Update fail2ban faq doc

docs/faq.rst

@@ -665,6 +665,8 @@ The above will block flagged IPs for a week, you can of course change it to you
 
 7. Add the /etc/fail2ban/action.d/docker-action.conf
   
+Option 1: Use plain iptables
+
 .. code-block:: bash
 
   [Definition]
@@ -685,6 +687,33 @@ The above will block flagged IPs for a week, you can of course change it to you
 
 Using DOCKER-USER chain ensures that the blocked IPs are processed in the correct order with Docker. See more in: https://docs.docker.com/network/iptables/
 
+Option 2:  Use ipset together with iptables
+IMPORTANT: You have to install ipset on the host system, eg. `apt-get install ipset` on a Debian/Ubuntu system.
+
+See ipset homepage for details on ipset, https://ipset.netfilter.org/.
+
+ipset and iptables provide one big advantage over just using iptables: This setup reduces the overall iptable rules.
+There is just one rule for the bad authentications and the IPs are within the ipset. 
+Specially in larger setups with a high amount of brute force attacks this comes in handy.
+Using iptables with ipset might reduce the system load in such attacks significantly.
+
+.. code-block:: bash
+
+  [Definition]
+
+  actionstart = actionstart = ipset --create f2b-bad-auth iphash
+                iptables -I DOCKER-USER -p tcp -m multiport --dports 1:1024 -m set --match-set f2b-bad-auth src -j DROP
+
+  actionstop = iptables -D DOCKER-USER -p tcp -m multiport --dports 1:1024 -m set --match-set f2b-bad-auth src -j DROP
+               ipset --destroy f2b-bad-auth
+
+
+  actionban = ipset --test f2b-bad-auth <ip> ||  ipset --add f2b-bad-auth <ip>
+
+  actionunban = ipset --test f2b-bad-auth <ip> && ipset --del f2b-bad-auth <ip>
+
+Using DOCKER-USER chain ensures that the blocked IPs are processed in the correct order with Docker. See more in: https://docs.docker.com/network/iptables/
+
 8. Configure and restart the Fail2Ban service
 
 Make sure Fail2Ban is started after the Docker service by adding a partial override which appends this to the existing configuration.