-When the tun interface is created, it is assigned the address
-specified here. If no address is given, 1.1.1.1 is used. Packets
-containing user traffic should be routed via this address if given,
-otherwise the primary address of the machine.
+It's the listen address of the l2tp udp protocol sent and received
+to LAC. This address is also assigned to the tun interface if no
+iftun_address is specified. Packets containing user traffic should be
+routed via this address if given, otherwise the primary address of the
+machine.
+</LI>
+
+<LI><B>iftun_address</B> (ip address)<BR>
+This parameter is used when you want a tun interface address different
+from the address of "bind_address" (For use in cases of specific configuration).
+If no address is given to iftun_address and bind_address, 1.1.1.1 is used.
+</LI>
+
+<LI><B>tundevicename</B> (string)<BR>
+Name of the tun interface (default: "tun0").