To onboard a server to Azure Arc, you will need to install the Azure Connected Machine Agent, which communicates outbound securely to Azure Arc over TCP port 443 with a couple of service tags and URLs. To check if the network connection for the Azure Arc Connected Machine Agent is blocked, I put together a couple of commands you can run on your machine. These commands allow you to see if the machine can connect to the specific URLs needed for the Azure Connected Machine agent. You can find the up-to-date documentation for the Azure Connected Machine agent on Microsoft