On Tue, 2004-08-17 at 10:01, Stuart Bailey wrote:
I'm having trouble synchronising the time of my network clients using NTP.
Stuart and I investigated this a bit more today.
However, the clients report that no time server can be found.
That was because the configured server wasn't synchronized -- that makes the server "stratum 16", and clients refuse to sync with that.
The reason that the server wasn't synchronized was that it never received responses to the packets it sent. Often that's due to the host firewall, the router firewall, or ISP port restrictions. But in this case it was because the dlink dsl300t adsl modem drops packets with Minimize-Delay IP_TOS set. http://www.magwag.plus.com/jim/tips-300t.html
With that fixed the server and clients now sync properly.
Random tips for others debugging ntp issues: - running ntpd in the foreground ("ntpd -u ntp:ntp -g -n -d -d") makes it easier to see what it's getting/sending - running tcpdump shows you what makes it out to the network - run "tcp-wait" to see if/when your server syncs - run "ntpq -c rv" to see the stratum of your server - check your ntp.conf file -- if you have something like "restrict default noquery notrust nomodify", then you need to explicitly reset the restriction for the upstream server you use, e.g. "restrict ntp.eclipse.co.uk noquery", otherwise ntpd will ignore the responses to the queries it sends out.
-- Martijn