NTP configuration on Cisco router and switches

Unanswered Question
Sep 22nd, 2008

I have a Linux NTP server that I use to

synchronize for all of my routers and switches. I would like routers and switches to poll the NTP servers every

60 seconds. How do I go about doing that

on Routers and Switches?

On my Linux servers, I use "ntpdate 192.168.1.1" and crontab this to run

every 60 seconds. I would like to do the

same thing on Cisco IOS routers and switches. How do I go about accomplishing

this?

Thanks.

I have this problem too.
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Richard Burts Mon, 09/22/2008 - 08:03

David

The link supplied by Collin is a nice description of how to configure NTP on Catalyst switches running CatOS. But I do not see anything in it about controlling the frequency with which the switch will querry the server. And in fact I am not aware of anything that would control the frequency with which the switch will querry the server. In Cisco's implementation the Cisco device acting as client will querry the server every 64 seconds in the beginning. And as the client receives responses from the server and the relationship stabilizes and the client believes that it is accurate, the client will querry at longer and longer intervals. I am not aware of a config option that would change this behavior.

HTH

Rick

John Blakley Mon, 09/22/2008 - 08:01

In global config mode you can use:

ntp server xxx.xxx.xxx.xxx

You need to make sure that the actual clock on the router/switch is set as close as possible, or the clock never syncs.

This is done in enable mode:

clock set 12:00:00 Sep 22 2008

HTH

John

singhsaju Mon, 09/22/2008 - 08:06

Hi,

I do not think we can define poll interval on Cisco routers and switches , it changes dynamically from 64 seconds to 1024 seconds .

From the link below:Network Time Protocol: Best Practices White Paper

"

An NTP client makes a transaction with its server over its polling interval (from 64 to 1024 seconds) which dynamically changes over time depending on the network conditions between the NTP server and the client. No more than one NTP transaction per minute is needed to synchronize two machines."

http://www.cisco.com/en/US/tech/tk869/tk769/technologies_white_paper09186a0080117070.shtml

HTH

Saju

John Blakley Mon, 09/22/2008 - 08:10

I misread the question. No, the polling frequency can't be changed.

HTH

John

cisco24x7 Mon, 09/22/2008 - 08:49

Thank you everyone for the feedback. I know how

to configure NTP on Cisco routers and switches.

My question has to do with controlling the

frequency of the routers and switches to poll

the NTP servers like "ntpdate 4.2.2.2" on Linux

servers. Is this something that can be done?

Thanks.

Richard Burts Mon, 09/22/2008 - 09:06

David

I thought that my answer:"I am not aware of a config option that would change this behavior" and the very similar answer from Saju were pretty clear that you can not change the poll interval.

HTH

Rick

cisco24x7 Mon, 09/22/2008 - 09:21

I was hoping that this may be a "new" feature

in IOS 12.4(T) or something like that.

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