diff --git a/Softether-using-vpncmd.md b/Softether-using-vpncmd.md
index 3bc1d57..afffdb9 100644
--- a/Softether-using-vpncmd.md
+++ b/Softether-using-vpncmd.md
@@ -63,4 +63,7 @@ sudo vpnclient stop
 
 # stop ipv4 forwarding
 sudo sysctl -w net.ipv4.ip_forward=0
-```
\ No newline at end of file
+```
+
+source:
+[Source](https://bbs.archlinux.org/viewtopic.php?id=233901)
\ No newline at end of file