General preparation steps
A VPN configuration defines relationships between the VPN devices and the private hosts, servers, or networks making up the VPN. Configuring a VPN involves gathering and recording the following information. You will need this information to configure the VPN.
• The private IP addresses of participating hosts, servers, and/or networks. These IP addresses represent the source addresses of traffic that is permitted to pass through the VPN. A IP source address can be an individual IP address, an address range, or a subnet address.
• The public IP addresses of the VPN end-point interfaces. The VPN devices establish tunnels with each other through these interfaces.
• The private IP addresses associated with the VPN-device interfaces to the private networks. Computers on the private networks behind the VPN gateways will connect to their VPN gateways through these interfaces.