I confirmed the package"4.2.6.p3+dfsg-1ubuntu3.9" solved the problem in Ubuntu Precise
NTP Version : 1:4.2.6.p3+dfsg-1ubuntu3.1
With no IPTABLES rule ==> Working $ ntpdate x.x.x.x 11 Feb 16:15:19 ntpdate[1243]: adjust time server x.x.x.x offset 0.190571 sec
With IPTABLES rule ==> Not working $ iptables -t nat -A POSTROUTING -p UDP --dport 123 -j SNAT --to-source y.y.y.y:100-122
$ntpdate x.x.x.x 11 Feb 16:15:36 ntpdate[1253]: no server suitable for synchronization found
With ntp (precise-proposed) + IPTABLE rules ==> Now working
NTP version: 1:4.2.6.p3+dfsg-1ubuntu3.9
$ iptables -t nat -A POSTROUTING -p UDP --dport 123 -j SNAT --to-source y.y.y.y:100-122
$ ntpdate x.x.x.x 11 Feb 16:21:26 ntpdate[1986]: adjust time server x.x.x.x offset 0.005394 sec
Eric
I confirmed the package" 4.2.6.p3+ dfsg-1ubuntu3. 9" solved the problem in Ubuntu Precise
NTP Version : 1:4.2.6. p3+dfsg- 1ubuntu3. 1
With no IPTABLES rule ==> Working
$ ntpdate x.x.x.x
11 Feb 16:15:19 ntpdate[1243]: adjust time server x.x.x.x offset 0.190571 sec
With IPTABLES rule ==> Not working
$ iptables -t nat -A POSTROUTING -p UDP --dport 123 -j SNAT --to-source y.y.y.y:100-122
$ntpdate x.x.x.x
11 Feb 16:15:36 ntpdate[1253]: no server suitable for synchronization found
With ntp (precise-proposed) + IPTABLE rules ==> Now working
NTP version: 1:4.2.6. p3+dfsg- 1ubuntu3. 9
$ iptables -t nat -A POSTROUTING -p UDP --dport 123 -j SNAT --to-source y.y.y.y:100-122
$ ntpdate x.x.x.x
11 Feb 16:21:26 ntpdate[1986]: adjust time server x.x.x.x offset 0.005394 sec
Eric