The Clock Interaction report quickly identifies the asynchronous relationship. It highlights clock pairs with no common primary clock or no common period (unexpanded). Clocks are still asynchronous even if clock periods are the same, when different sources generate them. Review asynchronous Clock Domain Crossing (CDC) paths carefully.
Ensure these paths use proper synchronization circuitry. This circuitry does not rely on timing correctness and must minimize the chance for metastability to occur. Asynchronous CDC paths usually have high skew and/or unrealistic path requirements. The default timing analysis must not time them because it cannot prove they are functional in hardware.