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Design and implement a DevOps infrastructure →hardMultiple ChoiceObjective-mapped

AZ-400 Design and implement a DevOps infrastructure Practice Question

This AZ-400 practice question tests your understanding of design and implement a devops infrastructure. 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.

Exhibit

resourceGroup: rg-shared
resources:
- type: Microsoft.Network/privateEndpoints
  name: pe-sqlsvr
  properties:
    privateLinkServiceConnections:
    - name: sqlConnection
      properties:
        privateLinkServiceId: /subscriptions/sub-123/resourceGroups/rg-sql/providers/Microsoft.Sql/servers/sqlsvr01
        groupIds: ["sqlServer"]
    subnet:
      id: /subscriptions/sub-123/resourceGroups/rg-shared/providers/Microsoft.Network/virtualNetworks/vnet-shared/subnets/subnet-endpoints
- type: Microsoft.Network/privateDnsZones/virtualNetworkLinks
  name: privatelink.database.windows.net/link-shared
  properties:
    virtualNetwork:
      id: /subscriptions/sub-123/resourceGroups/rg-shared/providers/Microsoft.Network/virtualNetworks/vnet-shared
    registrationEnabled: false

Refer to the exhibit. A Bicep file defines a private endpoint for Azure SQL Database and a private DNS zone link. After deployment, the SQL server cannot be resolved via private IP from a VM in vnet-shared. What is the most likely cause?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

  • Clue: "most likely"

    Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Exhibit

resourceGroup: rg-shared
resources:
- type: Microsoft.Network/privateEndpoints
  name: pe-sqlsvr
  properties:
    privateLinkServiceConnections:
    - name: sqlConnection
      properties:
        privateLinkServiceId: /subscriptions/sub-123/resourceGroups/rg-sql/providers/Microsoft.Sql/servers/sqlsvr01
        groupIds: ["sqlServer"]
    subnet:
      id: /subscriptions/sub-123/resourceGroups/rg-shared/providers/Microsoft.Network/virtualNetworks/vnet-shared/subnets/subnet-endpoints
- type: Microsoft.Network/privateDnsZones/virtualNetworkLinks
  name: privatelink.database.windows.net/link-shared
  properties:
    virtualNetwork:
      id: /subscriptions/sub-123/resourceGroups/rg-shared/providers/Microsoft.Network/virtualNetworks/vnet-shared
    registrationEnabled: false

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

✓

The private endpoint's subnet is missing a delegation or has network policies that block DNS resolution.

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.

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.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✓

    The private endpoint's subnet is missing a delegation or has network policies that block DNS resolution.

    Why this is correct

    Although not explicitly shown, a common issue is that the subnet does not have the 'Microsoft.Network/privateEndpoints' delegation or has 'privateEndpointNetworkPolicies' set to 'Disabled' (default is 'Enabled'), which can prevent DNS resolution. Also, the private DNS zone link might not be correctly associated, but the most likely cause is subnet configuration.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    CIDR notation defines the prefix length.

  • ✗

    The virtual network link has 'registrationEnabled' set to false, which prevents automatic registration of the private endpoint's private IP address in the DNS zone.

    Why it's wrong here

    RegistrationEnabled is for auto-registration of VMs, not for private endpoints. Private endpoints are registered automatically when created.

  • ✗

    The private DNS zone name is 'privatelink.database.windows.net' but it should be 'privatelink.sql.azuresynapse.net' for Azure SQL Database.

    Why it's wrong here

    For Azure SQL Database, the correct private DNS zone name is 'privatelink.database.windows.net'. This is correct.

  • ✗

    The private endpoint is in a different region than the SQL server.

    Why it's wrong here

    Private endpoints can be in a different region than the resource, but DNS resolution should still work if the DNS zone is linked correctly.

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

An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.

Visual reference

Client Recursive Resolver Root DNS (13 root servers) TLD DNS (.com, .org, …) Authoritative example.com query IP addr answer

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 AZ-400 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this AZ-400 question test?

Design and implement a DevOps infrastructure — This question tests Design and implement a DevOps infrastructure — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The private endpoint's subnet is missing a delegation or has network policies that block DNS resolution.

What should I do if I get this AZ-400 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-400 subnetting questions on CIDR, address ranges, and subnet selection.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

CIDR notation defines the prefix length.

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Last reviewed: Jul 4, 2026

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This AZ-400 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-400 exam.