Exam AZ-700 topic 2 question 66 discussion

I C is correct!! For App gateway V1 subnet of 27 is required and for V2 the recommended is 24 CIDR, however based on the current configuration i.e. whole Address space for the vnet is /24 and fact max we have is 10 App GWY instances deployed at anytime then we can assign /28 CIDR for the address space for the App GWY this allows for 16 IP address of which 5 are reserved for Azure resources and this leaves us with 11 which is about enough for 1 Private Endpoint and 10 App GWY instances as for the Public IP it has nothing to do with private IP unless the App GWY requires private IP in which is not the case here

In the exam 22/03/2025

C is correct, When you use a public endpoint for Azure Application Gateway, the public IP is allocated from the Azure public IP address pool, not from the subnet's IP address range. Thus, the public endpoint does not consume an IP address from the Application Gateway subnet. Calculation Given the above: Reserved by Azure: 5 IPs. Private frontend IP: 1 IP. Instances: 10 IPs (maximum). 5 (reserved)+1 (private IP)+10(instances)=16 IP addresses required To meet this requirement, the smallest subnet that supports at least 16 assignable IPs is a /28 opt E 20 is because you count 1 IP for public endpoint which is not required.

Without even looking at the specifics of the question we know that 5 IPs are used per subnet, and the size of a subnet is a power of 2. Therefore the only possible solution is C: add 5 to any other answer and you don't get a power of 2 :)

Application Gateway uses one private IP address per instance, plus another private IP address if a private frontend IP is configured. https://learn.microsoft.com/en-us/azure/application-gateway/configuration-infrastructure#size-of-the-subnet

Why not 12?