Draytek 5500 Series Enable Ping to keep alive, Ping to the IP, L2TP with …, PPP Authentication

	connection has been idled over the value, the router will drop
	the connection.
Enable PING to keep alive	This function is to help the router to determine the status of
	IPSec VPN connection, especially useful in the case of
	abnormal VPN IPSec tunnel disruption. For details, please
	refer to the note below. Check to enable the transmission of
	PING packets to a specified IP address.
PING to the IP	Enter the IP address of the remote host that located at the
	other-end of the VPN tunnel.
		Enable PING to Keep Alive is used to handle abnormal
		IPSec VPN connection disruption. It will help to provide
		the state of a VPN connection for router’s judgment of
		redial.
		Normally, if any one of VPN peers wants to disconnect
		the connection, it should follow a serial of packet
		exchange procedure to inform each other. However, if the
		remote peer disconnect without notice, Vigor router will
		by no where to know this situation. To resolve this
		dilemma, by continuously sending PING packets to the
		remote host, the Vigor router can know the true existence
		of this VPN connection and react accordingly. This is
		independent of DPD (dead peer detection).
ISDN	Build ISDN LAN-to-LAN connection to remote network. You
	should set up Link Type and identity like User Name and
	Password for the authentication of remote server. You can
	further set up Callback (CBCP) function below. This feature is
	useful for i model only.
PPTP	Build a PPTP VPN connection to the server through the
	Internet. You should set the identity like User Name and
	Password below for the authentication of remote server.
IPSec Tunnel	Build an IPSec VPN connection to the server through Internet.
L2TP with …	Build a L2TP VPN connection through the Internet. You can
	select to use L2TP alone or with IPSec. Select from below:
	None: Do not apply the IPSec policy. Accordingly, the VPN
	connection employed the L2TP without IPSec policy can be
	viewed as one pure L2TP connection.
	Nice to Have: Apply the IPSec policy first, if it is applicable
	during negotiation. Otherwise, the dial-out VPN connection
	becomes one pure L2TP connection.
	Must: Specify the IPSec policy to be definitely applied on the
	L2TP connection.
Server IP/Host Name for..	You can specify the IP address of the remote dial-out user.
User Name	This field is applicable when you select ISDN, PPTP or L2TP
	with or without IPSec policy above.
Password	This field is applicable when you select ISDN, PPTP or L2TP
	with or without IPSec policy above.
PPP Authentication	This field is applicable when you select ISDN, PPTP or L2TP
	with or without IPSec policy above. PAP/CHAP is the most
	common selection due to wild compatibility.
VigorPro5500 Series User’s Guide	113