You are designing the subnet configuration for an Azure virtual network named `vnet-prod` … — Microsoft Azure Administrator (AZ-104)

You are designing the subnet configuration for an Azure virtual network named `vnet-prod` that has an address space of $172.16.0.0/22$ . The virtual network currently contains a single subnet named `snet-web` with an address range of $172.16.0.0/24$ . You need to add two new subnets to `vnet-prod` to support the following requirements:
1. Deploy an Azure Bastion host to secure management access to virtual machines.
2. Deploy a Virtual Network Gateway to establish a hybrid connection with an on-premises datacenter.
You want to allocate the minimum recommended address space for both subnets while ensuring they are fully functional and compliant with Microsoft best practices. Which of the following configurations should you implement?

Create AzureBastionSubnet with the range $172.16.1.0/26$ and GatewaySubnet with the range $172.16.1.64/27$ .Answer
B
Create snet-bastion with the range $172.16.1.0/27$ and GatewaySubnet with the range $172.16.1.32/27$ .
C
Create AzureBastionSubnet with the range $172.16.1.0/26$ and GatewaySubnet with the range $172.16.1.64/27$ . To enable name resolution, you must create a Private DNS Zone and link it directly to AzureBastionSubnet and GatewaySubnet.
D
Create AzureBastionSubnet with the range $172.16.1.0/26$ and GatewaySubnet with the range $172.16.1.64/27$ . To route all outbound traffic from snet-web through the VPN gateway, you must associate a route table to snet-web with a route of $0.0.0.0/0$ and a next hop type of Virtual Appliance.

Answer

Create AzureBastionSubnet with the range

172.16.1.0/26

and GatewaySubnet with the range

172.16.1.64/27

The correct configuration uses the range

172.16.1.0/26

for a subnet named exactly AzureBastionSubnet and the range

172.16.1.64/27

for a subnet named exactly GatewaySubnet. This fulfills the naming requirements, respects the minimum subnet size requirement of /26 for Azure Bastion, and adheres to Microsoft's recommended /27 or larger subnet size for the GatewaySubnet.

Step-by-Step Solution

Determine the available remaining IP address space in the virtual network.

The virtual network has an address space of

172.16.0.0/22

(which spans

172.16.0.0

172.16.3.255

). The existing subnet snet-web uses

172.16.0.0/24

(

172.16.0.0

172.16.0.255

). The remaining unallocated space is

172.16.1.0

172.16.3.255

This identifies where the new subnets can be positioned without overlapping with existing resources.

Identify the minimum requirements for the Azure Bastion subnet.

The subnet must be named exactly AzureBastionSubnet and have a prefix of /26 or larger. A /26 subnet provides 64 total IP addresses, leaving 59 usable addresses after Azure reserves the first 4 and the last 1 address.

Azure Bastion will fail to deploy if the subnet name is incorrect or if the prefix size is smaller than /26 (such as /27).

Identify the recommended requirements for the Virtual Network Gateway subnet.

The subnet must be named exactly GatewaySubnet. While a /29 subnet is the absolute minimum size supported, Microsoft strongly recommends a prefix of /27 or larger to support future growth and routing capabilities.

Using the recommended size prevents IP exhaustion when adding new gateway types or configuring coexistence scenarios.

Align the ranges sequentially inside the unallocated space.

Assign

172.16.1.0/26

(occupies

172.16.1.0

172.16.1.63

) to AzureBastionSubnet. The next contiguous block starting at

172.16.1.64

with a /27 prefix (occupies

172.16.1.64

172.16.1.95

) is assigned to GatewaySubnet.

This allocates the minimum recommended ranges sequentially, leaving

172.16.1.96

172.16.3.255

free for future workloads.

Key Concept

Azure virtual network planning requires meeting strict name and prefix constraints for specialized service subnets, specifically a minimum of /26 for AzureBastionSubnet and a recommended minimum of /27 for GatewaySubnet.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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