- 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.
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.
When this WOULD be correct
A UDR would be correct if the spoke VMs could not reach the custom DNS server at 10.20.0.4 due to missing routing, e.g., if the hub and spoke are in different regions and the DNS server is not reachable via the default route. In that case, a UDR with next hop to the hub's virtual appliance would fix connectivity.
- ✓
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.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-104 exam frequently reuses these exact scenarios with slightly different constraints.
✓Set the spoke virtual network's custom DNS server to 10.20.0.4.Correct answer▾
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.
✗Add a user-defined route that sends DNS traffic to the hub virtual network.Wrong answer — click to see why▾
Why this is wrong here
A user-defined route (UDR) controls traffic flow, not DNS resolution. The spoke VMs can already reach Azure resources, so routing is fine; the issue is that they are not using the custom DNS server at 10.20.0.4 for name resolution.
★ When this WOULD be the correct answer
A UDR would be correct if the spoke VMs could not reach the custom DNS server at 10.20.0.4 due to missing routing, e.g., if the hub and spoke are in different regions and the DNS server is not reachable via the default route. In that case, a UDR with next hop to the hub's virtual appliance would fix connectivity.
Why candidates choose this
Candidates may confuse DNS resolution with network routing, thinking that if VMs cannot resolve names, traffic to the DNS server must be routed differently, rather than configuring the DNS server address on the spoke virtual network.
✗Create an NSG rule that allows UDP port 53 from the spoke subnet to the hub subnet.Wrong answer — click to see why▾
Why this is wrong here
The issue is DNS resolution, not network connectivity. NSG rules control traffic flow, but the spoke VMs can already reach Azure resources, indicating connectivity exists. The problem is that the spoke VMs are not using the custom DNS server, so allowing UDP 53 does not fix the DNS configuration.
★ When this WOULD be the correct answer
If the spoke VMs could not resolve any names (including Azure internal names) and connectivity tests showed that traffic to the hub DNS server was blocked, then creating an NSG rule to allow UDP 53 from the spoke subnet to the hub subnet would be correct.
Why candidates choose this
Candidates often confuse DNS resolution issues with network security rules, assuming that blocking DNS traffic is the cause when the actual problem is incorrect DNS server configuration on the spoke virtual network.
✗Enable gateway transit on the hub peering so name resolution flows through the VPN gateway.Wrong answer — click to see why▾
Why this is wrong here
Gateway transit is used to allow spoke VMs to use the hub's VPN gateway for outbound connectivity, not for DNS resolution. It does not configure DNS servers for the spoke virtual network.
★ When this WOULD be the correct answer
If the question asked how to allow spoke VMs to access on-premises resources through the hub's VPN gateway, enabling gateway transit on the hub peering and using remote gateways on the spoke peering would be correct.
Why candidates choose this
Candidates may confuse gateway transit with DNS forwarding, thinking that enabling transit allows DNS queries to flow through the hub's gateway to a DNS server on-premises.
Analysis generated from the official AZ-104blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
Visual reference
What to study next
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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.
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Last reviewed: Jun 11, 2026
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