FishermanXL
Contributor
Contributor

PTP time synchronization on ESXi - where does the PTP client get the absolute time from?

Hi guys,

I was just wondering about the time-source of an ESXi PTP client.

If using NTP you can set the time servers manually, but what about PTP?

So who provides the absolute time for an ESXi, if there are no PTP-Grandmasters in the LAN?

 

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5 Replies
vbondzio
VMware Employee
VMware Employee

If you mean the per VM PTP device, it syncs to the host which in return syncs using either NTP or PTP:
https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.vcenterhost.doc/GUID-0EE343F5-70E9-...

You can configure your requirement per VM:
https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.vm_admin.doc/GUID-4E6AE904-75C6-475...

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FishermanXL
Contributor
Contributor

Hi, i meant the time configuration of a single ESXi in a LAN.

If I choose NTP and put in time.google.com, then the ESXi will get the time information from time.google.com.

But if I choose PTP, who tells my ESXi what time it is? If it is 8am or 7pm? The ESXi must get this information from somewhere.

thx

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vbondzio
VMware Employee
VMware Employee

It will get the time from the master clock in the network you specify in the configuration. Whether that is some HW device or just a machine you sync via e.g. NTP externally and only us PTP for internal synchronization is up to you. You might be able to use your core switch depending on model.

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FishermanXL
Contributor
Contributor

Hi again, that is exactly what I meant. I need to specify the master clock.

Where are these settings hidden? On the ESXi all I can do is enable the service and select a network interface.

Thx

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vbondzio
VMware Employee
VMware Employee

And that vmk interface should be able to receive the multicast stream from the boundary / master device, enabling PTP opens UDP 319/320 on the ESXi FW.

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