[ntp:questions] Best Ntp Practice
David.Russell at dowjones.com
Mon Apr 13 12:23:54 UTC 2009
I would not recommend using Cisco devices as NTP servers if the time is important to you. There are bugs in the code that result in the offsets not getting any better than a few ms. Using the prefer command works around one of the problems but it still wanders around a lot.
I point all my network equipment to our own dedicated NTP servers which can handle thousands of requests/sec which is a lot more that would ever be generated.
Cisco has a new implementation in the 12.4T train that is a big improvement. This implementation finally lets you set the min and max polling rates which is making a big difference. I can get sub-ms offsets. There is still an issue where the accuracy is better with a single server than with two:
r01(config)#ntp server 10.1.1.1 ?
burst Send a burst when peer is reachable
iburst Send a burst when peer is unreachable
key Configure peer authentication key
maxpoll Maximum poll interval
minpoll Minimum poll interval
prefer Prefer this peer when possible
source Interface for source address
version Configure NTP version
From: questions-bounces+david.russell=dowjones.com at lists.ntp.org [mailto:questions-bounces+david.russell=dowjones.com at lists.ntp.org] On Behalf Of Towli
Sent: Monday, April 13, 2009 7:02 AM
To: questions at lists.ntp.org
Subject: [ntp:questions] Best Ntp Practice
We have found a decent location for our 2 DCF77 boxe's and I am going to
configure our environment for using these.
Would best practice be to configure 2 core (Cisco) switches to use the two
DCF boxes like this: ntp server (ip of DCF 1) prefer, ntp server (ip of DCF
2) and then hereafter i am considering entering a third "regular" reachable
Ntp-server. Will the servers be prefered in the order they are entered on
I will then point all our other networking equipment to the 2 mentioned core
switches for NTP data (in case you in here "ok's" it). How can i make sure
that the core switches is handing out ntp data (is there a special command
for this ?). The reason i am considering a setup like this is, that the DCF
looses their stratum 1 status when (if) they loose connectivity to
Frankfurt. With the setup i describe only the 2 cores switches needs to sync
to another NTP-server (like DCF nr 2 or the 3.rd configured server)
I am realy looking forward to a comment as i am a newbie on this.
Best regards from Denmark
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