- A
Add a user-defined route that sends DNS traffic to the hub virtual network.
Why wrong: Routes control packet forwarding, but they do not tell Azure which DNS server to use for name resolution.
- B
Set the spoke virtual network's custom DNS server to 10.20.0.4.
This directs VMs in the spoke to query the hub DNS server for internal names. In a hub-and-spoke design, peering alone does not make Azure use a custom DNS server automatically. Configuring the spoke VNet to use 10.20.0.4 ensures clients send DNS queries to the server that already hosts the corporate zone records.
- C
Create an NSG rule that allows UDP port 53 from the spoke subnet to the hub subnet.
Why wrong: An NSG can permit DNS traffic, but it does not configure which DNS server the VMs should query.
- D
Enable gateway transit on the hub peering so name resolution flows through the VPN gateway.
Why wrong: Gateway transit is for shared gateway routing to on-premises networks, not for selecting a DNS server in Azure.
Quick Answer
The answer is to set the spoke virtual network’s custom DNS server to 10.20.0.4. This is correct because Azure VNet peering does not automatically propagate DNS settings from a hub to a spoke; each virtual network must explicitly define its own DNS server. Without this configuration, spoke VMs fall back to Azure-provided DNS, which cannot resolve internal names like app01.corp.local that are hosted on a custom DNS server in the hub. On the AZ-104 exam, this scenario tests your understanding that DNS resolution is a per-VNet setting, not a peered property—a common trap is assuming peering inherits DNS. To remember, think: “Peering shares routes, not DNS servers.” The fix is straightforward: configure the spoke’s custom DNS server to point to the hub’s DNS IP, ensuring all internal name queries are forwarded correctly.
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: azure VNets default to Azure DNS for name resolution.. 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 company has a hub virtual network that contains a custom DNS server at 10.20.0.4. A new spoke virtual network is peered to the hub. VMs in the spoke can reach other resources in Azure, but they cannot resolve internal names such as app01.corp.local. What should the administrator configure to fix name resolution for the spoke VMs?
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
Set the spoke virtual network's custom DNS server to 10.20.0.4.
Option B is correct because the spoke virtual network must be configured to use the hub's custom DNS server (10.20.0.4) as its own DNS server. Azure virtual networks do not automatically inherit DNS settings from a peered hub; each virtual network must explicitly specify its DNS server. By setting the spoke's custom DNS server to 10.20.0.4, VMs in the spoke will send DNS queries to that server, enabling resolution of internal names like app01.corp.local.
Key principle: Azure VNets default to Azure DNS for name resolution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a user-defined route that sends DNS traffic to the hub virtual network.
Why it's wrong here
Routes control packet forwarding, but they do not tell Azure which DNS server to use for name resolution.
- ✓
Set the spoke virtual network's custom DNS server to 10.20.0.4.
Why this is correct
This directs VMs in the spoke to query the hub DNS server for internal names. In a hub-and-spoke design, peering alone does not make Azure use a custom DNS server automatically. Configuring the spoke VNet to use 10.20.0.4 ensures clients send DNS queries to the server that already hosts the corporate zone records.
Related concept
Azure VNets default to Azure DNS for name resolution.
- ✗
Create an NSG rule that allows UDP port 53 from the spoke subnet to the hub subnet.
Why it's wrong here
An NSG can permit DNS traffic, but it does not configure which DNS server the VMs should query.
- ✗
Enable gateway transit on the hub peering so name resolution flows through the VPN gateway.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse DNS resolution with network connectivity (NSG rules or UDRs) or assume that VNet peering automatically propagates DNS settings, when in fact each VNet must be explicitly configured with its own DNS server.
Detailed technical explanation
How to think about this question
When you set a custom DNS server on a virtual network, Azure updates the DHCP lease for VMs in that VNet to point to the specified DNS server IP. The hub's custom DNS server (10.20.0.4) must be configured with forwarders or conditional forwarders to resolve the corp.local zone, or host the zone itself. Without this configuration, even after setting the spoke's DNS server, the hub DNS server must be authoritative or have forwarding rules for the internal namespace.
KKey Concepts to Remember
- Azure VNets default to Azure DNS for name resolution.
- Custom DNS servers must be explicitly configured at the VNet level.
- Peering provides IP connectivity but doesn't change DNS server settings.
- VNet custom DNS settings apply to all VMs within that VNet.
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
Azure VNets default to Azure DNS for name resolution.
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.
What to study next
Got this wrong? Here's your next step.
Review azure VNets default to Azure DNS for name resolution., then practise related AZ-104 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this AZ-104 question test?
Implement and Manage Virtual Networking — This question tests Implement and Manage Virtual Networking — Azure VNets default to Azure DNS for name resolution..
What is the correct answer to this question?
The correct answer is: Set the spoke virtual network's custom DNS server to 10.20.0.4. — Option B is correct because the spoke virtual network must be configured to use the hub's custom DNS server (10.20.0.4) as its own DNS server. Azure virtual networks do not automatically inherit DNS settings from a peered hub; each virtual network must explicitly specify its DNS server. By setting the spoke's custom DNS server to 10.20.0.4, VMs in the spoke will send DNS queries to that server, enabling resolution of internal names like app01.corp.local.
What should I do if I get this AZ-104 question wrong?
Review azure VNets default to Azure DNS for name resolution., then practise related AZ-104 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Azure VNets default to Azure DNS for name resolution.
About these practice questions
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Same concept, more angles
1 more ways this is tested on AZ-104
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a hub virtual network with a DNS server VM at 10.50.0.4 that hosts internal names such as app01.corp.local. A spoke virtual network is already peered to the hub. VMs in the spoke can reach resources in the hub by IP address, but they cannot resolve the internal host names. The company wants to keep DNS centralized and avoid deploying another DNS server in the spoke. What should the administrator configure?
medium- A.Create a private DNS zone for corp.local and link it only to the spoke subnet.
- ✓ B.Set the spoke virtual network to use 10.50.0.4 as a custom DNS server.
- C.Add a user-defined route in the spoke to send DNS traffic to the hub VNet.
- D.Enable gateway transit on the peering and set use remote gateways on the spoke.
Why B: Option B is correct because the spoke virtual network must be configured to use the hub DNS server (10.50.0.4) as a custom DNS server. This ensures that all VMs in the spoke send DNS queries to the hub server, which hosts the internal zone for corp.local. Since the hub and spoke are already peered, DNS traffic can flow over the peering connection without additional routing, keeping DNS centralized.
Last reviewed: Jun 11, 2026
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