- A
Add an inbound NSG rule on the spoke subnet to allow UDP and TCP 53 to 10.8.0.4.
Why wrong: NSGs can allow or deny traffic, but they do not tell VMs which DNS server to query. The spoke still needs a DNS client configuration that points to the hub server.
- B
Configure the spoke VNet to use 10.8.0.4 as a custom DNS server.
A spoke VNet can inherit DNS behavior from a custom DNS setting on the VNet itself. Once the spoke VNet is configured to use 10.8.0.4, its VMs will send name-resolution queries to the hub DNS server over the peering connection. This is the right fix when direct IP connectivity works but internal names do not resolve.
- C
Create a service endpoint for Microsoft.Storage on the spoke subnet.
Why wrong: Service endpoints extend subnet identity to supported Azure services, but they do not affect DNS server selection or internal name resolution across peered VNets.
- D
Add a user-defined route for 10.8.0.4/32 pointing to the virtual network gateway.
Why wrong: A UDR changes packet forwarding, not DNS client settings. Sending traffic to the DNS server through a gateway is unnecessary when the VNet can already reach it.
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. 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 hub-and-spoke environment uses a DNS server VM in the hub VNet at 10.8.0.4 to resolve internal names such as app01.corp.local. The spoke VNet can reach hub VMs by IP after peering, but name resolution still fails from the spoke. What should the administrator configure so VMs in the spoke use the hub DNS server?
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
Configure the spoke VNet to use 10.8.0.4 as a custom DNS server.
Option B is correct because in Azure, a spoke VNet must explicitly be configured with a custom DNS server address to use a non-default DNS resolver. By setting the spoke VNet's DNS server to 10.8.0.4, all VMs in the spoke will send their DNS queries to that hub VM, resolving internal names like app01.corp.local. Without this configuration, the spoke VNet uses Azure-provided DNS, which cannot resolve custom private DNS zones hosted on the hub VM.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 an inbound NSG rule on the spoke subnet to allow UDP and TCP 53 to 10.8.0.4.
Why it's wrong here
NSGs can allow or deny traffic, but they do not tell VMs which DNS server to query. The spoke still needs a DNS client configuration that points to the hub server.
When this WOULD be correct
This option would be correct if the spoke VNet already had the hub DNS server configured, but VMs in the spoke could not reach it due to network security rules blocking DNS traffic (UDP/TCP 53). In that scenario, adding an inbound NSG rule on the spoke subnet to allow traffic to 10.8.0.4 would resolve the connectivity issue.
- ✓
Configure the spoke VNet to use 10.8.0.4 as a custom DNS server.
Why this is correct
A spoke VNet can inherit DNS behavior from a custom DNS setting on the VNet itself. Once the spoke VNet is configured to use 10.8.0.4, its VMs will send name-resolution queries to the hub DNS server over the peering connection. This is the right fix when direct IP connectivity works but internal names do not resolve.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a service endpoint for Microsoft.Storage on the spoke subnet.
Why it's wrong here
Service endpoints extend subnet identity to supported Azure services, but they do not affect DNS server selection or internal name resolution across peered VNets.
When this WOULD be correct
If the question were about securely accessing Azure Storage (e.g., a storage account) from a spoke VNet without using a public IP, configuring a service endpoint for Microsoft.Storage on the spoke subnet would be correct.
- ✗
Add a user-defined route for 10.8.0.4/32 pointing to the virtual network gateway.
Why it's wrong here
A UDR changes packet forwarding, not DNS client settings. Sending traffic to the DNS server through a gateway is unnecessary when the VNet can already reach it.
When this WOULD be correct
This option would be correct if the spoke VNet could not reach the hub DNS server by IP due to asymmetric routing or a missing route. For example, if the hub and spoke are connected via a VPN gateway and the spoke needs a specific route to send DNS traffic through the gateway to the hub DNS server.
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.
✓Configure the spoke VNet to use 10.8.0.4 as a custom DNS server.Correct answer▾
Why this is correct
A spoke VNet can inherit DNS behavior from a custom DNS setting on the VNet itself. Once the spoke VNet is configured to use 10.8.0.4, its VMs will send name-resolution queries to the hub DNS server over the peering connection. This is the right fix when direct IP connectivity works but internal names do not resolve.
✗Add an inbound NSG rule on the spoke subnet to allow UDP and TCP 53 to 10.8.0.4.Wrong answer — click to see why▾
Why this is wrong here
The issue is that the spoke VNet is not configured to use the hub DNS server for name resolution; NSG rules control traffic filtering, not DNS server assignment. Since connectivity via IP already works, an NSG rule is unnecessary and does not address the DNS configuration.
★ When this WOULD be the correct answer
This option would be correct if the spoke VNet already had the hub DNS server configured, but VMs in the spoke could not reach it due to network security rules blocking DNS traffic (UDP/TCP 53). In that scenario, adding an inbound NSG rule on the spoke subnet to allow traffic to 10.8.0.4 would resolve the connectivity issue.
Why candidates choose this
Candidates may think that since DNS uses port 53, a firewall or NSG rule is needed to allow the traffic, overlooking that the actual problem is the VNet's DNS server setting, not network security.
✗Create a service endpoint for Microsoft.Storage on the spoke subnet.Wrong answer — click to see why▾
Why this is wrong here
Service endpoints for Microsoft.Storage are used to secure Azure Storage resources to a VNet, not to configure DNS resolution. They do not affect how VMs resolve internal names like app01.corp.local.
★ When this WOULD be the correct answer
If the question were about securely accessing Azure Storage (e.g., a storage account) from a spoke VNet without using a public IP, configuring a service endpoint for Microsoft.Storage on the spoke subnet would be correct.
Why candidates choose this
Candidates may confuse service endpoints with DNS configuration because both involve network connectivity and IP addresses, leading them to think a service endpoint can direct DNS traffic to a specific server.
✗Add a user-defined route for 10.8.0.4/32 pointing to the virtual network gateway.Wrong answer — click to see why▾
Why this is wrong here
A user-defined route for 10.8.0.4/32 pointing to the virtual network gateway would not help because name resolution fails due to the spoke VNet not being configured to use the hub DNS server, not due to routing issues. The spoke VMs can already reach 10.8.0.4 by IP after peering, so routing is fine.
★ When this WOULD be the correct answer
This option would be correct if the spoke VNet could not reach the hub DNS server by IP due to asymmetric routing or a missing route. For example, if the hub and spoke are connected via a VPN gateway and the spoke needs a specific route to send DNS traffic through the gateway to the hub DNS server.
Why candidates choose this
Candidates may think that name resolution failure is caused by network connectivity issues and that adding a route to the DNS server IP will fix it, overlooking that the real problem is the VNet's DNS configuration.
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 assume VNet peering automatically forwards DNS queries to the hub's DNS server, but peering only provides IP-level connectivity, not DNS configuration; the spoke VNet must be explicitly set to use the custom DNS server address.
Detailed technical explanation
How to think about this question
Azure VNets have a DNS server setting at the VNet level that overrides the default Azure-provided DNS for all VMs in that VNet. When a custom DNS server IP is specified, Azure automatically configures the DHCP option 6 (DNS server) for each VM's network interface, so the VM's resolver uses that IP. In a hub-and-spoke topology, the hub DNS server must be reachable via VNet peering, which is already satisfied by IP connectivity; the missing piece is the spoke VNet's DNS configuration pointing to 10.8.0.4.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Visual reference
Quick reference
Common DNS Record Types
| Record | Purpose | Example |
|---|---|---|
| A | IPv4 address mapping | example.com → 93.184.216.34 |
| AAAA | IPv6 address mapping | example.com → 2606:2800::1 |
| CNAME | Alias to another hostname | www → example.com |
| MX | Mail server for domain | example.com → mail.example.com (priority 10) |
| TXT | Text data (SPF, DKIM, verification) | v=spf1 include:_spf.example.com ~all |
| NS | Authoritative name servers | example.com NS ns1.example.com |
| PTR | Reverse DNS (IP → hostname) | 34.216.184.93.in-addr.arpa → example.com |
| SOA | Zone authority record | Primary NS, admin email, serial, TTL defaults |
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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the spoke VNet to use 10.8.0.4 as a custom DNS server. — Option B is correct because in Azure, a spoke VNet must explicitly be configured with a custom DNS server address to use a non-default DNS resolver. By setting the spoke VNet's DNS server to 10.8.0.4, all VMs in the spoke will send their DNS queries to that hub VM, resolving internal names like app01.corp.local. Without this configuration, the spoke VNet uses Azure-provided DNS, which cannot resolve custom private DNS zones hosted on the hub VM.
What should I do if I get this AZ-104 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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