Draytek Vigor2830 Series User Manual page 267

Dial-Out Settings
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.
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).
PING to the IP - Enter the IP address of the remote host
that located at the other-end of the VPN tunnel.
Type of Server I am calling:
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 IPSec Policy - 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.
User Name - This field is applicable when you select,
PPTP or L2TP with or without IPSec policy above. The
maximum length for username is 49 characters.
Password - This field is applicable when you select PPTP
or L2TP with or without IPSec policy above. The maximum
length for password is 15 characters.
PPP Authentication - This field is applicable when you
select, PPTP or L2TP with or without IPSec policy above.
PAP/CHAP/MS-CHAP/MS-CHAPv2 is the most common
selection due to wild compatibility.
VJ compression - This field is applicable when you select
PPTP or L2TP with or without IPSec policy above. VJ
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Vigor2830 Series User's Guide