How to fix Error 1821 on Windows 11

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Windows 11 Error 1821: “The Requested Authentication Level Is Not Supported”

Why This Error Happens

Error 1821 typically occurs when the DCOM (Distributed Component Object Model) or RPC (Remote Procedure Call) authentication settings between the client and server do not match, often because the requested authentication level exceeds what the server or negotiated security package supports. This is commonly triggered by mismatched security policies, outdated authentication protocols (like NTLM vs. Kerberos), or corrupted registry entries related to DCOM security settings. It can also happen when Group Policy enforces a stricter authentication level than the target service is configured to accept.

Step-by-Step Resolution Guide

Step 1: Check DCOM Authentication Settings

  • Press Win + R, type dcomcnfg, and press Enter to open Component Services.
  • Navigate to Component Services > Computers > My Computer, right-click and select Properties.
  • Under the Default Properties tab, verify that Default Authentication Level is set to “Connect” or higher (not “None”).
  • Ensure Default Impersonation Level is set to “Identify.”

Step 2: Verify and Adjust Group Policy Security Settings

  • Open the Local Group Policy Editor by typing gpedit.msc in the Run dialog.
  • Go to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options.
  • Locate Network security: LAN Manager authentication level and set it to “Send NTLMv2 response only, refuse LM & NTLM” for consistency.
  • Run gpupdate /force in Command Prompt (Admin) to apply changes immediately.

Step 3: Check the WinRM (Windows Remote Management) Configuration

  • Open Command Prompt as Administrator and run:
winrm quickconfig
  • If prompted, confirm the changes to allow remote management.
  • Verify authentication settings using:
winrm get winrm/config/service/auth
  • Ensure Negotiate is set to true and Basic is disabled unless explicitly required.

Step 4: Reset or Repair the RPC/DCOM Registry Keys

  • Open regedit and navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole
  • Confirm that LegacyAuthenticationLevel and LegacyImpersonationLevel values are present and correctly configured (typically set to 2 for Connect-level authentication).
  • If values are missing or corrupted, export the key first as a backup, then recreate them manually or restore from a known-good system.

Step 5: Update Network Drivers and Windows Security Patches

  • Go to Settings > Windows Update > Check for updates and install any pending security or driver updates.
  • Update network adapter drivers via Device Manager > Network adapters > Right-click > Update driver.
  • Restart the system after applying updates to ensure authentication modules reload correctly.

Alternative or Verification Steps

  • To verify the fix, attempt the original action (e.g., remote connection, service call, or DCOM application launch) and confirm Error 1821 no longer appears in Event Viewer under Windows Logs > System.
  • If the issue persists, try running the built-in Network and Internet Troubleshooter (Settings > System > Troubleshoot > Other troubleshooters) or temporarily disable third-party antivirus/firewall software to rule out authentication interference.