diff --git a/package/iptables/files/firewall.init b/package/iptables/files/firewall.init
index 9d8a405ab0ff338b95fc8afeeb69bdf6925dabab..e1013fb8e7a6cb6ebfb3211f2f56854ad285e83e 100755
--- a/package/iptables/files/firewall.init
+++ b/package/iptables/files/firewall.init
@@ -11,6 +11,9 @@ start() {
 	config_get WAN wan ifname
 	config_get WANDEV wan device
 	config_get LAN lan ifname
+	config_get LAN_MASK lan netmask
+	config_get LAN_IP lan ipaddr
+	LAN_NET=$(/bin/ipcalc.sh $LAN_IP $LAN_MASK | grep NETWORK | cut -d= -f2)
 	
 	## CLEAR TABLES
 	for T in filter nat; do
@@ -105,10 +108,8 @@ start() {
 	iptables -t nat -A PREROUTING -j prerouting_rule
 	[ -z "$WAN" ] || iptables -t nat -A PREROUTING -i "$WAN" -j prerouting_wan
 	iptables -t nat -A POSTROUTING -j postrouting_rule
-	### Only RFC1918 addresses
-	[ -z "$WAN" ] || iptables -t nat -A POSTROUTING --src 192.168.0.0/16 -o $WAN -j MASQUERADE
-	[ -z "$WAN" ] || iptables -t nat -A POSTROUTING --src 172.16.0.0/12 -o $WAN -j MASQUERADE
-	[ -z "$WAN" ] || iptables -t nat -A POSTROUTING --src 10.0.0.0/8 -o $WAN -j MASQUERADE
+	### Only LAN
+	[ -z "$WAN" ] || iptables -t nat -A POSTROUTING --src $LAN_NET/$LAN_MASK -o $WAN -j MASQUERADE
 
 	iptables -t nat -A NEW -m limit --limit 50 --limit-burst 100 -j RETURN && \
 		iptables -t nat -A NEW -j DROP