Question 352 of 997

Monitoring, Logging and Runtime Security →mediumMultiple ChoiceObjective-mapped

How to Create a NetworkPolicy for Egress to a Specific IP and Port

This CKS practice question tests your understanding of monitoring, logging and runtime security. 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.

A developer reports that a pod cannot reach an external database at 192.168.1.100:3306. The pod's namespace is 'app'. You need to create a NetworkPolicy that allows egress to that IP only. Which policy is correct?

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

✓

apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: allow-egress namespace: app spec: podSelector: {} egress: - to: - ipBlock: cidr: 192.168.1.100/32 ports: - port: 3306 protocol: TCP policyTypes: - Egress

The correct NetworkPolicy must allow egress traffic from pods in the 'app' namespace to the specific IP 192.168.1.100 on port 3306. Option D meets this requirement by using 'podSelector: {}' to apply to all pods, specifying an egress rule to the ipBlock with the correct CIDR and port 3306, and setting 'policyTypes: [Egress]'. Option A is missing the port specification, so it would allow egress to the IP on any port, which is too permissive. Option B uses 'matchLabels: app: myapp', restricting the policy to pods with that label, and also lacks the port. Option C defines an ingress rule instead of egress, which does not address the egress requirement.

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.

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.

Visual reference

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

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FAQ

Questions learners often ask

What does this CKS question test?

Monitoring, Logging and Runtime Security — This question tests Monitoring, Logging and Runtime Security — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: allow-egress namespace: app spec: podSelector: {} egress: - to: - ipBlock: cidr: 192.168.1.100/32 ports: - port: 3306 protocol: TCP policyTypes: - Egress — The correct NetworkPolicy must allow egress traffic from pods in the 'app' namespace to the specific IP 192.168.1.100 on port 3306. Option D meets this requirement by using 'podSelector: {}' to apply to all pods, specifying an egress rule to the ipBlock with the correct CIDR and port 3306, and setting 'policyTypes: [Egress]'. Option A is missing the port specification, so it would allow egress to the IP on any port, which is too permissive. Option B uses 'matchLabels: app: myapp', restricting the policy to pods with that label, and also lacks the port. Option C defines an ingress rule instead of egress, which does not address the egress requirement.

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

What is the key concept behind this question?

CIDR notation defines the prefix length.

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