In computer networking a multicast address is an identifier for a group of hosts that have joined a
multicast group. Multicast addressing can be used in the Link Layer (OSI Layer 2), such as Ethernet
Multicast, as well as at the Internet Layer (OSI Layer 3) as IPv4 or IPv6 Multicast. Which two
descriptions are correct regarding multicast addressing?

A.
The first 23 bits of the multicast MAC address are 0x01-00-5E. This is a reserved value that
indicates a multicast application.

B.
The last 3 bytes (24 bits) of the multicast MAC address are 0x01-00-5E. This is a reserved
value that indicates a multicast application.

C.
To calculate the Layer 2 multicast address, the host maps the last 23 bits of the IP address
into the last 24 bits of the MAC address. The high-order bit is set to 0.

D.
The first 3 bytes (24 bits) of the multicast MAC address are 0x01-00-5E. This is a reserved
value that indicates a multicast application.

Explanation:
The point of this question is the form of multicast MAC address, and the conversion between the
multicast MAC address and IP address.
The multicast MAC address is 6 bytes(48 bits), the first 3 bytes (24 bits) of the multicast MAC address
are 0x01-00-5E, the last 3 bytes(24 bits) of the multicast MAC address =0 + 23 bit(the last 23 bit of
the IP address). “0x01-00-5E” is a reserved value that indicates a multicast application.