- [Instructor] Now in discussing our Ethernet cable types,
we have straight-through, crossover and rolled
but regardless we always use four wire pairs.
Now, in a straight-through cable we only need four wires
to connect Ethernet devices together.
It's relatively simple to create this type
and this graphic shows the four wires used
in a straight-through Ethernet cable.
Notice that pins one to one, two to two, three to three
and six to six are used.
So we just connect, like I said, one to one, two to two
and so on and you'll be up and networking in no time.
However, remember this will only be ten megabits,
maybe you can get a 100 megabits working today
but it's certainly not gonna work with gigabit, voice
or other LAN or WAN technologies for sure.
Now, let's take a look at a straight-through cable here,
what we would use it for.
So in this graphic here we can see that we typically
would have a host to a switch or hub and we transmit,
what's important to understand here is we transmit
on pins one and two.
So this is what's referred to as our transmit pairs
and they receive on pins one and two.
So their receive pair is my transmit pair,
which kinda makes sense
and my receive pairs are pins three and six.
Their transmit pins are three and six.
This is my typical set-up for 10BASE-T or 100BASE-T today.
Now when I have a connection like this where I have two
like Ethernet devices, for example, two switches.
Now I can't have the wiring the same
because they're like devices.
Now Ethernet says if you're a host connecting to a switch,
use a straight-through cable.
In this example here we'll use something called
a crossover cable, which means we cross the cables
or cross the pins from one to three and two to six.
So in this example here
I'm going to receive on pins one and two
and I'm gonna transmit on pins three and six
and this is going to be the opposite.
So the same four wires are used in a straight-through cable
what we use them in this cable,
we just connect different pins together.
Now it's important to remember
that this is the CCENT objectives.
It's unlikely today that any newish device
would need to have a crossover cable
because we use an auto detect mechanism
but it's important to understand for the CCENT objectives,
they don't use an auto detect mechanism
and if you have two switches, your answer for the objectives
is "I need a crossover cable".
So when would we use different kinds of cables
straight-through and cross-through, let's take a look.
If I have switch to switch, I have a crossover.
Switch to hub, crossover, that would only be at home I hope.
Hub to hub, router to router direct interface to interface
right, router to PC direct and certainly I'd do this,
you know for testing and directly connecting into the router
PC to PC, which you might do, crossover cables.
Most of the time with these devices the hubs either have
an uplink port you can plug into or push a button on
but switches will auto detect a crossover cable,
the routers will, router to PC typically will
and probably your PC to PC's as well.
Now for straight-through cables,
that's connect switch to anything,
switch to router, host, server, hub to PC
or hub to server, these are all really great examples
of when to use crossovers and straight-throughs,
for again, the CCENT objectives.
Now in the previous examples of 10BASE-T
what I was talking about with unshielded twisted pair wiring
or UTP wiring, only two wire pairs were used,
but that is not good enough for gigabit UTP transmission,
that would never work in the diagram shown in this graphic.
I need all four wire pairs to be used and so the advanced
centronics and every pair on the cable can transmit
simultaneously.
It's almost identical to my earlier 10 100 example
except that we'll use the other two pairs in the cable.
So for the straight-through cable it's still one to one,
two to two and so on up to pin eight but in this example
we've shown a gigabit crossover and so we cross one to three
and two to six but we'd also add four to seven
and five to eight, pretty straight forward.
And lastly, let's take a look at our rolled cable
and what this is used for is a console port as we see here.
If I want to take an RS-232 port out of a PC or laptop
goodluck finding that port on your laptop these days,
we can connect into the console port of our router
and switch.
This gives us what's called out-of-band management
which means we're connecting and configuring the device
out of the network not through the network like we would
as in-band protocol such as telnet and SSH or secure shell.