The correct answer is to use Azure ExpressRoute as the primary connection with a site-to-site VPN as backup, and VNet peering for VNet-to-VNet connectivity. This design ensures that if the ExpressRoute circuit fails, the site-to-site VPN automatically provides failover for the hybrid network, maintaining connectivity between on-premises and Azure. VNet peering is then used to enable direct, low-latency communication between multiple VNets without traversing the VPN gateway, which is critical for a redundant architecture. On the AZ-305 exam, this scenario tests your understanding of hybrid network redundancy patterns, often appearing as a distractor where candidates mistakenly choose Azure Firewall or VNet-to-VNet VPN as a backup solution. A common trap is assuming a VPN gateway alone can back up ExpressRoute, but the key is that both connections must terminate on the same gateway for automatic failover. Memory tip: think "ExpressRoute first, VPN second, VNet peering for the rest"—or simply "ER + VPN + Peering = Redundant Hybrid."
AZ-305 Design infrastructure solutions Practice Question
This AZ-305 practice question tests your understanding of design infrastructure solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 large enterprise is designing a hybrid network architecture. The company has an on-premises data center connected to Azure via ExpressRoute. They want to extend their on-premises network to Azure by using a site-to-site VPN as a backup connection. The company has multiple VNets in Azure that need to communicate with each other and with the on-premises network. The solution must be highly available and provide redundancy for the ExpressRoute connection. You need to recommend a network connectivity design. What should you include?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Azure ExpressRoute as the primary connection, and configure a site-to-site VPN as a backup. Use VNet peering for VNet-to-VNet connectivity.
Option D is correct because using ExpressRoute as the primary connection and a site-to-site VPN as backup provides redundancy. VNet peering allows VNets to communicate. Option A is wrong because Azure VPN Gateway alone does not provide ExpressRoute backup. Option B is wrong because Azure Firewall is not a connectivity solution. Option C is wrong because VNet-to-VNet VPN is for VNet communication, not for backup.
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.
✗
Use Azure ExpressRoute as the primary connection, and configure VNet-to-VNet VPN as a backup for ExpressRoute.
Why it's wrong here
VNet-to-VNet VPN is for VNet connectivity, not for backup of ExpressRoute.
✗
Use Azure VPN Gateway to connect the on-premises network to Azure, and use VNet peering for VNet-to-VNet connectivity.
Use Azure ExpressRoute as the primary connection, and use Azure Firewall to inspect traffic between VNets.
Why it's wrong here
Azure Firewall does not provide backup connectivity.
✓
Use Azure ExpressRoute as the primary connection, and configure a site-to-site VPN as a backup. Use VNet peering for VNet-to-VNet connectivity.
Why this is correct
ExpressRoute primary, VPN backup, VNet peering for VNet connectivity.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-305 question in full detail.
Identify which AZ-305 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Design infrastructure solutions — This question tests Design infrastructure solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Azure ExpressRoute as the primary connection, and configure a site-to-site VPN as a backup. Use VNet peering for VNet-to-VNet connectivity. — Option D is correct because using ExpressRoute as the primary connection and a site-to-site VPN as backup provides redundancy. VNet peering allows VNets to communicate. Option A is wrong because Azure VPN Gateway alone does not provide ExpressRoute backup. Option B is wrong because Azure Firewall is not a connectivity solution. Option C is wrong because VNet-to-VNet VPN is for VNet communication, not for backup.
What should I do if I get this AZ-305 question wrong?
Identify which AZ-305 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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