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Figure6-3. multicast MAC address
Figure6-4. IP multicast MAC address
Multicast MAC address can be either IP or non-IP. IP multicast MAC address is mapped from
Layer 3 IP multicast address (as shown in Figure6-4), where the first three bytes must be
rd
01:00:5e and the 23
bit be 0, and the rest 23 bits are the same as the lower 23 bits of IP
address, . Non-IP multicast MAC address includes all others excluding IP. For example,
01:00:5e:00:00:01 is IP multicast MAC address, while 01:00:ff:00:00:01 is non-IP.
3. Layer 2 multicast transmission mode
There are modes for using Layer 2 hardware multicast transmission table: unregistered or
registered.
For unregistered mode, if a matching entry is found in the table for a Layer 2 multicast flow, it's
transmitted according to the output ports list of the entry; Otherwise, if no entry is found, it's
transmitted as for broadcast, i.e., to all other ports in the VLAN.
For registered mode, it's different from unregistered mode in that data will be discarded if no
matching entry is found.
(Please refer to Chapter 3 "VLAN" for more info.)
On the iSpirit 3026 switch, if IGMP SNOOPING is off, unregistered mode will be used; registered
if otherwise.
4. Layer 2 static multicast and Layer 2 dynamic multicast
Entries of multicast MAC address can be added into the Layer 2 hardware multicast
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