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 <cr> David -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Towli Sent: Monday, April 13, 2009 7:02 AM To: [email protected] Subject: [ntp:questions] Best Ntp Practice Hello all 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 the switches? 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 /Towli _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
