Background: Automotive Ethernet has rapidly emerged as the backbone for in-vehicle high-speed data transport, supporting advanced driver assistance systems (ADAS), infotainment, and vehicle-to-everything (V2X) services; yet its deployment creates new challenges in the physical layer, chiefly electromagnetic interference (EMI), mode conversion, common-mode termination, and connector/media design. These challenges affect signal integrity, electromagnetic compatibility (EMC), and reliability under stringent automotive constraints (IEEE/ISO/IEC, 2021; Hank et al., 2013).  Objective: This paper synthesizes theoretical foundations and applied strategies to mitigate physical-layer challenges in automotive Ethernet, connecting standardization, media-dependent interface (MDI) design, measurement techniques, and targeted mitigation approaches such as shielding, termination strategies, and connector topologies (Wenchen et al., 2023; Gercikow et al., 2020; Hampe et al., 2020).

 Methods: Through integrative literature synthesis of standards, empirical measurement platforms, and electromagnetic analyses, we construct a conceptual framework that maps the sources and propagation mechanisms of EMI and outlines stepwise mitigation—ranging from cable geometry optimization to PCB shielding and termination schemes—grounded in established measurement methods. The approach treats the vehicle as a highly coupled multiphysics system that requires concurrent electrical, mechanical, and systems engineering perspectives (Zaiyuan et al., 2022; Karim, 2025).  Results: We articulate design patterns that reduce radiated emissions and susceptibility while preserving bit error rate (BER) performance for 2.5G/5G/10G automotive Ethernet links. Key outcomes include the importance of mode conversion control in twisted-pair designs, the efficacy of common-mode termination topologies for 1000BASE-T1 analogies extended to higher speeds, and the role of rigorous measurement platforms to validate mitigation efficacy (Wenchen et al., 2023; Hampe et al., 2020; Gercikow et al., 2020).

 Conclusions: Successful deployment of automotive Ethernet at multi-gigabit rates requires harmonized solutions across standards compliance, MDI hardware design, PCB and cable shielding practices, and robust measurement/validation. The paper concludes with prioritized recommendations for practitioners and a research agenda bridging modeling, measurement, and design optimization