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Operation Manual – MPLS L3VPN
H3C S9500 Series Routing Switches
Chapter 1 MPLS L3VPN Configuration
1-3
that are directly connected, rather than all VPN routing information on the provider
network.
A P device 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 devices function as
the transit LSRs.
1.1.2 MPLS L3VPN Concepts
I. Site
Site is often mentioned in the VPN. Its meanings are described as follows:
z
A site is a group of IP systems with IP connectivity that does not rely on any
service provider network to implement.
z
The classification of a site depends on the topology relationship of the devices,
rather than the geographical positions, though the devices at a site are adjacent to
each other geographically in most cases.
z
The devices at a site can belong to multiple VPNs.
z
A site is connected to a provider network through one or more CEs. A site can
contain many 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.
II. Address space overlapping
Each VPN independently manages the addresses that it uses. The assembly of such
addresses for a VPN is called an address space.
The address spaces of VPNs may overlap. For example, if both VPN 1 and VPN 2 use
the addresses on network segment 10.110.10.0/24, address space overlapping occurs.
III. VPN instance
In MPLS VPN, routes of different VPNs are identified by VPN instance.
A PE creates and maintains a separate VPN instance for each VPN at a directly
connected site. Each VPN instance contains the VPN membership and routing rules of
the corresponding site. If a user at a site belongs to multiple VPNs at the same time, the
VPN instance of the site contains information about all the VPNs.
For independency and security of VPN data, each VPN instance on a PE maintains a
relatively independent routing table and a separate label forwarding information base
(LFIB). VPN instance information contains these items: the LFIB, IP routing table,
interfaces bound to the VPN instance, and administration information of the VPN