Draytek Vigor 2925 Series User Manual page 365

Dial-In PPP Encryption
(MPPE)
Mutual Authentication
(PAP)
Assigned IP Start
LDAP Server Profiles for
PPP Authentication
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.
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.
The Mutual Authentication function is mainly used to
communicate with other routers or clients who need
bi-directional authentication in order to provide stronger
security, for example, Cisco routers. So you should enable
this function when your peer router requires mutual
authentication. You should further specify the User Name
and Password of the mutual authentication peer.
The length of the name/password is limited to 23/19
characters.
Enter a start IP address for the dial-in PPP connection. You
should choose an IP address from the local private network.
For example, if the local private network is
192.168.1.0/255.255.255.0, you could choose
192.168.1.200 as the Start IP Address.
You can configure up to four start IP addresses for LAN1 ~
LAN5.
Configured LDAP profiles will be listed under such item.
Simply check the one you want to enable the PPP
authentication by LDAP server profiles.
However, if there is no profile listed, simply click the link
of PPTP LDAP Profile to create/add some new LDAP
profiles you want.
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Vigor2925 Series User's Guide