An administrator is configuring a new virtual network named `vnet-prod` in an Azure subscr… — Microsoft Azure Administrator (AZ-104)

An administrator is configuring a new virtual network named `vnet-prod` in an Azure subscription. The virtual network is assigned the address space $192.168.1.0/24$ .

The administrator needs to deploy the following components:
- A Route-based VPN Gateway that supports future coexistence with ExpressRoute.
- An Azure Bastion host using the minimum supported subnet size.
- An application tier named `subnet-app` that must host at least 60 virtual machines.

Which subnet configuration meets all of these requirements while minimizing IP address waste?

A
subnet-app: $192.168.1.0/26$ ; AzureBastionSubnet: $192.168.1.64/26$ ; GatewaySubnet: $192.168.1.128/27$
subnet-app: $192.168.1.0/25$ ; AzureBastionSubnet: $192.168.1.128/26$ ; GatewaySubnet: $192.168.1.192/27$ Answer
C
subnet-app: $192.168.1.0/25$ ; AzureBastionSubnet: $192.168.1.128/27$ ; GatewaySubnet: $192.168.1.160/27$
D
subnet-app: $192.168.1.0/25$ ; AzureBastionSubnet: $192.168.1.128/26$ ; GatewaySubnet: $192.168.1.192/30$

Answer

The configuration with subnet-app as

192.168.1.0/25

, AzureBastionSubnet as

192.168.1.128/26

, and GatewaySubnet as

192.168.1.192/27

The correct configuration allocates a /25 prefix for the application subnet to support 60 virtual machines (providing 123 usable IP addresses after accounting for the 5 reserved addresses), a /26 prefix for AzureBastionSubnet (the minimum size required for Azure Bastion), and a /27 prefix for GatewaySubnet (the minimum size required for VPN Gateway and ExpressRoute coexistence). All subnets fit within the 192.168.1.0/24 address space without overlapping.

Step-by-Step Solution

Determine the required size for the application subnet.

A /25 subnet is required.

To host 60 virtual machines, we need at least 60 usable IP addresses. In standard IP networks, a /26 subnet (64 addresses) would work since it has 62 usable addresses. However, Azure reserves 5 IP addresses per subnet (first 4 and last 1 address). A /26 subnet in Azure only has 59 usable IP addresses (

64 - 5 = 59

), which is insufficient. Therefore, a /25 subnet (

128 - 5 = 123

usable addresses) is required.

Determine the required size for the Azure Bastion subnet.

A /26 subnet is required.

Azure Bastion requires a subnet named AzureBastionSubnet with a minimum prefix size of /26.

Determine the required size for the GatewaySubnet.

A /27 subnet is required.

For VPN Gateway and ExpressRoute coexistence, Azure requires a GatewaySubnet with a prefix size of /27 or larger.

Verify subnet boundary alignment and overlap within the 192.168.1.0/24 address space.

All subnets fit sequentially: subnet-app (192.168.1.0 to 192.168.1.127), AzureBastionSubnet (192.168.1.128 to 192.168.1.191), and GatewaySubnet (192.168.1.192 to 192.168.1.223).

The subnets must align with CIDR block boundaries. The /25 block must start at 0 or 128. The /26 block must start at a multiple of 64 (0, 64, 128, 192). The /27 block must start at a multiple of 32 (0, 32, 64, 96, 128, 160, 192, 224). This layout avoids overlapping and minimizes space.

Key Concept

Azure subnet sizing constraints including reserved IP addresses and requirements for specific services like Azure Bastion and GatewaySubnet.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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