diff --git a/docs/FAQ.xml b/docs/FAQ.xml
index 47908233c..5e9e55c4f 100644
--- a/docs/FAQ.xml
+++ b/docs/FAQ.xml
@@ -341,6 +341,12 @@ DNAT    net:<emphasis>address</emphasis>   loc:<emphasis>local-IP-address</empha
                 sniffer such as tcpdump or Wireshark to further diagnose the
                 problem.</para>
               </listitem>
+
+              <listitem>
+                <para>The traffic is entering your firewall on a different
+                interface (interfaces reversed in
+                <filename>/etc/shorewall/interfaces</filename>?).</para>
+              </listitem>
             </itemizedlist>
           </listitem>