VPN-Connections crashed regularly since Windows 10 Update (wodVPN)

by gpl, Monday, December 16, 2019, 16:05 (1586 days ago)

We also had this Problen in 2018, after the Rollout of Version 1803 of Windows 10: An established VPN-connection will go down, after data go through the VPN.
The solution then was to bring both station on the same version of Windows 10.

Since last week we have the same Problem at a Customer, after an update from 1903 to 1909 in Windows 10. The first Step was to check the Versions of both hosts, but in this case they are equal.

I make a lot of tests and find out, that it depents on the Packetsize and fagmentation of the Datapackets.
Example:
The VPN-Connection between two stations is established.
If I try to do a Ping over this connection with a packetsize of 1300 and activ "Not fragment"-Flag, the Ping runs without Problems. (Ping 192.168.55.6 -f -l 1300 )

If I do the same with a packetsize of 1360, the Ping answers 5 or 6 times and then connection will lost after a few seconds.

It seems, that the packet lost occur if the packetsize is near or greater than the MTU

I've found an interesting site about UDP and MTU with Windows 10, but I can't find a solution for my problem:
https://social.technet.microsoft.com/Forums/en-US/965e107e-d9b0-4240-ac3f-74797c91b476/...

Have someone the same problems? What can I do?