Reference Manual for th e Pr oSafe VPN F irewall 25 with 4 Gigabi t LAN a nd Dual WAN Por ts
Virtual Private Networking D-7
202-10085-01, March 2005

VPN Process Overview

Even though IPSec is standards-based, each vendor has its own set of terms and procedures for
implementing the standard. Because of these differences, it may be a good idea to review some of
the terms and the generic processes for connecting two gateways before diving into to the
specifics.

Network Interfaces and Addresses

The VPN gateway is aptly named because it functions as a “gatekeeper” for each of the computers
connected on the Local Area Network behind it.
In most cases, each Gateway will have a “public” facing address (WAN side) and a “private”
facing address (LAN side). These addresses are referred to as the “network interface” in
documentation regarding the construction of VPN communication. Please note that the addresses
used in the example.
Interface Addressing
This TechNote uses example addresses provided the VPN Consortium. It is important to
understand that you will be using addresses specific to the devices that you are attempting to
connect via IPSec VPN.
Figure 9-7: VPNC Example Network Interface Addressing
Gateway A
22.23.24.25
14.15.16.17
10.5.6.0/24 172.23.9.0/24
172.23.9.110.5.6.1
WAN IP WAN IP LAN IPLAN IP
Gateway B
VPNC Example
Network Interface Addressing