3Com 3C13636 Configuration Manual page 876

Router 3000 ethernet family

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3Com Router 3000 Ethernet Family

Configuration Guide

Ideally, each multi-AS VPN has a pair of subinterfaces for exchanging VPN routing

information.

Figure 3-9 Network diagram for managing VPN routes between ASBRs by using

subinterfaces

This method is easily to implement. No special configuration is required on the ASBRs.

However, it has weak extensibility. Because ASBR PEs need to manage all VPN routes

and create VPN instances on a per-VPN basis. This will lead to excessive VPN-IPv4

routes on PEs, and poses high performance requirements for the PEs.

II. Advertising Labeled VPN-IPv4 Routes Through MP-EBGP Between ASBRs

Two ASBRs, through MP-EBGP, exchange labeled VPN-IPv4 routes that they obtain

from respective AS PEs.

The routes are advertised following the procedures below:

PEs in AS 100 advertise labeled VPN-IPv4 routes to ASBR PE of AS 100 or the

Route Reflector (RR) of ASBR PE through MP-IBGP.

ASBR PE advertises labeled VPN-IPv4 routes to ASBR PE of AS 200 through

ASBR PE of AS 200 advertises labeled VPN-IPv4 routes to PEs in AS 200 or the

RR of ASBR PE through MP-IBGP.

In this way, special processing is needed for labeled VPN-IPv4 routes on ASBRs. So it

is also called ASBR extension method.

BGP/MPLS backbone

3Com Corporation

Chapter 3 BGP/MPLS VPN Configuration

BGP/MPLS backbone

Sub-interface

IP forwarding

Chapters

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3c13636-us - router 3036 3000 series