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You need to know how to read.
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MAC addresses and what they mean and to help us do that.
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Let's make this practical and use Packet Tracer.
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So please open packet tracer and follow me and make sure that you see something similar.
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The numbers that you get may be different but we'll manually configure MAC addresses in Packet Tracer
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because it's easy to do that.
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So make sure that you can view the MAC addresses and then gonna show you how to work with hexadecimal
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and how to convert numbers from binary to hex hexadecimal to decimal and so forth.
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So the first thing is let's get a switch and I'll get a 35 60 switch and drag that into the topology.
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I'll go the end devices.
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Grab a P.C. grab a laptop add that to the topology go to network connections and get a straight through
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cable and connect the pieces Ethernet interface to the switch on gigabit 001.
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You don't have to use exactly the same interfaces it's really up to you but what I've done here is connect
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the pieces to the switch to make it easier to follow.
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I'll go to preferences and I'll show the port labels in my diagram so fast.
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Ethan at 0 in the piece he is connected to gigabit 1 0 1 on the switch.
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I'll connect to the second gig interface to the laptop on fast ethernet zero so we've got our devices
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in our topology.
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The switch needs a power supply so grab a power supply and add that to the switch.
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And as you can see the switch is now booting up.
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But now let's view the MAC addresses on the devices it's on P.C. one go too fast ethernet a zero.
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This is the MAC address of the P.C. by default.
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I'm gonna give it an IP address of 10 1 1 1 with a subnet mask of slash 24 or 2 4 5 2 4 5 2 4 5 0.
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If you don't understand that yet don't worry too much we'll talk a lot about submitting in later videos
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but for the moment I've configured the P.C. with those details.
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I'll go to desktop.
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Command prompt and if we type IP config like you would on a Windows computer.
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Notice there's the IP address of the P.C. IP config slash all.
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There is the MAC address of the P.C. not easy to read.
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Will change that in a moment but for the moment I want to show you that the switch will learn those
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MAC addresses so hence it's important for you to learn hexadecimal on the laptop go to config first
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Ethan at 0.
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I'll configure this laptop with an IP address of 10 dot one that wanted to add a subnet mask of that
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2 4 5 2 4 5 2 4 5 0.
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There's the MAC address of this P.C. so if I go to command prompt on the laptop and TCP IP config slash
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all there's the IP address there's the MAC address back on the P.C..
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P.S. 1 P.S. starts with 0 0 0 4 laptop starts with triple 0 6 the first half of this address is the
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vendor code.
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Second half is a unique identifier for the MAC address but notice please when I type a command such
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as Opp dash a.
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It says there are no op entries.
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OP is used to find the MAC address of another device in the network.
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It's basically a broadcast sent out into the network saying who has this IP address and then that device
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will reply back with its MAC address.
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So back on the laptop.
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If I type OP dash a notice it says no op entries are found OP is used to discover the MAC address of
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a another device in ethernet devices have mac addresses allocated to them by vendors.
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If I want to talk to your device I need to know what your MAC address is to be able to send the traffic
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onto the ethernet network.
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So if the laptop pings the P.C. it's basically going to send a broadcast into the network saying who
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has this IP address and then that P.C. will reply back.
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Notice now when we type up dash a we see that this IP address is using this MAC address and that's correct.
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Per the information on P.C. one back on the P.C. IP config slash all shows us that the P.C. has this
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IP address and this MAC address the laptop has learnt the MAC address of the P.C. and in the same way
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the P.C. has learnt the MAC address of the laptop.
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So that's an example where hexadecimal values are used but it's not only there.
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If I have a look at the switch I'm going to bypass the initial configuration on the switch.
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Now don't worry too much if you don't know the commands on Cisco switches in a lot of detail yet you'll
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learn as we go along.
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Enable takes us to privilege mode and I can type show MAC address table to see the MAC address table
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on the switch the switch has learned to where the devices are the whole idea with a switch is when it
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receives traffic on one port it needs to switch that traffic out of another port needs to know where
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the devices are so that it can efficiently send the traffic to only the correct ports.
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So in other words if traffic arrives on this interface going to the laptop we only want to send it out
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of this interface.
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Now the switch doesn't have other interfaces connected at the moment but if we did we wouldn't want
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to send that traffic out of all interfaces we would want to limit it to this one interface.
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So the switch learns where devices are in the network.
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If we change the MAC address of the P.C. so going back to the pieces config will click on fast ethernet
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zero.
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I could as an example set the MAC address to 0 0 C0 and then just make it a number like that a whole
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bunch of ones notice a MAC address consists of six hexadecimal values this is hex which is the vendor
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code and then six hexadecimal values which is the unique identifier for the mac address a hex value
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is for binary bits and I'll explain that in more detail in a moment.
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This is a forty eight.
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But no we've got twelve hexadecimal values and a MAC address twelve times for 48 bits each number has
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a hexadecimal number.
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What I'll do now is change the MAC address of the laptop so go to config Foster Ethan 0.
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Let's make that 0 0 C0 2 2 2 2 and a bunch of twos.
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So I've changed the MAC address of the laptop as well if I type IP config that's the IP address to slash
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all.
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Make this bigger that shows us the MAC address of the P.C. has changed or the laptop in this case has
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changed.
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So now OPP dash a the OP cache has timed out or has been flushed in this example there are no op entries.
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If the laptop pings the P.C. and type OPP dash e now you can see that the Mac address of value has been
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updated.
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So the laptop has learnt the new mac address associated with the P.C. and in the same way the P.C. has
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learnt that was the previous entry but P.C. has learnt the new mac address of the laptop and the switch
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will have learnt the new mac addresses.
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Now it still has the old mac addresses in its MAC address table they will time out after a period of
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time but for the moment it's got both the old mac addresses and the new mac addresses in its MAC address
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table a switch learns where the MAC addresses of devices are in the network and then basically switches
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the traffic from one MAC address to another depending on who's talking to who.
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So as you can see here MAC addresses are used in a lot of places you need to know how to read MAC addresses
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you need to know what that means.
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If I tell you that that's a 48 but no you need to know that.
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Why why is it 48.
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So let's talk about the theory and I'll show you how to do conversions from one numbering system to
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another.
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Don't forget that IP version 6 also uses hexadecimal.
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So if I type IP conflict slash all on the.
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P.S. notice link local IP version 6 address DHEA P client identifier.
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These are all hexadecimal numbers.
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We've got a Bluetooth hexadecimal number hexadecimal is used in multiple places you need to know how
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to work with hexadecimal.
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So now let's talk about the theory of hexadecimal and how to do conversions.
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