Draytek VIGOR2925 SERIES User Manual page 418

Available settings are explained as follows:
Item
Dial-In Settings
Vigor2925 Series User's Guide
Description
Allowed Dial-In Type - Determine the dial-in connection
with different types.

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
trigger 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
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