diff --git a/main.go b/main.go
index 9327b56..afdb0e7 100644
--- a/main.go
+++ b/main.go
@@ -71,10 +71,16 @@ func main() {
 	})
 
 	http.HandleFunc("/info", func(resp http.ResponseWriter, req *http.Request) {
-		host, _, err := net.SplitHostPort(req.RemoteAddr)
-		if err != nil {
-			responseWithError(resp, http.StatusPreconditionFailed, errIPv4Only)
-			return
+		var host string
+		if argIp := req.FormValue("ip"); argIp != "" {
+			host = argIp
+		} else {
+			ip, _, err := net.SplitHostPort(req.RemoteAddr)
+			if err != nil {
+				responseWithError(resp, http.StatusPreconditionFailed, errIPv4Only)
+				return
+			}
+			host = ip
 		}
 		if net.ParseIP(host).To4() == nil {
 			responseWithError(resp, http.StatusPreconditionFailed, errIPv4Only)
diff --git a/mapping/map.go b/mapping/map.go
index 9d1ed7d..17e9e83 100644
--- a/mapping/map.go
+++ b/mapping/map.go
@@ -19,7 +19,8 @@ const (
 )
 
 var (
-	enableCNDomain = flag.Bool("enable-cn-domain", false, "Enable china mainland specific domain")
+	enableCNDomain     = flag.Bool("enable-cn-domain", true, "Enable china mainland specific domain")
+	enableCMExperiment = flag.Bool("cm-to-fsn", false, "Redirect all CM users to Hetzner FSN")
 )
 
 // Get returns the edge node that should be used for client.
@@ -29,6 +30,9 @@ func Get(ip string) string {
 	if err != nil {
 		return default_server + default_suffix
 	}
+	if *enableCMExperiment && info_en.IspDomain == "ChinaMobile" {
+		return HETZNER_FSN_1GE + CHINA_MAINLAND_SUFFIX
+	}
 	if *enableCNDomain && info_en.CountryCode == "CN" {
 		return default_server + CHINA_MAINLAND_SUFFIX
 	}