Mac Address to EUI-64 Converter

May 14, 2026

Mac Address to EUI-64 Converter

Convert a MAC address into modified EUI-64, IPv6 interface ID, and link-local preview with byte-order control and first-octet checks.

📶Preset Scenarios

⚙Conversion Inputs

MAC or hex source Paste a MAC, spaced bytes, or raw hex. Source style Helps the breakdown explain parsing. Source family Use 6 bytes for MAC or 8 bytes for a seed. Byte order Reverse packet dumps before conversion. Preview mode Choose how the 64-bit result is framed. Output format Controls how the EUI-64 bytes are shown. Output case Applies to the rendered bytes and preview. Padding mode Useful when source bytes are short or long. First-octet rule Shows the bit state after conversion. IPv6 prefix preview Used for the link-local or custom /64 preview.

Source MAC

normalized input

Clean source bytes

EUI-64 Bytes

64-bit output

Inserted FFFE if needed

IPv6 IID

4 hextets

Interface identifier view

IPv6 Preview

/64 address

Prefix plus interface ID

Full Breakdown

💻Spec Grid

6 bytes

MAC input

Classic MAC-48 and EUI-48 source length.

8 bytes

EUI-64 result

Inserted FFFE expands the source to 64 bits.

FF FE

Bridge bytes

The middle pair that links MAC to EUI-64.

U/L

First-bit rule

Flip the universal/local bit after insertion.

📈Reference Tables

Input Style	Example	Bytes	Parser Note
Colon pairs	A1:B2:C3:D4:E5:F6	6 bytes	Common network text
Dash pairs	A1-B2-C3-D4-E5-F6	6 bytes	Label friendly
Cisco dotted	A1B2.C3D4.E5F6	6 bytes	Four hex chars each
Packet dump	F6 E5 D4 C3 B2 A1	6 bytes	Reverse before use

Mode	Result	Best Use	Extra Note
Modified EUI-64	Insert FFFE	IPv6 derivation	Flip U/L bit
IPv6 interface ID	4 hextets	SLAAC checks	Same 64-bit body
Link-local preview	fe80::IID	Quick test	Uses /64 prefix
EUI-64 seed	Keep 8 bytes	Compare layouts	No insert step

Output Format	Layout	Example	Best For
Colon	AA:BB:CC	A1:B2:C3	Most tools
Dash	AA-BB-CC	A1-B2-C3	Inventory tags
Dotted	AAAA.BBBB	A1B2.C3D4	Vendor notes
IID	XXXX:XXXX	AABB:CCDD	IPv6 display

Preset	Source	Mode	Why It Helps
Desktop NIC	Colon	Modified	Normal hardware path
Little-Endian	Plain	Modified	Reversed dump fix
SLAAC Preview	Dash	Link-local	Shows full IPv6 form
Broadcast Edge	Plain	IID	Edge-case sanity test

Tip: Reverse packet captures before you expand a MAC into EUI-64.

Tip: The U/L bit should be flipped after the FFFE insertion step.

This converter keeps the source bytes, inserted bridge, 64-bit result, and IPv6 preview visible so you can verify vendor prefixes and interface IDs in one pass.

An IPv6 link-local address can be different from the MAC address of a device due to the EUI-64 conversion process that change the MAC address to an interface ID. The MAC address of a device are comprised of six byte of data. An IPv6 interface ID, however, is comprised of eight byte.

Through the EUI-64 conversion process, the process can change a six byte MAC address into an eight byte interface ID. This conversion process is necessary because IPv6 require interface IDs to be 64 bits in size for various processes, such as SLAAC autoconfiguration. The EUI-64 conversion process begin by taking the six-byte MAC address of a device.

How a MAC address becomes an IPv6 link-local address

The process splits the MAC address after the third byte. The byte FF:FE are inserted into the MAC address in the middle of the address to make it eight byte in length. These specific byte must be inserted into a MAC address during the EUI-64 process to mark the end of the devices MAC address and allow for the definition of an expanded identifier.

Following the insertion of the bytes FF:FE, the second-least-significant bit of the first octet of the MAC address are flipped from a 0 to a 1 or from a 1 to a 0. Flipping this bit is a requirement for the process to transform the address from a unicast hardware address to an interface ID. Should this bit not be flipped, the network will incorrectly identify the interface ID, and it will cause errors throughout the global namespaces of the network.

As with most process, errors can occur during the EUI-64 process. One reason for errors during the process is the complexity of the process. For instance, the bit flip may be forgoten.

Another reason for errors is that link-local IPv6 addresses does not respond to ping requests. These addresses may also be presented in a different order in the packet captures of the data being sent by the device. In this case, the order of the bytes in the MAC address must be normalized.

In addition to these issues, the Organizationally Unique Identifier of a device MAC address can be used to determine whether a MAC address has been locally administered. The OUI is visible during the EUI-64 process, and it can be used to determine if a MAC address was locally administered before the EUI-64 conversion process occur. Finally, various tool can assist in the EUI-64 process.

These tools can accept MAC addresses of various formats and convert them into the correct format. These tools can automatically determine the length of the MAC address and provide a clear explanation of each step of the EUI-64 process. Furthermore, these tools can display the raw bytes of the EUI-64 addresses, the interface IDs, or the link-local IPv6 addresses of the device.

Using these tools will help to avoid making mistake in the EUI-64 process and ensure that the link-local IPv6 address is mathematicaly correct.