Question 599 of 991

Services and Networking →hardMultiple ChoiceObjective-mapped

CKAD Services and Networking Practice Question

This CKAD practice question tests your understanding of services and networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

You have a NetworkPolicy that allows ingress from pods with label 'app: frontend' in any namespace, and also allows ingress from the IP range '10.0.0.0/8'. The policy is not working as expected. Which YAML snippet correctly implements both requirements?

Question 1hardmultiple choice

Full question →

A
ingress: - from: - namespaceSelector: {} podSelector: matchLabels: app: frontend - from: - ipBlock: cidr: 10.0.0.0/8
This correctly separates the two rules: one for pods with label app: frontend in any namespace, and one for the IP range.
B
ingress: - from: - namespaceSelector: {} - podSelector: matchLabels: app: frontend - ipBlock: cidr: 10.0.0.0/8
Why wrong: This incorrectly places the podSelector and ipBlock as separate items in the same from, meaning they are OR'd but the namespaceSelector applies to all? No, this is invalid syntax: from items must be a list of peers, and each peer can have multiple selectors that are ANDed. This structure is not valid because ipBlock cannot be combined with podSelector in the same from item without being in a separate peer. Actually, it is valid: you can have multiple peers in a from, each peer is an OR. This would match pods from any namespace (first peer), or pods with label app: frontend (second peer, but without namespaceSelector it only applies to same namespace), or IP range (third peer). That is not what we want. So incorrect.
C
ingress: - from: - podSelector: matchLabels: app: frontend - ipBlock: cidr: 10.0.0.0/8
Why wrong: Missing namespaceSelector, so it only selects pods in the same namespace.
D
ingress: - from: - namespaceSelector: {} podSelector: matchLabels: app: frontend - ipBlock: cidr: 10.0.0.0/8
Why wrong: This is actually valid but less common; however, the question expects a clearer separation. Option B is more standard.

Full breakdown with real-world context →

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

✓

ingress: - from: - namespaceSelector: {} podSelector: matchLabels: app: frontend - from: - ipBlock: cidr: 10.0.0.0/8

To allow ingress from pods with a specific label in any namespace, you use namespaceSelector: {} and podSelector with matchLabels. For IP range, you use ipBlock. Both rules should be in the ingress array. Option B is correct. Option A uses namespaceSelector with podSelector but the namespaceSelector {} is missing. Option C uses ipBlock incorrectly. Option D uses only from with both, but the structure is wrong.

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.

✓
ingress: - from: - namespaceSelector: {} podSelector: matchLabels: app: frontend - from: - ipBlock: cidr: 10.0.0.0/8
Why this is correct
This correctly separates the two rules: one for pods with label app: frontend in any namespace, and one for the IP range.
Related concept
CIDR notation defines the prefix length.
✗
ingress: - from: - namespaceSelector: {} - podSelector: matchLabels: app: frontend - ipBlock: cidr: 10.0.0.0/8
Why it's wrong here
This incorrectly places the podSelector and ipBlock as separate items in the same from, meaning they are OR'd but the namespaceSelector applies to all? No, this is invalid syntax: from items must be a list of peers, and each peer can have multiple selectors that are ANDed. This structure is not valid because ipBlock cannot be combined with podSelector in the same from item without being in a separate peer. Actually, it is valid: you can have multiple peers in a from, each peer is an OR. This would match pods from any namespace (first peer), or pods with label app: frontend (second peer, but without namespaceSelector it only applies to same namespace), or IP range (third peer). That is not what we want. So incorrect.
✗
ingress: - from: - podSelector: matchLabels: app: frontend - ipBlock: cidr: 10.0.0.0/8
Why it's wrong here
Missing namespaceSelector, so it only selects pods in the same namespace.
✗
ingress: - from: - namespaceSelector: {} podSelector: matchLabels: app: frontend - ipBlock: cidr: 10.0.0.0/8
Why it's wrong here
This is actually valid but less common; however, the question expects a clearer separation. Option B is more standard.

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 CKAD subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this CKAD question test?

Services and Networking — This question tests Services and Networking — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: ingress: - from: - namespaceSelector: {} podSelector: matchLabels: app: frontend - from: - ipBlock: cidr: 10.0.0.0/8 — To allow ingress from pods with a specific label in any namespace, you use namespaceSelector: {} and podSelector with matchLabels. For IP range, you use ipBlock. Both rules should be in the ingress array. Option B is correct. Option A uses namespaceSelector with podSelector but the namespaceSelector {} is missing. Option C uses ipBlock incorrectly. Option D uses only from with both, but the structure is wrong.

What should I do if I get this CKAD question wrong?

What is the key concept behind this question?

CIDR notation defines the prefix length.

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Last reviewed: Jun 21, 2026

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