Networking Policy
A Virtuozzo Server server should be isolated from the Internet. It should only have an internal IP address and firewall policies applied to it. To still be able to update the license and install updates from Virtuozzo Server repositories, you can set up a proxy server and follow the instructions in Using a Proxy Server to Activate Licenses and Using a Proxy Server to Install Updates.
Virtuozzo Server enables Linux kernel firewall during installation. To see the list of ports opened by default, refer to Configuring Server Ports.