It looks like there are two options for providing network time settings to a DHCP client; option 004 and option 042. The description for 004 is "Time Server", while 042 specifies NTP. Is there a reason to use one or the other, or is it just vendor preference? If the client uses option 042, is the time offset in option 002 still used?


From a Google search, first result:

Option 004 specifies servers that provide TIME/ITP (as per RFC 868). This is not a recommended protocol/service in a Windows environment.

Option 042 specifies servers that provide NTP/SNTP (RFC 1769). This is the preferred time service in a Windows environment (assuming the absence of Active Directory which maintains the time on your behalf).

  • Unfortunately that site is unreadable unless your referer is from Google. – Zoredache May 12 '09 at 20:57
  • Rats! Did not realized, thank you. Link updated. – user1797 May 12 '09 at 21:05
  • Thanks. I wound up answering the last question myself. The (non windows) device that I'm concerned with will look for option 042 then 004, and will use 002 for GMT offset. – TimM May 13 '09 at 14:58
  • Updated the link, so it will go directly to the source, without the need of going to Google. – user1797 May 15 '09 at 11:20
  • Option 042 refers to NTP (RFC 1769)
  • Option 004 refers to TIME/ITP (RFC 868)



The RFC 868 "time" service as specified by Option 4 is pretty much obsolete and only has 1s resolution.

Modern networks should always use NTP (Option 42).

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