ZyXEL Communications VPN Series Handbook page 771

How to Use Two Factor with Google Authenticator for Admin
Access?
In previous firmware versions, USG supports pin code by SMS/Email as two-factor
authentication method. However, SMS-based two-factor authentication is not safe.
Compared to SMS-based method, Google authenticator is the most secure method to
receive verification code for 2-factor authentication. Google authenticator gives a
new code every 30 seconds, so each code expires in just 30 seconds which make it a
secure option to generate codes for 2-step verification. Furthermore, Google
authenticator is free to download, easy to use, and is able to work without Internet. This
example illustrates how to set up two factor with Google Authenticator for admin
access.
Note: All network IP addresses and subnet masks are used as examples in this article.
Please replace them with your actual network IP addresses. This example was tested using
the USG FLEX 500 (Firmware Version: ZLD 4.60).
www.zyxel.com
771/810