User guide

206 Summit24e3 Switch Installation and User Guide
IP Multicast Routing
IGMP is enabled by default on the switch. However, the switch can be configured to disable the
generation of period IGMP query packets. IGMP query should be enabled when the switch is
configured to perform IP unicast or IP multicast routing.
IGMP Snooping
IGMP snooping is a layer 2 function of the switch. It does not require multicast routing to be enabled.
The feature reduces the flooding of IP multicast traffic. IGMP snooping optimizes the usage of network
bandwidth, and prevents multicast traffic from being flooded to parts of the network that do not need
it. The switch does not reduce any IP multicast traffic in the local multicast domain (224.0.0.x).
IGMP snooping is enabled by default on the switch. If you are using multicast routing, IGMP snooping
must be enabled. If IGMP snooping is disabled, all IGMP and IP multicast traffic floods within a given
VLAN. IGMP snooping expects at least one device in the network to periodically generate IGMP query
messages. Without an IGMP querier, the switch stops forwarding IP multicast packets to any port.
When a port sends an IGMP leave message, the switch removes the IGMP snooping entry after 10
seconds. The switch sends a query to determine which ports want to remain in the multicast group. If
other members of the VLAN want to remain in the multicast group, the router ignores the leave
message, but the port that requests removal is removed from the IGMP snooping table.
If the last port within a VLAN sends an IGMP leave message, the router does not receive any responses
to the query, and the router immediately removes the VLAN from the multicast group.
IGMP configuration commands can be found in Table 62.
Configuring IP Multicasting Routing
To configure IP multicast routing, you must do the following:
1 Configure the system for IP unicast routing.
2 Enable multicast routing on the interface using the following command:
enable ipmcforwarding {vlan <name>}
The enable ipmcforwarding command enables IP multicast forwarding on an IP interface. If no
options are specified, all configured IP interfaces are affected. By default,
ipmcforwarding is disabled
when you add a new IP interface.
Table 62 describes the commands used to configure the Internet Gateway Message Protocol (IGMP).