If you are using the Sonicwall Global VPN Client 4.10.2 on a Windows 10 machine you may experience an issue where your Internet speed will deteriorate. In most cases, I have seen internet speeds of up to 50-90mbps when off the VPN slow down to less then 1Mbps.
After a heap of troubleshooting with setting on the VPN client the issue was caused by the wifi adaptor as I will explain in the solution below.
Evidently, I found that this is an issue with Windows 10. The solution is to disable something called the Receive Segment Coalescing on the wireless adapter. Microsoft actually provides an automated fix as a download.
Details can be found at the following Microsoft Answers link:
(Recommended by Microsoft):
Disable “Receive segment coalescing” (Rsc)on your wireless adapter
Steps to disable Rsc using Microsoft’s automated tool:
1) Download the “.diagcab” file located here:
2) Run it, and let it see if it can determine the problem and fix it.
3) Re-test your wireless internet connection.
If you’d rather do it manually, then I have those steps below.
Steps to disable Rsc manually:
1) Open an Admin Command Prompt window:
Start > All Apps > Windows System -> Right-click “Command Prompt” > More > Run as administrator
2) Get your network adapter name:
3) Note your adapter’s name (mine is: Wi-Fi)
4) Get your network adapter “Receive segment coalescing” (Rsc) settings:
… Mine listed a table that had 1 row, for adapter name Wi-Fi, that had IPv4Enabled True, and IPv6Enabled True
5) Disable Rsc for your network adapter:
powershell Disable-NetAdapterRsc -Name ADAPTER_NAME_FROM_BEFORE
… Be sure to replace ADAPTER_NAME_FROM_BEFORE with whatever your network adapter name is, without quotes
6) Verify Rsc is disabled for ipv4 and ipv6, on your network adapter:
… Should now show IPv4Enabled False, and IPv6Enabled False, for your network adapter
7) Re-test your wireless internet connection.