How to modify the MTU in Windows 7 or Vista

The Windows operating system uses the maximum transmission Unit (MTU) to determine the maximum size of protocol packets (Protocol data packet) that can be transmitted over the network layer below. The MTU parameter usually occurs in communication with an interface (NIC, serial port, etc.), and each interface is set separately.

To achieve optimal network performance, and to prevent fragmentation (fragmentation), the MTU should be large enough that any IP datagram (datagram) can be accommodated by a single frame. IP datagrams that are larger than the MTU are split into fragments of multiples of 8-bit groups. Fragments are passed to the target host separately and then reassembled into frames before the datagram is processed. So, the value of a small MTU is not good for optimized network performance.

[For more information about this option on Windows, please refer to the last link.]

To modify a step:

1. Use the following command to see all the network cards, and the size of their MTU.

netsh interface ipv4 show subinterfaces

或

netsh interface ipv6 show subinterfaces

2. 使用下面的命令来设置一个新的MTU的值.

netsh interface ipv4 set subinterface "Local Area Connection" mtu=nnnn store=persistent

3. 重启机器,用以使新选项生效.

4. 使用下面的命令来检查修改是否已经生效.

netsh int ip show int

netsh interface ipv4 show subinterfaces

netsh interface ipv6 show subinterfaces

还可以使用注册表来进行同样的修改.

1.Run Registry Editor (RegEdit).

2.Navigate to the following registry key:
hkey_local_machine\system\currentcontrolset\services\tcpip\parameters\interfaces

3.Select the registry sub-key of the network interface that you want to the change its MTU. For example, {abcd1234-ef56-gh78-ij90-klmnop123456}. As a guide, you can look through the list of interface available, and find the one, have IP address or gateway IP addre SS which is matching.

4.Right Click on the blank area of the right pane, and select New, DWORD (32-bit) value, and name the new registry value As MTU

5.Right Click on MTU and select Modify, and enter the desired MTU value in Decimal. Common MTU values in decimal is 1300, 1400, 1462, 1480, and 1500.

Data sources

===============================

How to Set and change MTU in Windows 7 or Vista

http://www.mydigitallife.info/how-to-set-and-change-mtu-in-windows-7-or-vista/