How to fix Error 56 on Windows 11

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Why This Error Happens

Error 56 occurs when the Server service’s NetBIOS command queue becomes saturated, typically because the “Server” or “Workstation” service resource allocation is too low for the current network load. This is common on Windows 11 machines acting as file/print servers, syncing large amounts of SMB traffic, or connected to older network hardware/switches with duplex mismatches. Corrupted network driver bindings or outdated NIC drivers can also cause the buffer queue to overflow faster than it’s cleared.

Step-by-Step Resolution Guide

  1. Increase Server Service Buffer Registry Values
    Open Registry Editor (regedit) and navigate to:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
    Add or modify the following DWORD (32-bit) values:
  • MaxWorkItems = 65535
  • MaxMpxCt = 800
  • MaxRawWorkItems = 128
  • MaxFreeConnections = 64
  • MinFreeConnections = 20
    Restart the PC after applying changes.

  1. Update Network Adapter Drivers
    Go to Device Manager > Network Adapters, right-click your active NIC, select Update Driver, then choose Search automatically. If a newer driver exists on the manufacturer’s website (Intel, Realtek, Broadcom), install that version instead, as it often resolves buffer handling bugs.

  2. Check Duplex/Speed Settings
    In Device Manager > Network Adapters > [Your NIC] > Properties > Advanced, ensure the Speed & Duplex setting matches your switch/router (e.g., “1.0 Gbps Full Duplex”) rather than “Auto Negotiation,” which can cause packet retransmission storms leading to command queue backups.

  3. Disable NetBIOS Over TCP/IP (If Not Required)
    Go to Control Panel > Network and Sharing Center > Change adapter settings. Right-click your adapter → Properties → select Internet Protocol Version 4 (TCP/IPv4) → Properties → Advanced → WINS tab → select Disable NetBIOS over TCP/IP. This is safe on modern networks relying solely on DNS/SMB direct hosting.

  4. Restart the Server and Workstation Services
    Open Command Prompt as Administrator and run:

   net stop server
   net stop workstation
   net start workstation
   net start server

Alternative or Verification Steps

  • Open Event Viewer (eventvwr.msc) and check Windows Logs > System for recurring Event ID 56 entries after 24–48 hours of normal use to confirm the error has stopped.
  • If the issue persists, temporarily connect the machine to a different switch/port to rule out a faulty physical network component causing excessive retransmissions.