Running extension for VMSS using ARM Template

[abjai]

Hi,

What is the recommended way of running extension using ARM template without updating any other property of VMSS? As part of setting up the VMSS for the first time, we are passing network profile. But based on some conditions, we only want to run extension using ARM template without updating the other properties and we don't want to do any GET operation to create the same template?

We tried to run the template again removing the network profile property and could see that the extensions ran keeping the network profile intact. As per my understanding, if we are updating VMSS without passing some properties, those properties remain same and only the passed properties will be updated. Is this understanding correct?