Teach you how to build a network cable ..

A lan is to connect individual computers or terminals using networks to exchange information and share resources according to certain protocols. Commonly used network cables include twisted pair wires, coaxial cables, and optical fiber cables. Twisted Pair wires can be divided into shielded twisted pair wires (STP) and unshielded twisted pair wires (UTP) based on whether they are added with the screen layer of a wire mesh ). Most local networks use unshielded twisted pair wires (UTP-unshielded twisted pair) as the transmission medium for cabling.
The UTP network cable is composed of twisted pair wires of a certain length and RJ45 crystal heads.
Twisted Pair wires are divided into 4 pairs by 8 lines of different colors. The effect of twisted pair is to minimize the impact of electromagnetic radiation and external electromagnetic interference. In EIA/TIA-568 standards, the twisted pair wires are divided into three categories, four categories, five categories of cables according to electrical characteristics. Three types of cables and five types of cables are most commonly used in the network. Currently, more than six types of cables exist.
Connect the RJ45 crystal head to the RJ45 socket of the network device, such as the NIC or hub. The RJ45 plug-in seat is also divided into three types or five types of electrical characteristics. RJ45 crystal head consists of metal parts and plastic, making the network cable required RJ 45 crystal connector front end has 8 concave monk, referred to as "se" (Position, position ).
There are a total of 8 metal contacts in the groove, referred to as "8C" (contact, contact), so the industry has a "8p8c" alias. Special attention is the RJ45 crystal head pin number. When the metal is facing us, the serial number from left to right is 1 ~ 8. The serial number is very important for network connections and cannot be mistaken.
The maximum transmission distance of twisted pair wires is 100 m. To increase the transmission distance, a repeater can be installed between two twisted pair wires, and up to four relinks can be installed. For example, if four relinks are installed to connect five CIDR blocks, the maximum transmission distance is 500 mb.
The wiring standards of EIA/TIA define the line sequence 568a and 568b of the two twisted pair wires.
Standard 568a:
Green white -- 1, green -- 2, orange white -- 3, blue -- 4, blue white -- 5, orange -- 6, brown white -- 7, brown -- 8
Standard 568b:
Orange white -- 1, orange -- 2, green white -- 3, blue -- 4, blue white -- 5, green -- 6, brown white -- 7, brown -- 8
To maintain optimal compatibility, the EIA/TIA 568b standard is widely used to create network cables. A wiring method is applied in the whole network wiring, but the network connections with RJ-45 plug-in on both ends are feasible in both 568a standard and 568b standard. The twisted pair sequence corresponds to the serial number of the RJ45 head. 10 M Ethernet cable uses 1, 2, 3, 6 Core lines to transmit data, and m Nic needs to use four lines. The 10 m Nic can be created in M mode, and the twisted pair wires provide four pairs. Therefore, even if the 10 m Nic is used, the 10 m Nic is generally created in M mode.
In the standard, lines 1, 2, 3, 6, 4, 5, 7, and 8 must be twisted pair. This is because, in the transmission of data, in order to reduce and suppress external interference, the transmitted and received data are transmitted in a differential manner, that is, each pair of lines twist together to transmit a differential message
Number (this is also the source of the twisted pair name ).
The so-called differential signal refers to a line that transmits signals in the positive-electric square mode, and the other line transmits the same signal in the negative-level mode. When there is an interference signal in the line, the effect on the two wires is the same. Therefore, the interference signal can be shielded when the receiver restores the differential signal (which can be understood as the two differential signals for subtraction ). As can be seen from the principle of Interference Suppression by twisted pair wires, each pair of wires is twisted to suppress interference signals and improve transmission quality. Therefore, when we create a twisted pair connection, do not separate one pair of lines for differential transmission. Otherwise, the transmission quality of the network will be greatly affected.
The following describes how to create twisted pair wires in several application environments.
MDI indicates that this port is a cascade port, while MDI-X indicates that this port is a common port.
1. Ethernet nic and Hub Connection:
When a network device, such as a PC, is connected to the hub, the network cable is a direct line, the two ends of the twisted pair need to be a pair of lines, at this time, the hub is the mdix port, and the PC is the MDI port. 10 Mbps network cable only needs one pair of twisted pair cables at both ends. You do not need to consider the sorting of cables of different colors. If the cables are connected at a speed of M, they must be produced in strict accordance with the EIA/tia568a or 568b wiring standards, the connection reference is as follows.
Name pin cablecolor pin name
Tx + 1 white orange 1 Tx +
TX-2 orange 2 TX-
RX + 3 white-green 3 RX +
4 LAN 4
5 Bai Lan 5
RX-6 green 6 RX-
7 white Brown 7
8 brown 8
2. Connection between hubs, or direct connection between two computers:
During Inter-hub cascade, the cascade port control switch should be placed on the MDI (uplink) and connected with a direct connection line. If the Hub does not have a dedicated-level connection port, or you cannot use a level-level connection port, you must use a MDI-X port level connection, then we can use a line to achieve the purpose, the line reference is as follows.
Name nic1 nic2 name
Tx + 1 3 RX +
TX-2 6 RX-
RX + 3 1 Tx +
RX-6 2 TX-
3.100 M Hub Connection, or direct connection between two computers:
We should also know that the network cable length between the level-level connection hubs should not exceed 100 m, and the hub-level connection should not exceed 4 levels. Because the cross lines are rarely used, Special marking should be made to avoid future use of direct lines, resulting in line faults. In addition, the crossover network cable can be directly connected to two computers. The following table lists the connections.
Name pin name
Tx_d1 + 1 3 rx_d2 +
Tx_d1-2 6 rx_d2-
Rx_d2 + 3 1 tx_d1 +
Rx_d2-4 2 tx_d1-
Bi_d3 + 5 7 bi_d4 +
Bi_d3-6 8 bi_d4-
Bi_d4 + 7 4 bi_d3 +
Bi_d4-8 5 bi_d3-
At last, the line must be disconnected. When the cable tester is used for testing, all green lights should flash in turn. The most common method for software debugging is to use ping commands that come with Windows 95 and Windows 98. If the workstation receives a response from the server, it indicates that the line is normal and the network protocol is installed normally, which is the basis for the normal operation of network application software.