Draytek Vigor3910 Series, User Manual

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Vigor3910 Series User’s Guide 160
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This submenu only applies to PPP-related VPN connections, such as PPTP, L2TP, L2TP over
IPsec.
Available settings are explained as follows:
Item Description
Dial-In PPP Authentication PAP Only - elect this option to force the router to
authenticate dial-in users with the PAP protocol.
PAP/CHAP/MS-CHAP/MS-CHAPv2 - 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
(MPPE) Optional MPPE - This option represents that the MPPE
encryption method will 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
(PAP) The Mutual Authentication function is mainly used to
communicate with other routers or clients who need