Registry Guide for Windows Registry Guide for Windows
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Registry tweaks, tricks & hacks to optimize, enhance and secure Microsoft Windows.

Change the Maximum Transmission Unit (MTU) Size (Windows NT/2000/XP)
Category: Home > Network > Protocols > TCP-IP

This parameter specifies the Maximum Transmission Unit (MTU) for a network interface. By optimizing the MTU setting you can gain substantial network performance increases, especially when using dial-up modem connections.

MTU stands for Maximum Transmission Unit and in basic terms, it defines the maximum size of a packet that can be transferred in one frame over a network.

Open your registry and find the key below.

Create a new DWORD value, or modify the existing value, called "MTU" and set it to equal the required MTU size in decimal.

Recommended Values

  • 576 - Dial-up Connections
  • 1492 - PPPoE Broadband Connections
  • 1500 - Ethernet, DSL and Cable Broadband Connections

    Restart Windows for the change to take effect.

    Note: For Windows NT 4 the key is [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\ Tcpip\Parameters]

    Note: IP datagrams may span multiple packets. Values larger than the default for the underlying network will result in the transport using the network default MTU. Values smaller than 68 will result in the tranport using an MTU of 68.

    Registry Editor Example
    |NameTypeData|
    |(Default)REG_SZ(value not set)|
    |MTUREG_DWORD0x000005dc (1500)|
    -
    |HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\ I...|
    -

    Settings:
    System Key: [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\
    Interfaces\[Adapter ID]]
    Name: MTU
    Type: REG_DWORD (DWORD Value)
    Value: Default = 0xffffffff

    Related Tweaks

    Disclaimer: Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.

    Last Modified: March 20, 2002

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