15-3
Multimedia Traffic Control with IP Multicast (IGMP)
General Operation and Features
Multimedia Traffic Control
with IP Multicast (IGMP)
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 give n VLAN through all ports on
that VLAN (except the port on which it recei ved 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 mul ticast
traffic will be generated by one or more servers (inside or outside of the loca l
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 an d 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 15-10.)
Feature Default Menu CLI Web
view igmp configuration n/a —page 15-6 —
show igmp status for multicast
groups used by the selected
VLAN
n/a —Yes —
enabling or disabling IGMP
(Requires VLAN ID Context)
disabled —page 15-8 page 15-10
per-port packet control auto —page 15-9 —
IGMP traffic priority normal —page 15-9 —
querier enabled —page 15-10 —