Introduction to VPN instances
VPNs are isolated from one another and from the public network. As shown in Figure 10, VPN A and VPN B separately access the public network through PE devices.
Figure 10: VPN networking diagram
The P device belongs to the public network. The CE devices belong to their respective VPNs. Each CE device serves its own VPN and maintains only one set of forwarding mechanisms.
The PE devices connect to the public network and the VPNs. Each PE device must strictly distinguish the information for different networks, and maintain a separate forwarding mechanism for each network. On a PE device, a set of software and hardware that serve the same network forms an instance. Multiple instances can exist on the same PE device, and an instance can reside on different PE devices. On a PE device, the instance for the public network is called the public network instance, and those for VPNs are called VPN instances.