Inter-As Vprns; Figure 135: Inter-As Option-A: Vrf-To-Vrf Model - Alcatel-Lucent 7750 SR Manual

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VPRN Features

Inter-AS VPRNs

Inter-AS IP-VPN services have been driven by the popularity of IP services and service provider

expansion beyond the borders of a single Autonomous System (AS) or the requirement for IP VPN

services to cross the AS boundaries of multiple providers. Three options for supporting inter-AS

IP-VPNs are described in RFC 4364, BGP/MPLS IP Virtual Private Networks (VPNs).

The first option, referred to as Option-A

implementation. This method uses a back-to-back connection between separate VPRN instances in

each AS. As a result, each VPRN instance views the inter-AS connection as an external interface

to a remote VPRN customer site. The back-to-back VRF connections between the ASBR nodes

require individual sub-interfaces, one per VRF.

The second option, referred to as Option-B

Routers (ASBRs) as the interface between the autonomous systems. This approach enhances the

scalability of the eBGP VRF-to-VRF solution by eliminating the need for per-VPRN configuration

on the ASBR(s). However it requires that the ASBR(s) provide a control plan and forwarding

plane connection between the autonomous systems. The ASBR(s) are connected to the PE nodes

in its local autonomous system using iBGP either directly or through route reflectors. This means

the ASBR(s) receive all the VPRN information and will forward these VPRN updates, VPN-IPV4,

to all its EBGP peers, ASBR(s), using itself as the next-hop. It also changes the label associated

with the route. This means the ASBR(s) must maintain an associate mapping of labels received

and labels issued for those routes. The peer ASBR(s) will in turn forward those updates to all local

135), is considered inherent in any

136), relies heavily on the AS Boundary

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