UTStarcom iSpirit 3026 Manual page 154

2. Multicast MAC Address
Multicast address of IPv4 in Internet layer will be converted into Internet physic address (MAC
Address). For an unicast Internet address, through ARP protocol it can obtain the physic
address related with IP address. But under multicast mode ARP protocol cannot achieve this
kind of funtion, and you should in other ways to obtain physic address. The way to achieve this
convertion is described in following RFC document:
● RFC1112：Multicast IPv4 to Ethernet physical address correspondence
● RFC1390：Correspondence to FDDI
● RFC1469：Correspondence to Token-Ring networks
In the most Ethernet address, the conversion is like this: determine the first 24-digit of physic
address of Ethernet (MAC address) as 01:00: 5E, which is the important information digit. The
very next is determined into 0, other 23 digits are filled by the lower 23-digit in IPv4 multicast
address. About this convesion please refer to Figure 14-3:
Figure 14-3 Conversion From Multicast IP Address to Multicast MAC Address
for example:
multicast address is 224.0.0.5, and its Ethernet physic address is (MAC address)
01:00:5E:00:00:05.
3. Two Special Multicast Addresses
224.0.0.1: identify all host machines in sub-net. In the same sub-net all host machines with
multicast function are the members. 224.0.0.2: this address is used for identifying all routers with
multicast function in the Internet.