RGMP is a dynamic protocol that controls multicast traffic to multicast routers.
With RGMP, a switch must still use IGMP snooping to constrain multicast traffic to interested hosts.
RGMP can communicate only with routers that also run RGMP. Routers periodically send RGMP hello messages to switches.
Routers that are interested in receiving traffic for a multicast group send an RGMP join request to the switch. Otherwise, the switch will not forward multicast traffic to the router.
RGMP supports the use of PIM sparse mode only on multicast routers.
Configuration
1.
Enable IGMP snooping on the switch.
See section "9-1: IGMP Snooping" for the necessary switch configuration steps.
2.
Enable PIM sparse mode multicast routing on a router.
Refer to Cisco Field Manual: Router Configuration (ISBN 1-58705-024-2), section "7-7: IP Multicast Routing" for the router configuration steps.
3.
(Router only) Enable RGMP on the router:
IOS
(interface) ip rgmp
RGMP must be enabled on the router interfaces that connect to RGMP-capable switches.
4.
Enable RGMP on the switch:
COS
set rgmp {enable | disable}
IOS
N/A
By default, RGMP is disabled.
Displaying Information About RGMP
Table 9-5 lists some switch commands that you can use to display helpful information about RGMP.
Table 9-5. Switch Commands to Display RGMP Information
Display Function
Switch OS
Command
RGMP statistics
COS
show rgmp statistics [vlan]
IOS
N/A
Multicast groups requested by RGMP router
COS
show rgmp group [mac-addr] [vlan-id]
IOS
N/A
Number of multicast groups requested by RGMP router