[5005] Updated User's Guide - part about Hostname reservation.

doc/guide/dhcp4-srv.xml

@@ -2775,10 +2775,15 @@ It is merely echoed by the server
 
     <section id="reservation4-hostname">
       <title>Reserving a hostname</title>
-      <para>When the reservation for the client includes the <command>hostname
-      </command>, the server will assign this hostname to the client and send
-      it back in the Client FQDN or Hostname option, depending on which of them
-      the client has sent to the server. The reserved hostname always takes
+      <para>When the reservation for a client includes the <command>hostname
+      </command>, the server will return this hostname to the client in
+      the Client FQDN or Hostname option. The server responds with the Client
+      FQDN option only if the client has included Client FQDN option in its
+      message to the server. The server will respond with the Hostname option
+      if the client has included Hostname option in its message to the server,
+      or when the client has requested Hostname option using Parameter Request
+      List option. The server will return Hostname option even if it is not
+      configured to perform DNS updates. The reserved hostname always takes
       precedence over the hostname supplied by the client or the autogenerated
       (from the IPv4 address) hostname.</para>