Virtual Private Networks (VPNs) 12-3the receiving side, an IPsec-compliant device decrypts each packet. The Netopia 4752 supports the moresecure Tunnel mode.DES stands for Data Encryption Standard, a popular symmetric-key encryption method. DES uses a 56-bitkey. The Netopia 4752 offers IPsec DES encryption over the VPN tunnel.When used to initiate the tunnelled connection, the Netopia 4752 is called a PPTP Access Concentrator (PAC, inPPTP language), or a foreign agent (in ATMP language). When used to answer the tunnelled connection, theNetopia Router is called a PPTP Network Server (PNS, in PPTP language) or a home agent (in ATMP language).In either case, the Netopia Router wraps, or encapsulates, information that one end of the tunnel exchangeswith the other, in a wrapper called General Routing Encapsulation (GRE), at one end of the tunnel, and unwraps,or decapsulates, it at the other end.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 12-3 About IPsec Tunnels on page 12-7 About ATMP Tunnels on page 12-20Your 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.Note: You must choose which protocol you will be using, since you cannot both export PPTP and use ATMP, orvice versa, at the same time.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.
