NTP master/peer

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Feb 16th, 2008
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going through the CCIE LAB, i see sometimes used ntp master and others ntp peer, i looked into the command lookup but could not figure out!!!!

Any one knows the difference?

on the other hand do we need something else on the router to make it as ntp master, like startum...

Good day

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achellap Sat, 02/16/2008 - 22:43
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The NTP master command lets the NTP on the other device (ntp peer) to sync to the current node. A node could at the smae time serve time to many nodes and at the same time get synced to the many NTP masters.

twissam Sat, 02/16/2008 - 23:56
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Hi again,

i am confused, let us take the example below:

Router A: NTP Master

Router B, C and D: NTP peer; those will be servicing other clients, IP Phones for instance.

1)is this right?

2) how can we have multiple ntp masters!!!

Good day

pcameron Mon, 02/18/2008 - 04:12
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NTP master will set up the router to respond to NTP time requests for peer devices. All you need to do is is configure NTP master on one router and set the clock -

UC520.120#conf t

Enter configuration commands, one per line. End with CNTL/Z.




UC520.120(config)#ntp master




UC520.120#clock set 23:00:00 18 Feb 2008



UC520.120#sh ntp ?

associations NTP associations

status NTP status

UC520.120#sh ntp stat

Clock is synchronized, stratum 8, reference is

nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**18

reference time is CB63F54B.301CAAE6 (23:15:07.187 AEST Mon Feb 18 2008)

clock offset is 0.0000 msec, root delay is 0.00 msec

root dispersion is 0.02 msec, peer dispersion is 0.02 msec


[Resuming connection 1 to ... ]

on the peer router -

ntp peer


CWD.19.07-2800-3#sh ntp stat

Clock is synchronized, stratum 9, reference is

nominal freq is 250.0000 Hz, actual freq is 250.0002 Hz, precision is 2**18

reference time is CB63F55D.8D948760 (12:15:25.553 UTC Mon Feb 18 2008)

clock offset is -8.0557 msec, root delay is 2.11 msec

root dispersion is 9.57 msec, peer dispersion is 1.48 msec


All other devices peer off the master. So every peer device in the network points to the master reference.

twissam Mon, 02/18/2008 - 06:55
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thanks a lot for your help, what i understand is the following:

ntp master: (it will be the server giving the time to the peers)

ntp peer ipntpmaster

ntp server ipntpmaster

In such case what is the difference between the ntp peer and ntp server (i have read somewhere that with one of them it acts as a master as well!!!)

please advice

Good day

AJAZ NAWAZ Tue, 03/24/2009 - 09:30
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pcameron - what if the master is configured to source time from the internet?, i.e. the 'clock set' command is not used. If this device i.e. master fails to source time - will it continue to service time requests received from it's peers?



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