Dell Force10 C150 - Disabling Multicast Flooding; Specifying a Port as Connected to a Multicast Router; Configuring the Switch as Querier

Internet Group Management Protocol | 413
Figure 19-10. Enabling IGMP Snooping
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.
Configuring the Switch as Querier
Hosts that do not support unsolicited reporting wait for a general query before sending a membership
report. When the multicast source and receivers are in the same VLAN, multicast traffic is not routed, and
so there is no querier. You must configure the switch to be the querier for a VLAN so that hosts send
membership reports, and the switch can generate a forwarding table by snooping.
Configure the switch to be the querier for a VLAN by first assigning an IP address to the VLAN interface,
and then using the command
ip igmp snooping querier from INTERFACE VLAN mode.
• IGMP snooping Querier does not start if there is a statically configured multicast router interface in the
VLAN.
• The switch may lose the querier election if it does not have the lowest IP address of all potential
queriers on the subnet.
FTOS(conf-if-vl-100)#show config
!
interface Vlan 100
no ip address
ip igmp snooping fast-leave
shutdown
FTOS(conf-if-vl-100)#