The most secure authentication type for configuring EAP in a VoIP network is EAP-Transport Layer Security (TLS). EAP is a type of framework that provides a mechanism for authenticating and authorizing the users or the devices that access a network or a service, using various methods, such as passwords, certificates, tokens, or biometrics. EAP can support various types of networks or services, such as wireless, wired, or VoIP. VoIP is a type of technology that allows the transmission and delivery of voice communications and multimedia sessions over the internet or a network, using various protocols, such as Session Initiation Protocol (SIP) or Real-time Transport Protocol (RTP). VoIP can provide various benefits, such as reducing the communication cost or complexity, and enhancing the communication quality or functionality. EAP-TLS is a type of EAP method that uses Transport Layer Security (TLS) to provide a secure and mutual authentication and encryption for the users or the devices that access a network or a service, using certificates. EAP-TLS can provide various benefits, such as preventing or mitigating the attacks, such as man-in-the-middle, replay, or brute force, and ensuring the confidentiality, integrity, or availability of the communication or the data. EAP-TLS is the most secure authentication type for configuring EAP in a VoIP network, as it can protect the VoIP network or service from potential threats, such as eavesdropping, interception, modification, or denial of service
. References: [CISSP CBK, Fifth Edition, Chapter 4, page 356]; [100 CISSP Questions, Answers and Explanations, Question 15].