Инструкции По Установке для 3com S7906E

1-10

Figure 1-7 Network diagram for inter-provider VPN option A

VPN 1

CE 1

PE 1

PE 3

VPN 1

CE 3

CE 2

VPN 2

PE 2

PE 4

ASBR 1

(PE)

ASBR 2

(PE)

VPN LSP 1

VPN LSP 2

LSP 1

LSP 2

CE 4

IP Forwarding

EBGP

AS 100

AS 200

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 subinterface for each VPN also calls for higher

performance of the PEs.

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.

, 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.