Category: networking

How to fix
An authentication error has occurred.
The function requested is not supported.

When you are trying to connect to an older Windows Server, especially Windows Server 2012 or 2012 R2, from a newer Windows 10 or Windows 11 computer, you may run into the following Remote Desktop error:

An authentication error has occurred.
The function requested is not supported.
Remote computer: <computer name or IP>
This could be due to CredSSP encryption oracle remediation.
For more information, see https://go.microsoft.com/fwlink/?linkid=866660

I understand how frustrating this can be, especially when the device, VM, or application was working before and suddenly Remote Desktop refuses to connect.

This issue is usually related to CredSSP, which is the Credential Security Support Provider protocol used by Remote Desktop during authentication. Microsoft released updates for CVE-2018-0886 to address a CredSSP vulnerability, and systems with different patch levels or different CredSSP policy settings may fail to negotiate the RDP session correctly. Microsoft documents the CredSSP update behavior and the Encryption Oracle Remediation policy values as part of that security change.

Why This Happens

In many environments, newer Windows 10 or Windows 11 devices are fully patched, while older servers such as Windows Server 2012 may not have the same update level or policy configuration.

Physical Drive Connection and Hardware Requirements

• Power Down and Remove Drives: Ensure the ReadyNAS NV+ v2 is powered off. Gently remove all four 1 TB drives, labeling their bay order (1–4) to avoid confusion later.
• Connect Drives to a Linux Computer: Attach the drives to a PC running Linux. You can connect them via standard SATA ports or use USB-to-SATA docking adapters (make sure 3.5″ disks have adequate power)diskinternals.com. All drives should be connected simultaneously if possible (the RAID array needs at least all but one drive intact).
• No Special RAID Controller Needed: You do not need a dedicated RAID card or proprietary hardware. NETGEAR’s X-RAID2 is essentially a software-managed RAID (built on Linux mdadm RAID)forum.r-tt.com. A standard PC that can recognize the drives (through BIOS/OS) is sufficient. Ensure your SATA controller is in AHCI/standard mode (not set to RAID mode that might hide the drives). The “proprietary” aspect of X-RAID2 is mainly the expansion logic in the NAS’s firmware – the actual on-disk format is readable with normal Linux toolsforum.r-tt.com.
• Avoid Writing to Drives: Treat the NAS drives as read-only sources for recovery. Do not initialize or format them if prompted by any OS. (Windows, for example, will show them as unformatted – do not agree to any format prompts.) In Linux, do not let any auto-repair or RAID sync run. The goal is to mount and copy data, not to alter the NAS disks. If any drive shows signs of failure (clicking, I/O errors), consider imaging it first (e.g. using ddrescue) to avoid stressing it further.