This Article Applies to:
All the TP-Link VPN Routers, including ER605 and ER7206.
We received feedback that after a recent Windows 10 update (KB5009543), using the built-in VPN client cannot connect to ER605/ER7206 via L2TP over IPsec VPN anymore, the error message indicates “Can’t connect to VPN. The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer.” like the image below. While the same L2TP VPN setup works just fine on Mac, which seems to be the Windows issue.
Microsoft confirmed the issue and offered the resolution in the following link:
So this issue was resolved in the out-of-band update KB5010793 (https://support.microsoft.com/help/5010793) released on January 17, 2022.
If you suffer from this issue, please refer to the link above to install the update for the fix.
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TP-Link Support Team