Configure TCPIP Max Transfer Unit (MTU) size in Vista

5 July 2007 by Snakefoot | Comment » | Trackback Off
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 or connection loss.

Open an Elevated Command Prompt and run this command to view current MTU size of the available IPv4 sub-interfaces (Can also be done with IPv6):

netsh interface ipv4 show subinterfaces

To change the MTU size of sub-interface no. 1:

netsh interface ipv4 set subinterface "1" mtu=1500 store=persistent

Related Registry settings to Configure MTU size.
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Updated: 1 December 2007

Comments:

Comment by Phantom - 5 July 2008 @ 1:03 Reply

The show interfaces line reveals that the loopback is set to a much higher number, should that be changed to 1500 as well?

Comment by Coscu - 8 July 2008 @ 4:31 Reply

i have make a change with a friend in the MTU but now we want to delete it and we dont know the command =/ can someone help ?

Comment by kontol - 8 July 2008 @ 20:28 Reply

If you have more than one NICs and you want to see which subinterface is, you need to run:

netsh interface ipv4 show interfaces

The result will be like this:
Idx Met MTU State Name
— — —– ———– ——————-
1 50 4294967295 connected Loopback Pseudo-Interface 1
17 25 1500 connected Wireless Network Connection 1
19 25 1500 connected Wireless Network Connection 2

Hence, if you like to change MTU of “Wireless Netwrok Connection 1″, you should run command:

netsh interface ipv4 set subinterface “17″ mtu=1384 store=persistent

and so on for the other interfaces.

Comment by Snakefoot - 8 July 2008 @ 20:59 Reply

Phantom
The show interfaces line reveals that the loopback is set to a much higher number, should that be changed to 1500 as well?

The loopback adapter can only communicate with the local machine hence the name. No need to change the MTU.

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