NTP not work!!

Unanswered Question
May 26th, 2008

Hi someone can help me to troubleshoot this NTP case:

I have Linux NTP server and i try to sync time with my cat6509 but it's not work? I'm not sure i miss something, here this is config of cat6509

ntp clock-period 17180022

ntp source gig 5/1

ntp master 1

ntp update-calendar

ntp server

when i show ntp associations the master point to ref clock local and stratum is 0 :

address ref clock st when poll reach delay offset disp

*~ .LOCL. 0 34 64 377 0.0 0.00 0.0

~ 16 - 1024 0 0.0 0.00 16000.

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


I have this problem too.
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michael.leblanc Mon, 05/26/2008 - 12:41

I think you want to remove the "ntp master 1" command.

The "show ntp associations" output conveys that the Cisco device thinks its sense of time is more trusted than the linux server's sense of time.

Richard Burts Mon, 05/26/2008 - 18:24

I do not understand in the original post whether the Linux is attempting to learn NTP from the Catalyst or the Catlyst is attempting to learn NTP from the Linum. If I were clear about this I would probably have a better answer to the question.


I doubt that the specification of interface used to source NTP has much to do with the problem.

As Michael points out, as long as the Catalyst is configured with ntp master, then it will consider that it is an authoritative NTP time server and the configuration of this:

ntp server

will do not good.

Since the network 127.x.x.x is used for loopback, the show ntp association with 127 is just a way of indicating that the Catalyst has learned NTP time from its own internal clock (since it was configured to operate as an NTP master).



pccthailand Mon, 05/26/2008 - 19:39

Hi Rick

My Linux server is NTP master and sync time from Internet. Cat6509 will sync clock with Linux server and then all access-layer switch will sync the clock with Cat6509

Thanks for all reply

Richard Burts Mon, 05/26/2008 - 19:59

If the Linux server is the NTP server (it has sync with an Internet time source) then Michael was quite correct that configuring ntp master on the Catalyst was the problem. If you remove the ntp master from the Catalyst (and assuming that the configured ntp server address is the correct address of the Linux server) then things should work.



pccthailand Tue, 05/27/2008 - 00:14


If i want Cat6509 is master or center of the time for internal other switch. Should i configured "ntp master" on Cat6509 ?


Richard Burts Tue, 05/27/2008 - 03:00

No you should not configure the Catalyst with ntp master. Your original post shows the result of configuring the Catalyst with ntp master. Once your Catalyst has learned authoritative NTP time from an NTP server (such as your Linux server) then the Catalyst will serve NTP time to other devices and not require any additional configuration.

You should only configure ntp master is you want a Cisco to act as an NTP server and there is no way that the Cisco can learn NTP time from an NTP server.



michael.leblanc Tue, 05/27/2008 - 06:30

As Rick pointed out you don't want to reintroduce the NTP Master command that caused you the initial issue.

Instead, enter "ntp server" commands on the other Cisco devices that identify the Cat6509 as the NTP reference.

ntp server

In your case that would be the IP address of the "gig 5/1" interface, since that is what you have chosen as your "ntp source interface".

The result will be something like this:

other-cisco-devices#sh ntp ass

address ref clock st when poll reach delay offset disp

*~ 3 40 64 377 4.4 -21.72 18.1

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


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