L2Tp Overview; Introduction To Vpdn - 3Com MSR 50 Series Configuration Manual

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L2TP Overview

Introduction to VPDN

L2TP C
ONFIGURATION
When configuring L2TP, go to these sections for information you are interested in:
"L2TP Overview" on page 1601
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"L2TP Configuration Task List" on page 1607
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"Displaying and Maintaining L2TP" on page 1614
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"L2TP Configuration Example" on page 1614
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"Troubleshooting L2TP" on page 1621
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This section covers these topics:
"Introduction to VPDN" on page 1601
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"Introduction to L2TP" on page 1602
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A virtual private dial-up network (VPDN) is a virtual private network (VPN) that
utilizes the dial-up function of public networks such as ISDN or PSTN networks to
provide access services for enterprises, small internet service providers (ISPs), and
telecommuters.
The VPDN technology uses a proprietary encryption protocol to build secure VPNs
across public networks for enterprises. Branches away from the headquarters and
staff on business can remotely access the Intranet resources in the headquarters
through an encrypted virtual tunnel over public networks, while other users on the
public networks cannot.
A VPDN tunnel can be set up in two ways:
The network access server (NAS) directly connects users to an enterprise
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gateway (for instance, VPDN gateway) in PPP mode through tunneling
protocols like Layer 2 forwarding (L2F) or Layer 2 tunneling protocol (L2TP), so
as to establish a tunnel with the VPDN gateway. The configuration and creation
of a tunnel is transparent to users. Users only log in to the enterprise gateway
once to access the enterprise network responsible for user authentication and
address assignment, without the need for occupying public address. However,
the NAS needs to support the VPDN protocol and the authentication system
needs to support VPDN attributes.
The client establishes a tunnel with the VPDN gateway. This is done in such way
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that the client first accesses the Internet, and then establishes a tunnel with the
gateway through dedicated client software (for example, L2TP client supported
by Windows 2000).There is no limit to how and where users access the
Internet. ISPs are also not involved. The need for installing dedicated software