The three multi-factor authentication methods that can be used to authenticate access to the firewall are One-time Password (OTP), User Certificate, and Fingerprint.
One-time Password (OTP) is a form of two-factor authentication in which a token or code is generated and sent to the user over a secure connection. The user then enters the code to authenticate their access.
User Certificate is a form of two-factor authentication in which the user is required to present a valid certificate in order to access the system. The certificate is usually stored on a physical device, such as a USB drive, and is usually issued by the authentication service provider.
Fingerprint is a form of two-factor authentication in which the user is required to present a valid fingerprint in order to access the system. The fingerprint is usually stored on a physical device, such as a fingerprint reader, and is usually issued by the authentication service provider.