How is an EUI-64 format interface ID created from a 48-bit MAC address?
The modified EUI-64 format interface identifier is derived from the 48-bit link-layer (MAC) address by inserting the hexadecimal number FFFE between the upper three bytes (OUI field) and the lower three bytes (serial number) of the link layer address.
EUI-64 stands for Extended Unique Identifier 64-bit, which is used for identifying network interfaces. The EUI-64 format interface ID is created from a 48-bit MAC address by inserting the value 0xFFFE between the upper three bytes (OUI) and the lower three bytes (NIC) of the MAC address.
The correct answer is D. Here's a more detailed explanation of why:
A MAC address is a unique identifier assigned to network interfaces for communication on a network. A MAC address is 48 bits long and is typically represented in hexadecimal notation. EUI-64 is a method of generating a unique 64-bit interface identifier (IID) from a MAC address.
To create an EUI-64 format interface ID from a MAC address, the following steps are taken:
Take the 48-bit MAC address and split it into its upper 24 bits (OUI) and lower 24 bits (NIC).
Insert the value 0xFFFE between the upper 24 bits and the lower 24 bits. This creates a new 64-bit value.
The seventh bit (counting from the left) of the OUI is flipped from 0 to 1 to indicate that the address is locally administered. This is because the OUI is assigned by the IEEE, while the NIC is assigned by the device manufacturer.
For example, let's say we have a MAC address of 00:11:22:33:44:55. Here's how we would generate the EUI-64 format interface ID:
Split the MAC address into its OUI and NIC: 001122 for the OUI and 334455 for the NIC.
Insert 0xFFFE between the OUI and NIC: 001122FFFE334455.
Flip the seventh bit of the OUI: 021122FFFE334455.
So the EUI-64 format interface ID for this MAC address would be 0211:22FF:FE33:4455.
In summary, the EUI-64 format interface ID is created by inserting 0xFFFE between the upper three bytes and the lower three bytes of the MAC address, and flipping the seventh bit of the OUI to indicate that the address is locally administered.