--- loncom/configuration/Firewall.pm	2020/01/11 22:07:54	1.20
+++ loncom/configuration/Firewall.pm	2020/07/09 13:42:37	1.21
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Firewall configuration to allow internal LON-CAPA communication between servers   
 #
-# $Id: Firewall.pm,v 1.20 2020/01/11 22:07:54 raeburn Exp $
+# $Id: Firewall.pm,v 1.21 2020/07/09 13:42:37 raeburn Exp $
 #
 # The LearningOnline Network with CAPA
 #
@@ -181,10 +181,13 @@ sub firewall_open_port {
                         }
                     }
                 } else {
-                    print "no key found in $iphost hash ref\n";
+                    print "no key found in \$iphost hash ref.\n".
+                          "Domain Name Service (DNS) may not be available.\n".
+                          "If this LON-CAPA node is standalone, then you can fix this issue by modifying /etc/hosts.\n".
+                          "Use a text editor to add: IPaddress Hostname\n";
                 }
             } else {
-                print "$iphost is not a reference to a hash\n";
+                print "\$iphost is not a reference to a hash\n";
             }
             if (@lond_port_curropen) {
                 unless (grep(/^\Q$port\E$/,@opened)) {