| RE: Re: [chrony-users] Chrony 3.1 refuses to sync with ntp server |
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- To: "chrony-users@xxxxxxxxxxxxxxxxxxxx" <chrony-users@xxxxxxxxxxxxxxxxxxxx>
- Subject: RE: Re: [chrony-users] Chrony 3.1 refuses to sync with ntp server
- From: Assaf Vainsencher <assaf@xxxxxxxxxxxx>
- Date: Tue, 28 Nov 2017 21:28:26 +0000
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- Thread-topic: [External] Re: [chrony-users] Chrony 3.1 refuses to sync with ntp server
Thank you. I confirmed that using maxdistance 16 fixed the issue we're seeing. Looks like our root dispersion is just over 10 which is why we were seeing the issue with the default setting in version 3.1.
-----Original Message-----
From: Miroslav Lichvar [mailto:mlichvar@xxxxxxxxxx]
Sent: Tuesday, November 28, 2017 1:52 PM
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: [External] Re: [chrony-users] Chrony 3.1 refuses to sync with ntp server
On Tue, Nov 28, 2017 at 06:10:29PM +0000, Assaf Vainsencher wrote:
> We recently updated from RHEL 7.3 to RHEL 7.4 which updated chrony to version 3.1 and we can't get it to sync properly with NTP server running on windows server 2008R2 - chronyc sources reports ^? Status for any of the windows 2008 NTP servers we try. Version 2.1.1 in RHEL 7.3 syncs fine. One of our software engineers tried compiling and installing version chrony 3.2 and it still didn't work. Downgrading chrony fixes the issue. Is there a suggested fix for this that we can try with our chrony configuration or is this a known incompatibility issue?
>
> We also found this post on stackexchange with someone experiencing a similar, if not the same, issue:
>
> https://unix.stackexchange.com/questions/404046/chrony-3-1-refuses-to-
> sync-with-ntp-server
The debug output attached there shows that the NTP server has a root dispersion which is too large to pass the source selection in the default configuration. As I understand it, this is a common issue with the Windows NTP server if it uses a long polling interval. If you run "chronyc ntpdata", it should print the value from the last response.
There is a hardcoded limit of 16 seconds for the root distance, which includes the root dispersion, but since chrony-2.2 there is an additional requirement applied in the source selection. By default it is 3 seconds. If your server has a larger dispersion (and distance), you will need to increase the maximum distance with "maxdistance XX"
in chrony.conf.
--
Miroslav Lichvar
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