Brocade Communications Systems Brocate Ethernet Access Switch 6910 - Manual (Page 1110)

1060 Brocade 6910 Ethernet Access Switch Configuration Guide
53-1002581-01
Layer 2 IGMP (Snooping and Query)
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Command Usage
• IGMP Snooping – This switch can passively snoop on IGMP Query and Report packets
transferred between IP multicast routers/switches and IP multicast host groups to identify the
IP multicast group members. It simply monitors the IGMP packets passing through it, picks out
the group registration information, and configures the multicast filters accordingly.
NOTE
If unknown multicast traffic enters a VLAN which has been configured with a router port, the
traffic is forwarded to that port. However, if no router port exists on the VLAN, the traffic is
dropped if unregistered data flooding is disabled (default behavior), or flooded throughout the
VLAN if unregistered data flooding is enabled (see “Unregistered Data Flooding” in the
Command Attributes section).
• IGMP Querier – A router, or multicast-enabled switch, can periodically ask their hosts if they
want to receive multicast traffic. If there is more than one router/switch on the LAN performing
IP multicasting, one of these devices is elected “querier” and assumes the role of querying the
LAN for group members. It then propagates the service requests on to any upstream multicast
switch/router to ensure that it will continue to receive the multicast service.
Parameters
These parameters are displayed:
• IGMP Snooping Status – When enabled, the switch will monitor network traffic to determine
which hosts want to receive multicast traffic. This is referred to as IGMP Snooping. (Default:
Disabled)
When IGMP snooping is enabled globally, the per VLAN interface settings for IGMP snooping
take precedence (see
“Setting IGMP Snooping Status per Interface” on page 1067).
When IGMP snooping is disabled globally, snooping can still be configured per VLAN interface,
but the interface settings will not take effect until snooping is re-enabled globally.
• Proxy Reporting Status – Enables IGMP Snooping with Proxy Reporting. (Default: Disabled)
When proxy reporting is enabled with this command, the switch performs “IGMP Snooping with
Proxy Reporting” (as defined in DSL Forum TR-101, April 2006), including last leave, and query
suppression.
Last leave sends out a proxy query when the last member leaves a multicast group, and query
suppression means that specific queries are not forwarded from an upstream multicast router
to hosts downstream from this device.
When proxy reporting is disabled, all IGMP reports received by the switch are forwarded
natively to the upstream multicast routers.
• TCN Flood – Enables flooding of multicast traffic if a spanning tree topology change
notification (TCN) occurs. (Default: Disabled)
When a spanning tree topology change occurs, the multicast membership information learned
by switch may be out of date. For example, a host linked to one port before the topology change
(TC) may be moved to another port after the change. To ensure that multicast data is delivered
to all receivers, by default, a switch in a VLAN (with IGMP snooping enabled) that receives a
Bridge Protocol Data Unit (BPDU) with TC bit set (by the root bridge) will enter into “multicast
flooding mode” for a period of time until the topology has stabilized and the new locations of all
multicast receivers are learned.