ntp4xen.conf

# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
#===# this restricts who can talk to this server to obtain NTP information
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

# Permit all access over the loopback interface. This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
#===# self-explanatory
restrict 127.0.0.1
restrict -6 ::1


# Use Xen's public servers.
#===# This is in case your organization does not have its own internal NTP servers.
broadcast 192.168.0.255 key 42 # broadcast server
broadcastclient # broadcast client
#broadcast 224.0.1.1 key 42 # multicast server
#multicastclient 224.0.1.1 # multicast client
#manycastserver 239.255.254.254 # manycast server
#manycastclient 239.255.254.254 key 42 # manycast client

# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available.
#server 127.127.1.0 # local clock
#===# I add this to force the local machine to have a low stratum compared to external NTP servers.
fudge 127.127.1.0 stratum 10

# Drift file. Put this in a directory which the daemon can write to.
# No symbolic links allowed, either, since the daemon updates the file
# by creating a temporary in the same directory and then rename()'ing
# it to the file.
#===# This is where your machine stores its drift file, which is the estimated clock frequency error
driftfile /var/lib/ntp/drift

# Enable public key cryptography.
#crypto

includefile /etc/ntp/crypto/pw

# Key file containing the keys and key identifiers used when operating
# with symmetric key cryptography.
keys /etc/ntp/keys

# Specify the key identifiers which are trusted.
#trustedkey 4 8 42

# Specify the key identifier to use with the ntpdc utility.
#requestkey 8

# Specify the key identifier to use with the ntpq utility.
#controlkey 8

### our local specifics ###
#===# This deals with how self-modifying the local server can be to its own settings, as well
#===# as not permitting external queries.
#restrict X.Y.0.0 mask 255.255.0.0 nomodify notrap
restrict 192.168.0.0 mask 255.255.255.0 nomodify notrap

#===# A list of your local (organizational) NTP servers
server 212.244.36.232 iburst
server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst
#server 0.europe.pool.ntp.org iburst
#server 1.europe.pool.ntp.org iburst
#server 2.europe.pool.ntp.org iburst
#server 3.europe.pool.ntp.org iburst

#===# Here is the option to add local peers (within a subnet, server pool, etc.)
# peers in case the standard NTP servers cannot be reached. These are the three XenServers in the pool.
peer 192.168.0.177 burst iburst minpoll 4 maxpoll 4
peer 192.168.0.178 burst iburst minpoll 4 maxpoll 4
peer 192.168.0.179 burst iburst minpoll 4 maxpoll 4
peer 192.168.0.180 burst iburst minpoll 4 maxpoll 4