AZ-305 Design infrastructure solutions Practice Question
A company has multiple Azure virtual networks (VNets) in different regions. They want to connect all VNets to each other securely over the Microsoft backbone network, and also connect to their on-premises data center via ExpressRoute. What is the simplest Azure solution to enable connectivity between all VNets and on-premises?
⚠ Common exam trap
Many candidates assume VNet peering or a single ExpressRoute circuit can provide transitive connectivity between all VNets and on-premises, but they forget that VNet peering is non-transitive and ExpressRoute alone does not route between VNets without additional gateways or a hub.
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
✓
Azure Virtual WAN
Azure Virtual WAN is the simplest solution because it provides a hub-and-spoke architecture that automatically connects all VNets and on-premises sites over the Microsoft backbone network. It natively integrates ExpressRoute and VPN gateways into a single managed service, eliminating the need to manually configure multiple peering or gateway connections.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Azure Virtual WAN
Why this is correct
Azure Virtual WAN is a managed hub-and-spoke service built on the Microsoft global backbone. Each regional Virtual Hub automatically routes traffic between all connected VNets and branch sites (VPN or ExpressRoute) with transitive any-to-any connectivity, so a spoke VNet only needs to connect to its regional hub rather than peer directly with every other VNet. This design makes it the preferred solution when multiple VNets in different regions must communicate while also integrating on-premises connectivity without manual route management.
- ✗
VNet peering
Why it's wrong here
VNet peering creates a direct, non-transitive connection between exactly two VNets; the peered VNets can communicate, but a third VNet cannot use that peering as a hop to reach the other side. Connecting several VNets in different regions requires an O(n²) mesh of peerings, and each new VNet increases configuration and route-table complexity. It also lacks native integration with ExpressRoute or VPN sites as a managed hub, so while it is a fundamental building block, it is not a WAN solution.
- ✗
ExpressRoute
Why it's wrong here
ExpressRoute provides a dedicated private Layer 3 connection from on-premises to Azure, but it does not directly interconnect multiple VNets. For one VNet to reach another over an ExpressRoute circuit, you still need a VNet gateway, a hub VNet, and VNet peering or route-server route propagation, and the routing is not automatically transitive across many VNets and regions. ExpressRoute solves the on-premises-to-Azure connection, not the inter-VNet connectivity requirement described in the question.
- ✗
VPN Gateway
Why it's wrong here
A VPN Gateway terminates point-to-point IPsec tunnels on a single VNet or between two VNet gateways (VNet-to-VNet), but the path is non-transitive: a third VNet or another on-premises site cannot automatically route through that gateway unless you manually configure additional tunnels or complex route tables. Each VNet that requires VPN connectivity needs its own gateway, so scaling this across multiple regional VNets becomes operationally heavy and error-prone. It is not a centrally managed WAN and lacks the automatic transitive routing that Azure Virtual WAN provides.
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