3Com 4007, Implementation Manual, Page: 217 / 684

Processing IP Multicast Packets 217
Processing IP
Multicast Packets
Table 45 summaries how a Layer 2 Switching Module processes various
types of IGMP packets and other IP multicast packets.
* Except for the port on which the packet originated.
Some ports may not be available for carrying traffic. Two examples are:
ports that have been administratively disabled or ports that the Spanning
Tree Protocol has prevented from being in the forwarding state.
Table 45 How the System Processes IP Multicast Packets
Packet Type Is Forwarded To*
IGMP Membership
Reports Ports in the broadcast domain that lead to multicast
routers
Port that leads to the querier (if another device is the
querier)
IGMP Queries All ports in the broadcast domain
IGMP Leave-Group
Messages All ports in the broadcast domain
Packets with addresses
[224 – 139].[0,128].0.x
where x = 0 – 255
All ports in the broadcast domain
(See “Effects of MAC Address Aliasing” later in this
chapter.)
Packets addressed to
known (registered) IP
multicast group Ports on which IGMP membership reports for that
group have been heard
Ports that lead to multicast routers
Port that leads to the querier (if another device is the
querier)
Packets addressed to
unknown IP multicast
group (group for
which no host has
registered) No ports, except those that lead to multicast routers
and the querier (if another device is the querier).