3Com Switch 7750 Configuration Guide Guide

IGMP Snooping Configuration 393
■ Most devices broadcast unknown multicast packets. In order that multicast
packets are not sent to filtered ports as unknown multicast packets, this
function is generally used together with the unknown multicast drop function.
Configuring to Limit
Number of Multicast
Groups on a Port
With a limit imposed on the number of multicast groups on the switch port, users
can no longer have as many multicast groups as they want when demanding
multicast group programs. Thereby, the bandwidth on the port is controlled.
Configuring Suppression
on IGMP Host Report
Packets
When a Layer 2 switch receives IGMP host report packets from a host in a
multicast group, the switch will forward the packets to the port of a Layer 3 switch
that is connected to it. In this way, a Layer 3 switch will receive the same IGMP
host report packets from multiple hosts in a multicast group when there are
multiple hosts in this multicast group.
When suppression on IGMP host report packets is enabled, in a query interval, the
Layer 2 switch will forward only the first IGMP host report packet from a multicast
group to the Layer 3 switch, and drop the other IGMP host report packets from
the same multicast group.
Configuring Multicast
VLAN
In the current multicast mode, when users in different VLANs order the same
multicast packet, the multicast stream is copied to each of the VLANs. This mode
wastes a lot of bandwidth.
By configuring a multicast VLAN, adding switch ports to the multicast VLAN and
enabling IGMP Snooping, you can make users in different VLANs share the same
multicast VLAN. This saves bandwidth because multicast streams are transmitted
only within the multicast VLAN and also guarantees security because the multicast
VLAN is isolated from user VLANs completely. Therefore, multicast information
streams can be transmitted to users continuously if multicast VLAN is configured.
Perform the following configuration to configure multicast VLAN.
Table 313 Configure to limit number of multicast groups on a port
Operation Command Description
Enter system view system-view -
Enter Ethernet port view interface interface-type
interface-number
-
Configure the number of
multicast groups on a port
igmp-snooping group-limit
limit [ vlan vlan-list [
overflow-replace ] |
overflow-replace ]
Optional
The number of multicast
groups on a port is not limited
by default.
Table 314 Configure suppression on IGMP host report packets
Operation Command Description
Enter system view system-view -
Configure suppression on
IGMP host report packets
report-aggregation
Required
By default, suppression on
IGMP host report packets is
disabled.