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MVPN Hub and Spoke is achieved by separating core tunnels, for traffic sourced from hub sites, and spoke
sites. MDT hub is the tunnel carrying traffic sourced from all Hub sites, and MDT spoke carries traffic sourced
from all spoke sites. Such tunnel end-points are configured on all PEs participating in hub and spoke topology.
If spoke sites do not host any multicast sources or RPs, provisioning of MDT Spoke can be completely avoided
at all such routers.
Once these tunnels are provisioned, multicast traffic path will be policy routed in this manner:
1
Hub sites will send traffic to only MDT Hub.
2
Spoke sites will send traffic to only MDT Spoke.
3
Hub sites will receive traffic from both tunnels.
4
Spoke sites will receive traffic from only MDT Hub.
These rules ensure that hubs and spokes can send and receive traffic to or from each other, but direct spoke
to spoke communication does not exist. If required, interspoke multicast can flow by turning around the traffic
at Hub sites.
These enhancements are made to the Multicast Hub and Spoke topology in Cisco IOS XR Software Release
4.0:
•
Auto-RP and BSR are supported across VRFs that are connected through extranet. It is no longer restricted
to using static RP only.
•
MP-BGP can publish matching import route-targets while passing prefix nexthop information to RIB.
•
Route policies can use extended community route targets instead of IP address ranges.
•
Support for extranet v4 data mdt was included so that data mdt in hub and spoke can be implemented.
Label Switched Multicast (LSM) Multicast Label Distribution Protocol (mLDP)
based Multicast VPN (mVPN) Support
Label Switch Multicast (LSM) is MPLS technology extensions to support multicast using label encapsulation.
Next-generation MVPN is based on Multicast Label Distribution Protocol (mLDP), which can be used to
build P2MP and MP2MP LSPs through a MPLS network. These LSPs can be used for transporting both IPv4
and IPv6 multicast packets, either in the global table or VPN context.
Benefits of LSM MLDP based MVPN
LSM provides these benefits when compared to GRE core tunnels that are currently used to transport customer
traffic in the core:
•
It leverages the MPLS infrastructure for transporting IP multicast packets, providing a common data
plane for unicast and multicast.
•
It applies the benefits of MPLS to IP multicast such as Fast ReRoute (FRR) and
•
It eliminates the complexity associated PIM.
Cisco IOS XR Multicast Configuration Guide for the Cisco CRS Router, Release 5.2.x
28
Implementing Multicast Routing on Cisco IOS XR Software
Label Switched Multicast (LSM) Multicast Label Distribution Protocol (mLDP) based Multicast VPN (mVPN) Support