Cabling Query

hassantalal785

Pin Color Function Pin Color Function
1 White/Green TX+ 1 White/Green TX+

2 Green TX- 2 Green TX-

3 White/Orange RX+ 3 White/Orange RX+

6 Orange RX - 6 Orange RX-



Above shown is a table of a cable with pin configuration of the two ends given on left and right side .Well according to a writer it is supposed to be a straight through cable whereas i think it is a Cross over cable . Reason is that Pins 1,2 at one end are used for transmission and same 1,2 is used for transmission at other end .If i use it to connect a PC and switch as the writer says wouldn't it be wrong as PC uses PINS 1,2 to transmit and switch uses PINS 1,2 to receive where as here both ends have Pins 1,2 for transmission .Kindly Help ...

Diggs

That would be a straight through cable...568A to be exact.

You're transmitting frames on pins 1 & 2 and the switchport is set to receive on pins 1 & 2

A crossover cable would be 568A on one end and 568B on the other which would swap the send / receive pairs.

NetworkVeteran

hassantalal785 wrote: »

Pin Color Function Pin Color Function
1 White/Green TX+ 1 White/Green TX+

2 Green TX- 2 Green TX-

3 White/Orange RX+ 3 White/Orange RX+

6 Orange RX - 6 Orange RX-



Well according to a writer it is supposed to be a straight through cable whereas i think it is a Cross over cable .

Well, now you know better! That is a straight-through cable. The pinouts of various cable types are well-defined and can be found by doing a quick Google search.

hassantalal785

Diggs wrote: »

That would be a straight through cable...568A to be exact.

You're transmitting frames on pins 1 & 2 and the switchport is set to receive on pins 1 & 2

A crossover cable would be 568A on one end and 568B on the other which would swap the send / receive pairs.

I know its a cross over cable but both ends have PIN1 as TX+ and PIN2 as TX- , this is what i dont understand shouldn't it be opposite as the definition suggests ??

TehToG

Look at the two pairs. TX and RX. TX is the transmitting pair, RX the receiving pair.

In order to have a signal we need a voltage, the TX+ and the TX- compete the circuit and the voltage difference between the two is our signal.

Now if one side has TX and it's sending data, the other side (directly connected) has to be the RX in order to receive the sent data and vice versa

Diggs

A crossover cable does cross the send and receive pairs (1/2 with 3/6)....a straight through cable has the same pins ( 1 through 8 ) on both side of the cable. Some devices are designed to send on pins 1 & 2...while others are designed to receive on 1 & 2.

One way of remembering which type of cable to use is to remember that a crossover cable is used to connect 'like' devices such as a:

-Switch to a switch
-Router to a router
-Hub to a switch
-PC to a PC

Straight through cables connect 'unlike' devices such as a:

-Router to a switch
-Switch to a PC
-Router to a hub

Forsaken_GA

or you just buy switches with auto-MDIX and use whatever cable you can lay your hand on

Diggs

Yeah that'll work too....not sure that's an option on the exams though lol

TehToG

You need to know to know which cable to use for the Exams. In the real world you can use auto-mdix but if you're buying gear for that feature it's easier just to make yourself a crossover.

NetworkVeteran

TehToG wrote: »

You need to know to know which cable to use for the Exams. In the real world you can use auto-mdix but if you're buying gear for that feature it's easier just to make yourself a crossover.

In the real-world, I find it's cheaper to buy MDIX, because the cost in terms of engineer-time for even occasional miscabling is too high. I've instituted MDIX-only purchasing policies before.

DPG

Forsaken_GA wrote: »

or you just buy switches with auto-MDIX and use whatever cable you can lay your hand on

Unless you happen to grab a rollover cable.

Forsaken_GA

DPG wrote: »

Unless you happen to grab a rollover cable.

Well given that rollover cables tend to be flat and patch cables tend to be round, I would hope an engineer would realize their mistake. I consider rollover cables to be serial cables, the equivalent of a null modem cable, not real network cable.

Forsaken_GA

NetworkVeteran wrote: »

In the real-world, I find it's cheaper to buy MDIX, because the cost in terms of engineer-time for even occasional miscabling is too high. I've instituted MDIX-only purchasing policies before.

Indeed, the feature is incredibly time saving, not to mention it gives you more options, ie, lets say I need a 25 foot crossover cable, but all I have is a 25 foot straight through... auto-MDIX ports mean I don't have to care how the cables are pinned out. auto-MDIX is a good example of correcting a major inconvenience of the technology and eliminating engineering concerns for such a low level item.

Some folks consider it an imperative that a network engineer know cable pinouts and know how to make their own cables. I've always disagreed, I suck at making cables, and I keep a number of lengths of patch cables in my car, and I can honestly say I have not had a need to make my own cables for years.

KenC

Forsaken_GA wrote: »

...Some folks consider it an imperative that a network engineer know cable pinouts and know how to make their own cables. I've always disagreed, I suck at making cables, and I keep a number of lengths of patch cables in my car, and I can honestly say I have not had a need to make my own cables for years.

I'd have to disagree with your first statement above. However, more often than not, grabbing a new cable is the most efficient way of getting the job done, so you are right on the last part (just don't forget to bring your car!).

TehToG

I'd be more inclined in that situation to use a cross-over box I made. Clip it on to any straight-through cable, instant crossover. No relying on auto MDIX

DPG

Forsaken_GA wrote: »

Some folks consider it an imperative that a network engineer know cable pinouts and know how to make their own cables. I've always disagreed, I suck at making cables, and I keep a number of lengths of patch cables in my car, and I can honestly say I have not had a need to make my own cables for years.

And then this happens: