User guide

14-4 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
IP M
ULTICAST
R
OUTING
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 S
NOOPING
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. An optional
optimization for IGMP snooping is the strict recognition of multicast routers only if the
remote devices has joined the DVMRP (224.0.0.4) or PIM (244.0.0.13) multicast groups.
IGMP configuration commands can be found in Ta ble 1 4-2.
C
ONFIGURING
IP M
ULTICASTING
R
OUTING
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>}
3 Enable DVMRP or PIM on all IP multicast routing interfaces, using one of the
following commands:
config dvmrp add vlan [<name> | all]
config pim add vlan [<name> | all] {dense | sparse}