[ntp:questions] ntpd won't sync

Steve Kostecke kostecke at ntp.isc.org
Mon May 14 21:34:11 UTC 2007

On 2007-05-08, David Durrleman <0nrh2b802 at sneakemail.com> wrote:

> On 08 May 2007 11:45:24 GMT, Steve Kostecke kostecke-at-ntp.isc.org
> wrote:
>> On 2007-05-08, David Durrleman <0nrh2b802 at sneakemail.com> wrote:
>> > I am behind a NAT, but I don't have a firewall.
>> You may not have a local firewall, but your ISP may have one between
>> you and the world.
> I don't think so, however I'm not definitely 100% sure that the port
> 123 is not blocked. How can I check that ?

You could ...

* ask them if they are blocking 123/UDP and if they have a time server
for their customers to use

* start ntpd (on your system) and nmap your port 123/UDP from some
external location

* start ntpd and use a web-based tool to attempt to contact your ntpd:

	- http://ntp.isc.org/ntpq.php will query the IP address you are
	  browsing from

	- http://www.vanheusden.com/query_ntp.php will query any IP

* use 'ntpdate -u <list of time servers>' to see of you can contact
those time servers over an unpriviledged port; then try again without
the '-u'

>> Please check your ntp.conf very carefully for restrict statements.
> Yes, I know about that, but these are the only lines in my ntp.conf, except for the comments (i did a grep -v "^#" /etc/ntp.conf)

OK ... that's one option off the table.

>> > The output of ntpq -p -rv is:
>> >
>> > state=1, frequency=-1.348
>> Did you take this statistics snapshot shortly after starting ntpd?
> No, this was after ten minutes or so ...

If you've not let your ntpd ever run long enough to create the drift
file, ten minutes is too soon,

If you can't get the port opened there are a couple of options:

1. Run your own local ref-clock (e.g. GPS, WWVB, etc.)

2. Use cron to run  ntpdate (with '-u') periodically

3. Use HTP (HTTP Time Protocol) which works over port 80

Steve Kostecke <kostecke at ntp.isc.org>
NTP Public Services Project - http://ntp.isc.org/

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