Technical information

ADC Telecommunications, Inc.
460 C
HAPTER 17: IP MULTICAST
About IP Multicast
IP Multicast reduces traffic on a network by delivering a single stream of
information to multiple users at one time. The Cuda 12000 supports up to
500 multicast groups per chassis.
IGMP
Internet Group Management Protocol (IGMP) is required by all hosts and
routers to receive or forward multicast packets.
A host uses IGMP to report its multicast group memberships to directly
connected routers. When a host joins a multicast group, it sends an IGMP
host membership report message, declaring its membership in a specific
group. If the host has multiple interfaces, the host declares its membership in
a specific group for each interface on which it joins that group.A host can
join multiple multicast groups on a single interface.
When a host receives multicast traffic on an interface on which it has joined
a multicast group, it then forwards the traffic to each and every other
interface on which it has joined that same multicast group. For example, if
on interfaces A, B, and C, a host joins a multicast group, Group1, and
receives traffic destined for Group 1 on interface B, it can forward the traffic
on the other interfaces A and C.
One instance of IGMP runs on each interface. The IGMP for that interface
has no knowledge of any multicast groups on any other interfaces.
A multicast router uses IGMP to determine which multicast groups have
members that are directly connected to the router on each of the router’s
physical interfaces. It keeps a list of multicast group memberships for each
physical interface.
You can configure an IP interface on the Cuda 12000 IP Access Switch to
perform one of the following roles:
■ IGMP Querier Role — The Cuda 12000 IP Access Switch, through the IP
interface thus configured, periodically transmits IGMP queries to
determine which multicast groups are directly connected on an interface.