The Difference Between Straight Through, Crossover And Rollover Cables

There are generally three main types of networking cables: straight-through, crossover, and rollover cables. Each cable type has a distinct use, and should not be used in place of another. So how do you know which cable to use for what you need?

 

The Purpose of Straight-Through Cables

Straight-through cables get their name from how they are made. Out of the 8 pins that exist on both ends of an Ethernet cable, each pin connects to the same pin on the opposite side. 

Review the diagram below for a visual example:

Notice how each wire corresponds to the same pin. This kind of wiring diagram is part of the 568A standard. The 568B standard achieves the same thing, but through different wiring. It is generally accepted to use the 568A standard as pictured, since it allows compatibility with certain telephone hardware- while 568B doesn’t.

Straight-through cables are primarily used for connecting unlike devices. A straight-through cable is typically used in the following situations:

 

Use a straight-through cable when:

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• 1. Connecting a router to a hub
• 2. Connecting a computer to a switch
• 3. Connecting a LAN port to a switch, hub, or computer

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Note that some devices such as routers will have advanced circuitry, which enables them to use both crossover and straight-through cables. In general, however, straight-through cables will not connect a computer and router because they are not “unlike devices.”

 

The Purpose of Crossover Cables

Crossover cables are very similar to straight-through cables, except that they have pairs of wires that crisscross. This allows for two devices to communicate at the same time. Unlike straight-through cables, we use crossover cables to connect like devices.

 A visual example can be seen below:

Notice how all we did was switch the orange-white and green-white wires, and then the orange and green wires. This will enable like devices to communicate. Crossover cables are typically used in the following situations:

 

Use a crossover cable when:

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• 1. Connecting a computer to a router
• 2. Connecting a computer to a computer
• 3. Connecting a router to a router
• 4. Connecting a switch to a switch
• 5. Connecting a hub to a hub

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While the rule of thumb is to use crossover cables with like devices, some devices do not follow standards. Others provide support for both types of cables. However, there is still something that both crossover and straight-through cables can’t do.

 

The Purpose of Rollover Cables

Rollover cables, like other cabling types, got their name from how they are wired. Rollover cables essentially have one end of the cable wired exactly opposite from the other. This essentially “rolls over” the wires- but why would we need to do such a thing? Rollover cables,
also called Yost cables, usually connect a device to a router or switch’s console port. This allows a programmer to make a connection to the router or switch, and program it as needed. 

A visual example can be seen below:

Notice that each wire is simply “rolled over.” These types of cables are generally not used very much, so are usually colored differently from other types of cables.

A patch cable (also called a straight through cable) is configured with all 8 wires in the same order on both ends of the cable. There are two standard wiring configurations used for patch cables. They are 568A and 568B. Either configuration can be used, so long as the same
configuration is used at both ends of the cable.

With 568A:
Pin 1 – White/Orange
Pin 2 – Orange White
Pin 3 – White/Green
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Green/White
Pin 7 – White/Brown
Pin 8 – Brown/White

With 568B:
Pin 1 – White/Green
Pin 2 – Green/White
Pin 3 – White/Orange
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Orange/White
Pin 7 – White/Brown
Pin 8 – Brown/White

A cross over cable is configured with 4 of the wires in the same order on each end. The other four wires are crossed (hence the name). One end gets wired with the 568A configuration, while the other gets wired with the 568B configuration.

First End:
Pin 1 – White/Orange
Pin 2 – Orange White
Pin 3 – White/Green
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Green/White
Pin 7 – White/Brown
Pin 8 – Brown/White

Second End:
Pin 1 – White/Green
Pin 2 – Green/White
Pin 3 – White/Orange
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Orange/White
Pin 7 – White/Brown
Pin 8 – Brown/White

A rollover cable is wired with each pin on one end of the cable connected to the reverse pin on the other end. So the cable on Pin 1 on one end of the cable connects to Pin 8 at the other end, etc. Rollover cables are used to connect the serial port of a computer to the serial port of a network switch so that you can configure the network switch. These cables are not used for network connectivity.