diff --git a/Shorewall/releasenotes.txt b/Shorewall/releasenotes.txt
index cf4a8cb73..ff6a7d0b7 100644
--- a/Shorewall/releasenotes.txt
+++ b/Shorewall/releasenotes.txt
@@ -212,6 +212,25 @@ None.
         The above defines 32 classes with MARK values 100-131. Each
         class has a guaranteed rate of 1kbit/second.
 
+    As part of this change, the generation of class ids from mark
+    values has been changed. The class number is now
+
+	   ( <devnum> << 10 ) | <mask>
+
+    /sbin/shorewall has an 'encode' and 'decode' command to translate a
+    device number, mark pair to/from a classid:
+
+	   encode <devnum> <mark>
+	   decode <classnum>
+
+    Example:
+
+	$ shorewall decode 3172
+	Device = 3 Mark = 100
+        $ shorewall encode 3 100
+	Class number = 3172
+	$
+
 ----------------------------------------------------------------------------
                  N E W   F E A T U R E S   IN   4 . 3
 ----------------------------------------------------------------------------
diff --git a/Shorewall/shorewall b/Shorewall/shorewall
index f02fdf17d..d3231e86f 100755
--- a/Shorewall/shorewall
+++ b/Shorewall/shorewall
@@ -1444,9 +1444,11 @@ usage() # $1 = exit status
     echo "   check [ -e ] [ <directory> ]"
     echo "   clear [ -f ]"
     echo "   compile [ -e ] [ -d ] [ <directory name> ] [ <path name> ]"
+    echo "   decode <classnum>"
     echo "   delete <interface>[:<host-list>] ... <zone>"
     echo "   drop <address> ..."
     echo "   dump [ -x ]"
+    echo "   encode <devnum> <mark>"
     echo "   export [ <directory1> ] [<user>@]<system>[:<directory2>]"
     echo "   forget [ <file name> ]"
     echo "   help"
@@ -1992,6 +1994,14 @@ case "$COMMAND" in
 	shift
 	restore_command $@
         ;;
+    decode)
+	[ $# -eq 2 ] || usage 1
+	echo "Device = $(($2 >> 10)) Mark = $(($2 & 0x3ff))"
+	;;
+    encode)
+	[ $# -eq 3 ] || usage 1
+	echo "Class Number = $((($2 << 10) | $3))"
+	;;
     call)
 	get_config
 	[ -n "$debugging" ] && set -x