ethers(5)

ethers5

Ethernet address database

Overview

The ethers database contains information regarding known 48-bit ethernet addresses of hosts on an Internetwork. The data is stored in a file called /etc/ethers in the following format:

ethernet-address fully-qualified-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. A ``+'' at the start of a line will cause the ethers(3) library functions to use data stored in the NIS ethers.byname and ethers.byaddr maps in addition to the data in the /etc/ethers file.

An ethernet address is expressed in ASCII form as "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/ethers database should correspond to entries in the hosts(5) file.

The ether_line() function in the standard C library can be used to break individual lines in the /etc/ethers database into their individual components: a binary Ethernet address stored as an ether_addr structure, and a hostname stored as a character string.

Files

/etc/ethers

The ethers file resides in /etc.

Releases

87 releases since FreeBSD 2.0.5-RELEASE; the text changed 45 times.

  1. 2.0.5
  2. 2.1.5–2.1.7.1
  3. 2.2.2–2.2.5
  4. 2.2.6–2.2.8
  5. 2.2.9
  6. 3.0–3.2
  7. 3.3–3.4
  8. 3.5–3.5.1
  9. 4.0–4.2
  10. 4.3
  11. 4.4–4.5
  12. 4.6–4.11
  13. 5.0–5.5
  14. 6.0–6.3
  15. 6.4
  16. 7.0
  17. 7.1
  18. 7.2
  19. 7.3
  20. 7.4
  21. 8.0
  22. 8.1
  23. 8.2
  24. 8.3
  25. 8.4
  26. 9.0
  27. 9.1
  28. 9.2
  29. 9.3
  30. 10.0
  31. 10.1
  32. 10.2
  33. 10.3
  34. 10.4
  35. 11.0
  36. 11.1
  37. 11.2
  38. 11.3
  39. 11.4
  40. 12.0
  41. 12.1
  42. 12.2
  43. 12.3
  44. 12.4
  45. 13.0–13.2
  46. 13.3–16.0

History

The ethers format is based on the format used in SunOS 4.1.x.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.