Connecting an Ethernet cable
Overview
10/100 Mbps Ethernet uses category-5 twisted pair cables, while 1000 Mbps Ethernet uses category-5 enhanced or category-6 twisted pair cables. Twisted pair cables include straight-through cables and crossover cables.
Category-5 cables provide a transmission frequency of 100 MHz for voice and data transmission; they are mainly used in 100Base-T and 10Base-T networks. Category-5 cables are common Ethernet cables, which can also be used to transmit 1000 Mbps Ethernet data.
Category-5 enhanced cables feature low attenuation and crosstalk, providing higher attenuation to crosstalk ratio (ACR), less delay error and higher performance than category-5 cables. Category-5 enhanced cables are mainly used in 1000 Mbps Ethernet networks.
Category-6 cables provide a transmission frequency of 1 MHz to 250 MHz, and improve the performance on crosstalk and return loss. A fine better return loss performance is extremely important for new-generation full-duplex high-speed networks. Category-6 cables have sufficient power sum ACR (PS-ACR) when working at 200 MHz. They provide a bandwidth two times than that of category-5 enhanced cables, thus featuring a higher transmission performance. Therefore, category-6 cables are suitable for applications requiring a transmission speed of more than 1 Gbps.
The 10/100 Mbps Ethernet uses two pairs of cables, orange/white, orange, green/white and green cables, to transmit and receive data, while the 1000 Mbps Ethernet uses four pairs of cables to transmit and receive data.
An Ethernet twisted pair cable connects network devices through the RJ-45 connectors at the two ends. Figure 30 shows the pinouts of an RJ-45 connector.
Figure 30 RJ-45 connector pinout
PIN #8 
PIN #1 
EIA/TIA cabling specifications define two standards, 568A and 568B, for cable pinouts.
•Standard 568A—Pin 1: white/green stripe, pin 2: green solid, pin 3: white/orange stripe, pin 4:
blue solid, pin 5: white/blue stripe, pin 6: orange solid, pin 7: white/brown stripe, pin 8: brown solid.
•Standard 568B—Pin 1: white/orange stripe, pin 2: orange solid, pin 3: white/green stripe, pin 4:
blue solid, pin 5: white/blue stripe, pin 6: green solid, pin 7: white/brown stripe, pin 8: brown solid.
Ethernet twisted pair cables can be classified into straight-through and crossover cables based on their pinouts.
