NTP through DNS?

Danny Mayer mayer at pdmconsulting.net
Mon Sep 24 14:00:49 UTC 2018

On 9/22/2018 9:50 AM, Reindl Harald wrote:
> Am 22.09.18 um 03:39 schrieb Danny Mayer:
>>> but *nobody* cares about what is a good idea when the question was
>>> simply "does ntp discovery work" where the answer is simply no
>> No, that's not true. Consider what you are doing. You are substituting
>> SRV records for CNAME records. There is nothing magical here. NTP can
>> use the CNAME records. Either way the records have to be configured.
>> What do you think you are discovering? SRV records aren't magic
> * hell, the topic is "is ntp autodiscovery possible?"
> * that's done with SRV records for supported services
> * but nothing is using them in case of NTP
> * so the whole answer to the thread is simply "no"
> "NTP can use the CNAME records" makes no sense at all in this topic
> the topic is not about what NTP can use, the topic is about unconfigured
> machines *finding* the NTP server in the local network without any
> manually configuration - not more, mot less

This is very simple to do. It does not require SRV records to implement.
Note that I am only answering for the ntp reference implementation.

In your domain file add entries like this:

locationntp	CNAME ntp1.yourdomain
		CNAME ntp2.yourdomain
		CNAME externalntp.otherdomain
		CNAME externalntp.someotherdomain

In your ntp.conf file put the following line:
pool locationntp.yourdomain

This will cause it to use ALL of the entries listed. You can have as
many as 10 entries in your DNS and it will use all of them. Don't use
less than 3, 4 is better.

Simple enough?


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