D-Link DFL-1660 User Manual page 426

9.2.5. L2TP Roaming Clients with
Pre-Shared Keys
• Set Encapsulation Mode to Transport.
• Select the IKE and IPsec algorithm proposal lists to be used.
• Enable the IPsec tunnel routing option Dynamically add route to the remote network
when tunnel established.
• When all-nets is the destination network, as is the case here, the advanced setting option
Add route for remote network must also be disabled. This setting is enabled by default.
5. Define an PPTP/L2TP Server object (let's call this object l2tp_tunnel) with the following
parameters:
• Set Inner IP Address to ip_int.
• Set Tunnel Protocol to L2TP.
• Set Outer Interface Filter to ipsec_tunnel.
• Set Outer Server IP to ip_ext.
• Select the Microsoft Point-to-Point Encryption allowed. Since IPsec encryption is used
this can be set to be None only, otherwise double encryption will degrade throughput.
• Set IP Pool to l2tp_pool.
• Enable Proxy ARP on the int interface to which the internal network is connected.
• Make the interface a member of a specific routing table so that routes are automatically
added to that table. Normally the main table is selected.
6. For user authentication:
• Define a Local User DB object (let's call this object TrustedUsers).
• Add individual users to TrustedUsers. This should consist of at least a username and
password combination.
The Group string for a user can also be specified. This is explained in the same step in the
IPsec Roaming Clients section above.
• Define a User Authentication Rule:
Agent
PPP
7. To allow traffic through the L2TP tunnel the following rules should be defined in the IP rule
set:
Action
Allow
NAT
The second rule would be included to allow clients to surf the Internet via the ext interface on the
NetDefend Firewall. The client will be allocated a private internal IP address which must be NATed
if connections are then made out to the public Internet via the NetDefend Firewall.
8. Set up the client. Assuming Windows XP, the Create new connection option in Network
Auth Source
Local
Src Interface Src Network
l2tp_tunnel l2tp_pool
ipsec_tunnel l2tp_pool
426
Src Network Interface
all-nets l2tp_tunnel
Dest Interface Dest Network
any
ext
Chapter 9. VPN
Client Source IP
all-nets (0.0.0.0/0)
Service
int_net all_services
all-nets all_services