Table 9.6: Web Management Trunk Group Information (Continued)
Configuring IP Multicast Traffic Reduction (HP 6208M-SX only)
The HP 6208M-SX forwards all IP multicast traffic by default based on the Layer 2 information in the packets.
Optionally, you can enable HP switches to make forwarding decisions in hardware based on IP multicast group by
enabling the IP Multicast Traffic Reduction feature.
When this feature is enabled, the switch examines the IP multicast address in an IP multicast packet and forward
the packet only on the ports from which the switch has received Group Membership reports for that group. The
switch sends traffic for other groups out all ports.
When you enable IP Multicast Traffic Reduction, you also can configure the following features:
IGMP mode – When you enable IP Multicast Traffic Reduction, the switch passively listens for IGMP Group
Membership reports by default. If the multicast domain does not have a router to send IGMP queries to elicit
these Group Membership reports, you can enable the switch to actively send the IGMP queries.
Query interval – The query interval specifies how often the switch sends Group Membership queries. This
query interval applies only to the active IGMP mode. The default is 60 seconds. You can change the interval
to a value from 10 – 600 seconds.
Age interval – The age interval specifies how long an IGMP group can remain in the IGMP group table without
the switch receiving a Group Membership report for the group. If the age interval expires before the switch
receives another Group Membership report for the group, the switch removes the entry from the table. The
default is 140 seconds. You can change the interval to a value from 10 – 1220 seconds.
Forwarding policy – The switch forwards all IP multicast traffic by default but you can enable the switch to
forward IP multicast traffic only for groups for which the switch has received a Group Membership report, and
drop traffic for all other groups.
The following sections describe how to configure IP multicast parameters on an HP switch.
Enabling IP Multicast Traffic Reduction
By default, the HP 6208M-SX forwards all IP multicast traffic out all ports except the port on which the traffic was
received. To reduce multicast traffic through the switch, you can enable IP Multicast Traffic Reduction. This
feature configures the switch to forward multicast traffic only on the ports attached to multicast group members.
The switch determines the ports that are attached to multicast group members based on entries in the IGMP table.
Each entry in the table consists of an IP multicast group address and the HP switch ports from which the switch
has received Group Membership reports for that group.
By default, the switch broadcasts traffic addressed to an IP multicast group that doesn't have an entry in the IGMP
table. You can configure the switch to filter out traffic for these groups. See "Filtering Multicast Groups" on
After you enable IP Multicast Traffic Reduction, when the switch receives traffic for an IP multicast group, the
switch looks in the IGMP table for an entry for that group. If the switch finds an entry, the switch forwards the
group traffic out the ports listed in the group entry. If the table does not contain an entry for the group, the switch
broadcasts the traffic.
The IGMP table is populated by receipt of Group Membership messages from IP multicast group members. Each
Group Membership message contains the member's IP address and the group address. The HP switch can
populate the IGMP table using the active or passive IGMP mode, as described in "Changing the IGMP Mode" on
page 9-48. By default, the switch uses the passive mode.
The ports in the trunk group.
Configuring Basic Features
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