The answer is to change the spoke VNet address space so it does not overlap the hub. This is correct because VNet peering requires that the address spaces of peered virtual networks be unique and non-overlapping; overlapping address spaces create routing conflicts where Azure cannot differentiate between resources in the hub and spoke that share the same IP range, breaking connectivity. On the AZ-104 exam, this scenario tests your understanding of VNet peering prerequisites and is a common trap where candidates mistakenly try to adjust routes or subnets instead of fixing the root cause—overlapping CIDR blocks. A reliable memory tip is "Peering needs separation: no overlap, no conflict."
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.
Exhibit
HubVNet address space: 10.40.0.0/16
SpokeVNet address space: 10.40.1.0/24
Peering status: Failed
Error: Virtual network address space overlaps with another peered network
Based on the exhibit, the administrator cannot create VNet peering between the hub and spoke networks. What should be changed?
HubVNet address space: 10.40.0.0/16
SpokeVNet address space: 10.40.1.0/24
Peering status: Failed
Error: Virtual network address space overlaps with another peered network
A
Change the hub VNet to use a smaller subnet mask.
Why wrong: Peering problems caused by overlapping ranges are not fixed by simply resizing the hub network. The overlap must be removed between the two VNet address spaces first.
B
Change the spoke VNet address space so it does not overlap the hub.
This is the correct fix because Azure VNet peering requires non-overlapping IP ranges. The exhibit shows the spoke range sits inside the hub range, which causes the peering attempt to fail. Readdressing the spoke to a unique CIDR block resolves the conflict and allows the peering to be created.
C
Add a route table to the spoke VNet before creating peering.
Why wrong: Route tables control traffic flow after connectivity exists, but they do not solve CIDR overlap during peering creation. The error in the exhibit is about address space conflict, not routing.
D
Enable a service endpoint on both VNets.
Why wrong: Service endpoints extend access to supported Azure services, but they do not affect VNet-to-VNet address space validation. They cannot make overlapping peering ranges acceptable.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the spoke VNet address space so it does not overlap the hub.
VNet peering requires that the address spaces of the peered VNets do not overlap. Overlapping address spaces cause routing conflicts because Azure cannot distinguish between resources in the hub and spoke when IP addresses are identical or within the same CIDR range. Changing the spoke VNet address space to a non-overlapping range resolves this issue and allows peering to be established.
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.
✗
Change the hub VNet to use a smaller subnet mask.
Why it's wrong here
Peering problems caused by overlapping ranges are not fixed by simply resizing the hub network. The overlap must be removed between the two VNet address spaces first.
✓
Change the spoke VNet address space so it does not overlap the hub.
Why this is correct
This is the correct fix because Azure VNet peering requires non-overlapping IP ranges. The exhibit shows the spoke range sits inside the hub range, which causes the peering attempt to fail. Readdressing the spoke to a unique CIDR block resolves the conflict and allows the peering to be created.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a route table to the spoke VNet before creating peering.
Why it's wrong here
Route tables control traffic flow after connectivity exists, but they do not solve CIDR overlap during peering creation. The error in the exhibit is about address space conflict, not routing.
✗
Enable a service endpoint on both VNets.
Why it's wrong here
Service endpoints extend access to supported Azure services, but they do not affect VNet-to-VNet address space validation. They cannot make overlapping peering ranges acceptable.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse VNet peering prerequisites with routing or security features, mistakenly thinking route tables or service endpoints are required, when the core requirement is non-overlapping address spaces.
Detailed technical explanation
How to think about this question
VNet peering uses the Azure backbone to connect two VNets, and Azure checks for address space overlap during the peering creation process. If overlapping CIDR blocks are detected (e.g., both VNets use 10.0.0.0/16), the peering request fails with an error. In real-world hub-and-spoke designs, overlapping address spaces are a common misconfiguration that must be avoided by planning non-overlapping private IP ranges (e.g., RFC 1918) before deployment.
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: Change the spoke VNet address space so it does not overlap the hub. — VNet peering requires that the address spaces of the peered VNets do not overlap. Overlapping address spaces cause routing conflicts because Azure cannot distinguish between resources in the hub and spoke when IP addresses are identical or within the same CIDR range. Changing the spoke VNet address space to a non-overlapping range resolves this issue and allows peering to be established.
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.
About these practice questions
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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. Based on the exhibit, an administrator is trying to peer two VNets so workloads can communicate privately. The peering creation fails. What should the administrator do first?
medium
A.Create a user-defined route in VNet-Prod to force traffic through a firewall.
✓ B.Readdress one of the VNets so the address spaces no longer overlap.
C.Enable gateway transit on both VNets and retry the peering.
D.Add an NSG rule that allows traffic from the other VNet.
Why B: VNet peering requires that the address spaces of the two virtual networks do not overlap. Overlapping address spaces cause routing conflicts and prevent the peering from being established. The administrator must readdress one of the VNets so their IP ranges are unique before retrying the peering.
Variation 2. Based on the exhibit, what should the administrator do so the hub and spoke can be peered successfully?
easy
A.Keep the current ranges and enable gateway transit on the peering.
✓ B.Change the spoke VNet to a non-overlapping address space.
C.Add another subnet inside the spoke VNet and reuse the current address space.
D.Create a network security group on the spoke subnet before peering.
Why B: VNet peering requires that the address spaces of the peered VNets do not overlap. Overlapping IP ranges cause routing conflicts and prevent successful peering. Changing the spoke VNet to a non-overlapping address space resolves this issue and allows the peering to be established.
Last reviewed: Jun 11, 2026
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