Collin Clark Thu, 02/07/2008 - 09:27
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Configuration is pretty simple:


ntp server 192.168.11.13

ntp server 192.168.1.26


To verify it's working, try the following:


CORE1#show ntp associations


address ref clock st when poll reach delay offset disp

*~192.168.11.13 129.7.1.66 2 35 64 377 -0.0 18.46 2.1

+~192.168.1.5 192.168.11.13 3 35 64 377 -0.0 16.66 2.0

+~192.168.1.26 192.168.11.13 3 11 64 377 -0.0 18.78 0.3

* master (synced), # master (unsynced), + selected, - candidate, ~ configured


CORE1#show ntp status

Clock is synchronized, stratum 3, reference is 192.168.11.13

nominal freq is 250.0000 Hz, actual freq is 240.5256 Hz, precision is 2**18

reference time is CB55BD1D.75C290A0 (11:23:41.460 CST Thu Feb 7 2008)

clock offset is 18.4639 msec, root delay is 40.62 msec

root dispersion is 87.45 msec, peer dispersion is 3.31 msec

CORE1#


If you connect to an NTP server on the outside, make sure you open the port on the firewall (UDP 123).


HTH

dhaneshbhaskaran Mon, 03/16/2015 - 03:56
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Can a ios device which is currently acting as NTP server for the network be pointed to a dedicated NTP server and still act as NTP server.

 

 

Current config

 

ntp source Loopback0

ntp master

ntp update-calendar

ntp master 7

 

 

New config.

 

ntp source Loopback0

ntp master

ntp update-calendar

ntp master 7

 

ntp master x.x.x.x prefer

ntp master x.x.x.x

 

The reason for the change is UC call managers have a time lag because of that IP Phones and Domain PC have different time display  also these UC call Managers have license hard coded based on this NTP servers and if a change in that will lead to a license rehosting.For that I have planned to retain the existing IOS NTP Routers as master but make them fetch the Time from a different dedicated NTP server instead of using the internal clock.

Richard Burts Mon, 03/16/2015 - 05:41
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Especially since you have specified that your IOS device is stratum 7 there should be no problem in pointing it to an authoritative NTP server at a higher stratum and having your device learn time from the higher stratum server.

 

HTH

 

Rick


aijaz802 Sat, 02/09/2008 - 00:49
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Hi,


If you want to make the Core6506 as ntp master, then u need to add the command "ntp master" and set the time zone " clock timezone GMT +X". This switch will become as master for other switches. On edge switch configure "ntp server x.x.x.x (ip of 6506).


rate this if it helps..


*aijaz*

Goutam Sanyal Sat, 02/09/2008 - 02:41
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Hi Kaushik,


To treat a Cisco device as a NTP Server, you can do the following:


SW(config)#ntp master ( Act as NTP master clock )

SW#clock timezone GMT + (Ur Local time zone)


And if you want to make a Device that learn the NTP clock from a NTP Master, u can do the following:


#ntp source (physical/logical_IP_Address)

#ntp server x.x.x.x (ip address of Master Device)


Thanks


Goutam


Pls rate if its works


Mr. Kaushik,


I hope these configs are sufficient for running NTP in your network, but, if you are stil facing the problem kindlly let us know the topology in between your master and slave (NTP). Besides you can configure "ntp source Loopback0" for more stable time-sync. This will have source IP of the NTP packet as 'loopack address' of the communicating device, if you have configured the loopback at your device.


--gaurav

Richard Burts Sat, 02/09/2008 - 04:55
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Several of the posts have suggested configuring the 6506 as ntp master. While this is certainly possible I believe that it is not such a good idea, unless the switch has some really accurate time source that is locally connected.


If the 6506 is learning time from some NTP server then it will server NTP time to any other device in its network without needing the ntp master configuration. The key concept is whether the switch believes that it has authoritative time. If it is learning time from an ntp server then it is authoritative and if it is configured as ntp master then it is authoritative. And if it is authoritative then it will serve NTP time to other devices.


If the switch is learning time from an NTP server then it should be quite accurate. If the switch is not learning time from an NTP server then it relies on its own internal clock. While the internal clock is pretty accurate in human terms it is not so very accurate in NTP standards. It is much better for the switch to learn time from an NTP server (or from 2 or 3 for redundancy) than it is to rely on its own clock.


HTH


Rick

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