Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 135)

Multi-Service IronWare Multicast Configuration Guide 123
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IP multicast traffic reduction
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IP multicast traffic reduction
In Layer 2 mode, by default, the Brocade device forwards all IP multicast traffic out all ports except
the port on which the traffic was received. Forwarding decisions are based on the Layer 2
information in the packets. To reduce multicast traffic through the device, you can enable IP
Multicast Traffic Reduction. When this feature is enabled, forwarding decisions are made in
hardware, based on multicast group. The device will forward multicast traffic only on the ports
attached to multicast group members, instead of forwarding all multicast traffic to all ports.
By default, the device broadcasts traffic addressed to an IP multicast group that does not have any
entries in the IGMP table. When you enable IP Multicast Traffic Reduction, the device determines
the ports that are attached to multicast group members based on entries in the IGMP table. The
IGMP table entries are created when the VLAN receives a group membership report for a group.
Each entry in the table consists of an IP multicast group address and the ports from which the
device has received Group Membership reports.
When the device receives traffic for an IP multicast group, the device looks in the IGMP table for an
entry corresponding to that group. If the device finds an entry, it forwards the group traffic out the
ports listed in the corresponding entries, as long as the ports are members of the same VLAN. If
the table does not contain an entry corresponding to the group, or if the port is a member of the
default VLAN, the device broadcasts the traffic.
Configuration requirements
Consider the following configuration requirements and application notes:
• The IP Multicast Traffic Reduction feature is applicable to Layer 2 mode only.
• If the route-only feature is enabled on the Brocade device, then IP Multicast Traffic Reduction
will not be supported.
• This feature is not supported on the default VLAN of the Brocade device.
• When one or more Brocade devices are running Layer 2 IP Multicast Traffic reduction,
configure one of the devices for active IGMP and leave the other devices configured for passive
IGMP. However, if the IP multicast domain contains a multicast-capable router, configure all the
Brocade devices for passive IGMP and allow the router to actively send the IGMP queries.
• IP multicast traffic reduction and PIM SM Traffic Snooping are supported on the Brocade
device.
Configuring IP multicast traffic reduction
When you enable IP Multicast Traffic Reduction, you also can configure the following features:
• IGMP mode – When you enable IP Multicast Traffic Reduction, the device 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 device to
actively send the IGMP queries. The IGMP passive mode is also known as IGMP snooping and
facilitates IP Multicast Traffic Reduction.
• Query interval – The query interval specifies how often the device 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.