How to fix Error 11246 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 11246 – Corrupted Message with Duplicated Private Variable Data Element

Why This Error Happens

Error 11246 occurs when SQL Server’s Service Broker or Database Mirroring endpoint receives a TDS (Tabular Data Stream) message containing a duplicate private variable data element, indicating the message has been corrupted in transit or malformed at the source. This typically stems from network-layer interference such as a faulty network adapter, an intermediary proxy/firewall altering packet contents, or a mismatched TDS protocol version between SQL Server instances. In some cases, this can also result from outdated network drivers or NIC offloading features (like TCP Chimney or Checksum Offload) corrupting packets on Windows Server 2025 / Windows 11 systems.

Step-by-Step Resolution Guide

Step 1: Verify Network Integrity Between Endpoints

  • Check for packet loss or corruption using ping -t and pathping against the remote SQL Server instance.
  • Inspect Windows Event Viewer under Applications and Services Logs > Microsoft > Windows > NDIS for adapter-level errors.
  • Temporarily disable NIC offloading features via PowerShell: Disable-NetAdapterChecksumOffload -Name "*" and Disable-NetAdapterLso -Name "*".

Step 2: Validate Service Broker / Database Mirroring Configuration

  • Run SELECT * FROM sys.service_broker_endpoints; to confirm endpoint status and encryption settings.
  • Ensure both source and destination SQL Server 2025 instances use matching TDS protocol versions (check via SELECT SERVERPROPERTY('ProductVersion');).
  • Confirm certificates used for Broker encryption (if applicable) have not expired by querying sys.certificates.

Step 3: Reset and Rebuild the Affected Endpoint

  • Drop and recreate the Service Broker endpoint using:
  DROP ENDPOINT [Broker_Endpoint];
  CREATE ENDPOINT [Broker_Endpoint] STATE = STARTED AS TCP (LISTENER_PORT = 4022) FOR SERVICE_BROKER (AUTHENTICATION = WINDOWS, ENCRYPTION = REQUIRED);
  • Restart the SQL Server and SQL Server Agent services via services.msc or Restart-Service -Name MSSQLSERVER -Force.

Step 4: Update Network and Storage Drivers

  • Navigate to Device Manager > Network Adapters, right-click the active NIC, and select Update Driver.
  • Download the latest Windows Server 2025–certified NIC drivers directly from the hardware vendor (Intel, Broadcom, etc.) rather than relying on Windows Update.
  • Reboot the server after driver installation to ensure changes take effect at the kernel level.

Alternative or Verification Steps

  • After applying fixes, monitor the SQL Server Error Log (C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG) for 24–48 hours to confirm Error 11246 does not recur.
  • If the issue persists, capture a network trace using Wireshark or Microsoft Network Monitor during message transmission to identify the exact point of packet corruption, then escalate to your network team or ISP.