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Zorluk: ZorIPv6 Address Types and EUI-64

A Cisco router interface with a burned-in MAC address of `d46d.5012.abcd` is configured with the command `ipv6 address 2001:db8:100:1::/64 eui-64`. What is the complete 128-bit IPv6 global unicast address assigned to this interface?

Cevap: 2001:db8:100:1:d66d:50ff:fe12:abcd / 2001:DB8:100:1:D66D:50FF:FE12:ABCD / 2001:db8:100:1:d66d:50ff:fe12:abcd/64 / 2001:0db8:0100:0001:d66d:50ff:fe12:abcd

Cevap

2001:db8:100:1:d66d:50ff:fe12:abcd
To derive the IPv6 global unicast address using EUI-64, the router takes the assigned `/64` prefix `2001:db8:100:1::/64` and appends a 64-bit interface identifier generated from the interface's MAC address (`d46d.5012.abcd`). The MAC address is split into `d46d:50` and `12:abcd`, `FFFE` is inserted into the middle (`d46d:50ff:fe12:abcd`), and the 7th bit of the first byte is inverted (`d4` = `1101 0100` becomes `d6` = `1101 0110`). The final address is `2001:db8:100:1:d66d:50ff:fe12:abcd`.

Adım Adım Çözüm

1
Split the 48-bit MAC address into two 24-bit halves.
Left half: `d4:6d:50`, Right half: `12:ab:cd`.
EUI-64 process requires dividing the MAC address to insert the 16-bit midpoint padding.
2
Insert the 16-bit hexadecimal value `FFFE` between the two MAC halves.
Resulting 64-bit sequence: `d46d:50ff:fe12:abcd`.
EUI-64 expands a 48-bit MAC address into a 64-bit interface identifier using `FFFE`.
3
Invert the 7th bit (Universal/Local bit) of the first byte (`d4`).
Byte `d4` in binary is `1101 0100`. Inverting the 7th bit yields `1101 0110`, which is `d6` in hexadecimal. Modified interface identifier: `d66d:50ff:fe12:abcd`.
IEEE EUI-64 standard requires flipping the U/L bit (7th bit from left) to indicate global uniqueness.
4
Combine the configured `/64` IPv6 prefix with the modified 64-bit EUI-64 interface identifier.
Complete IPv6 address: `2001:db8:100:1:d66d:50ff:fe12:abcd`.
Appending the derived 64-bit Interface ID to the `2001:db8:100:1::/64` network prefix completes the 128-bit global unicast address.

Anahtar Kavram

Derivation of IPv6 EUI-64 Interface Identifier from a 48-bit MAC address
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IPv6 Address Types and EUI-64

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