How to Change Max Concurrent SMB Sessions in Regedit

Modifying the maximum number of concurrent Server Message Block (SMB) sessions in the Windows Registry allows workstations to handle higher volumes of network file transfers and prevent connection limits when communicating with servers. This guide explains how to adjust the client-side MaxCmds setting using the Windows Registry Editor (regedit) to optimize network throughput and prevent SMB session bottlenecks.

Step-by-Step Guide to Adjusting SMB Sessions

1. Open the Registry Editor

  1. Press Windows Key + R to open the Run dialog box.
  2. Type regedit and press Enter.
  3. If prompted by User Account Control (UAC), click Yes to grant administrative privileges.

In the address bar at the top of the Registry Editor, paste the following path and press Enter:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

3. Create or Modify the MaxCmds Value

  1. Check the right pane for a value named MaxCmds.
  2. If it does not exist:
    • Right-click an empty area in the right pane.
    • Select New > DWORD (32-bit) Value.
    • Name the new value MaxCmds and press Enter.
  3. Double-click the MaxCmds entry to edit it:
    • Set the Base to Decimal.
    • In the Value data field, enter your desired maximum number of concurrent network commands (commonly set between 256 and 2048 depending on workload requirements; default is typically 15 to 50).
  4. Click OK to save the changes.

Adjusting Inbound Sessions (LanmanServer)

If you are modifying a workstation to accept more inbound SMB sessions from other devices:

  1. Navigate to:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
  2. Create or open the MaxMpxCt DWORD (32-bit) value.
  3. Switch the base to Decimal and set a value matching or exceeding your MaxCmds requirement (e.g., 2048).
  4. Click OK.

Apply the Changes

Registry changes to SMB services require a service restart or system reboot to take effect:

  1. Open Command Prompt as an Administrator.

  2. Restart the workstation service by running:

    net stop lanmanworkstation /y
net start lanmanworkstation

  3. Alternatively, restart your computer.