Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
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
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Add an inbound NSG rule on the spoke subnet to allow UDP and TCP 53 to 10.8.0.4.
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
Best answer
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
Distractor review
Create a service endpoint for Microsoft.Storage on the spoke subnet.
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
Distractor review
Add a user-defined route for 10.8.0.4/32 pointing to the virtual network gateway.
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.
Common exam trap
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.
Technical deep dive
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A route table contains these entries: 10.0.0.0/8 with next hop Virtual appliance, and 10.1.1.0/24 with next hop Virtual network gateway. Which next hop will Azure use for traffic to 10.1.1.5?
Question 2
You are deploying a stateless web application on Azure virtual machines. The solution must automatically add and remove instances based on CPU demand and allow all instances to be managed as one logical group. Which Azure compute feature should you deploy?
Question 3
You are deploying a Windows Server VM for an internal app. The VM must support Secure Boot and vTPM later, its OS disk must survive host moves, and the team wants the lowest-cost managed disk tier that still behaves like a normal writable OS disk. Which two choices should you make? Select two.
Question 4
You need to deploy several identical virtual machines and ensure that the failure of a single Azure host does not affect all of them. Which feature should you use?
Question 5
You need to connect VNet-Hub and VNet-Spoke so that resources in both virtual networks can communicate privately over the Microsoft backbone. Both virtual networks are in the same region. What should you configure?
Question 6
You need to create a storage account that provides the lowest-cost redundant storage for non-critical data and only needs protection against local disk or server failure within a single datacenter. Which redundancy option should you choose?
FAQ
Questions learners often ask
What does this AZ-104 question test?
CIDR notation defines the prefix length.
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. — When a hub VNet contains a DNS server VM and spoke VNets must resolve internal names through it, the spoke VNet must be configured to use that DNS server address. Peering only provides network reachability; it does not automatically change DNS behavior. After setting the custom DNS server on the spoke VNet, VMs there will query 10.8.0.4 for internal records such as app01.corp.local. Why others are wrong: NSG rules can permit DNS traffic, but they do not assign a DNS server to clients. Service endpoints are for Azure PaaS access and are unrelated to name resolution. A UDR can influence routing, but DNS queries still go wherever the client is configured to send them, so it will not fix the name-resolution problem.
What should I do if I get this AZ-104 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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