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Appendix D Cables
This chapter describes cables used for connecting network ports.
Table 30 Cable description
Cable
Ethernet twisted pair cable
Optical fiber
Ethernet twisted pair cable
Introduction
An Ethernet twisted pair cable consists of four pairs of insulated copper wires twisted together. Every
wire uses a different color, and has a diameter of about 1 mm (0.04 in). A pair of twisted copper
cables can cancel the electromagnetic radiation of each other, and reduce interference of external
sources. An Ethernet twisted pair cable mainly transmits analog signals and is advantageous in
transmitting data over shorter distances. It is the commonly used transmission media of the Ethernet. The
maximum transmission distance of the Ethernet twisted pair cable is 100 m (328.08 ft). To extend the
transmission distance, you can connect two twisted pair cable segments with a repeater. At most four
repeaters can be added, which means five segments can be joined together to provide a transmission
distance of 500 m (1640.42 ft).
Ethernet twisted pair cables can be classified into category 3, category 4, category 5, category 5e,
category 6, and category 7 cables based on performance. In LANs, category 5, category 5e, and
category 6 are commonly used.
Table 31 Ethernet cable description
Type
Category 5
Category 5e
Category 6
Based on whether a metal shielding is used, Ethernet twisted pair cables can be classified into shielded
twisted pair (STP) and unshielded twisted pair (UTP). An STP cable provides a metallic braid between
the twisted pairs and the outer jacket. This metallic braid helps reduce radiation, prevent information
from being listened, and eliminate external electromagnetic interference (EMI) of external sources. STPs
have strict application requirements and are expensive although they provide better EMI prevention
performance than UTPs, so in most LANs, UTPs are commonly used.
An Ethernet twisted pair cable connects network devices through the RJ-45 connectors at the two
ends.
Figure 49
Port type
RJ-45 Ethernet ports
SFP/SFP+ ports
Description
Transmits data at a maximum speed of 100 Mbps.
Transmits data at a maximum speed of 1000 Mbps.
Transmits data at a speed higher than 1 Gbps.
shows the pinouts of an RJ-45 connector.
Application
Connects RJ-45 Ethernet ports to transmit data.
Connects the fiber ports to transmit data.
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Troubleshooting
