diff --git a/en_US.ISO8859-1/books/faq/book.sgml b/en_US.ISO8859-1/books/faq/book.sgml
index 652ff41608..fc4ab58f84 100644
--- a/en_US.ISO8859-1/books/faq/book.sgml
+++ b/en_US.ISO8859-1/books/faq/book.sgml
@@ -9297,6 +9297,23 @@ round-trip min/avg/max/stddev = 2.530/2.643/2.774/0.103 ms</screen>
             discouraged for the reasons listed above.</para>
         </answer>
       </qandaentry>
+
+      <qandaentry>
+        <question id="unknown-hw-addr-format">
+          <para>What are these <errorname>arp: unknown hardware
+            address format</errorname> error messages?</para>
+        </question>
+
+        <answer>
+          <para>This means that some device on your local Ethernet is
+            using a MAC address in a format that FreeBSD does not
+            recognize.  This is probably caused by someone
+            experimenting with an Ethernet card somewhere else on the
+            network.  You'll see this most commonly on cable modem
+            networks.  It is harmless, and should not affect the
+            performance of your FreeBSD machine.</para>
+        </answer>
+      </qandaentry>
     </qandaset>
   </chapter>