Configure Max Transfer Unit (MTU) size for the TCPIP stack

The default Max Transfer Unit (MTU) size for ethernet is 1500 bytes, if using a network with a different MTU size, then one should make sure to configure MTU in Windows to avoid packet fragmentation and loss of VPN connections.
  • Adapter MTU:

    [HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \Tcpip \Parameters \Interfaces \{Adapter-id/GUID}]
    MTU = 1500

    More Info MS KB900926

  • Point-To-Point Protocol (PPP) MTU for Modem DialUp Networking(DUN) or over Ethernet (PPPoE):

    [HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \NdisWan \Parameters \Protocols \0]
    ProtocolType = 0x00000800
    PPPProtocolType = 0x00000021
    ProtocolMTU = 1500

    More Info MS KB283165
    More Info MS KB826159

    More Info MS KB283070
    More Info MS KB317496
  • Virtual Private Network (VPN) Tunnel MTU:

    [HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \NdisWan \Parameters \Protocols \0]
    ProtocolType = 0x00000800
    PPPProtocolType = 0x00000021
    TunnelMTU = 1400

    More Info MS KB826159

Related Configure Max Transfer Unit (MTU) in Windows NT4
Related Configure Max Transfer Unit (MTU) in Windows Vista/2008/7

Updated: 10 October 2012

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