Cross line or straight line?
It is mentioned in many textbooks that similar devices are connected by cross lines, and different types of devices are connected by straight lines. This is true, and it is often taken in exams, but in reality, straight-through lines can be used in almost any situation, whether similar devices or non-similar devices are connected to each other. This is because the interfaces of current network devices have the function of automatic flipping. So it doesn't make much sense to use cross lines.
