TP-Link TL-SG2424 User Manual page 100

IPv4 Multicast Address
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1. IPv4 Multicast IP Address:
As specified by IANA (Internet Assigned Numbers Authority), Class D IP addresses are used as
destination addresses of multicast packets. The multicast IP addresses range from
224.0.0.0~239.255.255.255. The following table displays the range and description of several
special multicast IP addresses.
Multicast IP address range
224.0.0.0～224.0.0.255
224.0.1.0～224.0.1.255
239.0.0.0～239.255.255.255 Local management multicast addresses, which are
2. IPv4 Multicast MAC Address:
When a unicast packet is transmitted in an Ethernet network, the destination MAC address is the
MAC address of the receiver. When a multicast packet is transmitted in an Ethernet network, the
destination is not a receiver but a group with uncertain number of members, so a multicast MAC
address, a logical MAC address, is needed to be used as the destination address.
As stipulated by IANA, the high-order 24 bits of a multicast MAC address begins with 01-00-5E
while the low-order 23 bits of a multicast MAC address are the low-order 23 bits of the multicast IP
address. The mapping relationship is described as Figure 8-2.
Figure 8-2 Mapping relationship between multicast IPv4 address and multicast MAC address
The high-order 4 bits of the IP multicast address are 1110, identifying the multicast group. Only 23
bits of the remaining low-order 28 bits are mapped to a multicast MAC address. In that way, 5 bits
of the IP multicast address is not utilized. As a result, 32 IP multicast addresses are mapped to the
same MAC addresses.
IPv6 Multicast Address
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1. IPv6 Multicast Address
An IPv6 multicast address is an identifier for a group of interfaces, and has the following format:
Description
Reserved multicast addresses for routing protocols
and other network protocols
Addresses for video conferencing
used in the local network only
Table 8-1 Range of the special multicast IP
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