ntp.txt

udp: 

#> StratumNumber (1-15): assingn this number to become ntp server. According to ntp client lower is preferred.

# ntp master 2

ISP (ntp-master/server)------->R1(ntp-client/server)--------------->R2/R3/R4(ntp-client/server)--------->R5/R6/R7(ntp-client)

# ntp server 1.1.1.1
# show ntp assocaitions
# show ntp status

-----------------------------------------------------------------

# ntp authentication-key 1 md5 cisco
# ntp trusted-key 1
# ntp authenticate 

# ntp server 2.2.2.2 key 1 prefer  

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# ntp update-calendar
 
The 'ntp update-calendar' forces the hardware clock to synchronise with the system's software clock. After a couple of minutes, we check to see if the two clocks have synchronised:

# show clock
02:07:05.011 Athens Sun Apr 19 2009

# show calendar