Ethernet ten based two uses coaxial cable.
The specifications are different to the coaxial cable used in cable television, but the point I'm trying
to make is coaxial cable running a base band signal can only transmit or receive a single signal at
any given time.
Broadband uses coaxial cable, but allows for multiple signals to be sent across the wire at any given
time.
Ethernet uses base band signaling, in other words, ten base two or ten base five in the past.
So in ten base two coaxial cable was used.
BNC connectors were used to connect devices to the network.
A, B and C, RT Connector would connect the cable to the PC.
Don't worry too much about this.
This is just a bit of history so that you can understand why things are done in certain ways today.
What's important to realize is that a single piece of cable would have banked connectors, which would
allow you to connect devices to a single cable.
Multiple devices were connected across a single cable, and at the end you would have terminators to
stop signals bouncing back.
And here's an example of a Terminator.
So what a Terminator did is essentially terminate the signal or destroy the signal when it got to the
end of the wire.
So when the signal is sent across the wire, it shouldn't bounce back and cause collisions.
So the Terminator would terminate the signal to ensure that it didn't bounce back.
Once again, the reason for doing this is because base band is used.
Base band only allows a single signal to be sent across the wire or cable at any time.
So we couldn't have a signal bouncing back and causing a collision.
Hence Terminators we used.
Now, before we continue discussing the transmission of data in more detail, let's talk about what
a mac address is.
A media access control address or MAC address, also called a physical address, is a unique identifier
assigned to network interfaces.
A mac address is a layer two address, identifying a network interface card or NIC.
It is typically built in by the manufacturer.
In other words, it's burnt in to the network card by the NEC manufacturer and it's 48 bits in length.
The 48 bits are divided into two portions.
The UI portion is 24 bits in length and the station addresses also 24 bits in length.
The UI or organizational unique identifier identifies a vendor such as Cisco or HP or Dell or other
vendors that manufacture network devices or PCs or servers.
Each manufacturer is assigned an O UI, and each vendor in turn can create and assign end station addresses
to network interface cards.
The station addresses should be unique.
Now, I say should be unique because there have been cases where addresses have been duplicated by manufacturers.
So you may end up having a network with duplicate MAC addresses, which causes a lot of problems in
an Ethernet environment.
In an Ethernet environment, on a segment or a piece of cable, we're assuming that all devices have
a unique Mac address.
It's also possible in software to change device MAC addresses.
So on my interface card as an example, I can go to properties, go to configuration.
Selected once I can then go to locally administrated addresses and then I can change the value so I
could make it quadruple a.
Quadruple B.
Quadruple C and click.
Okay.
Opening a cmd prompt and typing IP config forward slash all and then scrolling up I'll be able to see
that my physical Mac address is now set to ABC.
I've just changed my Mac address from the Burnt Inn address set by the manufacturer to something else.
Now, if I did that on multiple PCs or multiple devices, I would be causing an issue with duplicate
Mac addresses.
So once again, the first portion of a mac address is the O UI, and the second portion is a unique
value assigned by the manufacturer.
So on my network card, I'll set it back to the default.
So now when I run IP config forward slash all notice the built in mac address on my local area.
Connection uses the unique value assigned by the manufacturer.
Wireshark has a nice tool to look at.
Oh UI codes.
So I've just added 0001e6 and that should list the manufacturer for that Mac address.
In this case you can see it's HP.
So Mac addresses that start with 0001e6 or HP Mac addresses.
I can also look on the Triple E website to see similar information.
Notice that both E6 and E seven codes are manufactured by HP.
There's a long list of different UI codes and you'll be able to see which O UI codes are associated
with which vendor.