You are planning the IP addressing schema for a new Azure Virtual Network named `VNet-Prod… — Microsoft Azure Administrator (AZ-104)

You are planning the IP addressing schema for a new Azure Virtual Network named `VNet-Prod` that has an allocated address space of $172.16.0.0/21$ . The network must host the following resources:
- A VPN Gateway, which requires a dedicated subnet named `GatewaySubnet` (minimum recommended size is $/27$ ).
- An Azure Bastion host, which requires a dedicated subnet named `AzureBastionSubnet`.
- A web application tier named `Subnet-Web` that must support at least $124$ concurrent virtual machines.
- An application tier named `Subnet-App` that must support at least $251$ concurrent virtual machines.

You propose the following subnet configuration:
- `AzureBastionSubnet`: $172.16.0.0/26$
- `GatewaySubnet`: $172.16.0.64/27$
- `Subnet-Web`: $172.16.0.128/25$
- `Subnet-App`: $172.16.1.0/24$

Determine if the following statement is true or false: The proposed configuration is valid, meets all resource requirements, and avoids any overlapping address spaces.

Answer: Answer

Answer

The statement is false because the proposed subnet block for the web tier does not provide enough usable IP addresses to support the minimum number of virtual machines.

The proposed statement is false because the web tier subnet configured with the

/25

prefix (

172.16.0.128/25

) provides only

123

usable IP addresses (

128 - 5

), which does not meet the requirement to support at least

124

virtual machines.

Step-by-Step Solution

Calculate the minimum number of IP addresses required for each subnet by adding the host requirements to the

5

IP addresses reserved by Azure in every subnet.

`Subnet-Web` requires

124 + 5 = 129

total IP addresses. `Subnet-App` requires

251 + 5 = 256

total IP addresses.

Azure reserves the first four and the last IP address of every subnet, making them unavailable for host allocation.

Evaluate the CIDR block sizes for the proposed configuration to determine their total and usable capacities.

- `AzureBastionSubnet` (

172.16.0.0/26

) provides

64

IPs (valid for Bastion).
- `GatewaySubnet` (

172.16.0.64/27

) provides

32

IPs (valid for VPN Gateway).
- `Subnet-Web` (

172.16.0.128/25

) provides

128

total IPs, resulting in

128 - 5 = 123

usable IPs.
- `Subnet-App` (

172.16.1.0/24

) provides

256

total IPs, resulting in

256 - 5 = 251

usable IPs.

This step determines whether the proposed CIDR scopes can accommodate the minimum required host counts.

Verify subnet boundary alignments and ensure no overlapping IP address ranges exist.

The subnets do not overlap, and all proposed ranges reside within the

172.16.0.0/21

virtual network range (

172.16.0.0

172.16.7.255

). However, because `Subnet-Web` only provides

123

usable IPs and requires

124

, the overall configuration is invalid.

Even though there are no overlaps, all individual subnet requirements must be satisfied for the proposed architecture to be valid.

Key Concept

Azure subnet IP address reservation rules and prefix calculation constraints.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics