Draytek Vigor 2925 Series User Manual page 476

Available settings are explained as follows:
Item
User account and
Authentication
Allowed Dial-In Type
Vigor2925 Series User's Guide
Description
Enable this account - Check the box to enable this function.
Idle Timeout- If the dial-in user is idle over the limitation of
the timer, the router will drop this connection. By default, the
Idle Timeout is set to 300 seconds.
PPTP - Allow the remote dial-in user to make a PPTP VPN
connection through the Internet. You should set the User Name
and Password of remote dial-in user below.
IPSec Tunnel - Allow the remote dial-in user to make an
IPSec VPN connection through Internet.
L2TP with IPSec Policy - Allow the remote dial-in user to
make 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-in VPN
connection becomes one pure L2TP connection.

Must -Specify the IPSec policy to be definitely applied
on the L2TP connection.
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