The rapid evolution of Software-Defined Networks (SDNs) brings numerous benefits to network management and operations but also introduces several security challenges, especially when it comes to discovering hosts. Predominant among these challenges is host hijacking/address spoofing, which can precipitate flow entries overflow in OpenFlow switches' flow tables and lead to Denial of Service (DoS) attacks on the SDN controller. Subsequently, our research offers MTLSAuth, an in-novative technique that integrates the robust principles of Mutual TLS (MTLS) protocol in host discovery and authentication. MTLSAuth is meticulously designed to bolster host authentication within the ever-expanding SDN infrastructures, catering to the increasing demands of modern network environments. Alongside proposing MTLSAuth, our research provides an in-depth analysis and evaluation of host hijacking/address spoofing within SDN networks, shedding light on their profound impact on OpenFlow switches and SDN controller. In a comparative evaluation against established methods, MTLSAuth distinctly outperforms, achieving a notable reduction in host-to-host delay time, with an improvement of 10% to 15% relative to the Port-Knocking approach. Beyond its empirical success, this research elaborates on MTLSAuth's foundational principles and potential applications. As SDNs increasingly form the underpinning of modern networking, solutions like MTLSAuth emerge as vital in establishing a secure, efficient, and resilient network landscape.