D-Link DFL-260E User Manual page 464

9.5.4. PPTP/L2TP Clients
Names of Assigned Addresses
Both PPTP and L2TP utilizes dynamic IP configuration using the PPP LCP protocol. When
NetDefendOS receives this information, it is stored in symbolic host/network names. The settings
for this are:
• Inner IP Address - The host name that is used for storing the assigned IP address. If this
network object exists and has a value which is not 0.0.0.0 then the PPTP/L2TP client will try to
get that one from the PPTP/L2TP server as the preferred IP.
• Automatically pick name - If this option is enabled then NetDefendOS will create a host name
based on the name of the PPTP/L2TP interface, for example ip_PPTPTunnel1.
• Primary/Secondary DNS Name - This defines the DNS servers from a list of predefined
network objects.
Authentication
• Username - Specifies the username to use for this PPTP/L2TP interface.
• Password - Specifies the password for the interface.
• Authentication - Specifies which authentication protocol to use.
• MPPE - Specifies if Microsoft Point-to-Point Encryption is used and which level to use.
If Dial On Demand is enabled then the PPTP/L2TP tunnel will not be set up until traffic is sent on
the interface. The parameters for this option are:
• Activity Sense - Specifies if dial-on-demand should trigger on Send or Recv or both.
• Idle Timeout - The time of inactivity in seconds to wait before disconnection.
Using the PPTP Client Feature
One usage of the PPTP client feature is shown in the scenario depicted below.
Here a number of clients are being NATed through NetDefendOS before being connected to a PPTP
server on the other side of the NetDefend Firewall. If more that one of the clients is acting as a
PPTP client which is trying to connect to the PPTP server then this will not work because of the
NATing.
The only way of achieving multiple PPTP clients being NATed like this, is for the NetDefend
Firewall to act as a PPTP client when it connects to the PPTP server. To summarize the setup:
• A PPTP tunnel is defined between NetDefendOS and the server.
• A route is added to the routing table in NetDefendOS which specifies that traffic for the server
should be routed through the PPTP tunnel.
Note: The default PPTP/L2TP route
A PPTP/L2TP server will not provide information such as gateway or broadcast
addresses, as this is not used with PPTP/L2TP tunnels. When using PPTP/L2TP, the
default route is normally routed directly across the PPTP/L2TP tunnel without a
specified gateway.
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Chapter 9. VPN