Chapter 22
| Multicast Filtering Commands
IGMP Snooping
– 593 –
The router/querier stops forwarding traffic for that group only if no host replies
to the query within the timeout period. (The timeout for this release is currently
defined by Last Member Query Interval (fixed at one second) * Robustness
Variable (fixed at 2) as defined in RFC 2236.).
◆ If immediate-leave is used, the switch assumes that only one host is connected
to the interface. Therefore, immediate leave should only be enabled on an
interface if it is connected to only one IGMP-enabled device, either a service
host or a neighbor running IGMP snooping.
◆ If the “by-host-ip” option is used, the router/querier will not send out a group-
specific query when an IGMPv2/v3 leave message is received. But will check if
there are other hosts joining the multicast group. Only when all hosts on that
port leave the group will the member port be deleted.
◆ This command is only effective if IGMP snooping is enabled, and IGMPv2 or
IGMPv3 snooping is used.
Example
The following shows how to enable immediate leave.
Console(config)#ip igmp snooping vlan 1 immediate-leave
Console(config)#
ip igmp snooping vlan
last-memb-query-
count
This command configures the number of IGMP proxy group-specific or group-and-
source-specific query messages that are sent out before the system assumes there
are no more local members. Use the no form to restore the default.
Syntax
ip igmp snooping vlan vlan-id last-memb-query-count count
no ip igmp snooping vlan vlan-id last-memb-query-count
vlan-id - VLAN ID (Range: 1-4094)
count - The number of proxy group-specific or group-and-source-specific
query messages to issue before assuming that there are no more group
members. (Range: 1-255)
Default Setting
2
Command Mode
Global Configuration
Command Usage
This command will take effect only if IGMP snooping proxy reporting or IGMP
querier is enabled (page 585).
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