A network administrator statically assigns a multicast address of 239.255.8.5 to an application running on a server. The NIC on the server is with the MAC address of AB.54.C1.01.B8.9F. Which Layer 2 multicast address will receivers use on their interfaces in order to receive the multicast feed?

When a receiver wants to receive multicast feed from a particular multicast service, it will send a IGMP join message with the multicast IP address of the service and then reprogram the receiver interface with the matching multicast MAC address. To find the matching MAC address, do the following:

Convert the IP multicast address 239.255.8.5 to binary form, 11101111.11111111.00001000.00000101
Separate the 23 low-order binary bits from the converted address, 1111111.00001000.00000101
Convert these bits to hexadecimal: 7F:08:05
Because the first 24bits of a multicast MAC address are 01.00.5E, The resulting multicast MAC address is then 01:00:5E:7F:08:05.