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Difficulty: HardCreate and Configure Virtual Networks and Subnets

Your company has an Azure subscription containing a resource group named RG1. You plan to deploy a new virtual network named VNet1 in RG1. VNet1 will use the 10.1.0.0/1610.1.0.0/16 address space.

You need to configure subnets within VNet1 to support the following requirements:
- Subnet-Web: Must support at least 250250 virtual machines.
- Azure Bastion: Must be deployed to secure management access.
- VPN Gateway: Must be deployed to support hybrid connectivity.

To conserve IP addresses for future subnets, you must minimize the address space allocated to each subnet.

Which subnet configuration should you use?

  1. Subnet-Web: 10.1.0.0/24; AzureBastionSubnet: 10.1.1.0/26; GatewaySubnet: 10.1.1.64/29Answer
  2. B
    Subnet-Web: 10.1.0.0/25; AzureBastionSubnet: 10.1.0.128/26; GatewaySubnet: 10.1.0.192/29
  3. C
    Subnet-Web: 10.1.0.0/24; AzureBastionSubnet: 10.1.1.0/27; GatewaySubnet: 10.1.1.32/29
  4. D
    Subnet-Web: 10.1.0.0/24; AzureBastionSubnet: 10.1.1.0/26; GatewaySubnet: 10.1.1.64/30

Answer

Subnet-Web: 10.1.0.0/24; AzureBastionSubnet: 10.1.1.0/26; GatewaySubnet: 10.1.1.64/29
The subnet configuration with Subnet-Web as 10.1.0.0/24, AzureBastionSubnet as 10.1.1.0/26, and GatewaySubnet as 10.1.1.64/29 is correct because it satisfies all size and host requirements without any overlapping ranges. The Web subnet provides 251251 usable IP addresses (256−5256 - 5 reserved) which meets the 250250 host requirement. The Bastion subnet meets the /26/26 minimum requirement, and the VPN Gateway subnet meets the /29/29 minimum requirement.

Step-by-Step Solution

1
Determine the minimum prefix size for Subnet-Web to support the host count.
A /24/24 prefix is required.
Subnet-Web must support at least 250250 hosts. Azure reserves 55 IP addresses in every subnet (first four and the last one). A /25/25 prefix offers 128−5=123128 - 5 = 123 usable hosts, which is insufficient. A /24/24 prefix offers 256−5=251256 - 5 = 251 usable hosts, satisfying the minimum requirement.
2
Determine the minimum prefix size for Azure Bastion.
A /26/26 prefix is required.
Azure Bastion must be deployed into a dedicated subnet named AzureBastionSubnet. Microsoft requires this subnet to have a prefix of /26/26 or larger.
3
Determine the minimum prefix size for the VPN Gateway.
A /29/29 prefix is required.
The VPN Gateway must be deployed into a dedicated subnet named GatewaySubnet. The minimum supported prefix size for a GatewaySubnet is /29/29.
4
Verify subnet IP ranges for overlaps and select the non-overlapping combination.
Subnet-Web: 10.1.0.0/24, AzureBastionSubnet: 10.1.1.0/26, GatewaySubnet: 10.1.1.64/29.
The range 10.1.0.0/2410.1.0.0/24 spans 10.1.0.010.1.0.0 to 10.1.0.25510.1.0.255. The range 10.1.1.0/2610.1.1.0/26 spans 10.1.1.010.1.1.0 to 10.1.1.6310.1.1.63. The range 10.1.1.64/2910.1.1.64/29 spans 10.1.1.6410.1.1.64 to 10.1.1.7110.1.1.71. These ranges are adjacent and do not overlap.

Key Concept

Azure Subnet sizing requirements and reserved IP addresses
Estimated Time:2m 0s
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Topics

Create and Configure Virtual Networks and Subnets