Reference Guide

Internet Group Management Protocol | 407
Enabling IGMP Immediate-leave
Configure the switch to remove a group-port association upon receiving an IGMP Leave message using the
command
ip igmp fast-leave from INTERFACE VLAN mode. View the configuration using the command
show config from INTERFACE VLAN mode, as shown in the example below.
FTOS(conf-if-vl-100)#show config
!
interface Vlan 100
no ip address
ip igmp snooping fast-leave
shutdown
FTOS(conf-if-vl-100)#
Disabling Multicast Flooding
If the switch receives a multicast packet that has an IP address of a group it has not learned (unregistered
frame), the switch floods that packet out of all ports on the VLAN.
On the E-Series, you can configure the switch to only forward unregistered packets to ports on a VLAN
that are connected to multicast routers (mrouter ports) using the command
no ip igmp snooping flood from
CONFIGURATION mode. When flooding is disabled, if there are no such ports in the VLAN connected to
a multicast router, the switch drops the packets.
On the C-Series and S-Series, when you configure
no ip igmp snooping flood, the system drops the packets
immediately. The system does not forward the frames on mrouter ports, even if they are present. On the
C-Series and S-Series, Layer 3 multicast must be disabled (
no ip multicast-routing) in order to disable
multicast flooding.
Specifying a Port as Connected to a Multicast Router
You can statically specify a port in a VLAN as connected to a multicast router using the command ip igmp
snooping mrouter from INTERFACE VLAN mode.
View the ports that are connected to multicast routers using the command
show ip igmp snooping mrouter
from EXEC Privilege mode.