The default MTU size for all PPP connections in Windows Server 2003, Windows 2000, and Windows XP, is a fixed size of 1500 bytes. The default MTU size for all VPN connections in Windows Server 2003, Windows 2000, and Windows XP, is a fixed size of 1400 bytes.NOTE: The above defaults apply to both clients and servers. I have scripted MTU.BAT to allow you to set, or reset, these MTU values.The syntax for using MTU.BAT is:he default MTU size for all VPN connections in Windows Server 2003, Windows 2000, and Windows XP, is a fixed size of 1400 bytes. NOTE: The above defaults apply to both clients and servers. I have scripted MTU.BAT to allow you to set, or reset, these MTU values. The syntax for using MTU.BAT is: