Cisco Systems 78-11741-02 manual IPC-529, Igmp

Configuring Router-Port Group Management Protocol

RGMP Overview

Figure 89 RGMP in a Switched Network
		Router A				Router B
		PIM SM				PIM SM
		RGMP				RGMP
	A
			B	Switched network		A
		A
Source for						B
group A					B
	A			Switch A	A
					Switch B
		A		RGMP	RGMP	B
Receiver 1			B	IGMP	IGMP
						A
				snooping	snooping
for group A
	A	Router C				Router D
		PIM SM				PIM SM
Receiver 2		RGMP				RGMP

for group A Traffic restricted by RGMP

B

Source for

group B

B

Receiver 1 for group B

B

Receiver 2

39165 for group B

In Figure 89, the sources for the two different multicast groups (the source for group A and the source for group B) send traffic into the same switched network. Without RGMP, traffic from source A is unnecessarily flooded from switch A to switch B, then to router B and router D. Also, traffic from source B is unnecessarily flooded from switch B to switch A, then to router A and router C. With RGMP enabled on all routers and switches in this network, traffic from source A would not flood router B and router D. Also, traffic from source B would not flood router A and router C. Traffic from both sources would still flood the link between switch A and switch B. Flooding over this link would still occur because RGMP does not restrict traffic on links toward other RGMP-enabled switches with routers behind them.

By restricting unwanted multicast traffic in a switched network, RGMP increases the available bandwidth for all other multicast traffic in the network and saves the processing resources of the routers.

Figure 90 shows the RGMP messages sent between an RGMP-enabled router and an RGMP-enabled switch.

Cisco IOS IP Configuration Guide

IPC-529