diff --git a/src/bin/hamcore/openvpn_sample.ovpn b/src/bin/hamcore/openvpn_sample.ovpn
index 83bc3df3..6ded2bf7 100644
--- a/src/bin/hamcore/openvpn_sample.ovpn
+++ b/src/bin/hamcore/openvpn_sample.ovpn
@@ -100,6 +100,12 @@ persist-key
persist-tun
client
verb 3
+
+###############################################################################
+# Authentication with credentials.
+#
+# Comment the line out in case you want to use the certificate authentication.
+
auth-user-pass
@@ -117,21 +123,22 @@ $CA$
###############################################################################
-# The client certificate file (dummy).
+# Client certificate and key.
#
-# In some implementations of OpenVPN Client software
-# (for example: OpenVPN Client for iOS),
-# a pair of client certificate and private key must be included on the
-# configuration file due to the limitation of the client.
-# So this sample configuration file has a dummy pair of client certificate
-# and private key as follows.
-
-
-$CERT$
-
-
-
-$KEY$
-
+# A pair of client certificate and private key is required in case you want to
+# use the certificate authentication.
+#
+# To enable it, uncomment the lines below.
+# Paste your certificate in the block and the key in the one.
+;
+;-----BEGIN CERTIFICATE-----
+;
+;-----END CERTIFICATE-----
+;
+;
+;-----BEGIN RSA PRIVATE KEY-----
+;
+;-----END RSA PRIVATE KEY-----
+;