200-901 Infrastructure and Automation Practice Question
This 200-901 practice question tests your understanding of infrastructure and automation. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Exhibit
Refer to the exhibit.
yang-module: Cisco-IOS-XE-native
container native
container ip
list route
key "prefix mask"
leaf prefix { type inet:ipv4-address; }
leaf mask { type inet:ipv4-prefix-length; }
leaf next-hop { type inet:ipv4-address; }
Refer to the exhibit. Based on the YANG model snippet, what is the data type of the 'mask' leaf?
Refer to the exhibit.
yang-module: Cisco-IOS-XE-native
container native
container ip
list route
key "prefix mask"
leaf prefix { type inet:ipv4-address; }
leaf mask { type inet:ipv4-prefix-length; }
leaf next-hop { type inet:ipv4-address; }
A
inet:ipv4-address
Why wrong: This is the type for the 'prefix' leaf, not 'mask'.
B
inet:ipv4-prefix-length
The exhibit shows the type as inet:ipv4-prefix-length.
C
uint8
Why wrong: While similar, the exact type is ipv4-prefix-length, which is typically derived from uint8 but specifically defined.
D
string
Why wrong: The type is not string; it's a numeric range.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
inet:ipv4-prefix-length
The 'mask' leaf is defined with the type 'inet:ipv4-prefix-length', which represents a decimal integer from 0 to 32 indicating the number of leading 1 bits in the subnet mask (e.g., 24 for /24). This is the correct data type for a prefix length in YANG models, not an IPv4 address or a generic string.
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.
✗
inet:ipv4-address
Why it's wrong here
This is the type for the 'prefix' leaf, not 'mask'.
✓
inet:ipv4-prefix-length
Why this is correct
The exhibit shows the type as inet:ipv4-prefix-length.
Related concept
Read the scenario before looking for a memorised answer.
✗
uint8
Why it's wrong here
While similar, the exact type is ipv4-prefix-length, which is typically derived from uint8 but specifically defined.
✗
string
Why it's wrong here
The type is not string; it's a numeric range.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between 'inet:ipv4-address' (a full address) and 'inet:ipv4-prefix-length' (the /N notation), tricking candidates who confuse the subnet mask value with its prefix length representation.
Trap categories for this question
Similar concept trap
While similar, the exact type is ipv4-prefix-length, which is typically derived from uint8 but specifically defined.
Detailed technical explanation
How to think about this question
The 'inet:ipv4-prefix-length' type is defined in RFC 6991 (Common YANG Data Types) and restricts values to 0-32, matching the CIDR notation used in routing protocols like OSPF and BGP. In a real-world scenario, using 'uint8' instead would allow invalid values like 33 or 255, which could cause configuration errors or security issues when the prefix length is applied to an interface or route.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Infrastructure and Automation — This question tests Infrastructure and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: inet:ipv4-prefix-length — The 'mask' leaf is defined with the type 'inet:ipv4-prefix-length', which represents a decimal integer from 0 to 32 indicating the number of leading 1 bits in the subnet mask (e.g., 24 for /24). This is the correct data type for a prefix length in YANG models, not an IPv4 address or a generic string.
What should I do if I get this 200-901 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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Question Discussion
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