Does Azure make networking modifications when shutting down a VM because of an open firewall rule?

Question

Does Azure make networking modifications when shutting down a VM because of an open firewall rule?

Wayne Clark 1

I recently created an Ubuntu VM and installed and ran Wireguard server. It was all working until I left an Azure firewall rule open (source = any). My VM was shut down by Azure as a result, and when I brought it back up, fixed the FW rule, and tried to start my WG service, it refuses to start. Status shows it as "exited". I'm new to Ubuntu, so not sure where to look for the issue. I when through the same setup steps when I installed the WG service. Are there other changes that Azure makes when shutting down a VM that need to be updated perhaps?

suvasara-MSFT 10,166 Reputation points Moderator

2020-12-09T05:25:23.78+00:00

@Wayne Clark , Are you opening VM ports using UFW program? If so, then need to check whether the rules are been reversed on a VM shutdown. There should not be any issue with a VM shutdown or VM restart.
Wayne Clark 1 Reputation point

2020-12-09T17:22:34.457+00:00

Thanks Suvasara,

Not sure I understand, so if you could provide a bit more detail, that would help. Why would rules be "reversed" on a VM shutdown? Not sure what "reversed" means in this context... turning rules from allow to deny you mean? I think what I will do is take some snapshots of my ip tables and AFW rules, then delete the resource, rebuild it, and compare the ip tables and rules to see what is going on. Part of this exercise is to script the creation of the VPN service, so this will give me another test run for my scripts ;0).
Wayne Clark 1 Reputation point

2020-12-09T22:10:48.507+00:00

FYI, turns out is was not being shut down due to FW rules... but rather this: https://stackoverflow.com/questions/55288334/vm-classic-keeps-shutting-down-and-deallocating-itself. So, I think I need to research the settings I make for WG and make sure they are durable across re-boots. Any advice WRT this appreciated!