Hello,
The reason is because, from physical connections perspective, both are
hosts. So, on all hosts (legacy hosts), the underlying hardware was designed
such that transmitter/receiver pins were fixed. So, when you connect router
to host, if you use a straight-through cable, the transmitters were
connected to transmitter and receivers were connected to receiver. This will
not help in establishing a meaningful communication. On the other hand, if
you use a crossover cable, the cables are flipped, so the transmitter of one
host is connected to receiver of the other host and vice versa.
However, most of the current hardware try to detect the cable and change the
pin role in software (Driver). This feature is called MDIX.
Hope this helps.
Regards,
NT
