12-3
Multimedia Traffic Control with IP Multicast (IGMP)
General Operation and Features
General Operation and Features
IGMP Features
In a network where IP multicast traffic is transmitted for various multimedia
applications, you can use the switch to reduce unnecessary bandwidth usage
on a per-port basis by configuring IGMP (Internet Group Management Proto-
col controls). In the factory default state (IGMP disabled), the switch simply
floods all IP multicast traffic it receives on a given VLAN through all ports on
that VLAN (except the port on which it received the traffic). This can result
in significant and unnecessary bandwidth usage in networks where IP multi-
cast traffic is a factor. Enabling IGMP allows the ports to detect IGMP queries
and report packets and manage IP multicast traffic through the switch.
IGMP is useful in multimedia applications such as LAN TV, desktop confer-
encing, and collaborative computing, where there is multipoint communica-
tion; that is, communication from one to many hosts, or communication
originating from many hosts and destined for many other hosts. In such
multipoint applications, IGMP will be configured on the hosts, and multicast
traffic will be generated by one or more servers (inside or outside of the local
network). Switches in the network (that support IGMP) can then be config-
ured to direct the multicast traffic to only the ports where needed. If multiple
VLANs are configured, you can configure IGMP on a per-VLAN basis.
Enabling IGMP allows detection of IGMP queries and report packets in order
to manage IP multicast traffic through the switch. If no other querier is
detected, the switch will then also function as the querier. (If you need to
disable the querier feature, you can do so through the IGMP configuration
MIB. Refer to “Changing the Querier Configuration Setting” on page 12-10.)
Feature Default Menu CLI Web
view igmp configuration n/a — page 12-6 —
show igmp status for multicast
groups used by the selected
VLAN
n/a — Yes —
enabling or disabling IGMP
(Requires VLAN ID Context)
disabled — page 12-8 page 12-10
per-port packet control auto — page 12-9 —
IGMP traffic priority normal — page 12-9 —
querier enabled — page 12-10 —
!Software.book Page 3 Thursday, October 10, 2002 6:10 PM
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