diff --git a/docs/standalone.xml b/docs/standalone.xml
index cb3ca86d8..868e31eef 100644
--- a/docs/standalone.xml
+++ b/docs/standalone.xml
@@ -411,7 +411,26 @@ root@lists:~# </programlisting>
     <para>Before starting Shorewall, <emphasis role="bold">you should look at
     the IP address of your external interface and if it is in one of the above
     ranges, you should remove the <quote>norfc1918</quote> option from the
-    entry in <filename>/etc/shorewall/interfaces</filename>.</emphasis></para>
+    entry in <filename>/etc/shorewall/interfaces</filename>.</emphasis><tip>
+        <para>To determine the IP address of your external interface, as root
+        type <command>ip addr ls dev &lt;interface&gt;</command> at the
+        command line where &lt;<emphasis>interface</emphasis>&gt; is your
+        external interface. The line beginning with inet identifies your IP
+        address.</para>
+
+        <para>Example:</para>
+
+        <programlisting>root@lists:~# ip addr ls dev eth0
+2: eth0: &lt;BROADCAST,MULTICAST,UP,10000&gt; mtu 1500 qdisc htb qlen 1000
+    link/ether 00:02:e3:08:48:4c brd ff:ff:ff:ff:ff:ff
+    inet <emphasis role="bold">206.124.146.176</emphasis>/24 brd 206.124.146.255 scope global eth0
+    inet6 fe80::202:e3ff:fe08:484c/64 scope link 
+       valid_lft forever preferred_lft forever
+root@lists:~# </programlisting>
+
+        <para>In this example, the IP address of the external interface is
+        206.124.146.176</para>
+      </tip></para>
   </section>
 
   <section id="Open">
diff --git a/docs/three-interface.xml b/docs/three-interface.xml
index 3755b93e0..0e2f28bb5 100644
--- a/docs/three-interface.xml
+++ b/docs/three-interface.xml
@@ -496,7 +496,26 @@ root@lists:~# </programlisting>
     the IP address of your external interface and if it is one of the above
     ranges, you should remove the <varname>norfc1918</varname> option from the
     external interface's entry in
-    <filename>/etc/shorewall/interfaces</filename>.</emphasis></para>
+    <filename>/etc/shorewall/interfaces</filename>.</emphasis><tip>
+        <para>To determine the IP address of your external interface, as root
+        type <command>ip addr ls dev &lt;interface&gt;</command> at the
+        command line where &lt;<emphasis>interface</emphasis>&gt; is your
+        external interface. The line beginning with inet identifies your IP
+        address.</para>
+
+        <para>Example:</para>
+
+        <programlisting>root@lists:~# ip addr ls dev eth0
+2: eth0: &lt;BROADCAST,MULTICAST,UP,10000&gt; mtu 1500 qdisc htb qlen 1000
+    link/ether 00:02:e3:08:48:4c brd ff:ff:ff:ff:ff:ff
+    inet <emphasis role="bold">206.124.146.176</emphasis>/24 brd 206.124.146.255 scope global eth0
+    inet6 fe80::202:e3ff:fe08:484c/64 scope link 
+       valid_lft forever preferred_lft forever
+root@lists:~# </programlisting>
+
+        <para>In this example, the IP address of the external interface is
+        206.124.146.176</para>
+      </tip></para>
 
     <para>You will want to assign your local addresses from one sub-network or
     subnet and your DMZ addresses from another subnet. For our purposes, we
diff --git a/docs/two-interface.xml b/docs/two-interface.xml
index 5913242fd..aefe1dd53 100644
--- a/docs/two-interface.xml
+++ b/docs/two-interface.xml
@@ -458,7 +458,26 @@ root@lists:~# </programlisting>
     the IP address of your external interface and if it is one of the above
     ranges, you should remove the 'norfc1918' option from the external
     interface's entry in <filename
-    class="directory">/etc/shorewall/</filename><filename>interfaces</filename>.</emphasis></para>
+    class="directory">/etc/shorewall/</filename><filename>interfaces</filename>.</emphasis><tip>
+        <para>To determine the IP address of your external interface, as root
+        type <command>ip addr ls dev &lt;interface&gt;</command> at the
+        command line where &lt;<emphasis>interface</emphasis>&gt; is your
+        external interface. The line beginning with inet identifies your IP
+        address.</para>
+
+        <para>Example:</para>
+
+        <programlisting>root@lists:~# ip addr ls dev eth0
+2: eth0: &lt;BROADCAST,MULTICAST,UP,10000&gt; mtu 1500 qdisc htb qlen 1000
+    link/ether 00:02:e3:08:48:4c brd ff:ff:ff:ff:ff:ff
+    inet <emphasis role="bold">206.124.146.176</emphasis>/24 brd 206.124.146.255 scope global eth0
+    inet6 fe80::202:e3ff:fe08:484c/64 scope link 
+       valid_lft forever preferred_lft forever
+root@lists:~# </programlisting>
+
+        <para>In this example, the IP address of the external interface is
+        206.124.146.176</para>
+      </tip></para>
 
     <para>You will want to assign your addresses from the same sub-network
     (subnet). For our purposes, we can consider a subnet to consists of a