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Another copper cable you may come across a direct attachment cable or DAC cable the cable comes in various

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lengths up to 15 meters use as copper twinax and has a set piece on each end.

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And SFP or small form factor pluggable is a hot pluggable transceiver and may support various media

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types such as fiber or copper.

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This replaces X or kickabout interface converters and the one shown here is an enhanced small form pluggable

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or SFP plus that supports data rates up to 10 gigabits per second.

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So a deck cable is inserted into an SFP plus slot and allows for a 10 gigabit per second connection

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between two devices on the PS or SFP Plus's will support fiber that can go to great lengths.

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But this cable allows for 10 gigabit copeck connectivity between two devices over a short distance such

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as seven meters a roll over cable is a special cable used to connect to the consuls of networking devices.

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It allows you to connect from the serial port on your PC or laptop to the console of a router or switch.

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So if you've got a serial port or comport on your PC you can connect directly to the console of a Rotto

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a switch using a rollover cable.

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However a lot of modern day PCs don't have serial ports so you'll need to get a USP to serial port converter

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which has a USP connection on one side and a D-B nine male connector on the other side.

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This would allow you to connect a D-B nine female console cable to your PC with either a Arjay 45 connector

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on the other side or another D-B 9 connector.

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Most Cisco switches and routers use an RJ 45 connector but you may come across some devices from other

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vendors such as HP that use a D-B 9 connector for the console port.

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So a DC 9 serial would connect to your PC and either an RJ 45 or nine serial would be connected to the

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console of the networking device that you want to configure in a rollover cable.

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All pins are inverted or rolled over.

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So pin one is connected to pinot pintu is connected to pin 7 3 to 6 and so forth and so on until you

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get to pin 8 which is connected to pin 1.

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You could use a standard cat 5 a cat 6 cable as a rollover cable and then just change the peanuts on

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the ends from straight through to rollover.

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But typically this is not required as most networking devices are shipped with console cables.

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This video has explained a lot about Ethernet and data flows in the next video.

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We'll look at how traffic is forwarded by Hubbs bridges switches and routers

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in

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now that we've looked briefly at cabling I'd like to explain how networked devices operate.

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And the first device that we're going to look at is a hub a hub is a layer one device in the overside

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model and you would use a cat 5 unshielded twisted pick cable with an RJ 45 connector to connect your

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laptop as an example to a port on a hub.

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Hubs aren't very popular today and have been superseded by switches and I'll explain in a few minutes

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why.

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But for now let's assume that you are connecting your PC to a hub.

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It's important that you understand how a hub operates however because the wireless operates in the same

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way like a physical hub would.

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So when you connect to a wireless network you'll often encounter the same issues that you would encounter

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when connecting to a physical hub.

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So for now let's assume that you are connecting your PC physically to a hub hubs have multiple ports

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and thus multiple devices can be connected to a hub at the same time.

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The number of ports available depends on the hub model.

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But as you can see in both of these examples a hub has various ports that you can connect devices to.

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So in this topology let's assume that you have four devices connected to a hub on ports one to four.

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It's important to realize that a hub is a physical layer device.

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It's not intelligent and does not understand the frames going through it.

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It's basically a multi port repeater and it will amplify or repeat the frames that it receives on one

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port.

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Out of all other ports.

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So it's once again simply a multi port repeater with no intelligence.

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The physical topology of a hub is a star topology in a star topology you have a central device which

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in this case is a hub and devices hanging off that central device as spokes which resemble the spokes

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in a bicycle wheel.

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Each spoke device is connected to the central device with its own cable and all transmission or communications

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between devices or through the central device.

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In other words if he wants to communicate with C the traffic will flow through the hub and will not

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flow directly between the two devices.

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They were some major advantages to using hubs and UDP rather than 10 base two.

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The first advantage is a cable break if a cable broke.

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In this typology it would only affect device a.

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And it would not affect the rest of the network in 10 days.

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2 If a cable broke it would affect all devices in that network here.

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However other devices such as C and B can still communicate even though the cable is broken to device

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say.

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Another advantage is that you can extend distances easily.

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A bus typology is limited in size in a 10 base t environment such as this.

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The distance between a device such as A and the hub needs to be 100 metres but you can extend the distance

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by adding another hub.

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In other words you add a nother multi-port repeater and repeat or regenerate the signal to extend the

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distance of the network to distances greater than 100 meters.

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So in this example E could be one hundred meters away from its hub and the two hubs could be 50 meters

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apart.

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So in this example we've extended the network further then the restriction of 100 meters.

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So a device E could be 100 metres from its hub it could be a cable length of 50 metres between the two

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hubs and a could be 100 metres away from its hub a network now has a length of 250 metres which is well

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over the limitation of 100 meters.

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Now there are restrictions on the number of hubs that you can daisy chain together.

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But the point is it's possible to extend that apology by adding more hubs and more devices to the network.

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These were therefore great reasons to move away from 10 base to and 10 base 5 and implement a UDP or

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untrusted pay networks using hubs.

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Another advantage is that UDP cabling is cheaper and easier to manage and therefore it became common

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to use hubs and 10 base T rather than 10 base 2 or 10 base 5 in the past.