Crimping twisted pair cables using a crossover method. Do-it-yourself local network: Selecting and crimping a network cable

Almost no local network can do without wired segments, where computers are connected to the network using cables. In this material you will learn what types and types of cables are used to create local networks, and you will also learn how to make them yourself.

Almost no local network, be it home or office, can do without wired segments where computers are connected to the network using cables. This is not surprising, because this solution for transferring data between computers is still one of the fastest and most reliable.

Types of network cable

In wired local networks, signal transmission is carried out using special cable entitled " twisted pair" It is called that because it consists of four pairs of copper strands twisted together, which reduces interference from various sources.

In addition, the twisted pair has a common external dense insulation made of polyvinyl chloride, which is also very little susceptible to electromagnetic interference. Moreover, on sale you can find both an unshielded version of the UTP (Unshielded Twisted Pair) cable and shielded varieties that have additional screen from foil - either common for all pairs (FTP - Foiled Twisted Pair), or for each pair separately (STP - Shielded Twisted Pair).

Using a modified twisted pair cable with a screen (FTP or STP) at home only makes sense when there is high interference or to achieve maximum speeds with a very long cable length, which should preferably not exceed 100 m. In other cases, a cheaper unshielded UTP cable, which can be found, will do at any computer store.

Twisted pair cable is divided into several categories, which are marked from CAT1 to CAT7. But you shouldn’t be immediately afraid of such diversity, since for building home and office computer networks Mostly unshielded cable CAT5 or its slightly improved version CAT5e is used. In some cases, for example, when the network is laid in rooms with large electromagnetic interference, you can use a sixth category cable (CAT6), which has shared screen in the form of foil. All of the categories described above are capable of providing data transmission at speeds of 100 Mbit/s when using two pairs of cores, and 1000 Mbit/s when using all four pairs.

Crimping schemes and types of network cable (twisted pair)

Twisted pair crimping is the process of attaching special connectors to the ends of a cable, which use 8-pin 8P8C connectors, which are usually called RJ-45 (although this is somewhat misleading). In this case, the connectors can be either unshielded for UTP cables or shielded for FTP or STP cables.

Avoid purchasing so-called insert connectors. They are designed for use with soft stranded cables and require some skill to install.

To lay the wires, 8 small grooves are cut inside the connector (one for each core), above which metal contacts are located at the end. If you hold the connector with the contacts up, the latch facing you, and the cable input is facing you, then the first contact will be located on the right, and the eighth on the left. Pin numbering is important in the crimping procedure, so remember this.

There are two main schemes for distributing wires inside connectors: EIA/TIA-568A and EIA/TIA-568B.

When using the EIA/TIA-568A circuit, wires from pins one through eight are laid out in the following order: White-Green, Green, White-Orange, Blue, White-Blue, Orange, White-Brown, and Brown. In the EIA/TIA-568B circuit, the wires go like this: White-Orange, Orange, White-Green, Blue, White-Blue, Green, White-Brown and Brown.

For the manufacture of network cables used for interconnection computer devices And network equipment V various combinations, there are two main cable crimping options: straight and crossover (crossover). Using the first, most common option, cables are made that are used to connect network interface computer and other client devices to switches or routers, as well as interconnection of modern network equipment. The second, less common option is used to make a crossover cable, which allows you to connect two computers directly to each other via network cards, without the use of switching equipment. Also crossover cable you may need to network old switches via up-link ports.

What to make straight network cable, it is necessary to crimp both ends the same scheme. In this case, you can use either option 568A or 568B (used much more often).

It is worth noting that for the manufacture of direct network cable It is not at all necessary to use all four pairs - two will be enough. In this case, using one twisted pair cable, you can connect two computers to the network at once. Thus, if high local traffic, the consumption of wires for building a network can be halved. However, keep in mind that at the same time, maximum speed data exchange on such a cable will drop 10 times - from 1 Gbit/s to 100 Mbit/s.

As can be seen from the figure, in in this example Orange and Green pairs are used. To crimp the second connector, the place of the Orange pair is taken by Brown, and the place of Green by Blue. In this case, the connection diagram to the contacts is preserved.

For the manufacture of crossover cable necessary one crimp its end according to circuit 568A, and second- according to the 568V scheme.

Unlike straight cable, to make a crossover you always need to use all 8 cores. At the same time, a crossover cable for data exchange between computers at speeds of up to 1000 Mbit/s is manufactured in a special way.

One end of it is crimped according to the EIA/TIA-568B scheme, and the other has the following sequence: White-green, Green, White-orange, White-brown, Brown, Orange, Blue, White-blue. Thus, we see that in circuit 568A the Blue and Brown pairs have swapped places while maintaining the sequence.

Finishing the conversation about circuits, we summarize: by crimping both ends of the cable according to the 568V circuit (2 or 4 pairs), we get straight cable to connect a computer to a switch or router. By crimping one end according to circuit 568A and the other according to circuit 568B, we get crossover cable for connecting two computers without switching equipment. The manufacture of a gigabit crossover cable is a special issue, where a special circuit is required.

Crimping a network cable (twisted pair)

For the cable crimping procedure itself, we will need a special crimping tool called a crimper. Crimper is a pliers with several working areas.

In most cases, knives for cutting twisted pair wires are placed closer to the tool handles. Here, in some modifications, you can find a special recess for stripping the outer insulation of the cable. Next, in the center work area, there are one or two sockets for crimping network (marking 8P) and telephone (marking 6P) cables.

Before crimping the connectors, cut a piece of cable of the required length at a right angle. Then, on each side, remove the common outer insulating sheath by 25-30 mm. At the same time, do not damage the own insulation of the conductors located inside the twisted pair.

Next, we begin the process of sorting the cores by color, according to the selected crimping pattern. To do this, unravel and straighten the wires, then arrange them in a row in in the right order, pressing tightly together, and then trim the ends with a crimper knife, leaving approximately 12-13 mm from the edge of the insulation.

Now we carefully place the connector on the cable, making sure that the wires do not get mixed up and that each of them fits into its own channel. Push the wires all the way until they rest against the front wall of the connector. With the correct length of the ends of the conductors, they should all fit into the connector all the way, and the insulating sheath must be inside the housing. If this is not the case, then remove the wires and shorten them somewhat.

After you have placed the connector on the cable, all that remains is to fix it there. To do this, insert the connector into the corresponding socket located on the crimping tool and smoothly squeeze the handles until they stop.

Of course, it’s good when you have a crimper at home, but what if you don’t have one, but you really need to crimp the cable? It is clear that you can remove the outer insulation with a knife, and use ordinary wire cutters to trim the cores, but what about the crimping itself? In exceptional cases, you can use a narrow screwdriver or the same knife for this.

Place a screwdriver on top of the contact and press it so that the teeth of the contact cut into the conductor. It is clear that this procedure must be done with all eight contacts. Finally, push the central cross section to secure it in the cable insulation connector.

And finally, I’ll give you a little advice: Before crimping the cable and connectors for the first time, buy with a reserve, since not everyone can perform this procedure well the first time.

Crossover cable, Also cross cable(English crossover cable) - a type of Ethernet cable required to connect computers directly, cross-connecting receive and transmit signals. Most often it is used to connect similar devices to each other, for example, two computers or two network switches, while a straight cable is intended to connect various by type of device, such as a computer with network switch or network hub.

Many devices today support Auto-MDI(X) compatibility, in which a patch cable can be used instead of a crossover cable, or vice versa, and the reception and transmission of signals will be adjusted automatically to obtain the desired result.

Review

10BASE-T and 100BASE-TX

The 10BASE-T and 100BASE-TX Ethernet standards use a single conductive pair for transmission in both directions. To do this, you need to connect the transmitting pair of each device to the receiving pair at the other end. The 10BASE-T standard is designed to be used with an already established direct twisted pair connection, making it easier to connect devices to each other.

When a terminal device is connected to a switch or hub, crossover occurs within the switch or hub. For this purpose the usual straight a cable in which each contact of a connector on one side is connected to a corresponding contact on the opposite connector.

One terminal device can be connected to another without any switches or hubs, but in this case, the crossing of contacts must occur at the cabling stage. 2 and 3 pairs must be crossed in the cable as they are used in 10BASE-T and 100BASE-TX. This cable is called cross. A crossover cable can also be used to connect two hubs or two switches using their uplink ports.

Since the only difference in the pin pair arrangement between T568A and T568B is that pins 2 and 3 are swapped, a crossover cable can be thought of as a cable with one modular connector en T568A and others T568B. This cable must work with 10BASE-T or 100BASE-TX standards.

The polarity of each pair is not reversed, but the pairs are crossed as a unit: two wires between each pair Not crossed.

1000BASE-T and faster

Unlike 10BASE-T and 100BASE-TX, 1000BASE-T (and faster) uses all four pairs to support round-trip transmission through the use of adaptive equalization and five-level pulse amplitude modulation(PAM-5). 1000BASE-T devices themselves determine the correct cable layout thanks to technology. Therefore, there is no need to use separated pairs for transmission and reception, and therefore there is no point in using crossover cables for 1000BASE-T. From 1000BASE-T onwards sublayer physical connection medium provides identification of the type of each pair and usually continues to operate even if the pairs in the cable are swapped or crossed.

2.5GBASE-T, 5GBASE-T, 10GBASE-T, and 40GBASE-T connections also do not require crossover cables.

However, in rare cases, a crossover cable may still be necessary when connecting a 100BASE-TX or 10BASE-T device (without Auto MDI-X) to a faster port.

Crossover Cable Pinout

twisted pair

In practice, it does not matter which standard, T568A or T568B, the cable conforms to, as long as both ends are crimped to the same standard. Typically, commercially available "pre-crimped" cables can be crimped in any manner, depending on the manufacturer. This means that the cables of one manufacturer are crimped in one way, and another in another way, nevertheless, both will work correctly. In any case, with a straight cable both ends will be routed either T568A or T568B, respectively in the column Connection 1 and column Connection 2.

Certain devices, including those that carry telephone and/or power interspersed with data in a single cable, may require pairs 1 and 4 (pins 4,5,7, and 8) to remain uncrossed.

Contact	Connection 1: T568A			Connection 2: T568B			Contacts on the connector
	signal	pair	color	signal	pair	color
1	BI_DA+	3	white/green stripe	BI_DB+	2	white/orange stripe
2	BI_DA-	3	green	BI_DB-	2	orange
3	BI_DB+	2	white/orange stripe	BI_DA+	3	white/green stripe
4		1	blue		1	blue
5		1	white/blue stripe		1	white/blue stripe
6	BI_DB-	2	orange	BI_DA-	3	green
7		4

Instructions

Buy two connectors for the network cable, or better yet four if you have never used a cable before. Technically they are called RJ-45 or 8P8С, they are sold in any store computer equipment. In addition, prepare the network cable itself and the crimping tool.

Measure required quantity eight-core network cable, if you already have a coil of this wire. Or measure the distance at which your computers will be located and buy a cable at the store. Network cable can be different types, shielded, double shielded, stranded or solid. For a room or for laying in the entrance Any will do cable, although multi-core will be more flexible, which is useful for connecting to a laptop.

Strip about 2.5 centimeters from each end of the cable from the insulation and shielding layer (if any). This can be done with a knife, wire cutters or a special tool - a stripper. Be careful not to damage the colored insulation of the cable cores themselves. If you notice a break or break in the wiring, simply cut off this part of the cable and re-strip a couple of centimeters of the cable on this side.

The wires are usually twisted together, which is why the network cable is called “twisted pair”. Unravel them so that the wires can be laid out in one line and align the length of all the wires. This can be done with scissors, wire cutters, or crimping pliers.

To crimp the cable according to the “cross” scheme, to connect a computer to a computer, a special arrangement of wires is used. At one end of the cable, the order of the cores should be: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. Lay the wires in a row, pinch them with two fingers and insert them into the connector until they stop. See how correctly the network cable cores fit into the grooves. Insert the plastic power connector with wires into the crimping pliers and firmly squeeze the handles of the crimping tool. Half the job is done - you have crimped one side of the crossover cable.

Arrange the cores of the free end of your cable in this order: white-green, green, white-orange, blue, white-blue, orange, white-brown, brown. As you can see, the layout is different. Look at the connector: on one side it is flat, and on the other it has a protrusion-lock. Insert the wires into the RJ-45 so that the brown one is on the right side of the row of wires. Check the order and how well the wires are laid in the connector. Insert into crimping pliers and squeeze firmly. If everything is done correctly, you have a completed crossover cable. You can check this on a network tester or try to set up communication between computers.

There are situations when you need to connect two computers over a network, but there is no network equipment through which you can do this. In this case, I’ll give you some tips on how to connect two computers on your own.

If one of the computers has two network cards installed, then it will be possible to open Internet access on both computers.

Let's consider two connection options. The first option is when both computers have only one network card installed. The second option is when one of the computers has two network cards installed, in which case it will be possible to connect the Internet to both computers.

What do we need to connect two computers over a network?

1. Of course, two computers that we will connect to the network.

2. Cross cable for connecting computers directly.

3. A pair of straight arms.

If you do not have a crossover cable, you can purchase one at any computer store or radio market. If you want to make it yourself, I’ll give its pinout below

The finished cable looks like this:

If you have a cable, you can start setting up a network between computers.

Connecting computer + computer (with one network card)

The first and most common option is when each of the connected computers has only one network card. In this case, computers can be connected to each other, but they will not have access to the Internet. The connection diagram is shown in the picture below:

After physically connecting the computers with a crossover cable, you need to configure the network. If you know how to set up a network on a computer, then you just need to set up the network as shown in the picture. If you don’t know how to set up a network, read on.

To configure the network, go to Control Panel — Network and Internet- click on the link “ Change adapter settings“.

Double-click on the network connection (I have two of them, physical map and virtual from )

and open the connection properties

In the window that opens, you need to open the properties “ Internet Protocol version 4 TCP/IPv4”

In the window that opens, check the box “ Use the following options” and indicate the network parameters

IP address: 192.168.0.1

Subnet mask: 255.255.255.0

Main gate: empty

After that, click “OK” - “Apply” and do the same manipulation on the second computer, only specify 192.168.0.2 in the IP address.

After this, the computers will start working on the same network. You can check this using ping. Open command line on the second computer (Win + R - “cmd” command) and enter the following in it:

ping 192.168.0.1

in response you should receive a report about the successful exchange of packets:

Check in the same way from the first computer, specifying the address 192.168.0.2. If you see the same thing, it means you did everything correctly and now you have two computers on the network. If the ping does not work, check what you did wrong. I also draw your attention to the fact that a firewall or antivirus can block the network.

We connect a computer + a computer with Internet access to the network

Now let's talk about how to connect two computers over a network with the ability for both to access the Internet. All this is possible provided that an additional LAN card, into which the Internet cable will be plugged

The settings are similar to those described above, the only difference is that you will need to specify the gateway on both computers.

Also, on a computer that has Internet access, you need to configure Internet distribution over the network. To do this, go to properties network connection(in which the address 192.168.0.1 is indicated) and in the “ tab Access” check the box

That's all, after this the Internet should work on both computers.

As you can see, connecting two computers over a network is not so difficult; if you have any questions, I’ll be happy to help in the comments.