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Difficulty: EasyIPv6 Address Types and EUI-64

When deriving an IPv6 64-bit interface identifier using the EUI-64 process from a 48-bit MAC address, which bit position (counted from left to right within the first octet) is inverted?

Answer: 7 / 7th / 7th bit / bit 7 / seventh / seventh bit

Answer

The 7th bit position (the Universal/Local bit) in the first octet of the MAC address is inverted.
During the EUI-64 calculation process, the 7th bit from the left of the MAC address's first octet (the Universal/Local bit) is inverted. For example, a universal MAC address starting with binary 00000000 (0x00) becomes 00000010 (0x02) after the 7th bit is flipped from 0 to 1.

Step-by-Step Solution

1
Identify the modification rules for converting a 48-bit MAC address to an EUI-64 64-bit interface identifier.
The two required modifications are inserting the 16-bit value FFFEFFFE into the middle of the MAC address and inverting the Universal/Local (U/L) bit.
EUI-64 formatting requires extending the 48-bit MAC address to 64 bits and adjusting the scope indicator.
2
Determine the exact location of the Universal/Local (U/L) bit.
The U/L bit is located at the 7th bit position from the left in the first octet of the MAC address.
In standard IEEE MAC address formatting, bit 7 specifies whether the address is universally administered (0) or locally administered (1).

Key Concept

EUI-64 Universal/Local Bit Inversion
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Topics

IPv6 Address Types and EUI-64

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