IGMP and multicast support
The Cisco Nexus 3550-F Fusion (formerly ExaLINK Fusion) includes support for IGMP snooping to optimize delivery of IPv4 multicast traffic.
Enabling IGMP snooping
IGMP snooping is available on a per switch/mux object basis.
IGMP snooping is disabled by default, but can be enabled using the
igmp snooping command within the switch or mux configuration mode:
admin@N3550-F(config-switch:my_switch)> igmp snooping
Enabled IGMP snooping on switch "my_switch"
You may review your IGMP snooping settings via 'show igmp snooping', note that by default IGMP snooping is disabled (an error will display to reflect this):
admin@N3550-F(config-switch:my_switch)> show igmp snooping
IGMP snooping : disabled
IGMP querier : disabled
Multicast router ports :
Flood unknown multicast : disabled
Fast leave : disabled
Error: IGMP snooping not enabled
Once enabled, it can be disabled using the no form of the command:
admin@N3550-F(config-switch:my_switch)> no igmp snooping
Disabled IGMP snooping on switch "my_switch"
IGMP groups
Groups that object ports are subscribed to can be reviewed at any time via the 'show igmp groups' command:
admin@N3550-F(config-switch:my_switch)> show igmp groups
Group Ports Version Timeout
---------- ----- ------- -------
224.2.0.52 B2 v2 259
224.2.0.55 C9 v3 63
IGMP querier
The Nexus 3550-F can also be configured as an IGMP querier
to periodically send IGMP queries originating from a particular IP address.
Use the igmp snooping querier command to enable IGMP querier functionality:
admin@N3550-F> configure switch my_switch igmp snooping querier 192.168.1.1
Configured IGMP querier on switch "my_switch" at address 192.168.1.1
The Nexus 3550-F will now periodically send IGMP queries from the designated address.
To disable the periodic sending of IGMP queries, use the no form of the command:
admin@N3550-F> configure switch my_switch no igmp snooping querier
Disabled IGMP querier on switch "my_switch"
Note: that the IGMP querier is enabled only if IGMP snooping is enabled.
IGMP Version
By default the Nexus 3550-F supports IGMPv3, however it can be configured to
use IGMPv1 or IGMPv2. Use the igmp snooping version command to set this:
admin@N3550-F> configure switch my_switch igmp snooping version 2
Set IGMP version 2 on switch "my_switch"
Multicast router ports
For IGMP snooping to function correctly, the switch needs to know which ports
are connected to multicast routers.
A port can be configured to be a multicast router port by using the
igmp mrouter command:
admin@N3550-F(config-switch:my_switch)> igmp mrouter A1
Configured port "A1" on switch "my_switch" as multicast router port
Multicast router ports can be removed by using the no form of the command:
admin@N3550-F(config-switch:my_switch)> no igmp mrouter A1
Removed port "A1" on switch "my_switch" as multicast router port
Unknown multicast groups
By default, all unknown multicast traffic will be suppressed on a
switch or mux object.
This behaviour can be changed using the igmp flood-unknown command.
admin@N3550-F(config-switch:my_switch)> igmp flood-unknown
Flooding unknown multicast traffic on switch "my_switch"
When this setting is enabled, traffic for a particular multicast group will be flooded before a host joins the group. Once a host joins the group, the group is no longer unknown and traffic will no longer be flooded for that group.
Use the no form of the igmp flood-unknown command to disable it:
admin@N3550-F(config-switch:my_switch)> no igmp flood-unknown
Suppressing unknown multicast traffic on switch "my_switch"
IGMP fast leave
IGMP snooping on the Nexus 3550-F supports "fast leave" functionality to reduce the time it takes for a host to leave a multicast group. When fast leave is enabled, a port is immediately removed from a multicast group when a IGMPv2 Leave message is received on the port.
Warning
At most one host can be connected to each non-router port when fast leave is enabled.
Ports with more than one host connected may be incorrectly dropped from multicast groups.
Use the command igmp snooping fast-leave to enable fast leave mode,
and the no form of this command to disable fast leave mode.
admin@N3550-F(config-switch:my_switch)> igmp snooping fast-leave
Enabling IGMP fast leave mode on switch "my_switch"
admin@N3550-F(config-switch:my_switch)> no igmp snooping fast-leave
Disabling IGMP fast leave mode on switch "my_switch"
Manually setting multicast filters
It is possible to manually add multicast filters instead of/as well as using IGMP snooping:
admin@N3550-F(config-switch:my_switch)> igmp static-group 225.1.1.1 port B1
Added static multicast group "225.1.1.1" for port "B1" on switch "my_switch"
This page was last updated on Feb-19-2021.