A virtual private network (VPN) allows your company to securely extend its private intranet over the existing framework of a public network, such as the Internet. VPN supports Layer 2 Tunnel Protocol (L2TP). L2TP solutions provide remote users with secure, and cost-efficient access to the corporate network. By establishing a voluntary tunnel to the L2TP network server (LNS), the remote client actually becomes an extension of the corporate network.
This conceptual scenario shows a remote client system connecting to its corporate network by creating an L2TP voluntary tunnel protected by VPN.
To begin, the remote client establishes a connection to the Internet through the Internet Service Provider (ISP). The ISP assigns the client a globally routable IP address.
Unknown to the ISP, the client initiates a VPN connection with the corporate VPN gateway. The gateway authenticates the client system which wants to access the corporate network.
After the client receives authentication from the gateway (making the connection secure), the client establishes the L2TP tunnel. The client is still using the IP address assigned by the ISP. The L2TP tunnel will eventually enable data to travel between the client system and the corporate gateway.
Once the L2TP tunnel (shown in yellow) is established, the LNS assigns the client an IP address within the corporate network's address scheme. There is no physical line assoc- iated with the connection, so a virtual line is created to allow PPP traffic to tunnel through the L2TP tunnel.
Now IP traffic can flow between the remote client system and any system within the corporate network.