Ok I have a really simple NTP setup for my local network, I only have one PC connected to the internet which receives NTP time, and then the other 2 computer use NTP to sync with this master server.
However, over the last week every few hours/days the "master" server's time becomes in the past, so it suddenly becomes 5-15 minutes behind the real time. The other 2 computers on the network don't usually sync to this PC as its time is probably considered incorrect.
All servers have Ubuntu 9.04 installed.
So the problem is something to do with the master time server receiving the correct time, here is its NTP.conf file:
# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help
# Enable this if you want statistics to be logged.
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
# You do need to talk to an NTP server or two (or three).
server ntp.ubuntu.com iburst
server pool.ntp.org iburst
fudge 127.127.1.0 stratum 10
# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details. The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
# might also be helpful.
# Note that "restrict" applies to both servers and clients, so a configuration
# that might be intended to block requests from certain clients could also end
# up blocking replies from your own upstream servers.
# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
# Local users may interrogate the ntp server more closely.
# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
restrict 169.254.1.1 mask 255.255.0.0 nomodify notrap
# If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
# If you want to listen to time broadcasts on your local subnet, de-comment the
# next lines. Please do this only if you trust everybody on the network!
Any ideas as to why its time could suddenly jump backwards?