IPv6 EUI 64 Calculator

Work out ipv6 eui 64 instantly with clear inputs, formula shown and shareable results.

About IPv6 EUI 64 Calculator

Modified EUI-64 turns a 48-bit MAC into a 64-bit interface identifier by inserting FFFE between the OUI and the NIC halves and inverting bit 1 of the first byte, the universal/local flag. Combined with a /64 prefix it produces the address that stateless autoconfiguration would assign, and with fe80:: it gives the link-local address.

Formula

Modified EUI-64

IID = (byte1 XOR 0x02) : byte2 : byte3 : FF : FE : byte4 : byte5 : byte6

byte1..6: The six bytes of the MAC address

Worked example

With the default values below, IPv6 EUI 64 Calculator returns EUI-64 interface identifier of 021a:2bff:fe3c:4d5e. Change any input above and every figure here is recalculated in your browser.

Inputs used

MAC address: 00:1A:2B:3C:4D:5E
IPv6 /64 prefix: 2001:db8:1:1

Results

EUI-64 interface identifier: 021a:2bff:fe3c:4d5e
Global address: 2001:db8:1:1:021a:2bff:fe3c:4d5e/64
Link-local address: fe80::021a:2bff:fe3c:4d5e/64
First byte transformation: 0x00 -> 0x02 (universal/local bit inverted)

Step by step

1Values used
2Modified EUI-64
3EUI-64 interface identifier= 021a:2bff:fe3c:4d5e
4Global address= 2001:db8:1:1:021a:2bff:fe3c:4d5e/64
5Link-local address= fe80::021a:2bff:fe3c:4d5e/64
6First byte transformation= 0x00 -> 0x02 (universal/local bit inverted)

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is bit 1 inverted?

In EUI-64 the bit means universal when set, the opposite of the MAC convention, so inverting keeps globally unique MACs mapping to universally scoped identifiers.

Do modern hosts still use EUI-64?

Many now prefer RFC 7217 stable opaque identifiers or RFC 8981 temporary addresses for privacy, but EUI-64 remains the default on plenty of routers and embedded stacks.