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When to Use a Straight Through Cable

When to Use a Straight Through Cable

You’d think using ethernet cables would be easy.

All you have to do is grab any cable you can find and plug it into the two devices you want to connect, right?

Unfortunately it’s not that simple.

I know what you’re thinking.

How can it be more complicated than that? All ethernet cables look exactly the same.

When it comes to ethernet cables, there’s a lot more to them than you’d think.

There are two major types of ethernet cables, and each cable type has multiple categories. The two main types of ethernet cables are straight through and crossover cables.

Of these two main types of cable, straight through cables are the ones you’re probably more familiar with.

Don’t be confused by their name. Straight through cables are just the regular ethernet cables you’re used to.

So the question is, if there’s more than one type of ethernet cable to choose from, when should you be using straight through cables?

The good news is, you can use straight through cables to connect any of your devices. Due to advancements in technology, you no longer need to use crossover cables in your network.

There are additional advantages to using straight through cables instead of crossover cables. Straight through cables are much easier to get than crossover cables, and they generally cost less as well.

In this post, I’ll provide all you need to know about using straight through cables. I’ll also break down the benefits of using them instead of crossover cables.

What is a straight through ethernet cable?

Straight through ethernet cables are the regular, everyday cables you’re probably using in your home network now. The truth is, when you think of ethernet cables, these are the ones you think about.

In other words, they’re the most “basic” type of ethernet cable. Especially when they’re compared with their crossover cable counterparts (which we’ll talk more about later).

Straight through cables were originally designed to connect two different types of devices together. This means they were designed to connect a:

On the other hand, they weren’t designed to connect two of the same type of device. This means they weren’t meant to connect a(n):

  • Computer to a computer
  • Ethernet switch to an ethernet switch
  • Router to a router

In the situations above, crossover cables were used.

When it comes to which type of ethernet cable was used more often, it’s straight through cables without a doubt.

In home networks, most people needed ethernet cables to connect two different types of devices together. It’s not very common that people needed to connect two of the same type of device. Historically, that was more often the case in advanced home networks and datacenters.

As you’ll find out later, things have changed when it comes to connecting these devices with ethernet cables, but this is still useful background information.

How do straight through cables work?

By the looks of them, straight through ethernet cables are very simple devices:

Coiled Ethernet cable
A straight through ethernet cable

See, nothing to exciting to look at.

Surprisingly, there’s a little more going on inside them than you’d think.

Inside an ethernet cable there are actually 4 pairs of copper wires that are twisted together.

Let’s get a closer look:

Ethernet cable copper wires
Inside an ethernet cable there are 4 pairs of copper wires twisted together

In the picture above, I’ve untwisted the 4 pairs of wires so you can see them better. Inside the cable itself, the two black wires are twisted together, as well as the two green, blue, and orange wires.

Here’s a visual of the wires when they’re twisted together.

Twisted wires inside ethernet cable
The 4 twisted pairs of wires inside an ethernet cable

When an ethernet cable is used to connect two devices together, the devices use the 8 copper wires inside the cable to send data to each other.

This data comes in the form of electrical pulses. Electrical pulses transmit the data from one system to the next. When the electric pulse arrives at the receiving system, the device translates the data into a message that the system can read.

Make sense so far?

That’s straight through cables 101. In fact, crossover cables work the same way.

As you’ll see in the next section, this is where their similarities end.

What does the wiring of a straight through cable look like?

Let’s take a second and think about what’s happening inside an ethernet cable.

We’ve already established that there are 8 copper wires inside any given ethernet cable (regardless of what type of cable it is). This basically means that there are 8 different paths that data can take as it’s transmitted through the cable.

Think of each wire like a lane on a highway.

A car can take any of the 8 lanes to get to their destination. With that said, if there are cars coming in the other direction in the same lane, that would lead to some serious problems.

Ethernet cables are no different. When two devices communicate with each other, data is traveling back and forth between the two.

If both devices send data to each other using the same wire inside the ethernet cable, it would lead to a lot of confusion.

To allow for seamless communication between the connected devices, each device has specific wires for transmitting data, as well as specific wires for receiving data.

Going back to our highway analogy, this is the same concept that you see when you’re driving. Some lanes are designated for traffic in one direction, while other lanes are designated for traffic in the other.

These rules of the road for ethernet cables are determined by wire pinout standards.

Ethernet cable pinout standards

In order to determine which wires are used for sending data and which are used for receiving data, ethernet cable pinout standards were developed. The goal of these standards was to make sure all manufacturers were wiring their ethernet cables the same way for a given type of cable.

A pinout basically refers to how the wires are laid out at each end of the cable. For example, let’s look at the end of an ethernet cable.

Can you see the colored wires all lined up inside the connector at the end of the cable?

Ethernet cable wire locations

The position of each wire in the ethernet cable connector will determine if it’s a sending or receiving wire. For example, the first two wires in the connector might be sending wires, while the next two might be receiving, and so on.

As you’ll see, this will also depend upon the pinout standard that the cable was manufactured to.

Ok, back to the pinout standards.

The two pinout standards for ethernet cables are T568A and T568B.

This is where straight through cables and crossover cables differ. Straight through cables will have the same pinout at both ends, while crossover ethernet cables will have one of each pinout configuration at each end.

Let’s take a closer look at what the T568A and T568B standards mean for straight through cables.

Straight through cable pinout standards

Ok, so we’ve established that straight through cables will have the same pinout standard at both ends.

This’ll make a lot more sense once you see the actual pinout for the cable. As the name suggests, wires in a straight through cable are laid out straight through the cable.

What does this mean, exactly?

It means that although pairs of copper wires are twisted together inside the cable, these pairs of wires don’t cross each other at the end of the cable. To simplify things, it means that the position of a certain wire at one end of the ethernet cable will be in the same position at the other end of the cable.

Let’s look at a few visuals for straight through cables.

A straight through cable will either have two T568A pinouts at the ends of the cable:

Straight through cable T568A wire pinout at both ends

Or they’ll have two T568B pinout at the ends of the cable:

Straight through cable T568B wire pinout at both ends

As you can see, the wires at the end of the cable on the left are in the same positions at the end of the cable on the right. In other words, the wire configuration is the same straight through the cable.

Here’s what it looks like in real life:

Comparing the above picture to the pinout diagrams before it, you can see that the above straight through cable has a T568B pinout at both ends.

It’s safe to say the straight through pinout standard is pretty straightforward (horrible pun intended).

How is the pinout of a straight through cable different from a crossover cable?

As mentioned in the previous section, the pinout of a straight through cable differs from the pinout of a crossover cable.

The difference is pretty easy to notice, as a crossover cable will have a different pinout at each end. In other words, a crossover cable will have one end with a T568A layout, and the other end will have a T568B pinout.

Here’s what it’ll look like:

Crossover cable pinout diagram

Here’s a real life visual:

Crossover ethernet cable wiring

In looking at the cable above, it’s easy to see that the blue wire on the left is not in the same position as the blue wire on the right.

As it’s name suggests, some of the wires inside a crossover cable actually cross over the others. That’s why some wires are in different positions at the different ends of the cable.

For more information about this, check out my previous post on crossover cables.

What does each wire do in a straight through cable?

Let’s refresh our memories before we move forward here.

If you recall, straight through cables were originally designed to connect two different types of devices such as a:

  • Computer to a router
  • Computer to an ethernet switch
  • Modem to a router

You may also remember that certain wire positions at the end of the cable are used for different purposes (e.g. transmitting or receiving data).

The reason this works is that while one type of device may transmit data out of the second wire position, the other device connected to the cable is expecting to receive data from that wire. If both devices were trying to send data to each other over the same wire, it would mess up the messages between the two.

So how are devices classified into types?

I’ll keep this at a high level.

Essentially, any endpoint device (like a computer or printer) is classified as one type of device, while networking equipment (like a switch or router) is classified as another.

If you want to take a deep dive into this topic, these two device classifications are called medium-dependent interface (MDI) devices and medium-dependent interface crossover (MDIX) devices.

Here’s an example of how each wire is used when connecting two different types of devices.

MDI-MDIX connection

As you can see, straight through cables are perfect for connecting these devices. For each wire that’s used by the computer to send data (pins 1 and 2), the switch uses that same wire to receive data. On the other end of the cable, the switch sends data on pins that the computer expects to receive data on (pins 3 and 6).

An interesting fact is that wires 4, 5, 7, and 8 in the cable aren’t used to send or receive data. Surprisingly, these wires aren’t used at all.

When should you use straight through cables?

Despite the fact that straight through cables were originally designed to connect two different types of devices, they can actually be used to connect any of your devices.

Yes, you read that correctly.

You can (and should) use straight through cables for all your ethernet connections.

You have technology to thank for that. Specifically, I’m referring to auto-MDI/MDIX here.

Auto-MDI/MDIX is a feature of most modern devices. It allows your devices to recognize the type of the device they’re connected to with an ethernet cable.

For example, if you use a straight through cable to connect two of the same type of device (e.g. two computers), you’d previously have to use a crossover cable.

With auto-MDI/MDIX, each computer will automatically recognize the type of device they’re connected to, and transmit and receive data accordingly. In other words, your device will automatically transmit data using the wires that the other device expects to receive data on. This’ll happen regardless if you’re using a straight through cable or crossover cable.

The main benefit? You get to use whatever ethernet cables you have on hand to connect your devices.

The bottom line is, you no longer have to think twice about which ethernet cables you need to use when connecting your devices.

With that said, I still recommend that you use straight through cables instead of crossover cables.

Why should I use straight through cables instead of crossover cables?

Although the type of cable you use in your network doesn’t matter, that doesn’t mean there isn’t a certain type of cable that’s better suited for the job.

That’s right, I’m talking about straight through cables.

Let me say up front that you won’t experience a difference in performance when it comes to straight through and crossover cables. Both types of cables will get the job done.

With that said, there are a few reasons why straight through cables are the better choice here.

Price

As with most things in life, price is always a factor.

If you’re looking to buy ethernet cables, you may notice a slight difference in price between straight through and crossover cables.

In general, straight through cables cost slightly less than crossover cables. This shouldn’t be surprising because straight through cables are less complicated than crossover cables.

This means straight through cables are easier (and cost less) to make. This usually results in a lower price for the customer.

Of course, depending upon the manufacturer and inventory at any point in time, you’ll probably be able to find crossover cables that are cheaper than straight through cables. It’ll also depend upon the color, length, and quantity of cables you buy.

Crossover and straight through ethernet cables are fairly inexpensive, so you won’t be breaking the bank either way here.

When it comes to deciding which type of cable to buy, the real difference is in the availability of each type.

Availability

The biggest difference between straight through and crossover cables is their availability.

Straight through cables have always been more available than crossover cables. That’s because when it mattered what type of cable you used, most of the time people needed straight through cables.

Once advancements in technology made crossover cables unnecessary, there was even less reason for companies to carry them.

As a result, straight through cables are much easier to find.

That’s not to say that you can’t find crossover cables at your local computer store. It just means that you’ll likely have many more choices in terms of color, length, and quantity if you get straight through cables.

It’s just best to make it easy on yourself and buy straight through cables for your network.

If for some reason you have older computer equipment and you still need to use crossover cables in your network, you can even buy crossover cable adapters for your straight through cables.

All the more reason to buy straight through cables.

Wrap up

It should be no mystery to you now. You can use straight through ethernet cables to connect any of the devices in your home.

If you have any questions about this information, please leave a comment below.

For more interesting reading on similar topics, check out these other posts I’ve written:

When to Use a Crossover Cable

How to Extend an Ethernet Cable

Shielded vs Unshielded Cables: A Full Comparison

Can Ethernet Cables Go Bad?

Does Ethernet Cable Length Affect Network Speed?

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