Chapter 7 Igmp; Igmp Snooping - Juniper EX2500 Configuration Manual

Chapter 7
IGMP

IGMP Snooping

Internet Group Management Protocol (IGMP) is used by IP Multicast routers to learn
about the existence of host group members on their directly attached subnet (see
RFC 2236). The IP Multicast routers get this information by broadcasting IGMP
Membership Queries and listening for IP hosts reporting their host group
memberships. This process is used to set up a client/server relationship between an
IP Multicast source that provides the data streams and the clients that want to
receive the data.
The EX2500 switch can perform IGMP Snooping, and connect to static multicast
routers (Mrouters).
The following topics are discussed in this chapter:
IGMP Snooping on page 71
FastLeave on page 72
IGMPv3 Snooping on page 73
IGMP Snooping Configuration Example on page 73
Static Multicast Router on page 74
IGMP snooping allows the switch to forward multicast traffic to only those ports
that request it. IGMP Snooping prevents multicast traffic from being flooded to all
ports. The switch learns which server hosts are interested in receiving multicast
traffic, and forwards it only to ports connected to those servers.
IGMP snooping conserves bandwidth. With IGMP Snooping, the switch learns
which ports are interested in receiving multicast data, and forwards multicast data
to those ports only. In this way, other ports are not burdened with unwanted
multicast traffic.
The switch can sense IGMP Membership Reports from attached clients and can act
as a proxy to set up a dedicated path between the requesting host and a local IP
Multicast router. After the pathway is established, the switch blocks the IP Multicast
stream from flowing through any port that does not connect to a host member,
thus conserving bandwidth.
71
IGMP Snooping