WEBVTT

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 With regards to my laptop, my laptop
 specifically that I'm working on

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 here, I was to draw this.

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 Well, my laptop is already here.

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 So here's my laptop.

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 And this laptop, it's not part of this
 picture here, but let me just put

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 in green, the terminal server, which
 was that special router with the

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 octal cable. Oops, terminal.

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 Oh, you just can't see the L.

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 Anyway, there we go.

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 So we know the terminal server had
 that octal cable coming out, which

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 then connected to the USB port.

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 I'll put that here as a little C.

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 That was connected to be that
 blue cable to my laptop.

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 And that was connected to the USB port
 on my laptop via that serial to

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 USB connector. Well the USB port on
 my laptop does not understand the

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 internet protocol.

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 It is not a place where
 I can put an IP address.

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 It can't send and receive packets
 to get me through this network.

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 So for that, I will need actually
 an ethernet connection.

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 I'll use brown here for that.

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 So I will still need to connect up to
 an access layer switch via ethernet.

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 And that's actually going to be the
 next section here I'm going to do

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 right here. I'm going to do
 these connections here.

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 I'm going to do an ethernet connection
 here between those two.

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 And I'm going to do an ethernet connection
 here between switch two and

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 router one. I've already drawn in my
 serial connections here, but I'll

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 just label them as serial.

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 Different kind of interface, different
 kind of protocol as far as how

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 we deal with electrical signaling.


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 And then we're going to
 go back to ethernet.

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 Of ethernet from router
 two to my switch.

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 And from the switch to this router
 over here which is serving as a web

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 server. So that's how I'm going
 to complete the cabling.

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 So right now the only cabling I've
 got are the green lines here.

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 My console cable going to my terminal
 server and then the octal port which

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 spreads out to the various
 console ports.

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 Let me just write that right here.


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 So each one of these little C's here represents
 the console port I'm connected

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 to on my various routers
 and switches.

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 But because I can't use that for actual
 sending and receiving of data

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 of IP packets, I need to get
 other types of interfaces.

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 Ethernet and serial involved.

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 So let me look at this
 here for a second.

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 Now you might be wondering, okay, well,
 for example, from the laptop to

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 the switch, how did you know you
 were supposed to use ethernet?

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 Well, so the device you're on, so the
 type of network connectivity you

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 will have is constrained by
 the device that you're on.

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 For example, if I'm talking about a
 smartphone or a tablet like an iPad

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 or something, I can't use wired ethernet
 because a smartphone and a tablet,

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 they don't have jacks that
 look like this, right?

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 They don't have RJ45 jacks
 anywhere on them.

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 I can't plug a cable into them.

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 I can plug in a power cable, but
 I can't plug in a network cable.

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 So the only way I can connect to a
 network on those devices is through

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 an internal nitcard that you can't see
 that's doing Wi-Fi, that's doing

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 radio frequencies.

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 Instead of sending electrical energy across
 a cable, it's sending it through

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 the air. It's using
 a Wi-Fi protocol.

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 Now so if I was to draw that, now this
 session here is all about wired

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 networking, but you can see
 these days are wireless.

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 So let's just put that in here.

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 Let's just say that I had a tablet,
 let's say an iPad, and the iPad does

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 Wi-Fi, so I'll just make these little marks
 here represent my Wi-Fi connection.

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 So that's because the iPad, the smartphone
 has a radio inside of it, just

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 like your car has a radio inside of
 it that's using electrical energy

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 to do Wi-Fi. Now your car radio
 can only receive, right?

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 You can't use your car radio
 to transmit anything out.

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 All it can do is receive various music
 and news talk stations and stuff

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 like that. But the radio inside of your
 iPad, inside of your cell phone

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 is capable of receiving
 and transmitting.

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 So we need something at the other end
 that's listening to your radio waves

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 and it's transmitting
 radio waves to you.

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 And that device, I'll just draw that
 here, I don't have this in my rack,

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 but that device is called
 a Wi-Fi access point.

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 So I'll say Wi-Fi AP.

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 It's providing you access, it's providing
 access to your Wi-Fi devices.

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 And so this here represents my antennas
 that are on this thing which are

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 listening for the Wi-Fi
 signals from my hosts.

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 And the Wi-Fi access point in turn would
 have a wired ethernet connection

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 back to most likely a switch.

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 So for example, in your home network,
 you're probably doing Wi-Fi.

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 You've probably got some Lynxis
 or Netgear Wi-Fi access point.

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 So that's talking to your iPad, that's
 talking to your smartphone, the

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 Wi-Fi signals. And then that wireless
 access point most likely has a wired

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 connection back to, it might be connecting
 back to your cable modem or

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 your DSL modem. Or if you have a little
 bit more of an advanced network,

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 maybe it's connecting back
 to a router or a switch.

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 But the Wi-Fi access point itself has
 to have a cable to connect it into

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 the network. Now I don't have that
 my topology here, but I just wanted

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 to show you how that would fit in
 to this whole kind of thing here.

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 So in my particular case, on
 my laptop, I've got both.

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 I've got a Wi-Fi radio inside of it,
 got a Wi-Fi NIC, and I have a wired

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 NIC. But this show is about
 wired networking.

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 So I'm going to use the RJ45 port on
 the side of my laptop, and I'm going

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 to connect it via ethernet because
 that RJ45 port on my laptop speaks

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 ethernet. It understands ethernet.


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 And ethernet as a protocol says, OK, use
 this kind of electrical signaling.

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 Send it for this long.

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 Here's when you can talk.

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 Here's when you have to be quiet.

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 All that is built into the rules of ethernet,
 which my NIC card understands

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 because it does ethernet.

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 Once I have a connection of all the devices
 with a console from the octal,

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 all right, so that's these green
 connections right here.

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 Is it only one way to connect later
 on, or can I connect Telnet to all

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 those devices? OK.

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 So these green connections here
 are not for sending IP packets.

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 So there's no IP packets here.

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 When I actually connect to the terminal
 server and I start typing in commands,

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 that terminal server, what happens
 when you type in your keyboard?

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 Let's forget about networking
 for a second.

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 When you type A on your keyboard or
 two on your keyboard, what's really

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 happening? Well, that key that you're
 pressing is generating an electrical

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 signal, right? It's creating some sort
 of electrical current which represents

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 the letter C or represents the
 number one or something.

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 So there's different electrical signals
 that represent these letters and

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 these numbers on our keyboards.

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 So when I'm in the terminal server and
 when I'm typing in a command, it's

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 taking those electrical signals of
 the AI pressed or the one I pressed

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 and sending over these green lines
 into the console port of the router

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 or the switch. These are not wrapped
 in IP packets because remember, what

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 is an IP packet?

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 An IP packet has some data behind it,
 maybe the same type of electrical

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 signals, maybe in the data portion
 of an IP packet is in the letter A,

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 the number one, the letter B, but that
 IP packet is IP because at the

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 front of it, it has an address.

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 It has an address of the IP address
 of my laptop where it's coming from

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 and an address, a destination address
 of where it's going through.

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 So that thing can travel through a network
 and get to the correct destination.

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 There's no addresses here.

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 Everything I'm sending across these
 green octal cables is just strictly

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 letters and numbers.

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 There's no IP at all.

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 So I cannot use these
 for IP connections.

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 Tell me is a particular protocol where
 I can take these letters and numbers

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 I'm typing on my keyboard and wrap
 it inside of an IP header.

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 So instead of needing to connect to the
 console port, I can send IP packets

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 to a router or a switch.

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 And when the router switch gets the
 IP packages, oh, here comes an IP

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 packet. Oh, it's got my name
 on it, my IP address.

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 This is for me. And then when it looks
 in the body, the packet says, oh,

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 the body of the packet
 is carrying telnet.

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 Oh, what's telnet?

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 Telnet says, someone's trying to talk
 to me, they're trying to get into

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 my brain and configure me
 and send commands to me.

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 That's what telnet is used for, to send
 commands from one device to another.

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 We can't do that over the octal cables
 because telnet relies on the IP

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 protocol. And all the communications
 across these green lines here, it's

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 not doing IP whatsoever.

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 So in order to do telnet, once again,
 I would need to put some sort of

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 IP address on one or more of the interfaces
 on these devices so I could

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 send my telnet packets inside
 of IP to get to them.

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 At that point, I wouldn't necessarily
 need the octal cables anymore.

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 Once I've got IP and all these devices
 and I can telnet to the devices

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 over Ethernet, I can remove
 my terminal server.

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 I won't need anymore to get
 access to the command line.

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 So the terminal server was initially
 just needed because there was no

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 IP on any of these devices.

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 So the only way I could get to them
 was by connecting to their console

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 ports. That's why I needed it.

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 So an octal cable is all a physical layer
 thing because there's no addressing.

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 There's no MAC addresses
 and no IP addresses.

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 It all resides at the physical
 layer of the OSI model.

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 That's where you would find it.

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 When I was in my terminal server, so here
 I am, when I went into a connection,

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 for example, switch one, and I issued
 some sort of a keyboard shortcut

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 which got me back here
 to the terminal server.

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 What is that keyboard shortcut
 I'm using to go back and forth?

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 So this is a common Cisco
 keyboard shortcut.

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 It is Control Shift 6.

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 So on my keyboard, I'm hitting all
 three keys at the same time.

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 Control Shift 6, all at the same
 time, I let go and I hit X.

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 Control Shift 6, let go and hit
 X within like a second or less.

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 So here I am in session three.

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 Control Shift 6, let go, hit X.

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 And it gets me back there.

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 Very useful to know.

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 All right, so building up my topology
 here, I know I now have to connect

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 these physical interfaces here.

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 Well, for example, let's take
 a look at switch one.

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 Here's switch one.

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 That's the one here on the bottom.


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 And my laptop is over here.

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 So I'm going to have
 to connect here.

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 And so my first choice I have to make
 is what interface do I want to select

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 on switch one? I could select any interface,
 but to me, I want to select

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 an interface I can
 easily remember.

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 If I just randomly plug this into interface,
 you know, 13 or 21 or something,

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 by the time I get done cabling this whole
 thing, I'm not going to remember

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 that stuff. So just to make it simple,
 I'm going to plug it into interface

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 number one. So I'll
 write that up here.

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 And the switch interfaces are numbered
 as zero slash and a number.

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 So this will be zero slash one.

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 And then I'll use the last interface
 to connect one switch to another.

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 So I'll do zero slash
 24 to zero slash 24.

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 So that'll help me remember the first
 interface goes to the laptop.

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 Last interface connects the
 switch to another switch.

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 And I'll repeat it right
 here on switch two.

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 I'll use his first interface to connect
 to the router and router one,

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 which is this top guy right here.

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 If I zoom in on this, it'll
 kind of blur out.

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 Well, no, maybe we can see it.

0:13:41.280000 --> 0:13:44.820000
 I don't know if you can see that, but
 here's the two ethernet interfaces

0:13:44.820000 --> 0:13:52.620000
 that it has. These
 are the two ethers.

0:13:52.620000 --> 0:13:55.000000
 So I can select one of these.

0:13:55.000000 --> 0:13:58.720000
 One is labeled fast, ethernet
 zero slash zero.

0:13:58.720000 --> 0:14:02.260000
 The other is zero slash one.

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 So why don't I do this?

0:14:04.360000 --> 0:14:06.860000
 Since all over here, I've already
 got zero slash one.

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 Why don't I keep it consistent and have
 it go into zero slash one right

0:14:10.600000 --> 0:14:14.920000
 here as well? So let me go now.

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 Okay, so I know what
 interfaces I want.

0:14:18.260000 --> 0:14:21.540000
 And I know, let me
 go back to this.

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 Make this a little bit larger
 so you can see it.

0:14:25.980000 --> 0:14:29.900000
 There we go. And I know that now I'm
 going to have to choose an ethernet

0:14:29.900000 --> 0:14:32.280000
 cable. I got a black one.

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 I got a red one.

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 I got a pink one and I got a
 big orange one right there.

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 So which one is appropriate?

0:14:38.800000 --> 0:14:42.880000
 What makes them different other than
 their color or are they different?

0:14:42.880000 --> 0:14:43.880000
 They are different.

0:14:43.880000 --> 0:14:45.660000
 Here's something else
 you need to know.

0:14:45.660000 --> 0:14:51.260000
 If I was to hold up these RJ45 jacks
 in front of my face real closely,

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 I would see in this where is it?

0:14:57.960000 --> 0:15:04.900000
 This one. There we go.

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 We would see that inside the RJ45
 jacket has these colored cables.

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 Now it might not necessarily be brown
 and green and blue like this, but

0:15:12.660000 --> 0:15:20.820000
 each individual wire is wrapped in a
 colored plastic or rubber coating.

0:15:20.820000 --> 0:15:30.200000
 And why this is important is because
 some of my cables, for example, I

0:15:30.200000 --> 0:15:33.160000
 just make this a little bit
 bigger, look like this.

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 I don't know if you can tell that, but
 if you can look at this here, you

0:15:38.940000 --> 0:15:45.680000
 can see that, for example, wire number
 two, which is right here, is sort

0:15:45.680000 --> 0:15:47.780000
 of an orange-ish brown color.

0:15:47.780000 --> 0:15:53.040000
 And at the other end of the cable, also
 wire number two is the same color.

0:15:53.040000 --> 0:15:56.320000
 It looks like right here that wire
 number, I can't really read it very

0:15:56.320000 --> 0:15:59.920000
 easily, but it looks like maybe
 wire number six is green.

0:15:59.920000 --> 0:16:03.580000
 And over here, wire
 number six is green.

0:16:03.580000 --> 0:16:10.080000
 So if I take my cables, for example,
 this one right here, and if I held

0:16:10.080000 --> 0:16:14.440000
 it up and I looked at the colors, I
 would see that the colors and the

0:16:14.440000 --> 0:16:18.940000
 order of the colors from left to right
 on this connector is exactly the

0:16:18.940000 --> 0:16:21.240000
 same as this connector.

0:16:21.240000 --> 0:16:24.700000
 I call that a straight
-through cable.

0:16:24.700000 --> 0:16:29.460000
 As opposed to or as compared to, if I
 take a look at this red cable right

0:16:29.460000 --> 0:16:33.220000
 here and I do the same thing, I hold
 the connectors up and I take a look

0:16:33.220000 --> 0:16:38.440000
 at that, that one is going
 to look like this.

0:16:38.440000 --> 0:16:39.620000
 Notice the difference here.

0:16:39.620000 --> 0:16:46.200000
 In this particular case, wire number
 one on one side, which is green and

0:16:46.200000 --> 0:16:51.140000
 white, goes to wire number
 three on the other side.

0:16:51.140000 --> 0:16:55.140000
 And wire number two, which is just
 a solid green, goes to wire number

0:16:55.140000 --> 0:16:57.660000
 six on the other side.

0:16:57.660000 --> 0:17:03.180000
 We call this, as it says,
 a crossover cable.

0:17:03.180000 --> 0:17:11.480000
 And a crossover cable, one on one side
 goes to three on the other, two

0:17:11.480000 --> 0:17:15.520000
 on one side goes to
 six on the other.

0:17:15.520000 --> 0:17:19.440000
 For example, look at
 this one right here.

0:17:19.440000 --> 0:17:23.200000
 Wire number two, which is sort of an
 orange-ish brown color, goes to wire

0:17:23.200000 --> 0:17:25.980000
 number six right here.

0:17:25.980000 --> 0:17:28.380000
 Two to six, one to three.

0:17:28.380000 --> 0:17:30.580000
 So that's a crossover cable.

0:17:30.580000 --> 0:17:36.360000
 So you can see that even though they
 look the same, once I actually look

0:17:36.360000 --> 0:17:38.820000
 at the wiring on the inside,
 they're not the same.

0:17:38.820000 --> 0:17:42.420000
 Some are straight through,
 some are crossover.

0:17:42.420000 --> 0:17:49.020000
 What does that have to
 do with my picture?

0:17:49.020000 --> 0:17:53.220000
 When you are connecting devices that
 are similar to each other, like a

0:17:53.220000 --> 0:17:58.020000
 switch to a switch, or if I was connecting
 an ethernet cable from one

0:17:58.020000 --> 0:17:59.860000
 router to another router.

0:17:59.860000 --> 0:18:02.020000
 So devices are similar.

0:18:02.020000 --> 0:18:05.020000
 That requires a crossover cable.

0:18:05.020000 --> 0:18:07.320000
 So I'll put that right here.

0:18:07.320000 --> 0:18:10.020000
 So I'm going to need
 a crossover for this.

0:18:10.020000 --> 0:18:15.380000
 When you're connecting devices that
 are dissimilar, that are unlike, we

0:18:15.380000 --> 0:18:17.340000
 use a straight through cable.

0:18:17.340000 --> 0:18:23.480000
 So most of my connections here are going
 to be straight through cables.

0:18:23.480000 --> 0:18:30.240000
 So this will be straight through
 this down here, switch to router.

0:18:30.240000 --> 0:18:34.480000
 It will be straight through
 serial cables.

0:18:34.480000 --> 0:18:35.600000
 You don't have to
 worry about that.

0:18:35.600000 --> 0:18:39.420000
 That this crossover in ethernet
 is only an ethernet.

0:18:39.420000 --> 0:18:42.820000
 Crossover in straight through
 is only an ethernet thing.

0:18:42.820000 --> 0:18:45.560000
 It does not apply to other
 types of cables.

0:18:45.560000 --> 0:18:48.700000
 Router to switch, those are different
 types of devices, so that will be

0:18:48.700000 --> 0:18:50.140000
 a straight through.

0:18:50.140000 --> 0:18:52.280000
 And once again, switch to router.

0:18:52.280000 --> 0:18:54.140000
 That will be a straight through.

0:18:54.140000 --> 0:19:01.800000
 All right, so let me connect up building
 number one here for a second.

0:19:01.800000 --> 0:19:07.100000
 So my laptop, I'm going to need a fairly
 long, straight through ethernet

0:19:07.100000 --> 0:19:14.100000
 cable. And I think this pink one
 right here will do it for me.

0:19:14.100000 --> 0:19:16.540000
 It's fairly long.

0:19:16.540000 --> 0:19:19.420000
 And of course, if I was doing this
 in a real network, I'd want to make

0:19:19.420000 --> 0:19:23.780000
 this nice and pretty and organized
 and use zip ties and cable ties and

0:19:23.780000 --> 0:19:26.680000
 everything, but I'm just doing
 this from scratch here.

0:19:26.680000 --> 0:19:28.200000
 So I'm just going to look at this.


0:19:28.200000 --> 0:19:32.440000
 The lighting in this room isn't the
 best, but I'm pretty sure of that

0:19:32.440000 --> 0:19:35.500000
 looking at the ends of this, this
 is a straight through cable.

0:19:35.500000 --> 0:19:41.460000
 So I'm going to connect one end of
 it to the RG45 jack on my laptop.

0:19:41.460000 --> 0:19:47.700000
 There we go. And connect the other end
 of it to a quarter of my diagram

0:19:47.700000 --> 0:19:50.480000
 port zero slash one
 and switch one.

0:19:50.480000 --> 0:19:53.660000
 All right, there we go.

0:19:53.660000 --> 0:19:56.820000
 Okay, so it is connected in.

0:19:56.820000 --> 0:20:05.640000
 Now what I'm doing here is my next step
 is usually a switch port, a port

0:20:05.640000 --> 0:20:08.380000
 on a switch, when you plug in a cable and
 that cable is plugged into something

0:20:08.380000 --> 0:20:12.240000
 else, instantly comes up and you should
 start seeing some lights flashing

0:20:12.240000 --> 0:20:13.320000
 on that interface.

0:20:13.320000 --> 0:20:15.400000
 And I'm not seeing that.

0:20:15.400000 --> 0:20:18.560000
 And I know I did this test yesterday
 and the lights did flash.

0:20:18.560000 --> 0:20:21.200000
 So I'm pretty sure this
 cable is messed up.

0:20:21.200000 --> 0:20:23.900000
 So let's just get rid of this
 cable and use a different one.

0:20:23.900000 --> 0:20:27.820000
 If I get the same type of behavior with
 a different cable where there's

0:20:27.820000 --> 0:20:32.320000
 no lights on my laptop and there's
 no lights on the switch interface,

0:20:32.320000 --> 0:20:36.560000
 then I'll have to do some additional
 troubleshooting.

0:20:36.560000 --> 0:20:37.880000
 So let's see here.

0:20:37.880000 --> 0:20:39.960000
 I got a nice big orange
 cable here.

0:20:39.960000 --> 0:20:44.460000
 I'm pretty sure this is a
 straight through cable.

0:20:44.460000 --> 0:20:53.000000
 So let's go ahead and try using this
 guy and see if I get better results.

0:20:53.000000 --> 0:21:00.800000
 And in reality, you know, your switch
 probably is located 20, 50, 100

0:21:00.800000 --> 0:21:03.260000
 feet away from your laptops.

0:21:03.260000 --> 0:21:07.560000
 Just depends on where the laptop is located,
 where's the cube in relationship

0:21:07.560000 --> 0:21:10.360000
 to where it is located.

0:21:10.360000 --> 0:21:14.960000
 So you probably will have to have quite
 a long cable to connect them.

0:21:14.960000 --> 0:21:23.160000
 All right. So I am still
 not getting anything.

0:21:23.160000 --> 0:21:25.180000
 So now troubleshooting.

0:21:25.180000 --> 0:21:28.900000
 Highly unlikely that
 both cables are bad.

0:21:28.900000 --> 0:21:32.860000
 So the next thing that would go through
 my mind is, well, either my Ethernet

0:21:32.860000 --> 0:21:34.880000
 net card has been disabled.

0:21:34.880000 --> 0:21:36.940000
 I don't think I did that.

0:21:36.940000 --> 0:21:40.860000
 Or the interface on
 the switch is down.

0:21:40.860000 --> 0:21:42.200000
 It's not working right now.

0:21:42.200000 --> 0:21:46.120000
 So let me use my terminal server and
 get into the command line of switch

0:21:46.120000 --> 0:21:48.760000
 number one and take a look.

0:21:48.760000 --> 0:21:54.980000
 And by the way, some Cisco routers and
 switches have interfaces that can

0:21:54.980000 --> 0:21:57.940000
 auto detect the cable.

0:21:57.940000 --> 0:22:01.420000
 In other words, you know, some switches,
 if I had two switches together

0:22:01.420000 --> 0:22:04.460000
 and I connected to straight through
 cable, nothing would happen.

0:22:04.460000 --> 0:22:05.600000
 It just wouldn't work.

0:22:05.600000 --> 0:22:07.780000
 But if they have these types of interfaces,
 and I think they're called

0:22:07.780000 --> 0:22:14.100000
 MDIX, I'm not sure what that stands for,
 Mary David Igloo X-ray, but MDIX

0:22:14.100000 --> 0:22:17.580000
 is an ability to auto
 detect the cable type.

0:22:17.580000 --> 0:22:21.020000
 So whether you have a straight through
 or a crossover, it'll automatically

0:22:21.020000 --> 0:22:23.360000
 detect that and account for it.

0:22:23.360000 --> 0:22:25.360000
 I don't think these interfaces
 do that though.

0:22:25.360000 --> 0:22:29.280000
 MDIX stands for medium dependent
 interface crossover.