diff --git a/Shorewall-perl/Shorewall/Chains.pm b/Shorewall-perl/Shorewall/Chains.pm
index e3a59d7b5..7118f8aef 100644
--- a/Shorewall-perl/Shorewall/Chains.pm
+++ b/Shorewall-perl/Shorewall/Chains.pm
@@ -125,6 +125,7 @@ our %EXPORT_TAGS = (
 				       get_interface_address
 				       get_interface_addresses
 				       get_interface_bcasts
+				       get_interface_gateway
 				       get_interface_mac
 				       set_global_variables
 				       create_netfilter_load
@@ -219,7 +220,9 @@ our $chainseq;
 our %interfaceaddr;
 our %interfaceaddrs;
 our %interfacenets;
+our %interfacemacs;
 our %interfacebcasts;
+our %interfacegateways;
 
 our @builtins = qw(PREROUTING INPUT FORWARD OUTPUT POSTROUTING);
 
@@ -315,10 +318,12 @@ sub initialize() {
     #
     # Keep track of which interfaces have active 'address', 'addresses' and 'networks' variables
     #
-    %interfaceaddr    = ();
-    %interfaceaddrs   = ();
-    %interfacenets    = ();
-    %interfacebcasts  = ();
+    %interfaceaddr      = ();
+    %interfaceaddrs     = ();
+    %interfacenets      = ();
+    %interfacemacs      = ();
+    %interfacebcasts    = ();
+    %interfacegateways  = ();
 }
 
 INIT {
@@ -1467,7 +1472,7 @@ sub mysplit( $ ) {
 #
 sub interface_address( $ ) {
     my $variable = chain_base( $_[0] ) . '_address';
-    "\U$variable";
+    uc $variable;
 }
 
 #
@@ -1479,7 +1484,7 @@ sub get_interface_address ( $ ) {
     my $variable = interface_address( $interface );
     my $function = interface_is_optional( $interface ) ? 'find_first_interface_address_if_any' : 'find_first_interface_address';
 
-    $interfaceaddr{$interface} = "$variable=\$($function $interface)";
+    $interfaceaddr{$interface} = "$variable=\$($function $interface)\n";
 
     "\$$variable";
 }
@@ -1489,7 +1494,7 @@ sub get_interface_address ( $ ) {
 #
 sub interface_bcasts( $ ) {
     my $variable = chain_base( $_[0] ) . '_bcasts';
-    "\U$variable";
+    uc $variable;
 }
 
 #
@@ -1505,12 +1510,39 @@ sub get_interface_bcasts ( $ ) {
     "\$$variable";
 }
 
+#
+# Returns the name of the shell variable holding the gateway through the passed interface
+#
+sub interface_gateway( $ ) {
+    my $variable = chain_base( $_[0] ) . '_gateway';
+    uc $variable;
+}
+
+#
+# Record that the ruleset requires the gateway address on the passed interface
+#
+sub get_interface_gateway ( $ ) {
+    my ( $interface ) = $_[0];
+
+    my $variable = interface_gateway( $interface );
+
+    if ( interface_is_optional $interface ) {
+	$interfacegateways{$interface} = qq($variable=\$(detect_gateway $interface)\n);
+    } else {
+	$interfacegateways{$interface} = qq($variable=\$(detect_gateway $interface)
+[ -n "\$$variable" ] || fatal_error "Unable to detect the gateway through interface $interface"
+);
+    }
+
+    "\$$variable";
+}
+
 #
 # Returns the name of the shell variable holding the addresses of the passed interface
 #
 sub interface_addresses( $ ) {
     my $variable = chain_base( $_[0] ) . '_addresses';
-    "\U$variable";
+    uc $variable;
 }
 
 #
@@ -1537,7 +1569,7 @@ sub get_interface_addresses ( $ ) {
 #
 sub interface_nets( $ ) {
     my $variable = chain_base( $_[0] ) . '_networks';
-    "\U$variable";
+    uc $variable;
 }
 
 #
@@ -1564,19 +1596,25 @@ sub get_interface_nets ( $ ) {
 # Returns the name of the shell variable holding the MAC address of the gateway for the passed provider out of the passed interface
 #
 sub interface_mac( $$ ) {
-    my $variable = join( '_' , chain_base( $_[0] )  , $_[1] , 'mac' );
+    my $variable = join( '_' , chain_base( $_[0] ) , chain_base( $_[1] ) , 'mac' );
     uc $variable;
 }
 
 #
-# Emit code to determine the MAC address of the passed gateway IP routed out of the passed interface for the passed provider number
+# Record the fact that the ruleset requires MAC address of the passed gateway IP routed out of the passed interface for the passed provider number
 #
 sub get_interface_mac( $$$ ) {
     my ( $ipaddr, $interface , $table ) = @_;
 
     my $variable = interface_mac( $interface , $table );
 
-    emit qq($variable=\$(find_mac $ipaddr $interface));
+    if ( interface_is_optional $interface ) {
+	$interfacemacs{$table} = qq($variable=\$(find_mac $ipaddr $interface)\n);
+    } else {
+	$interfacemacs{$table} = qq($variable=\$(find_mac $ipaddr $interface)
+[ -n "\$$variable" ] || fatal_error "Unable to determine the MAC address of $ipaddr through interface \\"$interface\\""
+);
+    }
 
     "\$$variable";
 }
@@ -1980,6 +2018,16 @@ sub set_global_variables() {
 	emit $_;
     }
 
+    for ( values %interfacegateways ) {
+	emit_comment unless $emitted_comment;
+	emit $_;
+    }    
+
+    for ( values %interfacemacs ) {
+	emit_comment unless $emitted_comment;
+	emit $_;
+    }    
+
     for ( values %interfaceaddrs ) {
 	emit_comment unless $emitted_comment;
 	emit_test    unless $emitted_test;
diff --git a/Shorewall-perl/Shorewall/Providers.pm b/Shorewall-perl/Shorewall/Providers.pm
index 6ebdd436a..3672b0691 100644
--- a/Shorewall-perl/Shorewall/Providers.pm
+++ b/Shorewall-perl/Shorewall/Providers.pm
@@ -198,6 +198,8 @@ sub add_a_provider( $$$$$$$$ ) {
 	fatal_error "Duplicate provider number ($number)" if $providerref->{number} == $number;
     }
 
+    fatal_error "Unknown Interface ($interface)" unless known_interface $interface;
+
     my $provider = chain_base $table;
     
     emit "#\n# Add Provider $table ($number)\n#";
@@ -213,11 +215,7 @@ sub add_a_provider( $$$$$$$$ ) {
 
     if ( $gateway eq 'detect' ) {
 	$variable = get_interface_address $interface;
-	emit  ( "gateway=\$(detect_gateway $interface)\n",
-		'if [ -z "$gateway" ]; then',
-		"    fatal_error \"Unable to detect the gateway through interface $interface\"",
-		"fi\n" );
-	$gateway = '$gateway';
+	$gateway  = get_interface_gateway $interface;
     } elsif ( $gateway && $gateway ne '-' ) {
 	validate_address $gateway, 0;
 	$variable = get_interface_address $interface;
@@ -253,7 +251,7 @@ sub add_a_provider( $$$$$$$$ ) {
 	     );
     }
 
-    my ( $loose, $optional, $track, $shared, $balance ) = (0,0,0,0,0);
+    my ( $loose, $track, $shared, $balance , $optional ) = (0,0,0,0,interface_is_optional( $interface ));
 
     unless ( $options eq '-' ) {
 	for my $option ( split /,/, $options ) {
@@ -266,6 +264,7 @@ sub add_a_provider( $$$$$$$$ ) {
 	    } elsif ( $option eq 'loose' ) {
 		$loose = 1;
 	    } elsif ( $option eq 'optional' ) {
+		set_interface_option $interface, 'optional', 1;
 		$optional = 1;
 	    } elsif ( $option eq 'shared' ) {
 		require_capability 'REALM_MATCH', "The 'shared' option", "s";
@@ -276,7 +275,13 @@ sub add_a_provider( $$$$$$$$ ) {
 	}
     }
 
-    $providers{$table} = { provider => $table, number => $number , mark => $val , optional => $optional , interface => $interface , gateway => $gateway, shared => $shared };
+    $providers{$table} = { provider  => $table,
+			   number    => $number ,
+			   mark      => $val ,
+			   interface => $interface ,
+			   optional  => $optional ,
+			   gateway   => $gateway ,
+			   shared    => $shared };
 
     if ( $track ) {
 	fatal_error "The 'track' option requires a numeric value in the MARK column" if $mark eq '-';
@@ -415,7 +420,7 @@ sub add_an_rtrule( $$$$ ) {
 
     emit ( "qt ip rule del $source $dest $priority" ) if $config{DELETE_THEN_ADD};
 
-    my ( $base, $optional, $number ) = ( chain_base( $provider ), $providers{$provider}{optional} , $providers{$provider}{number} );
+    my ( $base, $optional, $number ) = ( chain_base( $provider ) ,  $providers{$provider}{optional} , $providers{$provider}{number} );
 
     emit ( '', "if [ -n \$${base}_is_up ]; then" ), push_indent if $optional;
 
diff --git a/Shorewall-perl/Shorewall/Zones.pm b/Shorewall-perl/Shorewall/Zones.pm
index c62d7cc68..1e41b7f25 100644
--- a/Shorewall-perl/Shorewall/Zones.pm
+++ b/Shorewall-perl/Shorewall/Zones.pm
@@ -59,6 +59,7 @@ our @EXPORT = qw( NOTHING
 		  interface_is_optional
 		  find_interfaces_by_option
 		  get_interface_option
+		  set_interface_option
 		  validate_hosts_file
 		  find_hosts_by_option
 		 );
@@ -863,6 +864,15 @@ sub get_interface_option( $$ ) {
     $interfaces{$interface}{options}{$option};
 }
 
+#
+# Set an option for an interface
+#
+sub set_interface_option( $$$ ) {
+    my ( $interface, $option, $value ) = @_;
+
+    $interfaces{$interface}{options}{$option} = $value;
+}
+
 #
 # Validates the hosts file. Generates entries in %zone{..}{hosts}
 #
diff --git a/Shorewall-perl/prog.header b/Shorewall-perl/prog.header
index 569e1ec45..945392731 100644
--- a/Shorewall-perl/prog.header
+++ b/Shorewall-perl/prog.header
@@ -918,11 +918,9 @@ find_mac() # $1 = IP address, $2 = interface
 	\<*\>)
 	    ;;
 	*)
-	    [ -n "$result" ] && echo $result && return
+	    [ -n "$result" ] && echo $result
 	    ;;
     esac
-
-    fatal_error "Cannot determine the MAC address of $1 through $2"
 }
 
 ################################################################################