The answer is to link the private DNS zone of the ACR private endpoint to the AKS virtual network. This is correct because even with VNet peering in place, the AKS cluster cannot automatically resolve the ACR’s private endpoint IP address unless its virtual network is explicitly linked to the private DNS zone that hosts the ACR’s custom DNS records. Without that link, AKS falls back to public DNS, which fails since the private endpoint blocks internet traffic. On the Microsoft Azure Security Engineer Associate AZ-500 exam, this scenario tests your understanding of how private endpoints rely on DNS zone linking for cross-VNet resolution, a common trap where candidates assume peering alone handles DNS. A frequent mistake is to delete the private endpoint or reconfigure AKS DNS servers, but the issue is purely about DNS propagation. Remember the memory tip: “Peering gets you there, but DNS linking tells you how to find the door.”
AZ-500 Secure networking Practice Question
This AZ-500 practice question tests your understanding of secure 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.
Your company has deployed Azure Kubernetes Service (AKS) in a virtual network. The AKS cluster needs to pull images from a private Azure Container Registry (ACR) that has a private endpoint configured. The virtual network where AKS is deployed is peered to the ACR's virtual network. You have configured the AKS cluster to use managed identity for authentication to ACR. However, the AKS cluster is unable to pull images from the ACR. You need to resolve the connectivity issue without exposing the ACR to the internet. What should you do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Link the private DNS zone of the ACR private endpoint to the AKS virtual network.
Option A is correct: The AKS cluster needs a route to the ACR's private endpoint. Since the virtual networks are peered, the AKS cluster should be able to resolve the ACR's private endpoint DNS name to the private IP. However, by default, AKS might not use the custom DNS if it doesn't have the proper DNS configuration. The most common cause is that the private endpoint's private DNS zone is not linked to the AKS virtual network. Option A correctly links the private DNS zone to the AKS virtual network. Option B is incorrect because deleting the private endpoint would expose ACR to the internet. Option C is incorrect because the AKS cluster's DNS servers should be the Azure default unless custom. Option D is incorrect because the managed identity is already in use; the issue is network connectivity.
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.
✓
Link the private DNS zone of the ACR private endpoint to the AKS virtual network.
Why this is correct
This allows AKS to resolve the ACR's private endpoint DNS name to the private IP.
Update the AKS cluster's DNS server to use a custom DNS that can resolve the private endpoint.
Why it's wrong here
Not necessary if the private DNS zone is linked; the default Azure DNS will resolve.
✗
Delete the private endpoint and configure ACR firewall rules to allow the AKS subnet.
Why it's wrong here
This would expose ACR to the internet, violating security.
✗
Recreate the AKS cluster with a different managed identity that has ACR pull permissions.
Why it's wrong here
The issue is network connectivity, not permissions.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-500 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 AZ-500 subnetting questions on CIDR, address ranges, and subnet selection.
Secure networking — This question tests Secure networking — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Link the private DNS zone of the ACR private endpoint to the AKS virtual network. — Option A is correct: The AKS cluster needs a route to the ACR's private endpoint. Since the virtual networks are peered, the AKS cluster should be able to resolve the ACR's private endpoint DNS name to the private IP. However, by default, AKS might not use the custom DNS if it doesn't have the proper DNS configuration. The most common cause is that the private endpoint's private DNS zone is not linked to the AKS virtual network. Option A correctly links the private DNS zone to the AKS virtual network. Option B is incorrect because deleting the private endpoint would expose ACR to the internet. Option C is incorrect because the AKS cluster's DNS servers should be the Azure default unless custom. Option D is incorrect because the managed identity is already in use; the issue is network connectivity.
What should I do if I get this AZ-500 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 AZ-500 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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