---
name: "eui64"
section: "5"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/eui64/5"
---

# eui64(5)

IEEE EUI-64 address database

## NAME

**eui64** – IEEE EUI-64 address database

## DESCRIPTION

The **eui64** database contains information regarding known IEEE EUI-64s of hosts. The data is stored in a file called */etc/eui64* in the following format:

*EUI-64* *host-name*

Items are separated by any number of blanks and/or tab characters. A ‘#’ at the start of a line indicates the beginning of a comment that extends to the end of the line. Valid lines may also contain comments. A ‘+’ at the start of a line will cause the [eui64(3)](/eui64/3.md) library functions to use data stored in the NIS *eui64.byname* and *eui64.byid* maps in addition to the data in the */etc/eui64* file.

An EUI-64 is expressed in ASCII form as "x-x-x-x-x-x-x-x" where *x* is a hexadecimal value between 0x00 and 0xFF. The address values should be in network order. Hostnames specified in the */etc/eui64* database should correspond to entries in the [hosts(5)](/hosts/5.md) file.

## FILES

- */etc/eui64*

  The **eui64** file resides in */etc*.

## SEE ALSO

[eui64(3)](/eui64/3.md), [yp(8)](/yp/8.md)

## HISTORY

The **eui64** format is based on the [ethers(5)](/ethers/5.md) format.