Another copper cable you may come across is a direct attachment cable or DAC cable.
This cable comes in various lengths up to 15 meters.
Uses Copper Twin X and has tsps on each end.
An SFP or small form factor.
Pluggable is a hot pluggable transceiver and may support various media types such as fibre or copper.
This replaces G, bics or gigabit interface converters and the one shown here is an enhanced small form
pluggable or SFP plus that supports data rates up to ten gigabits per second.
So a DAC cable is inserted into an SFP plus slot and allows for a ten gigabit per second connection
between two devices.
Other SFP or SFP pluses will support fibre that can go to greater lengths.
But this cable allows for ten gigabit copper connectivity between two devices over a short distance,
such as seven metres.
A roll over cable is a special cable used to connect to the consoles of networking devices.
It allows you to connect from the serial port on your PC or laptop to the console of a router or switch.
So if you've got a serial port or comm port on your PC, you can connect directly to the console of
a router or switch using a rollover cable.
However, a lot of modern day PCs don't have serial ports, so you'll need to get a USB to serial port
converter, which has a USB connection on one side and a db9 male connector on the other side.
This would allow you to connect a DB nine female console cable to your PC with either a RJ 45 connector
on the other side or another DB nine connector.
Most Cisco switches and routers use an RJ 45 connector, but you may come across some devices from other
vendors such as HP that use a DB nine connector for the console port.
So a DB nine serial would connect to your PC and either an RJ 45 or DB nine Serial would be connected
to the console of the networking device that you want to configure in a rollover cable.
All pins are inverted or rolled over, so pin one is connected to PIN eight, PIN two is connected to
PIN seven, 3 to 6 and so forth and so on until you get to PIN eight, which is connected to pin one.
You could use a standard Cat five or Cat six cable as a rollover cable, and then just change the peanuts
on the ends from straight through to rollover.
But typically this is not required as most networking devices are shipped with console cables.
This video has explained a lot about Ethernet and data flows.
In the next video, we'll look at how traffic is forwarded by hubs, bridges, switches and routers.
Now that we've looked briefly at cabling, I'd like to explain how network devices operate and the first
device that we're going to look at is a hub.
A hub is a layer one device in the AC model and you would use a Cat five unshielded twisted pair cable
with an RJ 45 connector to connect your laptop as an example to a port on a hub hubs onto very popular
today and have been superseded by switches and I'll explain in a few minutes why but for now, let's
assume that you are connecting your PC to a hub.
It's important that you understand how a hub operates, however, because wireless operates in the same
way, like a physical hub would.
So when you connect to a wireless network, you'll often encounter the same issues that you would encounter
when connecting to a physical hub.
So for now, let's assume that you're connecting your PC physically to a hub.
Hubs have multiple ports, and thus multiple devices can be connected to a hub at the same time.
The number of ports available depends on the hub model.
But as you can see in both of these examples, a hub has various ports that you can connect devices
to.
So in this topology, let's assume that you have four devices connected to a hub on ports, 1 to 4.
It's important to realize that a hub is a physical layer device.
It's not intelligent and does not understand the frames going through it.
It's basically a multi port repeater and it will amplify or repeat the frames that it receives on one
port out of all other ports.
So it's once again simply a multi port repeater with no intelligence.
The physical topology of a hub is a star topology.
In a star topology you have a central device which in this case is a hub and devices hanging off that
central device as spokes which resemble the spokes in a bicycle wheel.
Each spoke device is connected to the central device with its own cable, and all transmission or communications
between devices are through the central device.
In other words, if A wants to communicate with sea, the traffic will flow through the hub and will
not flow directly between the two devices.
There were some major advantages to using hubs and UTP rather than ten based two.
The first advantage is a cable break.
If a cable broke in this topology, it would only affect device A and it would not affect the rest of
the network.
In ten bays two.
If a cable broke, it would affect all devices in that network here.
However, other devices such as C and B can still communicate, even though the cable is broken to device
A, another advantage is that you can extend distances easily.
A bus topology is limited in size in a ten based T environment such as this, the distance between a
device such as A and the hub needs to be 100 meters.
But you can extend the distance by adding another hub.
In other words, you add another multiport repeater and repeat or regenerate the signal to extend the
distance of the network to distances greater than 100 meters.
So in this example, E could be 100 meters away from its hub, and the two hubs could be 50 meters apart.
So in this example, we've extended the network further than the restriction of 100 meters.
So device E could be 100 meters from its hub.
It could be a cable length of 50 meters between the two hubs.
An A could be 100 meters away from its hub.
Our network now has a length of 250 meters, which is well over the limitation of 100 meters.
Now there are restrictions on the number of hubs that you can daisy chain together, but the point is
it's possible to extend the topology by adding more hubs and more devices to the network.
These were therefore great reasons to move away from ten based two and ten based five and implement
UTP or untrusted pair networks using hubs.
Another advantage is that UTP cabling is cheaper and easier to manage and therefore it became common
to use hubs and ten based rather than ten based two or ten based five in the past.