This is one I use regularly, so thought it might come in handy for you..
Assumption here is you are connected via PowerShell to your intended subscription..
A few key points:
The VM will need to be stopped to execute Check the Azure VM sizing to see how many NICs you can attach I have a pre-created Network Interface with my desired settings #Using OGV to target your objects $RG = Get-AzureRmResourceGroup | ogv -PassThru $NIC = Get-AzureRmNetworkInterface | ogv -PassThru $VM = Get-AzureRmVm | ogv -PassThru #The actual adding of the NIC to the VM $VM = Add-AzureRmVMNetworkInterface -VM $VM -Id $NIC.
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