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Circular ribbon flares are usually related to spine-fan type magnetictopology containing null-points. In this paper, we investigate an X-classcircular ribbon flare on 2012 October 23, using the multi-wavelength data fromthe \textit{Solar Dynamics Observatory}, \textit{Hinode}, and the\textit{Ramaty High Energy Solar Spectroscopic Imager}. In \ion{Ca}{2} Hemission, the flare showed three ribbons with two highly elongated ones insideand outside a quasi-circular one, respectively. A hot channel was displayed inthe extreme ultraviolet (EUV) emissions that infers the existence of a magneticflux rope. Two hard X-ray (HXR) sources in the 12--25 keV energy band werelocated at the footpoints of this hot channel. Using a nonlinear force-freemagnetic field extrapolation, we identify three topological structures: (1) a3D null-point, (2) a flux rope below the fan of the null-point, and (3) alarge-scale quasi-separatrix layers (QSL) induced by the quadrupolar-likemagnetic field of the active region. We find that the null-point is embeddedwithin the large-scale QSL. In our case, all three identified topologicalstructures must be considered to explain all the emission features associatedwith the observed flare. Besides, the HXR sources are regarded as theconsequence of the reconnection within or near the border of the flux rope.

On the 2012 October 23 circular ribbon flare: emission features and magnetic topology