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NTP server responses not being received

I have set up my Windows 10 PC as an NTP server by setting HKLM\SYSTEM\CurrentControlSet\services\w32time\TimeProviders\NtpServer\Enabled=1.
I have added a firewall rule to allow inbound UDP traffic on port 123 and I have even tried disabling the firewall completely.
When a client sends an NTP request to the NTP server, the response is never received by the client.
I enabled logging via the command, "w32tm /debug /enable /file:C:\Temp\w32t.log /size:64000 /entries:0-300" and I can see that the Windows 10 PC receives the request from the client and sends a response but the client never receives the response (I verified this by running Wireshark on the client).
Below is an excerpt from the log file showing the request being processed and a response being sent.
I have to assume that the UDP send is failing but the log does not show that.
The Windows 10 PC that is set up as the NTP server has 2 network cards but I disabled the second card to make sure it was not causing the problem.
Could the problem be the fact that the NTP server is binding to 0.0.0.0 instead of the actual IP address for the interface?
Is there anything I can do to resolve this issue?

153568 15:44:42.0957115s - ListeningThread -- DataAvailEvent set for socket 1 (0.0.0.0:123)
153568 15:44:42.0958423s - HA Pkt Rcv: delay:0 DestTimeStamp:132683318820958249
153568 15:44:42.0958890s - Rx timestamp not returned and may be unsupported on the current network interface.
153568 15:44:42.0959285s - ListeningThread -- response heard from 192.168.1.151:123 <- 192.168.1.159:123
153568 15:44:42.0959992s - /-- NTP Packet:
153568 15:44:42.0960106s - | LeapIndicator: 3 - not synchronized; VersionNumber: 3; Mode: 3 - Client; LiVnMode: 0xDB
153568 15:44:42.0960318s - | Stratum: 0 - unspecified or unavailable
153568 15:44:42.0960451s - | Poll Interval: 10 - 1024s; Precision: -6 - 15.625ms per tick
153568 15:44:42.0960732s - | RootDelay: 0x0000.0000s - unspecified; RootDispersion: 0x0001.03FEs - 1.01559s
153568 15:44:42.0961070s - | ReferenceClockIdentifier: 0x00000000 - unspecified
153568 15:44:42.0961276s - | ReferenceTimestamp: 0xE4723DC8392ABEF0 - 13268176968223308500ns - 153566 20:42:48.2233085s
153568 15:44:42.0961603s - | OriginateTimestamp: 0x0000000000000000 - unspecified
153568 15:44:42.0961850s - | ReceiveTimestamp: 0x0000000000000000 - unspecified
153568 15:44:42.0962106s - | TransmitTimestamp: 0xE4749AEA3D435265 - 13268331882239308500ns - 153568 15:44:42.2393085s
153568 15:44:42.0962484s - >-- Non-packet info:
153568 15:44:42.0962661s - | DestinationTimestamp: 153568 15:44:42.0962805s - 0xE4749AEA1887FB0B153568 15:44:42.0962947s - - 13268331882095824900ns153568 15:44:42.0963106s - - 153568 15:44:42.0958249s
153568 15:44:42.0963304s - | RoundtripDelay: -143483600ns (0s)
153568 15:44:42.0963587s - | LocalClockOffset: 71741800ns - 0:00.071741800s
153568 15:44:42.0963950s - --
153568 15:44:42.0964698s - TransmitResponse: sent 0.0.0.0:123()->192.168.1.151:123


windows-10-network
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Hi,


Just want to confirm the current situations.


Please feel free to let us know if you need further assistance.


Best Regards,
Sunny

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1 Answer

SunnyQi-MSFT avatar image
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SunnyQi-MSFT answered JimRhodes-9879 commented

Hi,

Welcome to Q&A platform.

Could the problem be the fact that the NTP server is binding to 0.0.0.0 instead of the actual IP address for the interface?

Please try to configure the NTP server bind to the actual IP address for the interface to see if the issue still existed.

Best Regards,
Sunny


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Please try to configure the NTP server bind to the actual IP address

I don't know how to configure the NTP server to bind to a specific IP address.

I have to believe that this is a bug in w32time.dll on Windows 10 Professional. On a different PC with Windows 10 Home, the NTP server works and I get slightly different log output on the "TransmitResponse" line.

Windows 10 Professional:
153568 15:44:42.0964698s - TransmitResponse: sent 0.0.0.0:123()->192.168.1.151:123

Windows 10 Home:
153569 06:59:15.5044251s - TransmitResponse: sent 0.0.0.0:123(192.168.1.63:123)->192.168.1.200:123

As you can see, the log from Windows 10 Home shows the actual IP address within the parentheses.

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Hi,

Many thanks for your update.

Kindly check if this similar thread was helpful:

How to prevent ntpd to listen on 0.0.0.0:123?
Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

Best Regards,
Sunny


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My question is about Windows. The link you reference is for Linux.

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