The answer is 10.42.0.0/24 because it provides 256 total IP addresses (251 usable), comfortably supporting the required 120 endpoints with room for growth, while avoiding overlap with the hub VNet’s 10.40.0.0/16 and the on-premises network’s 10.41.0.0/16. This is a core principle of Azure VNet address space selection: when peering spoke VNets to a hub, you must ensure no IP address overlap exists between the spoke, hub, or any connected on-premises network, or peering will fail. On the AZ-104 exam, this scenario tests your ability to choose a non-overlapping CIDR block that balances current needs with future expansion—a common trap is picking a /16 or /24 that conflicts with the hub or on-premises range. Remember the memory tip: “Keep your spokes in a separate subnet of the same /16 family, but never duplicate the hub or on-prem octet.”
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 is creating a new spoke virtual network that will be peered to an existing hub VNet. The hub uses 10.40.0.0/16, and an on-premises network already uses 10.41.0.0/16. The spoke must support about 120 endpoints now and should allow room for growth. Which address space should you assign to the new spoke VNet?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
10.42.0.0/24
Option B (10.42.0.0/24) is correct because it provides 256 IP addresses (251 usable) for the spoke, which exceeds the requirement of ~120 endpoints with room for growth, and it does not overlap with the hub VNet (10.40.0.0/16) or the on-premises network (10.41.0.0/16). This ensures successful VNet peering without IP address conflicts.
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.
✗
10.40.64.0/25
Why it's wrong here
This range is too small for 120 endpoints plus future growth, and it is carved from the hub's existing address space.
✓
10.42.0.0/24
Why this is correct
This is a non-overlapping private range that is large enough for the current requirement and leaves room for adding more subnets later.
Related concept
Read the scenario before looking for a memorised answer.
✗
10.41.128.0/24
Why it's wrong here
This would conflict with the on-premises network range and would create routing problems during connectivity setup.
✗
192.168.10.0/26
Why it's wrong here
This is a valid private range, but it is too small for the stated endpoint count and expected growth.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often overlook the on-premises address space (10.41.0.0/16) and mistakenly choose an overlapping range like 10.41.128.0/24, assuming only the hub VNet's address space must be avoided.
Detailed technical explanation
How to think about this question
VNet peering requires non-overlapping address spaces to enable direct routing between virtual networks; overlapping CIDR blocks cause routing conflicts and peering failures. Azure reserves the first four and last IP addresses in each subnet for protocol operations (e.g., network, gateway, Azure DNS, and broadcast), so a /24 subnet yields 251 usable addresses. In real-world scenarios, choosing a non-overlapping address space like 10.42.0.0/24 also avoids future complications when adding VPN gateways or ExpressRoute circuits that require unique address ranges.
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: 10.42.0.0/24 — Option B (10.42.0.0/24) is correct because it provides 256 IP addresses (251 usable) for the spoke, which exceeds the requirement of ~120 endpoints with room for growth, and it does not overlap with the hub VNet (10.40.0.0/16) or the on-premises network (10.41.0.0/16). This ensures successful VNet peering without IP address conflicts.
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
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 →
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 wants to peer a new spoke virtual network to an existing hub VNet. The hub uses 10.40.0.0/16, and the new spoke was created with 10.40.128.0/17 because that range seemed available in the branch office plan. Peering creation fails. What should the administrator do?
medium
A.Add a second address prefix to the spoke VNet and keep the overlapping range.
✓ B.Change the spoke VNet to a non-overlapping address space before peering.
C.Enable gateway transit on the hub VNet before retrying peering.
D.Create custom DNS records for the spoke VNet so the address ranges no longer conflict.
Why B: VNet peering requires that the address spaces of the peered virtual networks do not overlap. The hub uses 10.40.0.0/16, and the spoke uses 10.40.128.0/17, which is a subset of the hub’s range. Azure blocks peering when there is any overlap to prevent routing conflicts. The correct fix is to change the spoke VNet to a non-overlapping address space, such as a different RFC 1918 range like 10.1.0.0/16, before attempting to peer.
Variation 2. A company wants to peer a new spoke virtual network with an existing hub VNet. The hub uses 10.20.0.0/16. The spoke was created with 10.20.1.0/24 because that range was still available in the IPAM spreadsheet. VNet peering creation fails. What should the administrator do first?
medium
A.Enable gateway transit on the hub and retry the peering.
B.Add a route table to the spoke subnet so the networks can communicate.
✓ C.Change the spoke VNet address space to a non-overlapping range, then recreate or update peering.
D.Configure a custom DNS server in the spoke to translate the overlapping range.
Why C: VNet peering in Azure requires that the address spaces of the peered virtual networks do not overlap. The hub uses 10.20.0.0/16, and the spoke uses 10.20.1.0/24, which is a subset of the hub's range. This overlap causes the peering creation to fail. The administrator must first change the spoke's address space to a non-overlapping range (e.g., 10.21.0.0/24) and then recreate or update the peering.
Variation 3. A company needs to peer VNet-Prod, which uses 10.30.0.0/16, with VNet-Shared, which uses 10.30.64.0/18. The peering creation fails with an address-space overlap error. The team can renumber the shared environment, but they do not want to change any addresses in VNet-Prod. What should the administrator do before retrying the peering?
medium
A.Add an NSG that allows traffic between the two VNets.
✓ B.Reconfigure VNet-Shared to use a non-overlapping address range, then recreate its subnets and migrate workloads.
C.Rename VNet-Shared so Azure treats it as a different network.
D.Enable gateway transit on both VNets so Azure can route around the overlap.
Why B: VNet peering requires that the address spaces of the two VNets do not overlap. VNet-Prod uses 10.30.0.0/16, which includes the range 10.30.64.0/18 used by VNet-Shared, causing the overlap error. The only way to resolve this without changing VNet-Prod is to reconfigure VNet-Shared to use a non-overlapping address range, which involves deleting and recreating its subnets and migrating workloads, as stated in option B.
Variation 4. A company plans a new spoke virtual network that must be peered to an existing hub VNet using 10.0.0.0/16. The spoke will need two subnets: one sized for about 120 VMs and another for about 40 VMs. The new address space must not overlap the hub or the on-premises range 10.1.0.0/16. Which VNet address space is the best choice?
medium
A.10.0.1.0/24
B.10.1.0.0/22
✓ C.10.2.0.0/22
D.10.0.0.0/24
Why C: Option C (10.2.0.0/22) is correct because it provides a non-overlapping address space with the hub VNet (10.0.0.0/16) and on-premises (10.1.0.0/16). The /22 prefix offers 1024 IP addresses, which is sufficient for subnets supporting 120 VMs and 40 VMs, while avoiding any overlap with the existing ranges.
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