Mpls L3Vpn Concepts - 3Com MSR 50 Series Configuration Manual

1460 C 79: MPLS L3VPN C
HAPTER

MPLS L3VPN Concepts

ONFIGURATION
a router or a host. It neither can "sense" the existence of any VPN nor needs to
support MPLS.
Provider edge router (PE): A PE resides on a service provider network and
■
connects one or more CEs to the network. On an MPLS network, all VPN
processing occurs on the PEs.
Provider (P) router: A P router is a backbone router on a service provider
■
network. It is not directly connected with any CE. It only needs to be equipped
with basic MPLS forwarding capability.
Figure 405 shows the MPLS L3VPN model.
Figure 405 Network diagram for MPLS L3VPN model
VPN 1
Site 1
CE
PE
CE
Site 2
VPN 2
CEs and PEs mark the boundary between the service providers and the customers.
A CE is usually a router. After a CE establishes adjacency with a directly connected
PE, it advertises its VPN routes to the PE and learns remote VPN routes from the PE.
A CE and a PE use BGP/IGP to exchange routing information. You can also
configure static routes between them.
After a PE learns the VPN routing information of a CE, it uses BGP to exchange
VPN routing information with other PEs. A PE maintains routing information about
only VPNs that are directly connected, rather than all VPN routing information on
the provider network.
A P router maintains only routes to PEs. It does not need to know anything about
VPN routing information.
When VPN traffic travels over the MPLS backbone, the ingress PE functions as the
ingress LSR, the egress PE functions as the egress LSR, while P routers function as
the transit LSRs.
Site
Site is often mentioned in the VPN. Its meanings are described as follows:
P P
P
P
PE
VPN 2
Site 1
CE
PE
CE
Site 2
VPN 1