Layer 2 Tunneling Protocol Services Configuration Guidelines

The Layer 2 Tunneling Protocol (L2TP) enables you to set up client services for establishing Point-to-Point Protocol (PPP) tunnels across a network and negotiating Multilink PPP if it is implemented. Multiple L2TP PPP sessions can share the same remote peer IP address, which enables you to set up redundant sessions between the same links.

• If you configure Multilink PPP, the same remote IP address can be shared across multiple bundles, because the IP address negotiation takes place on the bundle rather than on each session.
• If Multilink PPP is not configured, multiple sessions can share the same remote IP address.

The last session or bundle to come up accomplishes the traffic transfer. When this session or bundle goes down, the traffic switches to the next-to-last session or bundle to come up. For example, if four sessions or bundles labeled A, B, C, and D share the same remote IP address and come up in alphabetical order, D initially handles the data transfer. If D goes down, traffic switches over to C, and so forth. If another session or bundle E subsequently comes up and has the same address, the traffic switches over to it.

To configure L2TP services, include the l2tp statement at the [edit services] hierarchy level:

Note: L2TP configurations are supported only on M7i, M10i, and M120 routers.

You configure other components of this feature at the [edit access] and [edit interfaces] hierarchy levels. Those configurations are summarized in this chapter; for more information, see the Junos System Basics Configuration Guide or the Junos Network Interfaces Configuration Guide.

This chapter contains the following sections:

• L2TP Services Configuration Overview
• L2TP Minimum Configuration
• Configuring L2TP Tunnel Groups
• Configuring the Identifier for Logical Interfaces that Provide L2TP Services
• AS PIC Redundancy for L2TP Services
• Tracing L2TP Operations
• Examples: Configuring L2TP Services