Catalyzes unidirectional fumarate reduction using artificial electron donors such as methyl viologen. The physiological reductant is unknown. a quinone + succinate = a quinol + fumarate Binds 1 FAD per subunit. Homodimer. By anaerobic growth on Fe(3+) ions. In the C-terminal section; belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily.