Instructor: In this lesson,
we're going to talk about coaxial cable.
Coaxial cable, also known as coax,
is one of the oldest categories of copper media
and it's still used in networking today.
Coaxial cables have an inner insulated conductor
or center wire that's going to pass all of our data over it,
and this is known as the center core.
Now, we also have this outer shell
that is a braided metal shield
to help shield it from any data transmission leakage
coming from inside the cable outward,
and it provides protection from the outside in
that gets electromagnetic interference
because of this braided metal shielding.
Now, on the outside, we have this plastic jacket
and then there's a metallic shield and an insulator.
And inside that insulator, we have that center core
where all the data is going to pass through.
Now, where might you find coaxial cables in modern networks?
Well, there's really two main places.
First, we're going to have RG-6,
which is commonly used by your local cable company
to connect their service to your home.
It's a very thick version of a coaxial cable.
Now, once you get inside your home,
you're going to use what's known as an RG-59
and this is going to carry composite video
between two nearby devices
or connect an outlet to a cable modem.
Now, if you have cable TV or satellite TV in your house,
you're probably using RG-59 cables
running from the cable or satellite box to your TV
or to the outlet jack on the wall.
This is commonly referred to as a coaxial cable or coax,
and it's the most common one you're going to find.
Now, how does a coaxial cable connect to your device?
Well, there's two commonly used type of connectors
when it comes to coaxial cables.
These are known as an F-type and a BNC connector.
Now most coaxial cables these days
are going to have an F-type connector.
This is basically a screw-on type of connector
that attaches to the cable box or to the wall jack.
This is commonly used in cable TV
and cable modems for consumer applications.
Now the second type of connector we have
is known as a BNC connector,
also called a Bayonet Neill-Concelman connector
or a British Naval connector.
Now, usually, network professionals
will simply refer to all of these as a BNC connector though.
Now, BNC connectors used to be used
really heavily in networking,
especially in the early days of computer networks.
In fact, if you ever come across an old 10BASE2
or 10BASE5 network from the early days of Ethernet,
somewhere around the 1970s or '80s,
this was the standard connector used by them.
It was a BNC connector.
So if all of these things are so old and obsolete,
why am I even mentioning them?
Well, because a lot of my students
will go on to work in jobs for the Department of Defense
or one of their military subcontractors
and they still use a lot of BNC connectors,
as well as RG-6 and RG-59 cabling
for some of their older network devices
because they simply haven't upgraded them yet
and they still work
for some of their older command and control systems.
So you may come across them
while you're working in the field,
and it's important for you to realize
what these things look like.
You have to realize that you don't have to fully screw on
one of these BNC connectors,
like you would an F-type connector.
Instead, a BNC connector is going to be used
by pushing the connector in
and then twisting it about a half a turn
to lock it in place.
Now, there is a newer style coaxial cable
that's being used in modern applications as well.
This one is known as twinaxial.
Now, a twinaxial cable is similar to a coaxial cable,
but instead of having just one conductor,
there's going to be two inner conductors to carry the data.
Twinaxial cables are used for very short range,
high-speed connections between devices.
For example, there's a use case for using an SFP+
direct-attached copper cable between two different switches
that are shorter than about seven meters apart.
Now, if you decide to use twinaxial cable for this,
you can avoid using fiber cables
and it'll save you a bit of money if your networking devices
will support this type of connection.
In this application,
you're going to be able to get speeds
of up to 10 gigabits per second over that twinaxial cable
and it uses a lot less energy than traditional copper cables
to achieve this level of speed.
That said, personally,
I've never had to use twinaxial cables in my life.
And instead, I've either relied on the twisted pair cable
or a fiber optic cable between my switches
for my high-speed trunks.