Cable	Port type	Application
Console cable	Console port at one end and 9-pin serial port at the other end	Enables users to perform debugging, configuration, maintenance, management, and software loading on the device.
USB console cable	USB console port at one end and USB port at the other end
Ethernet twisted pair cable	RJ-45 Ethernet ports	Connects RJ-45 Ethernet ports to transmit data.
Optical fiber	SFP+/SFP/QSFP+/QSFP28 ports	Connects the fiber ports to transmit data.
SFP+ DAC cable	SFP+ ports	Connects SFP+ ports to transmit data.
QSFP+ DAC cable	QSFP+ ports	Connects QSFP+ ports to transmit data.
QSFP+ fiber cable (see "QSFP+/QSFP28 fiber cable")	QSFP+ ports	Connects QSFP+ ports to transmit data.
QSFP28 fiber cable (see "QSFP+/QSFP28 fiber cable")	QSFP28 ports	Connects QSFP28 ports to transmit data.
QSFP+ to SFP+ DAC cable	QSFP+ port at one end, and SFP+ port at the other end	Connects a QSFP+ port to an SFP+ port.

Ethernet twisted pair cable

An Ethernet twisted pair cable consists of four pairs of insulated wires twisted together. It mainly transmits analog signals and is advantageous in transmitting data over shorter distances. The maximum transmission distance is 100 m (328.08 ft).

RJ-45 connector

An Ethernet twisted pair cable connects network devices through the RJ-45 connectors at the two ends. Figure 4-1 shows the pinouts of an RJ-45 connector.

Figure 4-1 RJ-45 connector pinout diagram

Cable pinouts

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.

Cable type

Based on performance

Ethernet cables can be classified into category 3, category 4, category 5, category 5e, category 6, and category 7 cable based on performance. In LANs, category 5, category 5e, and category 6 are commonly used.

Table 4-2 Ethernet cable description

Type	Description
Category 5	Transmits data at a maximum speed of 100 Mbps, with a bandwidth of 100 MHz.
Category 5e	Transmits data at a maximum speed of 1000 Mbps, with a bandwidth of 100 MHz.
Category 6	Transmits data at a maximum speed of 10 Gbps, with a bandwidth of 250 MHz.

NOTE:

The RJ-45 Ethernet ports use category 5 or higher Ethernet twisted pair cables for connection.

Based on pinouts

Ethernet twisted pair cables can be classified into straight through and crossover cables based on their pinouts.

· Straight-through—The pinouts at both ends comply with standard 568B, as shown in Figure 4-2.

· Crossover—The pinouts at one end comply with standard 568B, and those at the other end comply with standard 568A, as shown in Figure 4-3.

Figure 4-2 Straight-through cable

Figure 4-3 Crossover cable

Pin assignments

Select an Ethernet twisted pair cable according to the RJ-45 Ethernet port type on your device. An RJ-45 Ethernet port can be MDI (for routers and PCs) or MDIX (for switches). For the pinouts of RJ-45 Ethernet ports, see Table 4-3 and Table 4-4.

Table 4-3 RJ-45 MDI port pinouts

Pin	10BASE-T/100BASE-TX		1000BASE-T
Pin	Signal	Function	Signal	Function
1	Tx+	Send data	BIDA+	Bi-directional data cable A+
2	Tx-	Send data	BIDA-	Bi-directional data cable A-
3	Rx+	Receive data	BIDB+	Bi-directional data cable B+
4	Reserved	—	BIDC+	Bi-directional data cable C+
5	Reserved	—	BIDC-	Bi-directional data cable C
6	Rx-	Receive data	BIDB-	Bi-directional data cable B-
7	Reserved	—	BIDD+	Bi-directional data cable D+
8	Reserved	—	BIDD-	Bi-directional data cable D-

Table 4-4 RJ-45 MDI-X port pinouts

Pin	10BASE-T/100BASE-TX		1000BASE-T
Pin	Signal	Function	Signal	Function
1	Rx+	Receive data	BIDB+	Bi-directional data cable B+
2	Rx-	Receive data	BIDB-	Bi-directional data cable B-
3	Tx+	Send data	BIDA+	Bi-directional data cable A+
4	Reserved	—	BIDD+	Bi-directional data cable D+
5	Reserved	—	BIDD-	Bi-directional data cable D-
6	Tx-	Send data	BIDA-	Bi-directional data cable A-
7	Reserved	—	BIDC+	Bi-directional data cable C+
8	Reserved	—	BIDC-	Bi-directional data cable C-

To ensure normal communication, the pins for sending data on one port should correspond to the pins for receiving data on the peer port. When both of the ports on the two devices are MDI or MDIX, a crossover Ethernet cable is needed. A cross-over cable connects devices of the same type. When one port is MDI and the other is MDIX, a straight-through Ethernet cable is needed. A straight-through cable connects devices of different types.

If an RJ-45 Ethernet port with MDI/MDIX autosensing enabled can automatically negotiate pin roles. The RJ-45 Ethernet ports on the switch support MDI/MDIX. By default, MDI/MDIX is enabled on a port.

Making an Ethernet twisted pair cable

1. Cut the cable to length with the crimping pliers.

2. Strip off an appropriate length of the cable sheath. The length is typically that of the RJ-45 connector.

3. Untwist the pairs so that they can lie flat, and arrange the colored wires based on the wiring specifications.

4. Cut the top of the wires even with one another. Insert the wires into the RJ-45 end and make sure the wires extend to the front of the RJ-45 end and make good contact with the metal contacts in the RJ-45 end and in the correct order.

5. Crimp the RJ-45 connector with the crimping plier until you hear a click.

6. Repeat the above steps with the other end of the cable.

7. Use a cable tester to verify the connectivity of the cable.

Optical fiber

CAUTION:

Use the same types of transceiver modules, pigtail cords, patch cords, and fiber cables. If you use single-mode optical fibers, the transceiver modules, pigtail cords, patch cords, and fiber cables must be single-mode.

Optical fiber

Optical fibers are widely used in fiber-optic communications, which are advantageous for long-distance communications.

Optical fibers can be classified into the following types:

· Single mode fiber—It has a core size of 10 µm, and has a lower modal dispersion. It carries only a single ray of light. It is mostly used for communication over longer distances.

· Multi-mode fiber—It has a core size of 50 µm or 62.5 µm or higher, and has a higher modal dispersion than single-mode optical fiber. It is mostly used for communication over shorter distances.

Table 4-5 Allowed maximum tensile force and crush load

Period of force	Tensile load (N)	Crush load (N/mm)
Short period	150	500
Long term	80	100

Fiber cable

A fiber cable is a cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube. Fiber cables fall into single-mode and multi-mode.

Patch cord

A fiber that has connectors at both ends is called a patch cord. A patch cord connects one optical device to another for signal routing. Patch cords fall into single-mode and multi-mode patch cords.

· Single-mode patch cord—The jacket is yellow. It permits transmission over longer distances.

· Multi-mode patch cord—The jacket is orange. It permits transmission over shorter distances.

The length of a patch cord can be 0.5 m (1.64 ft), 1 m (3.28 ft), 2 m (6.56 ft), 3 m (9.84 ft), 5 m (16.40 ft), and 10 m (32.81 ft).

Pigtail cord

A pigtail cord is an optical fiber that has an optical connector on one end and a length of exposed fiber on the other. The end of the pigtail is fusion spliced to a fiber, connecting the fiber cable and transceiver.

Pigtail cords fall into single-mode (yellow) and multi-mode (orange).