- A
The NVA's private IP address is not reachable from VNet-B
Why wrong: If the NVA were unreachable, traffic would fail, but the question states traffic still flows directly, not that it fails.
- B
VNet peering system routes override user-defined routes
Why wrong: UDRs take precedence over system routes for the specified destination prefix. Peering system routes are overridden by UDRs.
- C
The UDR must be applied to the gateway subnet of VNet-B
Why wrong: The UDR should be applied to the subnet where the source VMs are located, not the gateway subnet. The configuration described is correct in terms of subnet selection.
- D
The NVA network interface does not have IP forwarding enabled
IP forwarding must be enabled on the NVA's NIC for it to forward traffic destined to other IPs. Without it, the NVA will drop the traffic, and the peering path remains active.
Quick Answer
The answer is that the NVA network interface does not have IP forwarding enabled. This is the most likely cause because a network virtual appliance must explicitly be configured to forward packets not destined for its own IP address; without IP forwarding enabled on the NIC, the NVA drops any traffic whose destination is another host, causing the user-defined route to be ignored and traffic to bypass the NVA via the direct VNet peering path. On the Microsoft Azure Security Engineer Associate AZ-500 exam, this scenario tests your understanding of how NVAs function as routers within a hub-and-spoke topology, and it’s a common trap to assume that simply setting a UDR is sufficient—you must also enable IP forwarding on the NVA’s network interface to troubleshoot NVA traffic not forwarding. Remember the memory tip: “If the NVA won’t forward, check the NIC’s IP forwarding switch.”
AZ-500 Secure networking Practice Question
This AZ-500 practice question tests your understanding of secure networking. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 company has two Azure virtual networks, VNet-A (hub) and VNet-B (spoke), connected via VNet peering. They deploy a network virtual appliance (NVA) in a subnet in VNet-A to inspect all traffic between the VNets. They configure a user-defined route (UDR) on the subnet in VNet-B with the destination address space of VNet-A (10.0.0.0/16) and the next hop set to the private IP of the NVA. However, traffic from VNet-B to VNet-A still bypasses the NVA and takes a direct path. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The NVA network interface does not have IP forwarding enabled
Option D is correct because a network virtual appliance (NVA) requires IP forwarding to be enabled on its network interface to forward traffic not destined for itself. Without this setting, the NVA drops packets that arrive with a destination IP other than its own, causing the traffic to bypass the NVA and follow the default VNet peering route. Enabling IP forwarding allows the NVA to act as a router and forward traffic between VNets as specified by the user-defined route.
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.
- ✗
The NVA's private IP address is not reachable from VNet-B
Why it's wrong here
If the NVA were unreachable, traffic would fail, but the question states traffic still flows directly, not that it fails.
- ✗
VNet peering system routes override user-defined routes
Why it's wrong here
UDRs take precedence over system routes for the specified destination prefix. Peering system routes are overridden by UDRs.
- ✗
The UDR must be applied to the gateway subnet of VNet-B
Why it's wrong here
The UDR should be applied to the subnet where the source VMs are located, not the gateway subnet. The configuration described is correct in terms of subnet selection.
- ✓
The NVA network interface does not have IP forwarding enabled
Why this is correct
IP forwarding must be enabled on the NVA's NIC for it to forward traffic destined to other IPs. Without it, the NVA will drop the traffic, and the peering path remains active.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a UDR alone is sufficient to force traffic through an NVA, overlooking the mandatory IP forwarding setting on the NVA's NIC, which is a common misconfiguration in Azure networking.
Detailed technical explanation
How to think about this question
Under the hood, when a VM in VNet-B sends traffic to VNet-A, the UDR directs packets to the NVA's IP. The NVA's network interface must have the 'Enable IP forwarding' property set to true (in Azure Resource Manager, this is a property on the NIC) to allow the OS to process and forward packets not destined for its own IP. Without it, the Azure host drops the packets at the virtual switch level, and the traffic falls back to the default system route for the peering connection. This is distinct from the NVA's own routing table, which must also be configured to forward traffic appropriately.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Secure networking — study guide chapter
Learn the concepts, then practise the questions
- →
Secure networking practice questions
Targeted practice on this topic area only
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FAQ
Questions learners often ask
What does this AZ-500 question test?
Secure networking — This question tests Secure networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The NVA network interface does not have IP forwarding enabled — Option D is correct because a network virtual appliance (NVA) requires IP forwarding to be enabled on its network interface to forward traffic not destined for itself. Without this setting, the NVA drops packets that arrive with a destination IP other than its own, causing the traffic to bypass the NVA and follow the default VNet peering route. Enabling IP forwarding allows the NVA to act as a router and forward traffic between VNets as specified by the user-defined route.
What should I do if I get this AZ-500 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on AZ-500
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 two Azure virtual networks, VNet-A (hub) and VNet-B (spoke), connected via VNet peering. They deployed a network virtual appliance (NVA) in a subnet in VNet-A to inspect all traffic. They configured a user-defined route (UDR) on the subnet in VNet-B that points the VNet-A address space (10.0.0.0/16) to the private IP of the NVA. However, traffic initiated from VNet-B to VNet-A still takes a direct path and bypasses the NVA. What is the most likely cause?
hard- ✓ A.The NVA does not have IP forwarding enabled on its network interface
- B.The UDR on VNet-B must also include a route for the default route (0.0.0.0/0) to force all traffic through the NVA
- C.VNet peering does not support user-defined routes
- D.The NVA must be deployed in the same subnet as the source VMs in VNet-B
Why A: The most likely cause is that the NVA's network interface does not have IP forwarding enabled. In Azure, a network interface must have the 'Enable IP forwarding' setting enabled to allow the NVA to receive traffic not destined to its own IP address and forward it to the intended destination. Without this setting, the NVA drops any traffic that is not addressed to its own IP, so even though the UDR on VNet-B directs traffic to the NVA's private IP, the NVA cannot forward it to VNet-A, and the traffic instead takes the direct VNet peering path.
Variation 2. A company has two Azure virtual networks, VNet-A and VNet-B, connected via VNet peering. They want all traffic between the VNets to be inspected by a network virtual appliance (NVA) deployed in a subnet in VNet-A. They have configured a user-defined route (UDR) on the subnet in VNet-B that points the destination address space of VNet-A to the private IP of the NVA. However, traffic between the VNets is still not passing through the NVA. What is the most likely cause?
hard- A.The UDR is not associated with the subnet in VNet-B.
- ✓ B.The NVA's network interface (NIC) does not have IP forwarding enabled.
- C.The VNet peering connection is not in a 'Connected' state.
- D.The NVA is deployed in the same subnet as the source VMs.
Why B: The most likely cause is that the NVA's network interface (NIC) does not have IP forwarding enabled. Even with a correctly configured UDR on VNet-B pointing traffic to the NVA's private IP, the NVA will drop any traffic not destined for its own IP unless IP forwarding is enabled on its NIC. This setting allows the NVA to accept packets with a destination other than itself and forward them based on its routing table, which is essential for traffic inspection scenarios.
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Last reviewed: Jun 11, 2026
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