Cisco Cisco IOS Software Release 12.4(4)T

The following prerequisites apply to implementing multicast service reflection:

Because virtual interface (Vif1) handling of replicated packets to the multicast code is done in the 
same switching context as the one in which it receives the initial packet, you must enable the ip 
mroute-cache command to avoid process switching.

Configure your multicast enabled network with the necessary infrastructure to run either 
Protocol-Independent Multicast-Sparse Mode (PIM-SM), Bidirectional PIM (bidir-PIM), or PIM 
Source Specific Multicast (PIM-SSM). The configuration process may include configuring RPs, 
interface boundaries, or SSM ranges. 

For configuration information, see the “Configuring Basic IP Multicast” module in the Cisco IOS 
IP Multicast Configuration Guide, Release 12.4.

Confirm that the Vif1 interface is installed in your border router and the Multicast Service 
Reflection application is installed and operational.

Each active receiver must initiate an Internet Group Management Protocol (IGMP) join to the 
multicast group that is defined on the router in the PIM domain.

The following restrictions apply to implementing multicast services reflection:

When translating groups of multicast packets that are destined for the same multicast group but are 
originating from different sources, as in the case when using Source Specific Multicast, all multicast 
packets destined for a particular SSM group will get mapped to a single (S, G) after translation has 
occurred. For example, if 10.1.1.1, 232.1.1.1 and 10.1.1.2, 232.1.1.1 need to be translated, they will 
appear as a single entry, for example, 192.168.1.2, 232.239.1.1, where 192.168.1.2 is an IP address 
that resides in the Vif1 IP subnet.

PIM/IGMP control packets are not translated.

The multicast services reflection feature is implemented only in the fast switching path. There is no 
hardware support.

To implement multicast service reflection, you should understand the following concepts: