Draytek 5500 Series manual PPP General Setup

3.11.2 PPP General Setup

This submenu only applies to PPP-related VPN connections, such as PPTP, L2TP, L2TP over IPSec.

Dial-In PPP	Select this option to force the router to authenticate dial-in
Authentication PAP Only	users with the PAP protocol.
PAP or CHAP	Selecting this option means the router will attempt to
	authenticate dial-in users with the CHAP protocol first. If the
	dial-in user does not support this protocol, it will fall back to
	use the PAP protocol for authentication.
Dial-In PPP Encryption	This option represents that the MPPE encryption method will
(MPPE Optional MPPE	be optionally employed in the router for the remote dial-in
	user. If the remote dial-in user does not support the MPPE
	encryption algorithm, the router will transmit “no MPPE
	encrypted packets”. Otherwise, the MPPE encryption scheme
	will be used to encrypt the data.

	Require MPPE (40/128bits) - Selecting this option will force
	the router to encrypt packets by using the MPPE encryption
	algorithm. In addition, the remote dial-in user will use 40-bit
	to perform encryption prior to using 128-bit for encryption.
	In other words, if 128-bit MPPE encryption method is not
	available, then 40-bit encryption scheme will be applied to
	encrypt the data.
	Maximum MPPE - This option indicates that the router will
	use the MPPE encryption scheme with maximum bits
	(128-bit) to encrypt the data.
Mutual Authentication	The Mutual Authentication function is mainly used to
(PAP)	communicate with other routers or clients who need
	bi-directional authentication in order to provide stronger
	security, for example, Cisco routers. So you should enable
	this function when your peer router requires mutual
	authentication. You should further specify the User Name
	and Password of the mutual authentication peer.
Start IP Address	Enter a start IP address for the dial-in PPP connection. You
	should choose an IP address from the local private network.
104	VigorPro5500 Series User’s Guide