EAP-TTLS (Tunneled Transport Layer Security) supports flexible inner authentication methods including:

MS-CHAPv2

EAP-GTC (Generic Token Card)

EAP-TLS (in some configurations)

This versatility allows EAP-TTLS to be used with a wide range of back-end authentication systems, while only requiring a server-side certificate.

Incorrect:

A. H-REAP (now FlexConnect) is a Cisco AP deployment mode, not an EAP type.

B. EAP-GTC is a simple authentication method and not a tunnel or container for others.

D. PEAP typically supports MS-CHAPv2 but not EAP-GTC or EAP-TLS as inner methods.

E. LEAP uses MS-CHAPv1 and is considered deprecated and insecure.