25 configuring vrf lite, 1 vrf and vrf lite overview, Figure 1 – CANOGA PERKINS CanogaOS Configuration Guide User Manual

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CanogaOS Configuration Guide

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25 Configuring VRF lite

25.1 VRF and VRF Lite Overview

In the MPLS-VPN model a VPN is defined as a collection of sites sharing a common routing
table. A customer site is connected to the service provider network by one or more interfaces,
where the service provider associates each interface with a VPN routing table. A VPN routing
table is called a VPN routing and forwarding(VRF) table. Figure 1 illustrates the fundamental
building blocks of an MPLS-VPN.

VRF

PE2

VRF-Lite

Topo 1

CE = Customer Edge
P = Provider Routers
PE = Provider Edge
VRF = VPN Routing and Forwarding Table

Topo 2

VPN1

VPN2

PE1

VRF

VRF-Lite

Finances

Engineering

Figure 1

VRF-Lite CE extends limited PE functionality to a CE router in an MPLS-VPN model. A CE
router now has the ability to maintain separate VRF tables in order to extend the privacy and
security of an MPLS-VPN down to a branch office rather than just at the PE router node. Each
VRF table can have separate address space.
CE routers use VRF interfaces to form a VLAN-like configuration on the customer side. Each
VRF on the CE router is mapped to a VRF on the PE router. With VRF-Lite CE, the CE router
can only configure VRF interfaces and support VRF routing tables. Multi-VRF CE extends
SOME of the PE functionality to the CE router—there is no label exchange, there is no LDP
adjacency, there is no labeled packet flow between PE and CE. The only PE-like functionality
that is supported is the ability to have multiple VRFs on the CE router so that different routing
decisions can be made. The packets are sent toward the PE as IP packets.
Benefits of VRF-Lite
1. Only one CE router is needed thus simplifying provisioning and network management rather
than a multiple CE router solution.
2. CE router has VRF functionality to provid VPN routing information. Less routing updates to
manage on PE route.