Question

Difficulty: MediumCreate and Configure Virtual Networks and Subnets

You are configuring a virtual network named `vnet-iot-ingress` in an Azure subscription. The virtual network is assigned the address space of $10.120.0.0/22$ . You need to create a subnet named `snet-devices` that will host 60 virtual machines. You assign the address range $10.120.2.128/26$ to the `snet-devices` subnet. Is the statement that the `snet-devices` subnet has a sufficient number of usable IP addresses to support the 60 virtual machines true?

Answer: Answer

Answer

The statement is false because the subnet only provides 59 usable IP addresses due to Azure reserving 5 IP addresses, which is insufficient for the 60 virtual machines.

The correct evaluation is false because Azure's specific reservation of 5 IP addresses per subnet reduces the usable IP count of a /26 subnet from 64 to 59, which is one address short of the required 60.

Step-by-Step Solution

1

Calculate the total number of IP addresses in a /26 subnet.

A /26 subnet has

2^{32 - 26} = 2^6 = 64

total IP addresses.

To determine the maximum number of potential addresses before applying reservations.

2

Subtract the Azure-reserved IP addresses from the total number of addresses.

64 - 5 = 59

usable IP addresses.

Azure reserves 5 IP addresses in every subnet: the first four IP addresses (.128, .129, .130, .131) and the last IP address (.191).

3

Compare the number of usable IP addresses to the virtual machine requirement.

59 usable IPs is less than the 60 required virtual machines.

To evaluate if the configuration meets the deployment requirement.

Key Concept

Azure Virtual Network Subnet IP Reservations

Estimated Time:1m 30s

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Topics

Create and Configure Virtual Networks and Subnets