Reference Guide

114 | Internet Group Management Protocol (IGMP)
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How IGMP Snooping is Implemented on an Aggregator
• IGMP snooping is enabled by default on the switch.
• FTOS supports version 1, version 2, and version 3 hosts.
• FTOS IGMP snooping is based on the IP multicast address (not on the Layer 2 multicast MAC
address). IGMP snooping entries are stored in the Layer 3 flow table instead of in the Layer 2
forwarding information base (FIB).
• FTOS IGMP snooping is based on draft-ietf-magma-snoop-10.
• IGMP snooping is supported on all M I/O Aggregator stack members.
• A maximum of 8k groups and 4k virtual local area networks (VLAN) are supported.
• IGMP snooping is not supported on the default VLAN interface.
• Flooding of unregistered multicast traffic is enabled by default.
• Queries are not accepted from the server side ports and are only accepted from the uplink LAG.
• Reports and Leaves are flooded by default to the uplink LAG irrespective of whether it is an mrouter
port or not.
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. To disable multicast flooding on all
VLAN ports, enter the
no ip igmp snooping flood command in global configuration mode.
When multicast flooding is disabled, unregistered multicast data traffic is forwarded to only multicast
router ports on all VLANs. If there is no multicast router port in a VLAN, unregistered multicast data
traffic is dropped.
Displaying IGMP Information
Use the show commands in Table 9-1 to display information on IGMP. If you specify a group address or
interface:
• Enter a group address in dotted decimal format; for example, 225.0.0.0.
• Enter an interface in one of the following formats: tengigabitethernet slot/port,
port-channel port-channel-number, or vlan vlan-number.
Table 9-1. Displaying IGMP Information
Command Output
show ip igmp groups [group-address [detail] |
detail | interface [group-address [detail]]
(Figure 9-6)
Displays information on IGMP groups.
show ip igmp interface [interface] (Figure 9-7) Displays IGMP information on IGMP-enabled interfaces.
show ip igmp snooping mrouter [vlan
vlan-number] (Figure 9-8)
Displays information on IGMP-enabled multicast router (mrouter)
interfaces.
clear ip igmp groups [group-address | interface] Clears IGMP information for group addresses and IGMP-enabled
interfaces.