You could leave both network adapters connected, allowing for access into both networks at the same time (the default gateway could be pointing to the test lab, stopping internet access). Remember to use the right network interface! right click on the network icon) to do than alter settings. Depending on the Virtualizing software, this is much easier (e.g. When switching networks, you can disable the adapter you don't want to be connected to, and enable the one which you do. The primary/master adapter should be connected into the lab network, and the secondary/salve one can be connected into the other network. However, if you're wanting to do this often, you may want to add another virtual network adapter (as most virtualizing software supports at least four or more adapters). Switching the network mode each time, forces you to double check the network mode, otherwise, the machine (should!) fail to connect to the 'correct' network. This may have to be done manually if there isn't a DHCP service running. As it's a new network, the IP range could be different from the lab network, so the IP address/Gateway/DNS may need to be updated to reflect the new network. You can then switch the network mode of the virtual machine, to connect the network with internet access.Disconnect from the lab network, restore to known state when you're ready to update it, connect to the network with internet access, update the machine, disconnect from the network, replace the snapshot with the updates applied, and connect back to lab network. If the virtualizing software supports snapshots, before attaching the machine to lab network, you can take a snapshot of a 'good clean' known state of the machine (if the machine is trusted not to have any malware on it to begin with!).The ones left on, make sure they do not contain any sensitive information, fully up-to-date, not running any unnecessary services and are using strong credentials.

Turn off/Un plug/Disconnect any other devices that are connected the network and are not essential.With that out of the way, you can help protect yourself with the following tips: VulnHub and its authors, cannot be held responsible. Any damages/loss/risk caused by doing so, is solely your responsibility.

Parallels bridged network