Cannot sync network time (NTP) on Win10 on BSNL FTTH

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vishalrao

vishalrao

The Global Village Idiot
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Hi guys,

Recently I am unable to get Win10 to do network time (NTP) sync on my BSNL FTTH connection. Seems to be working on my Airtel 4G wifi device.

I tried some troubleshooting and observed that Win10 NTP client is using UDP port 123 for BOTH the client side accept bind port and also the standard NTP server UDP port 123.

Because of this I feel BSNL is blocking the port (cannot receive response from the NTP time server) since it's not unprivileged port.

When I ran a free open source tool called "NetTime" it worked because the client side bind port was some high value (in 60,000 range) and also on linux the NTP time sync also works.

I observed the client port anomaly using the WireShark network traffic monitor tool.

Anyone else facing this issue?
 
This is the error I get:


Source
 
I noticed something odd, if I connect to BSNL FTTH via ONT directly I cannot sync time at all (even in the beginning moments of the connection) but if I connect via my Netgear router with ONT in bridge mode, then I can sync time for around 15-20 minutes it works, after that it stops working!
 
Could you post the wireshark file with just the NTP and ICMP packets? Wireshark should be running at the time the error occurs.
 
wireshark just shows one "NTP client" request with "src port 123" and "dest port 123" in win10 and no response received.

but when i run the NetTime tool on win10 then wireshark shows both NTP client request and NTP server response with "src port 63069" and "dest port 123".
 
Try using a different time server e.g. time.cloudflare.com in Control Panel -> Date and Time -> Internet Time -> Change settings and see if it makes any difference.

If NTP with souce port 123 was blocked by BSNL network then it wouldn't work when you're connecting through bridge mode either. So my guess is that either the firewall in the ONU is blocking it or that its a routing or server issue.

You can use the same server (via IP address) in Windows Time and NetTime to see if they gave the same result.
 
Yep, I tried various servers - all have the same issue - works in the NetTime tool but not with Win10 NTP client.
 
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