Switch User Manual

IGMP snooping 47

"IP multicast propagation with IGMP routing" (page 47)shows how IGMP

is used to set up the path between the client and server. As shown in this

example, the IGMP host provides an IP Multicast stream to designated

routers that forward the IP Multicast stream on their local network only

if there is a recipient.

The client/server path is set up as follows:

1. The designated router sends out a host membership query to the subnet

and receives host membership reports from end stations on the subnet.

2. The designated routers then set up a path between the IP Multicast

stream source and the end stations.

3. Periodically, the router continues to query end stations about whether

to continue participation.

4. As long as any client continues to participate, all clients, including

non-participating end stations on that subnet, receive the IP Multicast

stream.

Note: Although the non-participating end stations can ﬁlter the IP

Multicast trafﬁc, the IP Multicast trafﬁc still exists on the subnet and

consumes bandwidth.

IP Multicast can be optimized in a LAN by using IP Multicast ﬁltering

switches, such as the Nortel Ethernet Routing Switch 5500 Series.

As shown in "IP multicast propagation with IGMP routing" (page 47),a

non-IP Multicast ﬁltering switch causes IP Multicast trafﬁc to be sent to

all segments on the local subnet.

IP multicast propagation with IGMP routing

Nortel Ethernet Routing Switch 5500 Series

Conﬁguration-IP Routing Protocols

NN47200-503 03.01 Standard

5.1 27 August 2007