300-320 Question #226: Real Exam Question with Answer & Explanation

The correct answer is D: only the low-order 23 bits of the IP address are used to map MAC addresses. Ethernet & FDDI Multicast Addresses - The low order bit (0x01) in the first octet indicates that this packet is a Layer 2 multicast packet. Furthermore, the “0x01005e” prefix has been reserved for use in mapping L3 IP multicast addresses into L2 MAC addresses. - When mapping L3 t

Question

Which two design concerns must be addressed when designing a multicast implementation? (Choose two.)

Options

Aonly the low-order 23 bits of the MAC address are used to map IP addresses
Bonly the low-order 24 bits of the MAC address are used to map IP addresses
Conly the high-order 23 bits of the MAC address are used to map IP addresses
Donly the low-order 23 bits of the IP address are used to map MAC addresses
Ethe 0x01004f MAC address prefix is used for mapping IP addresses to MAC addresses
Fthe 0x01005e MAC address prefix is used for mapping IP addresses to MAC addresses

Explanation

Ethernet & FDDI Multicast Addresses - The low order bit (0x01) in the first octet indicates that this packet is a Layer 2 multicast packet. Furthermore, the “0x01005e” prefix has been reserved for use in mapping L3 IP multicast addresses into L2 MAC addresses. - When mapping L3 to L2 addresses, the low order 23 bits of the L3 IP multicast address are mapped into the low order 23 bits of the IEEE MAC address. Notice that this results in 5 bits of information being lost.

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