Draytek 2130 manual It means Max Transmit Unit for packet. The default

Password	Type in the password provided by ISP in this field.
Redial Policy	If you want to connect to Internet all the time, you can choose
	Always On. Otherwise, choose Connect on Demand.

Idle Time Out	Set the timeout for breaking down the Internet after passing
	through the time without any action. When you choose Connect
	on Demand, you have to type value here.

MTU Size	It means Max Transmit Unit for packet. The default
	setting is 1442. Leave blank for default value.
Enable/Disable	Click Enable for activating this function. If you click Disable,
	this function will be closed and all the settings that you adjusted
	in this page will be invalid.
Clone MAC Address	It is available when the box of Enable is checked. Click Clone
	MAC Address. The result will be displayed in the field of
	MAC Address.

After finishing all the settings here, please click OK to activate them.

36 Vigor2130 Series User’s Guide