MAC address resolution-characteristics of broadcast address, multicast address, and unicast address

The MAC address is divided into three categories, namely broadcast address, multicast address and unicast address. First of all, FF:FF:FF:FF:FF:FF is undoubtedly the broadcast address. Each NIC is shipped with a single unicast address, and the first 24 digits are the manufacturer's number, assigned by the IEEE (Institute of Electrical and Electronics Engineers), and the latter 24 are the only number that the device manufacturer has developed for the NIC. For example, 08:00:20:0A:8C:6D is an example of a unicast address where 08:00:20 is the famous CPU manufacturer AMD's number. A unicast address is characterized by a 8-bit minimum of 0, and a unicast address has a total of 47-bit address space.
Another type of address is the multicast address. The feature of Mac multicast address is that the lowest bit of the first 8 digits is 1, so the MAC multicast address space is quite large---------minus 1 47-bit address space. For example, 01:80:c2:00:00:00 is a multicast address that represents a 802.1D Network Bridge multicast group. Network Bridge is to use this address, Exchange configuration information between each other, run a distributed spanning tree algorithm, eliminate the network topology structure of the loop.

The IP layer also has the concept of unicast, multicast, and broadcast. A total of 23 bits of 01:00:5e:00:00:00 to 01:00:5E:7F:FF:FF in Mac multicast addresses correspond to IP multicast addresses. Given an IP multicast address, its low 23-bit and 01:00:5e:00:00:00 lower to take "and" operations, can be to a Mac multicast address. However, the IP multicast address has 28-bit address space, the corresponding MAC multicast address is only 23 bits, so that every 32 IP multicast addresses are mapped to the same MAC address.
The MAC multicast address space is much larger than the IP multicast address space. If the network layer has only IP protocol, the IP multicast address can be mapped one-to-one to the MAC multicast address. But the MAC address is a data link layer concept, the upper layer of the network is far more than IP.

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