:interfaces/interface=Loopback100
Why it's wrong here
That URL would be for a specific interface, but the payload contains the interface list.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 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 350-401 subnetting questions on CIDR, address ranges, and subnet selection.
REST APIs and Data Models — This question tests REST APIs and Data Models — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: POST /restconf/data/ietf-interfaces:interfaces — To create a new resource, the POST method is used. The URL should point to the collection of interfaces. The payload includes the 'ietf-interfaces:interface' list. The correct URL is '/restconf/data/ietf-interfaces:interfaces'.
What should I do if I get this 350-401 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 350-401 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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Question Discussion
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