2
Figure 1 Basic MPLS L3VPN architecture
MCE-related MPLS L3VPN concepts
Site
A site has the following features:
•
A site is a group of IP systems with IP connectivity that does not rely on any service provider
networks.
•
The classification of a site depends on the topology relationship of the devices, rather than the
geographical positions. However, the devices at a site are, in most cases, adjacent to each
other geographically.
•
The devices at a site can belong to multiple VPNs, which means that a site can belong to
multiple VPNs.
•
A site is connected to a provider network through one or more CEs. A site can contain multiple
CEs, but a CE can belong to only one site.
Sites connected to the same provider network can be classified into different sets by policies. Only
the sites in the same set can access each other through the provider network. Such a set is called a
VPN.
VPN instance
VPN instances implement route isolation, data independence, and data security for VPNs.
A VPN instance has the following components:
•
A separate Label Forwarding Information Base (LFIB).
•
An IP routing table.
•
Interfaces bound to the VPN instance.
•
VPN instance administration information, including route distinguishers (RDs), route targets
(RTs), and route filtering policies.
To associate a site with a VPN instance, bind the VPN instance to the PE's interface connected to the
site. A site can be associated with only one VPN instance, and different sites can be associated with
the same VPN instance. A VPN instance contains the VPN membership and routing rules of
associated sites.
VPN 1
CE
Site 1
VPN 2
CE
CE
CE
Site 3
VPN 2
PE
VPN 1
Site 2
Site 4
PE
PE
P
P
P
P
