Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

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Each customer site that is connected to a particular PE router is also associated with a
VPN routing and forwarding instance (VRF). As shown in Figure 70 on page 388, each VRF
has its own forwarding table distinct from that of other VRFs and from the virtual router’s
global forwarding table.
Figure 70: BGP/MPLS VPN Components
A given VRF’s forwarding table includes only routes to sites that have at least one VPN
in common with the site that is associated with the VRF. For example, in Figure 70 on
page 388, the forwarding table in VRF B stores routes only to sites that are members of
at least one of the VPNs to which Customer Site 3 belongs.
VRFs exist within the context of a virtual router (VR). A given virtual router can have zero
or more VRFs, in addition to its global routing table (which is not associated with any
VPN, CE router, or customer site). A router can support up to 1000 forwarding tables;
that is, up to a combined total of 1000 VRs and VRFs.
You assign one or more interfaces or subinterfaces to a given VRF. If multiple customer
sites are members of the same set of VPNs, they can share a VRF—that is, you do not
need to create a specific VRF for each customer site. In Figure 70 on page 388, Customer
Sites 1 and 2 share VRF A; both sites belong to the same set of VPNs. The router looks
up a packet’s destination in the VRF associated with the interface on which the packet
is received. The VRFs are populated by BGP while it learns routes from the VPN. If a
customer site is a member of multiple VPNs, the routes learned from all those VPNs
populate the VRF associated with the site.
Copyright © 2010, Juniper Networks, Inc. 388
JunosE 11.2.x BGP and MPLS Configuration Guide