For most of our network internal services (firewall, NAT, VPN, Radius. etc..), we use Zeroshell. Zeroshell is a small open-source Linux distribution for servers and embedded systems which aims to provide network services. Its administration relies on a web-based graphical interface; no shell is needed to administer and configure it. Zeroshell is available as Live CD and CompactFlash images, and VMware virtual machines.

Many thanks to Fulvio Ricciardi the Zeroshell creator and maintainer.