setting ntp with dhcp

Mel Beckman mel at
Fri Oct 1 15:29:35 UTC 2021


While Murkund’s point about some devices ignoring this option (I’m not sure why any cellphones would accept it, for example, Android or otherwise, since they get time from the cellular network), it’s pretty much an industry standard that desktop and WiFi *VoIP* phones all use it. It’s how they get the time to display on their little screens :)

Other than that major device segment, though, I’ve only seen other devices support direct hard-coded configuration of an NTP server. Windows is certainly that way, and even has a way to distribute time from the ubiquitous Windows server. 

I think hard coding is still the defacto standard for everything other then VoIP. 


> On Oct 1, 2021, at 8:08 AM, Mukund Sivaraman <muks at> wrote:
> 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
> completely.
> 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.
>        Mukund

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