Intermittent "The L2TP connection attempt failed because the security layer encountered a processing

[Nortrhoom]

Good day,

I have an interesting problem where a VPN client Intermittently disconnects and then refuses to reconnect with the error:

"The LT2P connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer"

After 10-15 minutes, I am able to re-establish the connection. This happens several times a day.

In the past, after the January 2022 dreadful update I had to uninstall the latest security patch and then in August 2022 I had to add registry keys as per this article. But these issues normally resulted in a completely unusable VPN connection. Now this is on and off. I am at a loss.

Any idea what the issue is this time? Thank you.

Applliance: MX64, MX 16.16

Windows 10

[PhilipDAth]

This is commonly a CPE firmware issue.  Try checking to see if your CPE has any updated firmed available.

You could also try power cycling the CPE in case it has gotten into a sad state.

[Nortrhoom]

Thank you. The only update I see is MX 16.16.6. Would that be it?

Also, what is CPE 🙂

[PhilipDAth]

No.  I'm talking about the CPE that the user with the client VPN is sitting behind.

[Nortrhoom]

Ah, the only thing the client has is Windows 10 laptop > ISP router. I'll check the ISP router but it is likely up to date.

[PhilipDAth]

Try giving that ISP router a power cycle as well in case it is in a sick state.

The issue is usually related to bugs processing UDP flows and timing them out prermaturely.

[Nortrhoom]

Thanks,

I'll ask the client to power cycle their modem.

I also updated to MX 16.16.6 since it is a stable patch

[Mack023]

My issue is fixed by uninstalling latest security updates.