When you begin dealing with network cables such as Ethernet cables, you may hear terms such as straight-through cables, crossover cables, or even roll over.
You may not understand the terms, and all the straight network cable you see appear to be the same. However, once you go to use one and find out you can’t connect to the internet on your computer, you can then begin to learn the differences between straight cable types and those that are crossover.
In this guide, you can learn all the differences between these. Here you can learn all about the type of cable differences there are, and how you can use them.
Cabling Differences
The network cable you may know the most (Cat 5 or 6 Ethernet cable) will comprise “unshielded twisted pair” (UTP). It is set for Ethernet wiring and controlled by the Institute of Electrical and Electronics Engineers (IEEE) by the 802.3 wiring standard.
It is when you begin looking at the others; you quickly see differences and why they won’t just work even if they appear the same.
The difference between straight through, crossover and rollover cables is through the way the ends terminate in the connectors. UTP cables contain eight wires. Each of these single wires is covered in coloured plastic coatings and encased in an outer shell.
Using the twisted pair configuration, four pairs are made from the eight wires, and you connect two different wires are twisted around each other to prevent interference. Pairings are easy to see inside, as one will be a solid colour and the other white with a spiral stripe matching the pair’s colour. Colours of cables used are:
- Green
- Orange
- Blue
- Brown
Cable Connectors
While nearly everyone in the industry calls the connectors RJ45, they are called 8P8C connectors. The wiring standard came up with this from ‘eight positions, eight connectors.’
The order of the colours you can see inside the connectors are as follows:
- Pin 1: Orange stripe
- Pin 2: Orange solid
- Pin 3: Green stripe
- Pin 4: Blue solid
- Pin 5: Blue stripe
- Pin 6: Green solid
- Pin 7: Brown stripe
- Pin 8: Brown solid
A rollover cable differs here because it isn’t intended to carry data. They are used as an interface to a device. The wiring standard for this, has cable pinouts of 1 to 8, 2 to 7 and so on.
This carries on until the cable crossover reverses the cables from one end to the other.
When Would You Use a Crossover Cable?
Once you need to begin using these cables, you will need to pay attention to the ones you pick up.
An excellent example of where to use an Ethernet crossover cable is from a computer to a network printer.
Where are Straight Through and Crossover Cables Used?
While you use a crossover cable to connect your computer directly to a printer, things differ once you have more than one computer on your network.
In this instance, you need to purchase a network switch where all your computers connect, as does your printer. In this instance, you connect using a straight-through Ethernet cable because the devices are unalike.
Once you have like devices such as two computers, a computer, and a printer or switch to switch, it is here you connect using an Ethernet crossover cable.
Adding to this, if your network uses switches and routers, you will use a patch cable. While the pinout configurations are the same, a patch cable will be used to connect two devices of the same type that are very close to each other (switch to switch or switch to router).
Patch cables are thus a straight-through cable and most often not seen outside of server rooms or anywhere else aside from connecting a patch panel to a switch.
Can I Use Crossover Cable for Router?
To make things easier, it helps to know about DTE and DCE devices. You may think it is not very clear adding more terms into the mix, yet once you understand it is straightforward to remember.
- DCE to DCE: crossover cable such as two switches
- DTE to DTE: crossover cables used for computer on one end to the printer
- DTE to DCE: straight through ethernet cable for a computer to switch
- DCE to DTE: straight-through cable is used to connect a computer to a router
DTE to DCE or vice versa devices have no cable crossover. Pin 1 is to pin 1 etc.
In words, you will see this as the following.
If you wish to connect two devices of different types, you must make sure a straight-through cable is used to connect.
If you connect devices which are the same type together (two switches, or two computers), a crossover network cable is used.
All cables will be straight through when you insert a network device between two devices of the same kind such as computer – switch – computer.
You may find one difference here that can be confusing as it goes against all the above.
If you connect a router to a router, these are two of the same sort of devices, and it should require crossover Ethernet cables.
However, you can connect two routers with a straight-through Ethernet cable instead of using a crossover cable in certain circumstances.
Suppose one or both of the routers implement the MDI (Medium Dependent Interface), where it detects which of the wires listen for incoming data. It will then determine which wires are to be used for transmission.
If this scenario is to occur, the configuration of the wiring inside the connector, ending the Ethernet cables, doesn’t matter. Thus, in theory, it won’t matter if you use a straight-through cable or a crossover type of cable to connect a router with another.
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