User`s guide

218
Entity
Instance
Parameter
Values
Equivalent Web Parameter
l2tp n ans OFF,ON
Allow this L2TP tunnel to answer
incoming ISDN calls
l2tp n msn Up to 9 digits MSN
l2tp n sub Up to 17 digits Sub-address
Configuration – Network > Virtual Private Networking (VPN) > PPTP
The Point-to-Point tunnelling protocol (PPTP) is a common way of creating a VPN tunnel to a
Microsoft Windows™ server.
PPTP works by ending a regular PPP session to the peer encapsulated by the Generic
Routing Encapsulation (GRE) protocol. A second session on TCP port 1723 is used to initiate
and manage the GRE session. PPTP connections are authenticated with Microsoft MSCHAP-
v2 or EAP-TLS. VPN traffic is protected by MPPE encryption. PPTP does not work with
GPRS/HSDPA mobile operators that assign a private IP address and then apply NAT to the
traffic before it leaves their network. This because the server tries to build a tunnel back to
the router on port 1723 but fails when the traffic is blocked by the mobile operators’
firewall.
Configuration – Network > Virtual Private Networking (VPN) > PPTP >
PPTP n
Description
The text string in this text box is a name to aid the identification of the router.
Remote Host a.b.c.d
The value in this text box specifies the IP address of the remote host, i.e. the device that
will terminate the PPTP connection.
Use Interface x,y
The interface to be used for the PPTP tunnel is selected from this drop-down list, the text
box next to it is for the interface instance. Specifying these parameters allow the router to
raise the interface should it be disconnected. The interface options are; Auto, PPP and
Ethernet.
Accept incoming PPTP connections
When checked, this checkbox allow the router to act as a PPTP server and accept incoming
VPN connections.
Enable Server mode
When checked, this checkbox causes the router to send call_out call requests to the remote
device. In the default state which is unchecked, the router will send a call_in request to the
remote device.
Enable Socket mode
When checked, this checkbox enables the use of a Digi proprietary mode whereby PPP
packets are sent via the PPTP control socket rather than in GRE packets.
Encrypt control data using SSL version n
When checked, this checkbox causes the router to encrypt the control data using SSL. This
is a Digi proprietary function and is not part of standard PPTP. The drop-down list allows the
SSL version to be selected. The available options are; Use default, TLSv1 only SSLv3 only
and SSLv2 only.
Enable PPTP debug
When checked, this checkbox enables debug tracing.