Multimedia Traffic Control with IP Multicast (IGMP) 
IGMP General Operation and Features 
IGMP General Operation and Features 
IGMP Features 
Feature  Default  Menu  CLI  Web 
view igmp configuration  n/a  —  page 4-6  — 
show igmp status for multicast 
n/a  —  Yes  — 
groups used by the selected 
VLAN 
enabling or disabling IGMP 
(Requires VLAN ID Context) 
disabled  —  page 4-8  page 4-11 
per-port packet control  auto  —  page 4-9  — 
IGMP traffic priority  normal  —  page 4-10  — 
querier enabled — page 4-10 — 
fast-leave  disabled  —  page 4-13  — 
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. 
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