If you are learning AZ-303, and changes are you will encounter the same error when following the Exercise – Create an NVA and virtual machines (unit 5-7) by the time i’m writing this document (11/07/2021).

I have reported this issue with the Exercise, but it might not be fixed anytime soon.  so just in case you need help with completing your Exercise. I tried to document the issue in Exercise, and the solution how you can resolve them.


What’s the issue

The requirement is to create vnent with 3 subnets



in Unit 5 of 7 , it provides the code as below for creating the 1st VM in subnet dmzsubnet.  The problem with the below command is it doesn’t specify the subnet address prefix, therefor by default, it will be  You won’t yet get any error at this stage, as it’s the first subnet. Although it’s already not matching the design.


You will then get an error when you are following the Exercise along the way in Unit 6 of 7 with below code.  you can’t create subnet with conflict address.


What’s the Solution

Adding  “--subnet-address-prefix” when you create VMs. There are more optional parameters for creating VM you can find here.

here is the example code you can use

az vm create \
     --resource-group learn-4bd2e66c-7759-446c-9a49-071b27237a7f \
     --name public \
     --vnet-name vnet \
     --subnet publicsubnet \
     --image UbuntuLTS \
     --admin-username azureuser \
     --no-wait \
     --custom-data cloud-init.txt \
     --subnet-address-prefix \
     --admin-password <changeme123>