IGMP and multicast support

The 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:

[email protected](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):

[email protected](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:

[email protected](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:

[email protected](config-switch:my_switch)> show igmp groups
Group      Ports Version Timeout
---------- ----- ------- ------- B2    v2      259 C9    v3      63

IGMP querier

The ExaLINK Fusion 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:

[email protected]> configure switch my_switch igmp snooping querier
Configured IGMP querier on switch "my_switch" at address

The ExaLINK Fusion 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:

[email protected]> 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 ExaLINK Fusion supports IGMPv3, however it can be configured to use IGMPv1 or IGMPv2. Use the igmp snooping version command to set this:

[email protected]> 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:

[email protected](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:

[email protected](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.

[email protected](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:

[email protected](config-switch:my_switch)> no igmp flood-unknown
Suppressing unknown multicast traffic on switch "my_switch"

IGMP fast leave

IGMP snooping on the ExaLINK Fusion 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.


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.

[email protected](config-switch:my_switch)> igmp snooping fast-leave
Enabling IGMP fast leave mode on switch "my_switch"

[email protected](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:

[email protected](config-switch:my_switch)> igmp static-group port B1
Added static multicast group "" for port "B1" on switch "my_switch"

This page was last updated on Mar-27-2018.