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How to configure dial access to MPLS VPN integration

Core Issue

The Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) architecture provides the service providers with a peer-to-peer model, which combines the best features of overlay and peer-to-peer models.  MPLS VPN technology enables a service provider to easily provision scalable and efficient VPNs across the core of its network for each customer.

The remote access to MPLS VPN solution integrates various access VPN services used on dial, Digital Subscriber Line (DSL), cable and wireless technologies with MPLS VPN in the service provider's core. This solution permits service providers to offer bundled end-to-end VPN service to their Internet Service Provider (ISP) customers and enterprise customers.


Dial access integration provides the remote Customer Edge (CE) router-to-Provider Edge (PE) router link that integrates dial users into their MPLS VPNs.

These dial access methods are supported for integration:

  • Layer 2 Tunnel Protocol (L2TP) dial in is designed for service providers who want to offer wholesale dial service to their customers. It allows the users or a CE router to dial to a Network Access Server (NAS) functioning as a L2TP Access Concentrator (LAC), which then builds a L2TP tunnel to the PE router functioning as L2TP Network Server (LNS). The LNS or PE router dynamically creates a virtual access interface for the user and includes it in the appropriate Virtual Routing and Forwarding (VRF) instance for the customer and integrates it with the MPLS VPN backbone.
  • In direct ISDN PE dial in, the NAS functions as both NAS and PE. Users or the CE router dialing into the NAS are placed directly in the appropriate VRF for the MPLS VPN.
  • Dial backup is used for providing backup for a primary connection between a CE and PE router and can use the L2TP dial-in feature in turn to provide this functionality.
  • In dial-out access, instead of a remote user or CE router initiating a call into the MPLS VPN, you can allow a connection to be established by traffic coming from the MPLS VPN backbone and triggering a call from the dial-out router to the remote CE. It can use either L2TP or direct ISDN architecture.

For related information on L2TP, refer to Configuring Virtual Private Networks.