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Difficulty: MediumCreate and Configure Virtual Networks and Subnets

An organization has a virtual network configured with the address space 172.24.0.0/21172.24.0.0/21. An administrator needs to create a new subnet named `snet-appdev` to deploy exactly 2828 virtual machine instances. The administrator proposes assigning the address prefix 172.24.2.0/27172.24.2.0/27 to the new subnet. Does the proposed address prefix provide a sufficient number of usable IP addresses for the virtual machine instances?

Answer: Answer

Answer

No, the proposed address prefix does not provide a sufficient number of usable IP addresses.
The correct response is false because a /27/27 subnet provides 3232 total IP addresses. Azure reserves 55 IP addresses in each subnet (the first four and the last one). This leaves 2727 usable IP addresses (32−5=2732 - 5 = 27). Since 2828 virtual machine instances need to be deployed, the subnet is too small.

Step-by-Step Solution

1
Determine the total number of IP addresses in the proposed subnet prefix.
A /27/27 subnet prefix contains 232−27=322^{32-27} = 32 total IP addresses.
To calculate the base pool of IP addresses before reservations.
2
Subtract the Azure-reserved IP addresses from the total.
There are 32−5=2732 - 5 = 27 usable IP addresses.
Azure reserves the first four IP addresses and the last IP address of every subnet for internal services, routing, and DNS.
3
Compare the usable IP addresses with the required host count.
The subnet provides 2727 usable IP addresses, which is less than the required 2828 virtual machines.
To verify if the proposed range satisfies the host deployment constraints.

Key Concept

Azure-specific subnet constraints including the five reserved IP addresses.
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Topics

Create and Configure Virtual Networks and Subnets