Asus RT-AC66U - Manual (Page 23)

5GHz security settings
3. On the Wireless name (SSID) field, key in a unique name for
your wireless network.
. From the Security Level dropdown list, select the encryption
method for your wireless network.
IMPORTANT! The IEEE 802.11n standard prohibits using High
Throughput with WEP or WPA-TKIP as the unicast cipher. If you use these
encryption methods, your data rate will drop to IEEE 802.11g 54Mbps
connection.
5. Key in your security passkey.
. Click Apply when done.