«««Windows: how to find the best value for the MTU

9:59 pm April 25, 201714246

it comes in the online connection to problems such as broken downloads or faltering Web applications, the MTU may be to blame for this. Read how you optimally adjust parameters for network communication this.

as a free tool optimizes the MTU setting

  1. you get the program TCP optimizer , with Windows 10, 8, 7, XP and several server vision works.
  2. the program requires no installation: run it by right mouse click and select run as Administrator .
  3. wait until the tool for completed the analysis of the system and set your Internet connection speed in MBit / s on the slide.

    Startbildschirm TCP Optimizer
    Adjust how fast your Internet connection is on the slide.

  4. choose the network card, which uses your PC to the Internet, in the box below the slider. You are unsure, you hook adapter check the box next to modify all network.
  5. click the button apply changes .
  6. now shows you the tool to all changes, which makes it. Safety set backup Unticking the option .

    TCP Optimizer zeigt geänderte Einstellungen
    TCP optimizer will show you which settings will change and provides a backup of the current settings.

  7. after incorporating the changes, the program will request usually a restart. Admit it.

so you can test the courage for different server

  1. you want to determine the best MTU with various remote stations, go MTU/latency, into the program on the tab.
  2. select one of the predefined server addresses under URL or enter a custom URL via edit .
  3. let the program with the largest MTU try different values button, until it finds the optimum setting.

    Beste MTU finden
    In this tab you can optimize MTU for different servers.

to go back to the old settings

  1. the problems should have increased more after the TCP optimizer, start the program again in the Admininstator mode.
  2. , click the menu item file – restore backed up settings .
  3. in the dialog that appears, locate the file that for created the backup option before. The files are created in the same directory, where is the tool itself and say for example sg_backup_2017-04-24-1535.spg.
  4. now appears again the well-known modification screen, only without the backup facility, which would make sense here too.
  5. then the tool will propose again a reboot, after which everything is back.

If you have no backup or be unsafe after several passes, what setting is correct, use the point file – restore Windows default settings , what the defaults are loaded by Windows.

therefore, an incorrect MTU causes problems

the MTU (maximum transmission unit) determines how large the TCP/IP data packets must be maximum, which submits your computer. The problem is too great a value. Since then the packet on its way to the finish in two parts must be sent further divided. This can happen on any node on the Internet.

such fragmented packets are by some waypoints – how about a router or a firewall – not tolerated and therefore easily discarded. This can lead to a suspended download or a broken connection.

so there is a maximum value for the size of the package, where the fragmentation does not occur. The MTU on your PC for a higher value, there are problems. It is below the limit of a small loss in data throughput occurs because the ratio of payload is worse to control data (for example, the packet headers).

to display the current MTU without additional program on

you type on the command line a

 netsh interface ipv4 show interfaces 

now you will receive a list of the active network adapter and the respective MTU values. On a system with virtual NICs for VMWare that looks for example like this:

MTU anzeigen


MTU is interesting only the row named “Local area connection…”. Maybe not a number behind you, example PC for but few to configurations behind it, that’s why the “6”.

if the value displayed here is larger than the MTU path recommendation, you should change it. He is small, however, so you can leave the setting. This minimal power losses arise.

to set a new MTU

the MTU is stored in the registry. There is a convenient way to set this value without direct work with the registry, but about netsh .

because this setting requires special rights, should start before the command line as an administrator. That didn’t work, the following command will not work.

the following command sets the value recommended by MTU path in the example call of “1476”. This is the identification of the network adapter on its index, so the first column from the previous list. In the example, he for the number 25

 netsh interface ipv4 set subinterface 25 mtu store = persistent 

= 1476 to check whether the command is really worked, again type the command with …show interfaces . Where the new value should now be visible.

the change is reflected immediately on the traffic. You can repeat a problematic download so in the browser and find out whether the change for brought an improvement.