UTStarcom iSpirit 3026 Manual page 85

A multicast entry includes multicast group address, member ports, VLAN ID, Age and Type.
IGMP SNOOPING learns a multicast entry dynamically. When a port receives a IGMP REPORT
packet, IGMP SNOOPING will create a new multicast group with the ingress port of the
REPORT packet being added to the group; When a IGMP QUERY packet is received, if the
multicast group already exists in the switch, its ingress port will also be added to the group,
otherwise the QUERY packet is just be transmitted. IGMP SNOOPING also supports the Leave
method of IGMP V2, if IGMP SNOOPING is configured with immediate leave being enabled,
when a IGMP LEAVE packet is received, its ingress port will be removed from the group
immediately.
IGMP SNOOPING has two refreshing methods: the Leave method mentioned above and the
aging method. It usually use the aging method to delete old groups. When a group is added by
IGMP SNOOPING, it's time stamped; and the group will be deleted later when it's over the
configured age-time.
2. Layer 2 dynamic multicast with Layer 2 static multicast
Entries of multicast MAC address can be added into the Layer 2 hardware multicast
transmission table either by learning dynamically from IGMP SNOOPING, or by static
configuration. IGMP SNOOPING will only include IP address, while static configuration may
have non-IP address.
As said before, unregistered mode will be used for the hardware transmission table if IGMP
SNOOPING is closed, when no address will be added through dynamic learning. So the table
will be empty without static configuration. To limit broadcast range, users can add static multicast
entries that can specify the output ports list and thus reduce multicast data flow in the network.
When multicast is widely used in the network, users can enable IGMP SNOOPING on the switch
in order to limit multicast data flow. Then registered mode will be used, and multicast address
can be learned dynamically. Only multicast flow with matched entries will be transmitted. For
those that can't be learned but need to be transmitted, users can add static addresses to the
table.
When both of static configuration and dynamic learning have the same entry, the output ports list
will be the union of their ports. When deleting static entries, only static configured ports are
removed, while dynamic ones are kept; and so is deleting dynamic entries, i.e., when dynamic
entries become invalid, only dynamic ports are deleted, while static ones are kept.
3. To add a group
When a host wants to join in a group, it will send an IGMP REPORT packet, which has the
multicast group address the host wants to join. When a switch (with IGMP SNOOPING on)