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MAX 6000/3000 Network Configuration Guide 11-1
11
Setting Up Virtual Private Networks
Introduction to Virtual Private Networks
Virtual Private Networks (VPNs) provide low-cost remote access to private LANs via the
Internet. The tunnel to the private corporate network can be from an ISP, enabling mobile
clients to dial in to a corporate network, or it can provide a low-cost Internet connection
between two corporate networks. Lucent currently supports three VPN schemes: Ascend
Tunnel Management Protocol (ATMP), Point-to-Point Tunneling Protocol (PPTP) and Layer 2
Tunneling Protocol (L2TP).
An ATMP session can occur only between two Lucent units and must use UDP/IP. The MAX
encapsulates all packets passing through the tunnel in standard Generic Routing Encapsulation
(GRE) as described in RFC 1701. ATMP creates and tears down a cross-Internet tunnel
between the two Lucent units. In effect, the tunnel collapses the Internet cloud and provides
what looks like direct access to a home network. The tunnels do not support bridging. All
packets must be routed with IP or IPX.
The Microsoft Corporation developed Point-to-Point Tunneling Protocol (PPTP) to enable
Windows 95 and Windows NT Workstation users to dial into a local ISP to connect to a private
corporate network across the Internet.
Version 8 of the Internet Engineering Task Force (IETF) draft titled Layer Two Tunneling
Protocol “L2TP,” dated November, 1997, specifies the Layer 2 Tunneling Protocol (L2TP).
L2TP enables you to connect to a private network by dialing into a local MAX, which creates
and maintains an L2TP tunnel between itself and the private network.
Note: Any MAX unit supporting PPTP or L2TP does not display a terminal-server prompt to
dial-in users, because all dial-in calls are immediately transferred to PPTP or L2TP servers.
Introduction to Virtual Private Networks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1
Configuring ATMP tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2
Configuring PPTP tunnels for dial-in clients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-27
Configuring L2TP tunnels for dial-in clients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-31
Using Tunnel Options to support tunneling protocols. . . . . . . . . . . . . . . . . . . . . . . . 11-44
SNMP MIB for L2TP Added. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-45
Configuring Virtual Routers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-47