Why the Ethernet cable are differentiate two type?

We all knows that we have two types of network cables, first one is Cross cable and another one is Straight cable. 

A cross cable is used to connect two devices to each other.And straight cables are used when we need to connect different devices.

Have you ever thought why these are two types, cross and straight?

This is because of MDI & MDIX dependency in different devices. switches use the MDI-X configuration & all other nodes such as personal computers, workstations, servers and routers used an MDI interface.

Now let's discuss what this MDIX amd MIDI is.

MDIX

An MDIX (for MDI crossover) is a version of MDI that enables connection between like devices.

MDI

Medium dependent interface (MDI) refers to an Ethernet port connection that is used to connect network devices (hubs and switches) with other hubs and switches without the use of a crossover cable or null modem.

The requirement of connecting the transmitter of one side to the receiver on the other side and vice versa makes it necessary to always have an odd number of crossovers between two devices, with an MDI-X port containing an internal crossover . Straight through cables connect pins 1 and 2 (transmit) on an MDI device to pins 1 and 2 (receive) on an MDI-X device. Thus, connecting MDI to MDI-X requires a straight-through cable (one crossover in total). Connecting MDI to MDI (no crossover) or MDI-X to MDI-X (two crossovers) requires a(nother) crossover in the cable to get an odd number.

Where to use straight & where to use crossover cables

Straight Cable

1)Connect a computer to a switch/hub's normal port.

2) Connect a computer to a cable/DSL modem's LAN port.

3) Connect a router's WAN port to a cable/DSL modem's LAN port.

4) Connect a router's LAN port to a switch/hub's up link port. (normally used for expanding network)

5) Connect 2 switches/hubs with one of the switch/hub using an up link port and the other one using normal port.

Crossover Cable

1) Connect 2 computers directly.

2) Connect a router's LAN port to a switch/hub's normal port. (normally used for expanding network)

3) Connect 2 switches/hubs by using normal port in both switches/hubs.