Resize MTU in Windows – Zyxel Support Campus EMEA

How to change MTU size in Windows OS?

In Windows operating systems, you can change the MTU size through special programs for setting up an Internet connection (for example, SG TCP Optimizer ), using the netsh utility, or through the Registry Editor , which is included with operating systems. If necessary, you can reduce the MTU value (by default, Windows is set to MTU = 1500 bytes) or increase it for passing large Jumbo Frame Ethernet frames (usually, from 1500 to 9000 bytes).

Option 1 . Download the special free utility SG TCP Optimizer , which is designed for additional configuration of the Internet connection. Using this utility, you can easily change the TCP / IP protocol settings (for example, MTU size) in the Windows registry.

In the Choose Settings settings, select the Custom value and in the MTU field specify the desired value. Click the Apply changes button to apply the specified settings and restart the computer.

Option 2 . In Windows operating systems, the MTU size can be changed using the special netsh utility or through the Registry Editor .

2.1 Changing MTU size in Windows Vista / 2008/7

Run the Windows command prompt as administrator (Start> Run> cmd). Run the commands to view the current MTU values:

netsh interface ipv4 show subinterfaces

MTU MediaSenseState Bytes In Bytes Out Interface
-------- ------------------------ ----------- ------- ------- -------------
4294967295 1 0 1348 Loopback Pseudo-Interface 1
1500 1 3734 2824 Local Area Connection

Next, run the command to set the new MTU value (for example, 1452; by default, Windows uses the MTU value = 1500):

netsh interface ipv4 set subinterface "Local Area Connection" mtu = 1452 store = persistent

or for wireless interface:

netsh interface ipv4 set subinterface "Wireless Network Connection" mtu = 1452 store = persistent

Then restart the computer.

To view the current MTU values, run the command again:

netsh interface ipv4 show subinterfaces

If necessary, to reset the MTU values to the default settings, run the following command:

netsh interface ipv4 reset

and restart the computer.

2.2. Resizing MTUs through Registry Editor

At the Windows command prompt (Start> Run> cmd), type regedit to start the Registry Editor.

In the Registry Editor utility window that opens, open the following registry branch:
HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ Class \ {4D36E972-E325—11CE-BFC1—08002bE10318}
It will contain subsections 0000, 0001, 0002, etc. Carefully review the contents of these subsections and stop at the fact that the value of the DriverDesc parameter is similar to the name of your network adapter through which you connect to the Internet. In this subsection, find and remember the value of the NetCfgInstanceId parameter.

Then navigate to the following registry key:
HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Tcpip \ Parameters \ Interfaces
Find the subkey that corresponds to the value of the NetCfgInstanceId parameter that you found earlier.

Double-click on the MTU parameter and enter the value 1400 in decimal format.
Close the Registry Editor and restart the computer.

If there is no MTU parameter, you need to create it. In the Registry Editor, select Edit> New> DWORD Value .

Enter the parameter name - MTU . Then double-click on the MTU parameter, enter the desired value (in our example, the decimal value is MTU = 1400), then click OK .

Close the Registry Editor and restart the computer.

KB-00456

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