WEBVTT

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 So I actually came up with this
 topology here yesterday.

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 It's just a real simple topology to
 use considering the devices I have.

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 So this is what I'm going to do.

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 In the real world, hosts like your laptop,
 your PC, connect to switches.

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 So I'll put a switch right here.

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 And web servers probably connect
 to switches as well.

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 So I'll put a switch right here.

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 And in the real world, I would
 probably have lots of hosts.

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 Let's imagine all these circles are
 hosts connecting into the switch.

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 And I might need more than one.

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 I might have a switch on one floor connecting
 to a switch on another floor.

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 So to try to simulate a real world environment,
 let's just put a second

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 switch here. And then that switch
 is going to connect to a router.

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 And maybe all of this
 is in one building.

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 So we'll just say here,
 building one.

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 So let's just say
 this is my laptop.

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 And we'll call this switch one.

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 We'll call this guy switch two.

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 We'll call this guy router one.

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 And this guy over here
 will be switch three.

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 Now, if this over here was in a different
 building, which it probably

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 is, right? I mean, most likely the location
 of the web server is not in

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 the same building as me.

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 It's probably several states
 or several countries away.

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 Well, then we're going to
 need a router over here.

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 So I'll call this guy router two.

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 And we're going to have some in the real
 world some sort of WAN wide area

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 network. All right.

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 Now, this might be provided as like your
 cable modem or your DSL connection

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 or maybe metro Ethernet.

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 But one building is going to need
 to connect to a service provider.

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 That's your WAN provider.

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 Another building, you know, a few states
 or miles or countries away is

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 going to connect to
 a service provider.

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 And that service provider will
 provide your connections.

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 And that's usually, I'm going to
 use serial connections here.

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 So what is a serial connection?

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 It's just a different
 type of port.

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 For example, if I zoom
 in right here to this.

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 All right. So, what's
 going to happen here?

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 We're going to plug
 a cable into this.

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 And why are we plugging
 a cable into this?

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 Well, because we're going to have electrical
 energy come in and out of

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 that cable, right?

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 The whole idea is when I say that I'm
 sending a packet, an IP packet from

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 my laptop to a server, I'm sending
 a packet to a server.

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 Or from the server to me, what
 is an IP packet fundamentally?

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 It's a bunch of data, right?

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 Well, what is the data?

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 It's energy, right?

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 It's energy that's representing
 what I've typed.

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 It's energy representing a picture
 or a movie or a sound file so that

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 energy has to flow
 across something.

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 If we're talking about electrical energy,
 it's flowing across a cable.

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 So, there are certain protocols
 that say, how do you do that?

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 For example, how do you, you know, when
 the energy is flowing across the

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 cable, who can talk?

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 In other words, can two devices connect
 that cable talk at the same time?

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 Or the rules say that only one person
 can talk and then the other person

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 can talk? The protocol
 dictates that.

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 The protocol dictates how strong
 does energy need to be?

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 All right. Do I need a battery the size
 of a refrigerator to power this

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 cable? Or do I need a tiny
 little battery to do it?

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 Different protocols have
 different rules for that.

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 Some protocols say, okay, once I put
 something on the cable, how far can

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 that energy go so that the device at
 the other end can recognize it as

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 being legitimate data, as opposed to
 just being random electrical garbage

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 that doesn't mean anything?

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 So, Ethernet is one type of a protocol
 that defines that stuff.

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 Ethernet defines, okay, how
 long can the cable be?

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 How many wires should
 be inside of it?

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 What's the energy going to look like
 when it pops in or pops out of this

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 interface to be recognizable
 as data?

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 Now, Ethernet as one example of a protocol
 is used in local area networks.

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 When we're connecting things that are
 fairly close together, like for

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 example in your office or in your building
 or on your floor connecting

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 one computer to another or connecting
 a switch to a router, things are

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 fairly close. So, this is what we call
 a LAN, a local area network interface.

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 But when I want to connect across vast
 distances, for example, if I want

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 to connect my router to my service provider,
 who's a few miles away, they

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 might not support Ethernet.

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 That's where another kind of
 interface comes into play.

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 This is called a serial
 interface right here.

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 And notice, you know, in addition to
 the name being different, Ethernet

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 versus serial, there's some
 tangible differences.

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 You can see the form factor
 is totally different.

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 It's going to use a lot more pins,
 a lot more wires and Ethernet.

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 The cabling is going
 to look different.

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 How it actually deals with electrical
 energy is going to be different

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 than Ethernet. So, just to give some
 variation here in my topology, what

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 I'm going to do is I'm going
 to connect like this.

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 So, let's put my laptop over here.


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 All right, so my laptop has a network
 interface card that supports Ethernet.

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 And that's going to connect to, let's
 just say, port number one on this

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 switch. And then I'm going to take the
 last port here, connect it to the

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 last port of this switch.

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 All right, so that's my laptop going
 to switch one to switch two.

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 Switch two then is going to connect
 to an Ethernet port on my router.

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 So, that's router one.

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 Actually, this router doesn't
 have a serial interface.

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 So, that's not going to work.

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 Hold on just a second there.

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 So, we'll have this.

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 Let me just make that a little bit
 more elegant there so that you can

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 sort of follow the line.

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 So, I have this come along and
 go right there into that.

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 Okay, so this right here, so my laptop,
 switch one, let's say switch one

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 right here, switch two right here,
 and router one right here.

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 That represents all the devices
 in my building number one.

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 And then we're pretending that there's
 a space of miles between router

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 one and router two.

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 So, even though they're actually physically
 located right next to each

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 other, let's just imagine that
 they're separated by miles.

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 And so, I have a serial connection
 connecting them both together.

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 So, we're just imagining that my service
 provider is like in the middle

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 right here. All right, so
 that's router number two.

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 And then he's going to
 connect to a switch.

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 Okay, so right there.

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 And then he's going to connect to this
 other router, which is acting as

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 my web server. Because remember I said
 that Cisco iOS has a web server

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 built into it. So, imagine that instead
 of this being a router, this is

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 actually like a server,
 a web server.

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 So, that's how I'm going to
 connect things together.

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 So, knowing that, this defines now
 how my OctoCable connects out.

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 I'm going to say, all right, well I'm
 going to put OctoCable number one

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 right here. OctoCable
 number two right here.

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 And we'll have number three right here,
 because that all represents building

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 number one. And we'll have OctoConection
 four right there.

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 We'll have OctoConection
 five right there.

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 And then my sixth console connection
 on the OctoCable will be right there.

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 So, let me go ahead and connect
 up my OctoCable to do that.

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 So, right now you can't see me, but I'm
 plugging this into the interfaces

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 of my terminal server.

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 So, I'm plugging that long.

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 So, right now I'm connecting
 this right here.

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 I'm connecting one end of
 that OctoCable to this.

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 I just did that.

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 Hopefully it's nice and tight.

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 And now I'm going to look
 at the other ends.

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 They have RJ45 on them and
 see how they're labeled.

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 All right, let's find number one.

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 Where is number one?

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 All right, so here's number one.

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 So, I'm going to plug that into
 my switch on the bottom.

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 Okay. All right, that's
 plugged in there.

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 Number two, we'll plug
 into another switch.

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 Okay. And my project editor will just edit
 all of the stuff in the recording.

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 So, I'm sure it's boring the
 daylights out of you guys.

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 But, hey, we did say we connect something
 from the ground up, right?

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 So, this is part of that process.

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 And number three, we'll go into
 router one on the top there.

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 All right. So, you see, by designing
 my network, it helps me to connect

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 my OctoCable in a way that's logical,
 that makes sense to me.

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 And number four goes into that router
 who's second from the top.

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 Okay. And then number five goes
 into that switch there.

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 Okay. And, lastly, number six goes
 into the router, which is going to

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 be acting as my terminal server.

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 Right there. All right.

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 That some routers and switches have
 the USB port as like you can have

0:11:58.740000 --> 0:12:03.600000
 a USB key as like an extra security feature
 where even if someone's connected

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 to the console port, if a USB key is
 not plugged in, they can't get access

0:12:07.740000 --> 0:12:09.220000
 to the console port.

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 Other routers and switches, youNeg
 can plug in a USB like memory stick

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 and you could use that as an additional
 memory source for like storing

0:12:14.780000 --> 0:12:17.820000
 Cisco iOS software
 images and stuff.

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 Specifically on this equipment, I'm
 not sure what that USB port is used

0:12:21.920000 --> 0:12:24.680000
 for. Sometimes it's
 not even active.

0:12:24.680000 --> 0:12:28.620000
 Sometimes it's there and it's just not
 turned on by the hardware manufacturer.

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 All right. Great.

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 So, let's go ahead
 and now connect.

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 So, let's go ahead and so right now
 all my console ports are connected.

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 So, I'm going to go ahead
 and go into secure CRT.

0:12:52.940000 --> 0:13:02.020000
 Okay. So, what you're seeing here
 is the Cisco iOS command line.

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 This router has already been pre-configured
 with a name called access

0:13:09.320000 --> 0:13:14.580000
 server. What I just typed
 in right there.

0:13:14.580000 --> 0:13:17.900000
 So, where I'm at right now, so Cisco
 iOS and I'm not going to go into

0:13:17.900000 --> 0:13:22.680000
 a lot of details of this because
 I go into this in my CCNA videos.

0:13:22.680000 --> 0:13:30.320000
 But Cisco iOS has, let's see here, hold
 on, I'm just looking for a certain

0:13:30.320000 --> 0:13:35.120000
 button that I'm looking for here.

0:13:35.120000 --> 0:13:40.900000
 There we go. Cisco iOS has different
 modes or levels of configuration.

0:13:40.900000 --> 0:13:48.040000
 For example, this right here, not that,
 not that, but this right there.

0:13:48.040000 --> 0:13:53.760000
 The fact that you see that says access
 server and then that, the greater

0:13:53.760000 --> 0:13:56.560000
 than sign, tells me
 what mode I'm in.

0:13:56.560000 --> 0:13:59.120000
 That tells me I'm in exec mode.

0:13:59.120000 --> 0:14:01.780000
 And in exec mode, I can't really
 do much of anything.

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 So, I want to get to the next mode
 and I type in the command for that,

0:14:06.980000 --> 0:14:10.020000
 which is enable.

0:14:10.020000 --> 0:14:14.640000
 And now you can see that the sign
 has changed to a hash sign.

0:14:14.640000 --> 0:14:18.140000
 And that tells me I'm in what's
 called privileged exec mode.

0:14:18.140000 --> 0:14:22.520000
 From here, I can actually have access
 to configuring the device, monitoring

0:14:22.520000 --> 0:14:24.900000
 device. I can do a lot more stuff.


0:14:24.900000 --> 0:14:28.740000
 Now, to actually configure it, I need
 to go into another mode, which is

0:14:28.740000 --> 0:14:33.340000
 called configuration mode.

0:14:33.340000 --> 0:14:35.420000
 Configured terminal.

0:14:35.420000 --> 0:14:38.780000
 And that gives me a
 configuration mode.

0:14:38.780000 --> 0:14:42.960000
 Now, if I get out here for a second, if
 I look at the configuration, you'll

0:14:42.960000 --> 0:14:44.820000
 see one of the commands in here.

0:14:44.820000 --> 0:14:52.820000
 Come on. Is the host name
 command right there.

0:14:52.820000 --> 0:14:55.120000
 That's why this thing
 says access server.

0:14:55.120000 --> 0:14:58.220000
 Because before the show started, I got
 in here and I typed in host name

0:14:58.220000 --> 0:15:04.640000
 access-server. Otherwise, by default,
 it would just say router.

0:15:04.640000 --> 0:15:09.440000
 And here's how I've set
 up the octal cable.

0:15:09.440000 --> 0:15:13.440000
 So, nor for this to work, the access
 server, number one, has to have an

0:15:13.440000 --> 0:15:18.080000
 IP address. Now, where did
 I put that IP address?

0:15:18.080000 --> 0:15:20.900000
 Let's go ahead and I'll show
 you a little bit more here.

0:15:20.900000 --> 0:15:29.700000
 Show run. Now, remember that I said
 that any interface on a router or

0:15:29.700000 --> 0:15:32.500000
 switch, let's just talk about
 routers for a moment here.

0:15:32.500000 --> 0:15:33.720000
 So, these routers.

0:15:33.720000 --> 0:15:39.380000
 So, this interface here
 needs an IP address.

0:15:39.380000 --> 0:15:42.360000
 This interface here
 needs an IP address.

0:15:42.360000 --> 0:15:45.740000
 This serial interface
 needs an IP address.

0:15:45.740000 --> 0:15:50.100000
 These interfaces, think
 of it like this way.

0:15:50.100000 --> 0:15:53.920000
 Think of what, let's go right back to postal
 addresses again, home addresses.

0:15:53.920000 --> 0:15:55.320000
 So, think about your
 street, right?

0:15:55.320000 --> 0:15:57.020000
 Your street has a name.

0:15:57.020000 --> 0:15:58.840000
 Let's say Elm Street.

0:15:58.840000 --> 0:16:01.500000
 So, Elm Street would
 be like the network.

0:16:01.500000 --> 0:16:04.380000
 Would you ever send a
 letter to Elm Street?

0:16:04.380000 --> 0:16:07.020000
 No, because you're not going to
 send a letter to the street.

0:16:07.020000 --> 0:16:08.880000
 That's just concrete
 and asphalt, right?

0:16:08.880000 --> 0:16:12.700000
 You're going to send a letter to
 some location on that street.

0:16:12.700000 --> 0:16:15.260000
 So, your house might
 be one Elm Street.

0:16:15.260000 --> 0:16:18.520000
 Your next door neighbor
 might be two Elm Street.

0:16:18.520000 --> 0:16:21.960000
 So, a network has a bunch
 of IP addresses on it.

0:16:21.960000 --> 0:16:25.360000
 All those IP addresses have something
 in common which is like the name

0:16:25.360000 --> 0:16:31.540000
 of the street. So, for example, if this
 is my cable, I might say, okay,

0:16:31.540000 --> 0:16:34.920000
 everybody on this cable is going to
 have an IP address beginning with

0:16:34.920000 --> 0:16:39.060000
 ten. So, PC number one
 here might be ten.

0:16:39.060000 --> 0:16:41.120000
 One. One. One. One.

0:16:41.120000 --> 0:16:43.140000
 PC number two might be ten.

0:16:43.140000 --> 0:16:50.900000
 One. One. Two. But all the devices,
 whether they be PCs or laptops or

0:16:50.900000 --> 0:16:55.420000
 servers, are going to have an IP address
 because they all connect to this

0:16:55.420000 --> 0:16:59.260000
 network. And because they're connecting
 to the same network, what they

0:16:59.260000 --> 0:17:03.280000
 have in common is the name of the network
 which is ten and then a unique

0:17:03.280000 --> 0:17:08.500000
 identifier like one Elm Street, two
 Elm Street, three Elm Street.

0:17:08.500000 --> 0:17:11.720000
 Well, in this particular case,
 Elm Street's coming at the end.

0:17:11.720000 --> 0:17:13.200000
 That's what they all
 have in common.

0:17:13.200000 --> 0:17:16.800000
 And what's unique is their individual
 street addresses on Elm Street.

0:17:16.800000 --> 0:17:20.240000
 Here with IP addresses, the name
 of the street comes first.

0:17:20.240000 --> 0:17:23.620000
 The name of the network comes first
 which in this case is ten and then

0:17:23.620000 --> 0:17:26.180000
 I've got one one two
 which is a laptop.

0:17:26.180000 --> 0:17:28.160000
 One one three which is a laptop.

0:17:28.160000 --> 0:17:35.540000
 So, just like a laptop or a PC is a unique
 entity on a particular network.

0:17:35.540000 --> 0:17:39.220000
 And so it needs to have the address
 of that network and its own unique

0:17:39.220000 --> 0:17:41.120000
 identifier on that network.

0:17:41.120000 --> 0:17:47.020000
 Similarly, on a router, every interface
 on a router is like a unique entity

0:17:47.020000 --> 0:17:49.620000
 on a network. Right?

0:17:49.620000 --> 0:17:54.900000
 For example, when you think
 about your laptop, right?

0:17:54.900000 --> 0:17:56.300000
 Here's my laptop.

0:17:56.300000 --> 0:17:57.600000
 Well, what is your laptop?

0:17:57.600000 --> 0:18:00.200000
 Really, it's a whole bunch of components
 put together, right?

0:18:00.200000 --> 0:18:02.520000
 You've got your monitor
 right there.

0:18:02.520000 --> 0:18:06.000000
 You've got some keyboard
 right here.

0:18:06.000000 --> 0:18:12.700000
 Okay. Well, the IP address, in order
 to give this laptop an IP address,

0:18:12.700000 --> 0:18:14.280000
 you've got to put it somewhere.

0:18:14.280000 --> 0:18:15.900000
 You don't put it on your monitor.

0:18:15.900000 --> 0:18:17.900000
 You don't put it on your keyboard.


0:18:17.900000 --> 0:18:20.020000
 Those things aren't connected
 to the network.

0:18:20.020000 --> 0:18:21.500000
 What is connected to the network?

0:18:21.500000 --> 0:18:25.040000
 Well, you have a special card in your
 laptop called a network interface

0:18:25.040000 --> 0:18:32.400000
 card. A NIC. So if you actually look
 like I can't lift up my laptop right

0:18:32.400000 --> 0:18:35.120000
 now, but if I was able to lift up my
 laptop and show you, you'd see it

0:18:35.120000 --> 0:18:39.960000
 has an RJ45 port in it, just like
 these routers have an RJ45 port.

0:18:39.960000 --> 0:18:44.880000
 That RJ45 port is connected to a network
 interface card, a specific component

0:18:44.880000 --> 0:18:53.400000
 of my laptop. That network interface
 card is what needs the IP address.

0:18:53.400000 --> 0:18:56.080000
 And we'll see as I build up this network,
 I'm going to have to give my

0:18:56.080000 --> 0:18:59.140000
 laptop an IP address so it
 can talk to the network.

0:18:59.140000 --> 0:19:00.440000
 We'll talk about that.

0:19:00.440000 --> 0:19:01.260000
 Well, guess what?

0:19:01.260000 --> 0:19:04.800000
 There's a network interface card
 right here in the router.

0:19:04.800000 --> 0:19:08.600000
 Just like my laptop has a network interface
 card, the router's interface

0:19:08.600000 --> 0:19:10.300000
 has a network interface card.

0:19:10.300000 --> 0:19:15.060000
 Just like my laptop needs an IP address
 because his NIC is a unique host

0:19:15.060000 --> 0:19:20.480000
 on the network. This right here
 is a unique host on the network.

0:19:20.480000 --> 0:19:25.560000
 It just so happens that while a laptop
 just has a single NIC, a router

0:19:25.560000 --> 0:19:30.840000
 can have multiple NICs because it
 connects to multiple networks.

0:19:30.840000 --> 0:19:34.840000
 Your laptop just sits on one
 network like the 10 network.

0:19:34.840000 --> 0:19:39.100000
 Whereas this router, this interface
 might connect to the 10 network.

0:19:39.100000 --> 0:19:41.980000
 This interface might connect
 to the 99 network.

0:19:41.980000 --> 0:19:44.980000
 The serial interface might
 connect to the 200 network.

0:19:44.980000 --> 0:19:48.000000
 So right now this router has the ability
 to connect to three different

0:19:48.000000 --> 0:19:52.220000
 networks. So I'm eventually going to
 have to configure IP addresses on

0:19:52.220000 --> 0:19:54.500000
 these router interfaces.

0:19:54.500000 --> 0:19:57.580000
 What does that have to do down
 here with my terminal server?

0:19:57.580000 --> 0:20:06.920000
 In order to send information out the
 async line to a console port, I have

0:20:06.920000 --> 0:20:13.100000
 to provide a configuration in the router,
 which looks like this, the IP

0:20:13.100000 --> 0:20:18.520000
 host command. And the components of
 the IP host command are like this.

0:20:18.520000 --> 0:20:23.100000
 I should just do this right here.

0:20:23.100000 --> 0:20:30.400000
 Okay, there we go.

0:20:30.400000 --> 0:20:38.480000
 So IP host. And then the next thing right
 here is going to be just a descriptive

0:20:38.480000 --> 0:20:42.020000
 name. Like in my case, I'm going to
 call it switch one switch to, but

0:20:42.020000 --> 0:20:43.200000
 you could call it anything, right?


0:20:43.200000 --> 0:20:46.460000
 You could call it building one router,
 building three router, but you're

0:20:46.460000 --> 0:20:48.560000
 going to have some sort
 of descriptive name.

0:20:48.560000 --> 0:20:56.580000
 Followed by the line number.

0:20:56.580000 --> 0:20:59.120000
 Oops, that's way too high there.

0:20:59.120000 --> 0:21:08.060000
 Line number. Now what
 is that line number?

0:21:08.060000 --> 0:21:11.300000
 Remember when I showed you that octal
 cable, how it was labeled like one,

0:21:11.300000 --> 0:21:14.660000
 two, three, four at the end of each
 one, that's what this line number

0:21:14.660000 --> 0:21:20.240000
 is. So for example, 2001 is terminating
 at octal cable number one.

0:21:20.240000 --> 0:21:22.720000
 2002 is octal cable number two.

0:21:22.720000 --> 0:21:26.580000
 And then lastly, we need to
 provide it an IP address.

0:21:26.580000 --> 0:21:30.300000
 Not going to get into a lot of details
 as to why what you can do is you

0:21:30.300000 --> 0:21:34.480000
 can research. If you want to find out,
 go to Google and type in these

0:21:34.480000 --> 0:21:39.080000
 search terms. Type
 in reverse telnet.

0:21:39.080000 --> 0:21:44.400000
 So reverse like going in reverse, reverse
 telnet octal cable, octal like

0:21:44.400000 --> 0:21:49.300000
 OCTAL. So we're using something called
 reverse telnet here, and reverse

0:21:49.300000 --> 0:21:51.560000
 telnet requires an IP address.

0:21:51.560000 --> 0:21:54.680000
 And that's all I'm going to get in because
 that gets a little bit complicated.

0:21:54.680000 --> 0:21:58.620000
 So this terminal server
 needs an IP address.

0:21:58.620000 --> 0:22:00.780000
 Well, where's it getting it from?

0:22:00.780000 --> 0:22:02.460000
 I could have put it.

0:22:02.460000 --> 0:22:04.640000
 So if I go back to my image here.

0:22:04.640000 --> 0:22:10.800000
 So the terminal server itself, which
 is this guy right here, actually

0:22:10.800000 --> 0:22:13.580000
 has some networking interfaces.

0:22:13.580000 --> 0:22:20.620000
 I could put an IP address on this right
 here, on this right here, or on

0:22:20.620000 --> 0:22:21.180000
 this right here.

0:22:21.180000 --> 0:22:24.100000
 He also can connect to three
 different networks.

0:22:24.100000 --> 0:22:28.500000
 And then I could have referenced that
 IP address as part of my IP host

0:22:28.500000 --> 0:22:33.680000
 command. Instead, I'm putting the IP
 address on what's called a logical

0:22:33.680000 --> 0:22:37.420000
 interface, which is called
 a loopback interface.

0:22:37.420000 --> 0:22:39.460000
 Now right there, that might
 be something new.

0:22:39.460000 --> 0:22:40.560000
 Logical interface.

0:22:40.560000 --> 0:22:41.840000
 What does that mean?

0:22:41.840000 --> 0:22:46.040000
 Up until now, what I've been showing
 you has been physical interfaces.

0:22:46.040000 --> 0:22:49.420000
 In other words, interfaces, you can
 actually plug a cable directly into

0:22:49.420000 --> 0:22:55.320000
 that interface. A logical interface
 is an interface that you just make

0:22:55.320000 --> 0:22:59.780000
 up from scratch that doesn't exist,
 which is just like a placeholder for

0:22:59.780000 --> 0:23:02.700000
 an IP address. Why do
 I want to do that?

0:23:02.700000 --> 0:23:04.140000
 Well, let's think about this.

0:23:04.140000 --> 0:23:12.240000
 Let's say that theoretically, I put an
 IP address on this physical serial

0:23:12.240000 --> 0:23:16.960000
 interface. Maybe that's where
 I put my 100.111 address.

0:23:16.960000 --> 0:23:18.480000
 So that's where it sits.

0:23:18.480000 --> 0:23:25.940000
 100.111, and I can figure it
 on this interface right here.

0:23:25.940000 --> 0:23:29.860000
 Okay. And then I start putting my IP
 host commands, which allows me to

0:23:29.860000 --> 0:23:33.780000
 connect to the console port of this
 router right here, or the console

0:23:33.780000 --> 0:23:37.100000
 port of this one, or the console
 port of this one right here.

0:23:37.100000 --> 0:23:38.680000
 Here's the problem.

0:23:38.680000 --> 0:23:43.320000
 If something happened to this interface,
 if it went down, like if I yanked

0:23:43.320000 --> 0:23:47.200000
 the cable out of this interface or
 I disabled the interface, now those

0:23:47.200000 --> 0:23:49.640000
 IP host commands, they
 wouldn't work.

0:23:49.640000 --> 0:23:53.700000
 I wouldn't be able to use my my Octo
 cable now to get into the console

0:23:53.700000 --> 0:23:58.540000
 ports of the various devices, because
 it needs that IP host command needs

0:23:58.540000 --> 0:24:04.740000
 those IP addresses to be up and functional,
 so the Octo cable will work.

0:24:04.740000 --> 0:24:10.400000
 So if the IP address it's referencing is
 on a physical interface and something

0:24:10.400000 --> 0:24:14.420000
 happens to that physical interface,
 now I've lost my ability to get into

0:24:14.420000 --> 0:24:16.700000
 the console ports of
 my various devices.

0:24:16.700000 --> 0:24:19.280000
 That Octo cable is useless to me.

0:24:19.280000 --> 0:24:26.240000
 But I can create a logical interface, in
 this case called a loopback interface,

0:24:26.240000 --> 0:24:30.260000
 and a loopback interface is
 not dependent on a cable.

0:24:30.260000 --> 0:24:34.380000
 A loopback interface, because I create
 it from scratch, this interface

0:24:34.380000 --> 0:24:38.340000
 will always be up as long as
 my terminal server is up.

0:24:38.340000 --> 0:24:42.380000
 As long as my terminal server is up
 and functional, this loopback will

0:24:42.380000 --> 0:24:45.480000
 be up and functional, and this IP
 address will be up and functional.

0:24:45.480000 --> 0:24:51.440000
 So it's a much more stable IP address
 that I can reference in my IP host

0:24:51.440000 --> 0:24:56.080000
 commands. So now that I've configured
 my IP host commands referencing

0:24:56.080000 --> 0:25:02.460000
 this IP address, how do I actually
 get into the console port of, let's

0:25:02.460000 --> 0:25:06.580000
 say, well, let's start here.

0:25:06.580000 --> 0:25:10.740000
 Let's start with switch one.

0:25:10.740000 --> 0:25:15.060000
 Well, I just called it, I know that
 switch one is connected to my first

0:25:15.060000 --> 0:25:19.780000
 Octo cable, and I've just given it
 a descriptive name of S1, so I just

0:25:19.780000 --> 0:25:26.540000
 type in S1, hit enter, and
 now I'm in the switch.

0:25:26.540000 --> 0:25:31.180000
 I can go back to the terminal server,
 and I can type S2 to get into one

0:25:31.180000 --> 0:25:31.700000
 of the other devices.

0:25:31.700000 --> 0:25:36.040000
 So now, as if having to plug and unplug,
 plug and unplug things into the

0:25:36.040000 --> 0:25:39.540000
 console ports, I can just go back and
 forth between my terminal server

0:25:39.540000 --> 0:25:45.380000
 and getting into those devices by virtue
 of the fact that I configure

0:25:45.380000 --> 0:25:48.600000
 these IP host commands.

0:25:48.600000 --> 0:25:51.420000
 So I'm going to go ahead and stop
 this recording right here.

0:25:51.420000 --> 0:25:55.960000
 So at this point, I have explained what
 a terminal server is, I have explained

0:25:55.960000 --> 0:25:59.820000
 what an Octo cable is and how everything's
 connected in, and I've explained

0:25:59.820000 --> 0:26:05.680000
 the basics of what I need to configure
 on the terminal server to be able

0:26:05.680000 --> 0:26:06.840000
 to use that Octo cable.