It is available in Live CD or Compact Flash image and you can configure and administer via a web browser.
Anyone with a little familiarity with such hardware can reuse an old PC and turn it into the router (all at no cost!).
Among the many features provided by this tool I found very interesting:
1) the Net Balancer that can operate in two modes a) "Load Balancing and Failover" where the requests for access to the Internet are balanced automatically and in proportion to the weight of each gateway and, in the event of failure of one gateway, this is excluded from the Automatic
balance b) "Failover" only one link is active at a time (the one with highest weight among those who are not in the state of Fault). The others are in the state of Spare, ready to attend in case of interruption of the active link.
2) the Virtual Private Network (LAN-to-LAN), the ability to create links encrypted (permanent and automatic) over networks points that are geographically dispersed (using Internet).
I use a Zeroshell with two ADSL balancedconnections with different ISPs and different speeds.
On two other Zeroshell I use a VPN LAN-to-LAN to easily connect a company that has two offices located in different cities using their ADSL connection.
Here are some of the most important features: