• Single-Provider Inter-AS—A service provider whose internal network consists of multiple autonomous
systems.
• Intra-Provider Inter-AS—Multiple service providers that need to coordinate their networks to provide
inter-AS support.
To establish a Multicast VPN between two autonomous systems, a MDT-default tunnel must be setup between
the two PE routers. The PE routers accomplish this by joining the configured MDT-default group. This
MDT-default group is configured on the PE router and is unique for each VPN. The PIM sends the join based
on the mode of the groups, which can be PIM SSM, or sparse mode.
PIM-Bidir is not supported on MVPN.Note
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
IPv6 Connectivity over MVPN
On the Cisco ASR 9000 Series Routers, in Cisco IOS XR Software starting Release 4.2.1, IPv6 connectivity
is supported between customer sites over an IPv4-only core network with a default VRF. VPN PE routers
interoperate between the two address families, with control and forwarding actions between IPv4-encapsulated
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 5.1.x
19
Implementing Layer-3 Multicast Routing on Cisco IOS XR Software
Multicast VPN
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