The correct answer is to deploy an Azure Firewall or another Network Virtual Appliance (NVA) in the hub, then configure user-defined routes (UDRs) and IP forwarding. This works because Azure’s default routing does not allow transitive routing through a hub; spoke VNets can reach the hub but not each other. By adding a UDR on each spoke subnet with a next hop pointing to the firewall’s private IP, you force spoke-to-spoke traffic through the hub firewall, enabling centralized inspection. On the AZ-104 exam, this scenario tests your understanding of forced tunneling and hub-and-spoke topology limitations—a common trap is assuming VNet peering alone provides transitive connectivity. Remember the key: peering is non-transitive, so you must explicitly route traffic through the firewall. A helpful mnemonic is “Peering is Point-to-Point, not Pass-Through”—you need UDRs to make the hub a mandatory inspection point.
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 VNet is peered to two spoke VNets. The spokes can reach the hub, but they cannot communicate with each other through the hub. The administrator wants centralized inspection in the hub. What should be deployed and configured?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
An Azure Firewall or other NVA in the hub, plus user-defined routes and forwarding support.
Option A is correct because Azure Firewall or an NVA in the hub can inspect traffic between spokes, but by default, Azure routing does not forward spoke-to-spoke traffic through the hub. To force this traffic through the firewall, you must configure user-defined routes (UDRs) on the spoke subnets with a next hop of the firewall's private IP, and enable IP forwarding on the NVA. This setup enables centralized inspection and transitive routing through the hub.
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.
✓
An Azure Firewall or other NVA in the hub, plus user-defined routes and forwarding support.
Why this is correct
Peering is non-transitive, so centralized inspection requires a forwarder and explicit routing.
Related concept
Read the scenario before looking for a memorised answer.
✗
Only additional peering links between the hub and both spokes.
Why it's wrong here
Extra hub peering already exists and still does not create transitive spoke-to-spoke routing.
✗
A private endpoint in the hub for each spoke subnet.
Why it's wrong here
Private endpoints expose services privately, not general transit between VNets.
✗
A service endpoint on each spoke subnet to the hub VNet.
Why it's wrong here
Service endpoints are for PaaS access and do not provide VNet transit or inspection.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume VNet peering is transitive by default, similar to a router, but Azure explicitly requires UDRs and a forwarding device to enable spoke-to-spoke communication through a hub.
Detailed technical explanation
How to think about this question
Under the hood, Azure VNet peering is non-transitive per RFC 1918 semantics; to achieve transitive routing, you must override the system routes with UDRs that point to the firewall's IP. The firewall must have IP forwarding enabled (on Linux NVAs, net.ipv4.ip_forward=1) and be configured with appropriate DNAT/SNAT rules to inspect and forward traffic. In a real-world scenario, this is commonly used for forced tunneling or east-west traffic inspection, where the hub firewall logs and filters all inter-spoke communication.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-104 question in full detail.
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: An Azure Firewall or other NVA in the hub, plus user-defined routes and forwarding support. — Option A is correct because Azure Firewall or an NVA in the hub can inspect traffic between spokes, but by default, Azure routing does not forward spoke-to-spoke traffic through the hub. To force this traffic through the firewall, you must configure user-defined routes (UDRs) on the spoke subnets with a next hop of the firewall's private IP, and enable IP forwarding on the NVA. This setup enables centralized inspection and transitive routing through the hub.
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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Question Discussion
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