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    Best Practice for Time Sync for Active Directory Domain Controllers

    IT Discussion
    windows active directory ntp sntp
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    • D
      Dashrender
      last edited by

      Here's the command to set your PDC emulator to sync with a time source

        w32tm /config /manualpeerlist: peers /syncfromflags:manual /reliable:yes /update 
      

      Replace peers with your FQDN or IP of the desired time servers.

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      • S
        scottalanmiller @Dashrender
        last edited by

        @Dashrender said:

        Shouldn't this be in IT discussions? It's technical in nature.

        Hmmm... I didn't choose the category, it just did it.

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        • S
          scottalanmiller @Dashrender
          last edited by

          @Dashrender said:

          I guess my desire here was to have the ESXi host be the main source for time inside my network. It of course would pull time from the internet.

          It sounds like this isn't going to work. So instead I have to have my PDC emulator pull it's own time from the internet, and the VM Hosts will have to be managed separately.

          ESXi can pull time from the Internet. If it is correct and the DC is getting its time from the ESXi clock then the ESXi is setting the DC which, in turn, uses SNTP to talk to the rest of the network.

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            scottalanmiller
            last edited by

            Here is vmware's older paper on how they recommend that this be set up:

            http://www.vmware.com/files/pdf/Virtualizing_Windows_Active_Directory.pdf

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            • S
              scottalanmiller
              last edited by

              Here is a more recent one:

              http://www.vmware.com/files/pdf/solutions/Virtualizing-Active-Directory-Domain-Services-on-VMware-vSphere.pdf

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              • S
                scottalanmiller
                last edited by

                VMware definitely recommends that you use an external time source to control drift, not using the ESXi virtualized clock.

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                • D
                  dafyre
                  last edited by

                  I would set ESXi host to use $external_NTP... and then point the DCs to $external_NTP and then all of the clients will magically sync with DCs.

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                  • J
                    Jason Banned
                    last edited by

                    You set your PDC Emulator to pull from a reliable NTP server then the rest will sync from that ex:

                    w32tm.exe /config /manualpeerlist:”0.us.pool.ntp.org 1.us.pool.ntp.org 2.us.pool.ntp.org 3.us.pool.ntp.org” /syncfromflags:manual /reliable:YES /update

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                    • S
                      scottalanmiller
                      last edited by

                      I just heard to the tune of "Free your mind, and the rest will follow..." in my head:

                      Sync your time, and the rest will follow...

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                      • D
                        Dashrender
                        last edited by

                        Alright - I read through the document that Scott provided about VMWare and time syncing.

                        The reason VMWare wasn't changing my PDC emulator's clock was that time syncing between ESXi and the VM was disabled (default behavior).

                        Edit the VM session, Click on the Options tab, click on VMware Tools and you'll see these two check boxes at the bottom on the right.

                        time-vmware.JPG

                        Make your desired choices, save and you're good.

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                        • D
                          Dashrender @scottalanmiller
                          last edited by

                          @scottalanmiller said:

                          VMware definitely recommends that you use an external time source to control drift, not using the ESXi virtualized clock.

                          I wouldn't ever rely solely on their virtual clock, I'd definitely like ESXi itself to be syncing to something.

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                            Dashrender @dafyre
                            last edited by

                            @dafyre said:

                            I would set ESXi host to use $external_NTP... and then point the DCs to $external_NTP and then all of the clients will magically sync with DCs.

                            With concerns about Windows and Time, the only server that you should have syncing with an outside source is the PDC emulator. All other domain devices will sync from that machine.

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                            • S
                              scottalanmiller @Dashrender
                              last edited by

                              @Dashrender said:

                              @scottalanmiller said:

                              VMware definitely recommends that you use an external time source to control drift, not using the ESXi virtualized clock.

                              I wouldn't ever rely solely on their virtual clock, I'd definitely like ESXi itself to be syncing to something.

                              Of course, no clock anywhere just relies on itself!

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                                scottalanmiller @Dashrender
                                last edited by

                                @Dashrender said:

                                @dafyre said:

                                I would set ESXi host to use $external_NTP... and then point the DCs to $external_NTP and then all of the clients will magically sync with DCs.

                                With concerns about Windows and Time, the only server that you should have syncing with an outside source is the PDC emulator. All other domain devices will sync from that machine.

                                Only if the PDC emulator is using NTP. If it is using the local clock then the hypervisor has to fulfill that role.

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                                • D
                                  Dashrender @scottalanmiller
                                  last edited by

                                  @scottalanmiller said:

                                  @Dashrender said:

                                  @dafyre said:

                                  I would set ESXi host to use $external_NTP... and then point the DCs to $external_NTP and then all of the clients will magically sync with DCs.

                                  With concerns about Windows and Time, the only server that you should have syncing with an outside source is the PDC emulator. All other domain devices will sync from that machine.

                                  Only if the PDC emulator is using NTP. If it is using the local clock then the hypervisor has to fulfill that role.

                                  I did say Windows and Time. If the PDC emulator is using the local clock, that local clock would be Windows outside source, but if that's all you're doing, then definitely you should be syncing the local clock (ESXI, Hyper-V XenServer, etc) with an atomic source if possible.

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                                  • S
                                    scottalanmiller
                                    last edited by

                                    I see.

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