server cronos.cenam.mx prefer
server time.nist.gov
server ntp2a.audiotel.com.mx

fudge 127.127.1.1 stratum 10
logfile /var/log/ntp.log
driftfile /etc/ntp/ntp.drift

restrict 127.0.0.1 nomodify
restrict 192.168.0.1 mask 255.255.255.0 nomodify
restrict 192.168.0.105 mask 255.255.255.0 nomodify notrap
restrict 192.168.0.104 mask 255.255.255.0 nomodify notrap