Operation Manual – MPLS L3VPN
H3C S9500 Series Routing Switches
Chapter 1 MPLS L3VPN Configuration
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The PEs acting as ASBRs are connected through multiple VLAN interfaces. Each of
them treats the other as a CE of its own and advertises IPv4 routes through
conventional EBGP. Within an AS, packets are forwarded using two-level label
forwarding as VPN packets. Between ASBRs, conventional IP forwarding is used.
Ideally, each inter-provider VPN has a pair of VLAN interfaces to exchange VPN routing
information.
Figure 1-9
Network diagram for inter-provider VPN option A
This kind of solution is easy to carry out because no special configuration is required on
the PEs acting as the ASBRs.
However, it has limited scalability because the PEs acting as the ASBRs have to
manage all the VPN routes and create VPN instances on a per-VPN basis. This leads
to excessive VPN-IPv4 routes on the PEs. Moreover, the requirement to create a
separate VLAN interface for each VPN also calls for higher performance of the PEs.
II. Inter-provider VPN option B
In this kind of solution, two ASBRs use MP-EBGP to exchange labeled VPN-IPv4
routes that they have obtained from the PEs in their respective ASs.
As shown in
Figure 1-10
, the routes are advertised through the following steps:
1) PEs in AS 100 advertise labeled VPN-IPv4 routes to the ASBR PE of AS 100 or
the route reflector (RR) for the ASBR PE through MP-IBGP.
2) The ASBR PE advertises labeled VPN-IPv4 routes to the ASBR PE of AS 200
through MP-EBGP.
3)
The ASBR PE of AS 200 advertises labeled VPN-IPv4 routes to PEs in AS 200 or
to the RR for the PEs through MP-IBGP.
The ASBRs must perform the special processing on the labeled VPN-IPv4 routes,
which is also called ASBR extension method.
