diff --git a/README.md b/README.md
index b3bb7ba..59e804f 100644
--- a/README.md
+++ b/README.md
@@ -12,3 +12,11 @@ You have to run this script under a user that have access to the bird socket.
 [bird*]
 user root
 ```
+
+The plugin must be named bird_v6 for IPv6 routes and bird_v4 for legacy.
+
+```
+$ ls -lh /usr/local/etc/munin/plugins/bird_v*
+lrwxr-xr-x  1 root  wheel    36B May  7 11:29 /usr/local/etc/munin/plugins/bird_v4 -> /usr/local/share/munin/plugins/bird_
+lrwxr-xr-x  1 root  wheel    36B May  7 11:29 /usr/local/etc/munin/plugins/bird_v6 -> /usr/local/share/munin/plugins/bird_
+```