For Nexus:
You cannot enable IGMP manually on an interface. IGMP is automatically enabled when you perform one of the following configuration tasks on an interface:
- Enable PIM
- Statically bind a local multicast group
- Enable link-local group reports
Source: http://www.cisco.com/en/US/docs/switches/datacenter/sw/nx-os/multicast/configuration/guide/b_multicast_chapter_011.html
For Catalyst:
By default, IGMP snooping is globally enabled on the switch. When globally enabled or disabled, it is also enabled or disabled in all existing VLAN interfaces. IGMP snooping is by default enabled on all VLANs, but can be enabled and disabled on a per-VLAN basis.
Global IGMP snooping overrides the VLAN IGMP snooping. If global snooping is disabled, you cannot enable VLAN snooping. If global snooping is enabled, you can enable or disable VLAN snooping.
Beginning in privileged EXEC mode, follow these steps to globally enable IGMP snooping on the switch:
conf t
ip igmp snooping !Globally enable IGMP snooping in all existing VLAN interfaces.
end
Source: http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_55_se/configuration/guide/swigmp.html
