Brocade TurboIron 24X Series Configuration Guide - Manual (Page 814)

780 Brocade TurboIron 24X Series Configuration Guide
53-1003053-01
Configuring IGMP snooping
IGMP V3 membership tracking and fast leave
IGMP V3 gives clients membership tracking and fast leave capability. In IGMP V2, only one client on
an interface needs to respond to a router's queries. This can leave some clients invisible to the
router, making it impossible to track the membership of all clients in a group. When a client leaves
the group, the device sends group-specific queries to the interface to see if other clients on that
interface need the data stream of the client who is leaving. If no client responds, the device waits a
few seconds before it stops the traffic. You can configure the wait time using the ip multicast
leave-wait-time command.
IGMP V3 requires every client to respond to queries, allowing the device to track all clients. When
tracking is enabled, and an IGMP V3 client sends a leave message and there is no other client, the
device immediately stops forwarding traffic to the interface. This feature requires the entire VLAN
be configured for IGMP V3 with no IGMP V2 clients. If a client does not send a report during the
specified group membership time (the default is 260 seconds), that client is removed from the
tracking list.
Every group on a physical port keeps its own tracking record. However, it can only track group
membership; it cannot track by (source, group). For example, Client A and Client B belong to group1
but each receives traffic streams from different sources. Client A receives a stream from (source_1,
group1) and Client B receives a stream from (source_2, group1). The device still waits for the
configured leave-wait-time before it stops the traffic because these two clients are in the same
group. If the clients are in different groups, then the waiting period is not applied and traffic is
stopped immediately.
Enabling IGMP V3 membership tracking and fast leave for the VLAN
To enable the tracking and fast leave feature for VLAN 20, enter the following commands.
TurboIron(config)#vlan 20
TurboIron(config-vlan-20)#multicast tracking
Syntax: [no] multicast tracking
The membership tracking and fast leave features are supported for IGMP V3 only. If any port or any
client is not configured for IGMP V3, then the multicast tracking command is ignored.
Fast leave for IGMP V2
When a device receives an IGMP V2 leave message, it sends out multiple group-specific queries. If
no other client replies within the waiting period, the device stops forwarding traffic. When
fast-leave-v2 is configured, when the device receives a leave message, it immediately stops
forwarding to that port. The device does not send group specific-queries. You must ensure that no
snooping-enabled ports have multiple clients. When two devices connect together, the querier
should not be configured for fast-leave-v2, since the port might have multiple clients through the
non-querier. The number of queries, and the waiting period (in seconds) can be configured using
the ip multicast leave-wait-time command. The default is 2 seconds.
Enabling fast leave for IGMP V2
To configure fast leave for IGMP V2, enter the following commands.
TurboIron(config)#vlan 20
TurboIron(config-vlan-20)#multicast fast-leave-v2