(Beginner networking) Can I use a crossover cable to connect a PC to a hub that has an uplink feature?

I am taking a class on Computer Networking and part of a lab we did earlier this week involved connecting our PC to a hub using a straight-through cable. It worked. Then we had a small experiment with connecting our hub to another group's hub using a straight-through cable instead of a crossover cable. We were not connected at the point, but then we enabled the "uplink" button which apparently lets us emulate a crossover cable by physically reversing the circuitry, and we became connected.

Now I am wondering if it would be possible to do something different. Would it be possible to connect a PC to the hub we were using with only a crossover cable if we used the uplink feature as well? (We used straight-through previously).

Thanks in advance!

cable

Mei

Posted 2015-01-09T06:12:43.437

Reputation:

Answers

The simple answer is yes you can. Lets start with the basics that you described:

Host   >  X Cable   >  Host
Host   >  Straight  >  Switch
Switch >  X Cable   >  Switch

This is because there are two types of devices in networking, DTE (Data Terminal Equipment) or DCE (Data Communications Equipment). And devices of the same type need a Cross over cable to connect them, those of different types can be connected with a straight cable. Here are some examples of types:

DCE              DTE
Switch           PC
Hub              Printer
                 Router

One of the first improvements made to switches was to add a manual uplink button as you describe, this puts add a cross to any cable; a straight cable becomes a cross, and a cross becomes a double cross (really angry?) which is the same a straight. So then you can have:

Switch  >  Straight  > Uplink  >  Switch
Host    >  X cable   > Uplink  >  Switch

New switches can have a feature called Auto MDI-X. Which detects the combination of cable type you have used and what the end device is and automatically sets the port for you, so like magic it just works!

Acyclic Tau

Posted 2015-01-09T06:12:43.437

Reputation: 146

Network interfaces in (non-switch) devices have also supported Auto MDI-X for a long time now. – Daniel B – 2015-01-10T22:45:43.060

The uplink feature you refer to is Auto MDI-X.
Its common for a hub to have several MDI interfaces and one Auto MDI-X interface.
If all ports were Auto MDI-X it wouldn't matter which type of cable you used, straight through or crossover.

alib_15

Posted 2015-01-09T06:12:43.437

Reputation: 101

If there is an 'uplink' button then I am not sure this will be Auto MDI-X, it sounds more manual to me :) – Acyclic Tau – 2015-01-09T15:36:54.833

Auto is just that: automatic (There's no button) The "uplink" button is a switch that physically swaps the TX/RX pairs. – Ricky Beam – 2015-01-10T01:11:31.590