Easy way to remember Cross or Straight cable.

notheory

Hi all,

it might sound weird, but I'm really struggling with it. I have narrowed down my weakness after taking my first practice exam.
I couldn't believe, during the exam, that I had such a problem and was so confused after a while if it is Cross or Straight through cable.

Is there an easy way to remember it?
How do you guys memorize it?

Dynaice

Do you mean having issues with trying to remember when to use a xover or straight through?

If so, I always found it's easiest to remember by like devices or opposite devices.

I.E. Router - Router = crossover. I think of a Router as having a CPU like a desktop has a CPU so those would also be like devices.

PC/Laptop - Router = crossover.

Switches and Hubs, well they do not deal with layer 3 unless it is a layer 3 switch, so think of those as like devices.

Switch to Hub = Crossover.

Anything that isnt a like device will connect via straight through.

PC/Laptop to Switch = straight through
Switch to Router = straight through

Hope that helps out.

instant000

Like devices connect with a crossover cable.

Unlike devices connect with a straight-thru cable.

Is this what you're talking about?

PC's and Routers are alike
Hubs and switches are alike

Crossover:
PC-Router
PC-PC
Router-Route
Switch-Switch
Hub-Hub
Switch-Hub

Does this make sense?

Straight-thru, on different devices:
PC-Switch
PC-Hub
Router-Switch
Router-Hub


----

The hardware reason behind it is that, originally, these devices were designed to send and receive on certain pairs of wires. (physical layer thing)
Well, if you connect two of the same types of devices to each other, then their send pairs would collide, and their receive pairs would collide, thus leading to NO communications.

to make up for this, you CROSSOVER the send/receive pairs, so they can match up properly.

As the Bridges were designed to connect to Hosts (PC or Routers can be called hosts), their send/receive would be automatically flipped.

I hope this makes sense, and I hope this line of thought helps you figure it out.

Let me find a link:

Straight-through cable: the opposite of crossover cable

Crossover cable

I believe it helps to learn, if you can understand and visualize WHY the cables are utilized. I believe that the way most texts present this portion, they kind of tell you what to do, but not WHY, or, they just gloss over why.

I hope this helps.

AndyLPJr

Well, just like the name straight is means the cable used to connect between computer - router - computer, crossover is for computer directly to another computer.

for more info please look at my tutorial too.

How To Make Straight And Cross UTP Cable | Our Smart Info

mendysue

The reason behind using a cross over cable for like devices is because these like device us the same pins to send and receive, so they need a cross over cable to communicate. Dissimilar devices are using different pins already so they cable doesn't need to be crossed to connect the circuit.

theodoxa

For the Color Codes:

Ethernet = University of Miami (Flip the Orange and Green Pairs)
T1 = University of Florida (Flip the Orange and Blue Pairs)

NOTE: For Gigabit from what I've read, its a bit more complicated.

As for when to use each...I think of it as connecting devices:

You would connect a PC to a Switch and a switch to a router. All of these require straighthrough cables. OTOH, to connect like devices (Switch -> Switch, Router -> Router, PC -> PC) or to skip an intermediate device (PC -> Router) you would need crossover.

WilyOne

instant000 wrote: »

Like devices connect with a crossover cable.

Unlike devices connect with a straight-thru cable.

This is it.

Like to like* = crossover.
Unlike to unlike = straight-through

* The only trick here is to remember that routers are considered computers. So that means PC to Router is like to like, hence crossover required.

darndatdavid

Dynaice wrote: »

Do you mean having issues with trying to remember when to use a xover or straight through?

If so, I always found it's easiest to remember by like devices or opposite devices.

I.E. Router - Router = crossover. I think of a Router as having a CPU like a desktop has a CPU so those would also be like devices.

PC/Laptop - Router = crossover.

Switches and Hubs, well they do not deal with layer 3 unless it is a layer 3 switch, so think of those as like devices.

Switch to Hub = Crossover.

Anything that isnt a like device will connect via straight through.

PC/Laptop to Switch = straight through
Switch to Router = straight through

Hope that helps out.

Thank you! You've helped me finally get this !!