diff --git a/src/cloud/ec2/etc/econe.conf b/src/cloud/ec2/etc/econe.conf
index 6d71e86e56..151279862d 100644
--- a/src/cloud/ec2/etc/econe.conf
+++ b/src/cloud/ec2/etc/econe.conf
@@ -24,6 +24,9 @@
 # SSL proxy that serves the API (set if is being used)
 #:ssl_server: fqdm.of.the.server
 
+# Authentication protocol for the econe server:
+#   ec2, default Acess key and Secret key scheme
+#   x509, for x509 certificates based authentication
 :auth: ec2
 
 # VM types allowed and its template file (inside templates directory)