Virtual Private Networks (VPNs) 11-3In either case, the Netopia Router wraps, or encapsulates, information that one end of the tunnelexchanges with the other, in a wrapper called General Routing Encapsulation (GRE), at one end of thetunnel, and unwraps, or decapsulates, it at the other end. IPsec stands for IP Security, a set of protocols that supports secure exchange of IP packets at the IP layer.IPsec is deployed widely to implement Virtual Private Networks (VPNs). IPsec supports two encryptionmodes: Transport and Tunnel. Transport mode encrypts only the data portion (payload) of each packet, butleaves the header untouched. The more secure Tunnel mode encrypts both the header and the payload. Onthe receiving side, an IPsec-compliant device decrypts each packet. The Netopia 4741 supports the moresecure Tunnel mode.DES stands for Data Encryption Standard, a popular symmetric-key encryption method. DES uses a 56-bitkey. The Netopia 4741 offers IPsec DES encryption over the VPN tunnel.Configuring the Netopia Router for use with the different protocols is done through the console-based menuscreens. Each type is described in its own section: About PPTP Tunnels on page 11-3 About IPsec Tunnels on page 11-7 About ATMP Tunnels on page 11-19Your configuration depends on which protocol you (and the router at the other end of your tunnel) will use, andwhether or not you will be using the VPN client software in a standalone remote connection.Having both an ATMP tunnel and a PPTP export is not possible because functions require GRE and the router’sPPTP export/server does not distinguish the GRE packets it forwards. Since it processes all of them, ATMPtunneling is impaired. For example, you cannot run an ATMP tunnel between two routers and also have PPTPexported on one side.SummaryA Virtual Private Network (VPN) connects the components of one network over another network. VPNsaccomplish this by allowing you to tunnel through the Internet or another public network in a manner thatprovides the same security and features formerly available only in private networks.VPNs allow networks to communicate across an IP network. Your local networks (connected to the NetopiaRouter) can exchange data with remote networks that are also connected to a VPN-capable router.This feature provides individuals at home, on the road, or in branch offices with a cost-effective and secure wayto access resources on remote LANs connected to the Internet with Netopia Routers. The feature is builtaround three key technologies: PPTP, IPsec, and ATMP.About PPTP TunnelsTo set up a PPTP tunnel, you create a Connection Profile including the IP address and other relevant informationfor the remote PPTP partner. You use the same procedure to initiate a PPTP tunnel that terminates at a remotePPTP server or to terminate a tunnel initiated by a remote PPTP client.
