Showing active IGMP proxy VLANs
switch(config)# show igmp-proxy vlans
IGMP PROXY VLANs
VID Multicast Domain Active entries
------ ---------------- --------------
1 George 1
1 Sam 1
1 Jane 0
2 George 1
4 George 0
4 Bill 0
IGMP general operation and 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. 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 multicast 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 conferencing, and collaborative computing,
where there is multipoint communication, 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 is
configured on the hosts, and multicast traffic is generated by one or more servers (inside or outside of the local
network.) Switches in the network (that support IGMP) can then be configured 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 used to manage IP multicast traffic through
the switch. If no other querier is detected, the switch then also functions as the querier. If you need to disable the
querier feature, you can do so using the IGMP configuration CLI commands, see
on page
24.
NOTE:
IGMP configuration on the switches operates at the VLAN context level. If you are not using VLANs,
configure IGMP in VLAN 1 (the default VLAN) context.
More information
Options
With the CLI, you can configure these additional options:
Forward with high priority
Disabling this parameter (the default) causes the switch or VLAN to process IP multicast traffic, along with
other traffic, in the order received (usually, normal priority.) Enabling this parameter causes the switch or
VLAN to give a higher priority to IP multicast traffic than to other traffic.
Auto/blocked/forward
You can use the console to configure individual ports to any of the following states:
Chapter 2 Multimedia traffic control with IP multicast (IGMP)
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