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Difficulty: EasyIPv6 Address Types and EUI-64

During the standard EUI-64 process used to derive a 64-bit IPv6 interface identifier from a 48-bit MAC address, what 16-bit hexadecimal value is inserted into the middle of the MAC address?

Answer: FFFE / fffe / 0xFFFE / 0xfffe

Answer

FFFE
To create a 64-bit interface identifier using the IEEE EUI-64 format, a host takes its 48-bit MAC address, splits it into two 24-bit halves (OUI and NIC identifier), and inserts the 16-bit hexadecimal value FFFE (0xFFFE) in the middle. Additionally, the 7th bit (Universal/Local bit) of the first byte is inverted.

Step-by-Step Solution

1
Split the 48-bit MAC address into two equal 24-bit halves
The first 24 bits represent the Organizationally Unique Identifier (OUI) and the last 24 bits represent the Extension Identifier.
EUI-64 modification requires inserting a specific 16-bit sequence between these two halves.
2
Insert the 16-bit value FFFE into the midpoint between the two 24-bit halves
The 48-bit address expands to a 64-bit value containing FFFE in the center.
Inserting 0xFFFE creates the mandatory 64-bit structure required for an EUI-64 interface identifier.

Key Concept

EUI-64 Interface Identifier Generation
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Topics

IPv6 Address Types and EUI-64

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