CHAPTER 1
MPLS L3VPN Overview
Before defining an MPLS VPN, VPN in general must be defined. A VPN is:
• An IP-based network delivering private network services over a public infrastructure
• A set of sites that are allowed to communicate with each other privately over the Internet or other public
or private networks
Conventional VPNs are created by configuring a full mesh of tunnels or permanent virtual circuits (PVCs) to
all sites in a VPN. This type of VPN is not easy to maintain or expand, as adding a new site requires changing
each edge device in the VPN.
MPLS-based VPNs are created in Layer 3 and are based on the peer model. The peer model enables the service
provider and the customer to exchange Layer 3 routing information. The service provider relays the data
between the customer sites without customer involvement.
MPLS VPNs are easier to manage and expand than conventional VPNs. When a new site is added to an MPLS
VPN, only the edge router of the service provider that provides services to the customer site needs to be
updated.
The following figure depicts a basic MPLS VPN topology.
Figure 1: Basic MPLS VPN Topology
These are the basic components of MPLS VPN:
L3VPN Configuration Guide for Cisco NCS 540 Series Routers, IOS XR Release 6.3.x
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