Add article for BINAT with IPSEC like in core/#440 (#12)

source/manual/how-tos/ipsec-s2s-binat.rst

@@ -0,0 +1,18 @@
+===============
+IPSec BINAT
+===============
+
+Assume company A has local LAN 10.0.1.0/24 and company B has local LAN 10.0.2.0/24.
+Also we assume that on both sides the other networks are already in use, e.g. in company A the network 10.0.2.0/24 is used for Voice and in company B network 10.0.1.0/24 is used for Guest Wifi.
+
+We have to define new networks for the Phase 2 with unused ones and create NAT entries to reach the final systems.
+
+To make it easier we create a Phase with company A using 192.168.1.0/24 and company B using 192.168.2.0/24.
+Now we need to add on each side the local LAN in the field "Manual SPD entries". So for company A we set 10.0.1.0/24 in the field and for B 10.0.2.0/24.
+This allows the NAT process to speak with the Security Policy Database.
+
+Finally we have to create NAT entries since a client in LAN A (10.0.1.10) tries to reach 192.168.2.10, but this address has to be rewritten to 10.0.2.10 on Firewall B.
+
+Create the rule like in the screenshot and vice versa on Firewall A: 
+
+.. image:: images/opnsense_nat_binat_ipsec.png

source/manual/vpnet.rst

@@ -66,6 +66,10 @@ IPsec Site-to-Site
 -----------------------
 :doc:`how-tos/ipsec-s2s`
 
+IPsec Site-to-Site with BINAT
+-----------------------
+:doc:`how-tos/ipsec-s2s-binat`
+
 OpenVPN/SSL Road Warrior
 ------------------------
 :doc:`how-tos/sslvpn_client`