Below is part of a graphic which depicts the A5/1 state space generated when checking if the correct key has been determined from a rainbow table lookup. Once a key candidate has been found using the rainbow tables, the A5/1 cipher needs to be advanced (forward clocked) and undone (back-clocked) to verify that the candidate key is correct.
The grey paths represent states that are not accessible through forward clocking, and the green paths have many ancestor states leading to the same key stream. Red paths have few ancestor states leading to the same key stream. The graphic is from the A5/1 rainbow table generation project led by Karsten Nohl.