A PCB netlist often contains serial resistors or capacitors in transmission lines. Many designers only set the functional name of the net on one side or the resistors, the other side gets an system generated name. When such a net with a system generated name then connects to another board the verification fails as the system generated name is not functional.
Other components which can be reduced in the netlist are parallel capacitors (often present for noise suppression) and serial/parallel resistors. Multiple components are than reducted to only one component.
Below is a simplified example of an LVDS signal pair ('DQS') which is connected to connector P1 using a serial resistor in both signals. When this boards connects to connector J1 on board 2 the netnames seen on both sides of the connector pair do not match.
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