Benefits of MVPN Inter-AS Support
The MVPN Inter-AS Support feature provides these benefits to service providers:
•
Increased multicast coverage to customers that require multicast to span multiple services providers in
an MPLS Layer 3 VPN service.
•
The ability to consolidate an existing MVPN service with another MVPN service, as in the case of a
company merger or acquisition.
InterAS Option A
InterAS Option A is the basic Multicast VPN configuration option. In this option, the PE router partially plays
the Autonomous System Border Router (ASBR) role in each Autonomous System (AS). Such a PE router in
each AS is directly connected through multiple VRF bearing subinterfaces. MPLS label distribution protocol
need not run between these InterAS peering PE routers. However, an IGP or BGP protocol can be used for
route distribution under the VRF.
The Option A model assumes direct connectivity between PE routers of different autonomous systems. The
PE routers are attached by multiple physical or logical interfaces, each of which is associated with a given
VPN (through a VRF instance). Each PE router, therefore, treats the adjacent PE router like a customer edge
(CE) router. The standard Layer 3 MPLS VPN mechanisms are used for route redistribution with each
autonomous system; that is, the PEs use exterior BGP (eBGP) to distribute unlabeled IPv4 addresses to each
other.
Option A allows service providers to isolate each autonomous system from the other. This provides better
control over routing exchanges and security between the two networks. However, Option A is considered
the least scalable of all the inter-AS connectivity options.
Note
BGP Requirements
PE routers are the only routers that need to be MVPN-aware and able to signal remote PEs with information
regarding the MVPN. It is fundamental that all PE routers have a BGP relationship with each other, either
directly or through a route reflector, because the PE routers use the BGP peering address information to derive
the RPF PE peer within a given VRF.
PIM-SSM MDT tunnels cannot be set up without a configured BGP MDT address-family, because you
establish the tunnels, using the BGP connector attribute.
See the Implementing BGP on Cisco IOS XR Software module of the
Cisco IOS XR Routing Configuration
Guide for the Cisco CRS Router
for information on BGP support for Multicast VPN.
Multitopology Routing
Multitopology routing allows you to manipulate network traffic flow when desirable (for example, to broadcast
duplicate video streams) to flow over non-overlapping paths.
At the core of multitopology routing technology is router space infrastructure (RSI). RSI manages the global
configuration of routing tables. These tables are hierarchically organized into VRF tables under logical routers.
By default, RSI creates tables for unicast and multicast for both IPv4 and IPv6 under the default VRF. Using
multitopology routing, you can configure named topologies for the default VRF.
Cisco IOS XR Multicast Configuration Guide for the Cisco CRS Router, Release 5.2.x
22
Implementing Multicast Routing on Cisco IOS XR Software
Multitopology Routing