diff --git a/DynDNS/dyndns.lua b/DynDNS/dyndns.lua
index cc85ccf..071c7dd 100644
--- a/DynDNS/dyndns.lua
+++ b/DynDNS/dyndns.lua
@@ -66,6 +66,14 @@ function count(T)
 	return count
 end
 
+function read_file(path)
+    local file = io.open(path, "rb")
+    if not file then return nil end
+    local content = file:read "*a"
+    file:close()
+    return content
+end
+
 
 array = {}
 
@@ -117,16 +125,19 @@ for key,value in pairs(array) do
 	local mac = key
 	local ip = value["ip"]
 	local hostname = value["hostname"]
-	if hostname ~= "?" then
+	if hostname ~= "?" and hostname ~= "*" then
 		for key,value in pairs(ip) do
-			if non_fqdn then config = config .. "\r\n" .. value .. " " .. hostname end
-			if network_domain then config = config .. "\r\n" .. value .. " " .. hostname .. "." .. network_domain  end
+			line = value
+			if non_fqdn then line = line .. " " .. hostname end
+			if network_domain then line = line .. " " .. (hostname .. "." .. network_domain) end
+			if line ~= value then config = config .. "\r\n" .. line end
 		end
 	end
 end
 
-file = io.open(output_file, "w")
-file:write(config)
-file:close()
-
-os.execute(reload_command)
+if read_file(output_file) ~= config then
+	file = io.open(output_file, "w")
+	file:write(config)
+	file:close()
+	os.execute(reload_command)
+end
\ No newline at end of file