setting ntp with dhcp

Mukund Sivaraman muks at
Fri Oct 1 15:05:54 UTC 2021

Hi Giovane

On Fri, Oct 01, 2021 at 04:12:15PM +0200, Giovane C. M. Moura via NANOG wrote:
> hello folks,
> So DHCP can also be used to set NTP servers on clients, for both
> IPv4[rfc2132] and IPv6[rfc5908].
> I'm looking for statistics on setting NTP servers on clients using DHCP,
> in the wild. Does anyone know if there is any available somewhere?
> I'm also looking for reports from operators and their experiences on
> this, and why they use (or not) this DHCP feature, and what types of
> networks is this deployed, and their motivations, etc.

Some PC OSs such as Linux distributions obey the "ntp-servers" ISC DHCP
option (mapped to option code 42 in RFC 2132 section 8.3) and configure
the client's NTP service with it.

But not all DHCP clients do. E.g., Android phones ignore this option

We use this option in our office to configure a local timeserver (uses a
Garmin GPS 18x LVC receiver), but it only works on client machines that
attempt to make use of that option.

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