Cisco ASR 9000 Series Software Manual page 148

Configuring Multicast Hub and Spoke Topology: Example
ip multicast-routing vrf A1-Hub-4
ip multicast-routing vrf A1-Spoke-2
interface Loopback10
ip vrf forwarding A1-Hub-4
ip address 103.10.10.103 255.255.255.255
ip pim sparse-mode
!
ip pim vrf A1-Hub-4 autorp listener
ip pim vrf A1-Hub-4 send-rp-announce Loopback10 scope 32
ip pim vrf A1-Hub-4 send-rp-discovery Loopback10 scope 32
Hub and Spoke with Turnaround: Example
Multicast turnaround mandates a 2-interface connection to the hub site
To configure a CE as a turnaround router, it is connected to its respective PE through two interfaces and each
interface is placed in a separate hub site vrf called hub-x-in vrf and hub-x-out vrf. Hub-x-in vrf carries joins
that come from the receiver spoke site through the Hub Tunnel and hub-x-out vrf will carry the same joins
towards the source spoke site through the Spoke Tunnel without violating the four basic rules below. The
source spoke sends traffic to the spoke tunnel to hub-x-out which is turned around to the hub-tunnel on the
hub-x-in interface.
1 Hub sites sends traffic only to MDTHub.
2 Spoke sites sends traffic only to MDTspoke.
3 Hub sites receives traffic from both tunnels.
4 Spoke sites receives traffic only from MDTHub.
A2-Spoke-1 A2-Hub-2
A2-Spoke-2 A2-Hub-3in
A2-Hub-2out
A2-Spoke-3 (spoke has auto-rp)
Figure 13: Example for CE1PE1PE2 CE2Multicast Hub and Spoke Topology with Turnaround
CE1------------------ PE1 ------------------------------------------------ PE2 ------------------ CE2
Routes exported by hub sites are imported by hub sites and spoke sites. Routes exported by spoke sites are
imported by both hub-x-out and hub-x-in and hub site exports spoke routes back into the core by hub VRF
route targets. This causes routes originated from one spoke site to be learned by all other spoke sites but with
the nexthop of hub-x-out. For example, Spoke2 will see the RPF for Spoke1 reachable with nexthop of
A2-Hub-3in. This is the fundamental difference in leaking of routes which helps in achieving turnaround of
multicast traffic.
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 5.1.x
148
Implementing Layer-3 Multicast Routing on Cisco IOS XR Software