An NTP service receives its time information from a time source with a higher level of authority than itself. The authority of a particular time servicer is indicated by its stratum. An NTP server that connects directly to an authoritative, external time source, such as an atomic clock or global positioning system (GPS) unit, is considered a stratum 1 NTP server. Stratum 1 devices are considered the most authoritative sources of clock information in the NTP hierarchy. A stratum 1 NTP server distributes time information to devices in the higher strata. For example, stratum 2 devices function as NTP clients to stratum 1 devices and as NTP servers to devices in the higher strata.
Operation order :
Check if there is a NTP server already configure :
#show ntp status
Always setup the clock 1st on the NTP Server .
#clock set (hours xx:xx:xx) (day) (month) (year)
If nothing is configured :
(config)#ntp master 3
(config)#ntp server (ip address of ntp server)
For security :
(config)#ntp authenticate
(config)ntp authentication-key (#) md5 (password)
(config)#ntp trusted-key (#)
(config)#ntp server (ntp server ip address) key (#)
