We will perform the change using the CMD utility.
First, you need to open the command prompt as an administrator. Then, use the corresponding command to view all existing network interfaces and their MTU values.

netsh interface ipv4 show subinterfaces

You will receive output similar to this:

Where 1500 (default) is the MTU value.
Ethernet is the standard interface name.

Next, we will change the MTU value using a special command:

netsh interface ipv4 set subinterface "Ethernet" mtu=1400 store=persistent

Where Ethernet is the name of the network interface.
1400 is the new MTU value to be set.

You will get the result.