WEBVTT

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 In this video, I'm going to introduce
 you to the concept of something

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 that you can configure on multi-layer
 switches called switched virtual

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 interfaces. We're going to look at switched
 virtual interfaces and their

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 usage in two different ways.

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 We're going to look at how you can use
 them in the management plane and

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 how you can use them
 in the data plane.

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 In the event that you're not familiar
 with these terms of management plane

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 and data plane, I'm going to draw something
 real quickly here to help

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 identify these concepts.

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 All right, so first of all,
 the management plane.

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 Here is your laptop.

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 You are the network administrator.


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 And let's say that here is a router or
 it could be a switch, any networking

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 device that you want to manage.

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 In other words, you want to get in and
 control the command line interface.

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 So you can configure troubleshoot
 and debug this device.

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 Well, the management plane is
 all of those physical things.

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 For example, your net card, the cable
 connected to your net card, the

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 net card on the router, and the logical
 things such as the software, such

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 as the iOS on the router that responds
 to your incoming management request.

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 So for example, if I was managing this
 router via the console port, well,

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 then the physical things would be my
 serial or USB port on my laptop,

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 the blue sort of flat satin cable that
 they give you, the console port

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 on the router itself, and then the software
 processes within the router

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 or the switch that respond to whatever
 is connected to that console port.

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 All of that would be part
 of the management plane.

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 If we're talking about wanting to manage
 this router or switch, once again,

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 remotely via Telnet, okay, well, then
 the management plane also includes

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 things like what is the Telnet client
 that you're using on your laptop?

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 Are you using putty secure
 CRT hyper terminal?

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 The choice of that application and what
 that application is doing is operating

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 in the management plane because putty
 secure CRT hyper terminal, they're

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 designed to help you manage or control
 a remote device like a router or

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 a switch or a firewall.

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 Similarly, when your Telnet session
 goes across your Ethernet cable and

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 terminates on the router, what is it
 on the router that's terminating

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 or I should say responding
 to that Telnet session?

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 Well, in the router, it would be something
 called a VTY line, right?

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 A VTY line is what terminates
 a Telnet session.

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 You would also need an interface, like
 a fast Ethernet interface or something

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 that has an IP address on it.

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 If this interface here doesn't have
 an IP address, you're telling that

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 packets of no place they can go.

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 So that interface and its IP address
 are part of the management plane.

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 So think of like a geometric plane and
 all as you're trying to get from

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 your laptop to manage a device, all the
 things your data has to go across

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 physically and logically.

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 Software processes included that have
 to handle that data till ultimately,

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 when I guess for its remote destination,
 that is the management plane.

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 Now, the data plane is simply another
 plane, but this is actually the

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 forwarding of data.

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 As data is leaving your laptop and going
 to iene.com or google.com, once

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 again, the data plane is your, well,
 whatever software you're using, like

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 hyper terminal or not hyper terminal,
 like your web browser, Google Chrome,

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 Internet Explorer, Microsoft
 Edge, right?

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 That stuff is not really designed
 to manage network devices.

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 It's designed to create data and then
 send data to a server somewhere.

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 So if that software, that application
 would be part of the data plane,

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 then it goes down to your nip card
 out on the ethernet cable.

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 That's part of the data plane.

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 And then similarly, as that data is going
 along, okay, when it first hits

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 probably a network switch, this physical
 interface where it's coming in,

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 part of the data plane.

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 Now, when that ethernet frame gets
 to the switch, whatever the switch

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 uses to look up that frame to determine,
 what do I do with this thing?

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 Do I forward it?

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 Do I drop it? If I do forward
 it, where does it go?

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 However, it answers that question wherever
 it looks to find the answer

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 to that is part of the data plane.


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 So for example, we might be talking
 about a MAC address table.

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 So the MAC table in the switch is a
 classic example of a table that's

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 used to forward the data to decide
 what to do with this data.

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 The outgoing interface part of the
 data plane, if we get to a router,

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 it's incoming interface.

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 Now, when it looks something up, it's
 going to look it up in the routing

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 table. Okay, well, the routing table
 is also part of the data plane.

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 Without a router, without a routing
 table, this data stops.

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 It can't keep going along the plane
 until it gets to its destination.

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 It has to stop, this router would
 have no idea what to do with it.

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 So those are concepts of management
 plane and data plane.

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 So it all starts with management means I'm
 talking about management information.

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 I'm trying to manage, I'm trying to get
 to the command line or maybe send

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 SNMP or send telnet.

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 Basically, I'm trying to manage a networking
 device and you have to sort

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 of visualize, okay, what all is happening
 in your laptop to make that

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 happen. That's part of the management
 plane and all the processes and

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 physical things until it gets
 to its remote destination.

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 That's part of the
 management plane.

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 Data plane is actual user data, web
 browsing, email, file transfer.

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 That's all considered.

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 So in that case, when data is flowing
 through a router switch.

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 So as data comes into a router switch,
 if that data is not trying to manage

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 the device, if that data is just trying
 to get through that router switch

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 to ultimately get to a server at the remote
 end, then we have to ask ourselves,

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 okay, what are the components, which
 they're facilitating getting that

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 data through, whatever those components
 are, they reside in the data plane.

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 Okay. So that being the case.

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 Let's talk about first of all, what
 this thing called a switched virtual

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 interface is from the perspective
 of the management plane.

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 How can this help us
 manage a switch?

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 Remember, what we're talking about now
 is this, this thing I'm going to

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 talk about, switch virtual interface
 is how do I use it?

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 How can it be a tool for me so I can
 manage the switch so I can get access

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 to the command line of the switch so
 I can maybe ping the switch, tell

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 me it's the switch.

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 How is it helpful for that?

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 Okay. So this circle here
 represents a VLAN.

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 You know, we've talked a little
 bit about VLANs in this series.

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 I'm sure you guys have studied VLANs
 extensively in your own research.

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 And all of these little sort of rectangles
 or boxes here represent layer

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 three devices, devices
 with IP addresses.

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 Let's just stick with IP version four
 for now just to keep it simple.

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 So these are all devices with IP before
 addresses that are in this VLAN.

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 Okay. So if they're in the VLAN, we're
 talking about devices that are

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 hardwired devices have ethernet
 cables running to them.

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 So servers, laptops, PCs,
 you know, maybe phones.

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 Okay. So those are all
 layer three devices.

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 So each device has an IP address.

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 Their networking bits are all the same
 because they're all in the same

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 VLAN. And what is sort
 of keeping them secure?

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 What's sort of enforcing the boundaries
 of the VLAN is the switch that

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 they're connected to.

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 Now, if I am a network administrator,
 so for example, if I'm sitting on

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 this device right here, if that's me,
 my laptop, and I say, well, I'm

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 happy that these switch ports are providing
 me my boundary of my VLAN.

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 I'm happy to know that my laptop is
 only constrained to talking in here,

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 that any broadcast I send will
 only stay in that circle.

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 Great. But I actually want to
 be able to get to the switch.

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 I want to be able to send packets to
 the switch itself so I can tell net

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 to it so I can establish
 an SSH connection to it.

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 I want to send IP packets so
 I can manage the switch.

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 I can get access to its command line
 and configure and troubleshoot it.

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 Well, these interfaces right here are
 layer two switch ports by default,

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 which means they expect
 one of two things.

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 They either expect to be in a single
 VLAN, switch port mode access means

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 they're in one VLAN, like VLAN X, or
 they're expecting to be in multiple

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 VLANs, configured as trunks.

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 Now in this case, I would expect all
 these interfaces to be configured

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 as access to this is.

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 One thing they do not support
 are IP addresses.

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 If I try to go on to a switch's interface
 and put an IP address on that

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 interface like I would do on
 a router, it will not let me.

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 You'll say this is a
 layer two interface.

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 This is not a standalone host in a group
 like this or like this or like

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 this. This interface is just sort of
 facilitating group communication.

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 It's sort of bundled with a bunch of
 other interfaces are in the exact

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 same group in the same VLAN, but it
 does not support an IP address.

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 So that leaves me with
 a perplexing question.

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 How do I ping or tell not to the switch
 if I can't put an IP address on

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 it? Because I need an IP address.

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 It's at the exact same subnet as
 the VLAN that I'm in right now.

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 And the solution to that is, well, we
 take an unused IP address in this

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 VLAN and instead of configuring it right
 on a physical interface, we're

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 going to create a logical interface
 called a switched virtual interface

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 or an SVI. And we're going to put
 our IP address right there.

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 So once again, we're talking about
 management purposes here.

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 So if this as an example, if all this,
 if I had created this circle as

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 VLAN, let's say eight and all these
 interfaces here, we're switch ports

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 in VLAN eight. And all the devices are
 eight dot eight dot eight dot something

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 slash twenty four.

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 That is the subnet that
 I'm using for this VLAN.

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 Then I first have to ask myself, what
 is an unused address in that subnet

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 that's not used currently by
 all these orange devices?

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 Maybe eight dot eight dot eight
 dot twenty slash twenty four.

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 Okay, that's an unused device.

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 I want to put an unused
 IP address.

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 I want to put that IP address on the
 switch somewhere so I can ping it

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 so I can tell that to
 it so I can SSH to it.

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 Can't put on a physical interface.


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 So what I would do is I would go into
 the switch and I would create an

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 interface that didn't exist before, a
 logical switched virtual interface.

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 So from global configuration mode.


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 To create a switch virtual interface,
 all you type is interface VLAN.

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 And remember, what is this interface
 VLAN being used for?

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 It's going to be a place where I stick
 my eight, eight, eight, twenty

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 IP address. Well, for eight dot eight
 dot eight dot twenty to be reachable

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 by all those devices in the circle,
 all those devices in the circle are

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 in VLAN eight. So that IP address I'm
 configuring eight, eight, eight,

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 twenty also has to be reachable
 via VLAN eight.

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 So my switched virtual interface
 would be interface VLAN eight.

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 And then from here, so that's going
 to put me into config dash if mode

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 as if I was in a physical interface, which
 I'm not, I'm in a logical interface,

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 an interface I just made
 up in the software.

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 And from here, I can
 type my IP address.

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 So I have just created a switched
 virtual interface.

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 A lot of people call them interface VLANs
 because that's the way you configure

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 it is by typing interface
 VLAN and then a number.

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 But technically this thing is called
 a switched virtual interface.

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 Now, let me make one big, very important
 point of clarification here.

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 A lot of times people who are just learning
 about this get confused between

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 the difference between a VLAN and
 a switched virtual interface.

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 Okay. So this interface VLAN right here
 has nothing to do with this circle.

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 I shouldn't say has nothing to do with
 the circle, but I mentioned in

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 the previous video and other CCNA videos
 that you may have watched that

0:13:23.140000 --> 0:13:27.340000
 when you decide that you want to group
 a bunch of devices into a single

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 VLAN. First thing you have to ask yourself
 is, okay, what VLAN number

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 am I going to select?

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 I need to select a VLAN number
 that's currently unused.

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 Let's say I said VLAN eight, let's say
 VLAN eight is not used right now.

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 I said, okay, once you've selected your
 VLAN number, working with layer

0:13:44.560000 --> 0:13:47.320000
 two VLANs. So we're talking about working
 with broadcast domains now.

0:13:47.320000 --> 0:13:51.280000
 Nothing to do with layer three with the
 networking layer of the OSI model,

0:13:51.280000 --> 0:13:52.660000
 purely layer two.

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 Working with layer two VLANs,
 I said was a two step process.

0:13:56.100000 --> 0:14:00.960000
 Step number one was you created
 the broadcast domain.

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 In other words, you gave the broadcast
 domain a name VLAN eight.

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 So look at the difference here.

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 On the left, I have just created a broadcast
 domain known as VLAN eight.

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 That's not what I'm
 doing on the right.

0:14:18.020000 --> 0:14:23.700000
 On the right, I'm just putting a layer
 three interface into that existing

0:14:23.700000 --> 0:14:26.560000
 broadcast domain known
 as VLAN eight.

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 This is just a layer three interface
 in that VLAN, the same as all these

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 sort of reddish orange boxes are also
 layer three interfaces in the VLAN.

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 So once I create my VLAN, then I can go
 to my very, my physical interfaces.

0:14:44.900000 --> 0:14:50.720000
 Like interface fast, Ethan, at zero
 one, which puts me in a config dash

0:14:50.720000 --> 0:14:57.520000
 I F mode. And now I can assign that
 interface as one port among many in

0:14:57.520000 --> 0:15:05.040000
 that VLAN. I say switch port mode access,
 which means you are allowed

0:15:05.040000 --> 0:15:06.580000
 to be in one VLAN only.

0:15:06.580000 --> 0:15:10.520000
 Now he's going to assume it's VLAN
 one until I tell him differently.

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 So then I say switch port
 access VLAN eight.

0:15:19.740000 --> 0:15:22.340000
 So those are differences
 right here.

0:15:22.340000 --> 0:15:27.740000
 Here I have created a broadcast
 domain and given it a name.

0:15:27.740000 --> 0:15:35.660000
 Here I have placed a physical
 interface into that group.

0:15:35.660000 --> 0:15:40.840000
 Here I have created a logical interface
 and put it in that group.

0:15:40.840000 --> 0:15:44.700000
 Just simply by telling the logical
 interface the number eight, it puts

0:15:44.700000 --> 0:15:46.980000
 it into this group.

0:15:46.980000 --> 0:15:51.220000
 So here I have just created this.

0:15:51.220000 --> 0:16:01.380000
 Now it used to be on some older switching
 platforms that if you created

0:16:01.380000 --> 0:16:06.380000
 a switched virtual interface, before
 you created the VLAN itself.

0:16:06.380000 --> 0:16:10.860000
 Like let's say I typed in interface
 VLAN eight and enter, but I had not

0:16:10.860000 --> 0:16:14.860000
 yet actually created the broadcast
 domain known as VLAN eight.

0:16:14.860000 --> 0:16:18.720000
 It used to be that the switch virtual
 interface would just stay in the

0:16:18.720000 --> 0:16:22.660000
 downstate. And there's nothing it could
 do because you had created a layer

0:16:22.660000 --> 0:16:26.460000
 three interface for VLAN and the switch
 said, well, I'm not aware of any

0:16:26.460000 --> 0:16:29.180000
 VLAN, whatever. I'm not
 aware of any VLAN eight.

0:16:29.180000 --> 0:16:32.540000
 So this layer three interface, I'm just
 going to have to hold it and pause

0:16:32.540000 --> 0:16:37.080000
 until you tell me that VLAN
 eight actually exists.

0:16:37.080000 --> 0:16:41.020000
 In most switches these days, however,
 if you create a layer three interface,

0:16:41.020000 --> 0:16:46.340000
 for example, like interface VLAN 27,
 but you don't have VLAN 27 itself

0:16:46.340000 --> 0:16:51.220000
 configured yet, the switch will be
 smart enough to say, oh, well, if I

0:16:51.220000 --> 0:16:55.100000
 have an interface VLAN 27, that means
 I need to have a broadcast domain

0:16:55.100000 --> 0:16:56.480000
 known as VLAN 27.

0:16:56.480000 --> 0:17:00.540000
 And since I don't have one,
 I'll create one myself.

0:17:00.540000 --> 0:17:04.360000
 So in most newer switches these days,
 Cisco switches, if you create the

0:17:04.360000 --> 0:17:08.520000
 interface VLAN, it will create the VLAN
 by itself dynamically on the side.

0:17:08.520000 --> 0:17:12.000000
 But but practically speaking,
 that's the wrong order.

0:17:12.000000 --> 0:17:13.800000
 You really don't want to
 do it in that order.

0:17:13.800000 --> 0:17:18.700000
 The correct order is create the layer
 two VLAN first, put all of your

0:17:18.700000 --> 0:17:23.640000
 switch ports into that VLAN that need
 to be in that VLAN, and then create

0:17:23.640000 --> 0:17:26.580000
 your switched virtual interface.

0:17:26.580000 --> 0:17:29.360000
 Now let's go back to that idea of a
 switch virtual interface here for

0:17:29.360000 --> 0:17:33.440000
 just a second. So let's
 say I create that.

0:17:33.440000 --> 0:17:41.520000
 So once again, this, uh, this VLAN
 is VLAN eight, which I have already

0:17:41.520000 --> 0:17:46.460000
 created at the global configuration
 level previously, like that.

0:17:46.460000 --> 0:17:51.040000
 And I've already assigned these interfaces
 here to be part of eight.

0:17:51.040000 --> 0:17:55.800000
 So let's just assume
 that that's all done.

0:17:55.800000 --> 0:18:00.900000
 Now I create interface VLAN eight.


0:18:00.900000 --> 0:18:02.940000
 Put my IP address into that.

0:18:02.940000 --> 0:18:07.860000
 My IP address that is not used
 yet in this particular subnet.

0:18:07.860000 --> 0:18:13.300000
 There we go. Well, this logical interface
 is actually going to come up

0:18:13.300000 --> 0:18:17.660000
 with a layer two MAC address, just
 like a physical interface would.

0:18:17.660000 --> 0:18:20.180000
 Let's you don't have
 to configure it.

0:18:20.180000 --> 0:18:21.840000
 It's going to come up
 with it by itself.

0:18:21.840000 --> 0:18:24.840000
 So let's just say that I'm going to
 put in parentheses here, but let's

0:18:24.840000 --> 0:18:30.900000
 say that it's MAC address was zero two
 one one two two two two three three

0:18:30.900000 --> 0:18:34.700000
 three three. Let's say that it that
 was its layer two MAC address.

0:18:34.700000 --> 0:18:44.960000
 Now when I am right here, so
 let's say that this is me.

0:18:44.960000 --> 0:18:51.300000
 I am the network admin.

0:18:51.300000 --> 0:18:58.200000
 Net admin PC. And I want to
 tell net to this switch.

0:18:58.200000 --> 0:19:01.220000
 Well, now I have an IP address
 I can use to get to it.

0:19:01.220000 --> 0:19:04.180000
 I could tell net to eight
 eight eight twenty.

0:19:04.180000 --> 0:19:09.140000
 Now when I do that, now my PC, let's
 say my PC is eight eight eight dot

0:19:09.140000 --> 0:19:14.160000
 seven. When I tell net to eight eight
 twenty, my laptop's going to say,

0:19:14.160000 --> 0:19:17.960000
 oh, that's in the same broadcast domain
 as me because I am eight eight

0:19:17.960000 --> 0:19:23.260000
 eight. And my subnet mask is slash
 twenty four and the destination I'm

0:19:23.260000 --> 0:19:26.540000
 trying to reach is
 eight eight eight.

0:19:26.540000 --> 0:19:29.140000
 So therefore my device will arp.

0:19:29.140000 --> 0:19:33.700000
 It'll send an ARP request for
 eight eight eight twenty.

0:19:33.700000 --> 0:19:37.760000
 When that ARP request comes in, it's
 coming in on an interface that's

0:19:37.760000 --> 0:19:40.040000
 configured to be in VLAN eight.

0:19:40.040000 --> 0:19:45.680000
 The switch will broadcast that ARP request
 out as well as processing that

0:19:45.680000 --> 0:19:49.860000
 ARP request itself because the switch
 will say, hey, I also have a layer

0:19:49.860000 --> 0:19:51.620000
 three IP address in VLAN eight.

0:19:51.620000 --> 0:19:53.980000
 So maybe this ARP is for me.

0:19:53.980000 --> 0:19:55.580000
 And sure enough it is.

0:19:55.580000 --> 0:19:59.600000
 When the switches CPU unpacks the ARP
 request and looks at it, it will

0:19:59.600000 --> 0:20:03.800000
 realize, oh, somebody's actually arping
 for me at eight eight twenty.

0:20:03.800000 --> 0:20:06.940000
 And because I'm in interface because
 I'm in VLAN eight, I can respond

0:20:06.940000 --> 0:20:10.820000
 to that. And so that interface VLAN
 that switch virtual interface will

0:20:10.820000 --> 0:20:12.360000
 send an ARP reply back.

0:20:12.360000 --> 0:20:17.560000
 And now my laptop, my net admin
 PC will learn the MAC address.

0:20:17.560000 --> 0:20:19.640000
 This associate with that SVI.

0:20:19.640000 --> 0:20:27.400000
 Now, if I had other interfaces on the
 switch and they were in a different

0:20:27.400000 --> 0:20:33.500000
 VLAN, like let's say
 VLAN seventy seven.

0:20:33.500000 --> 0:20:37.480000
 And I want to provide them with an
 IP address on the switch that they

0:20:37.480000 --> 0:20:40.380000
 could use. Let's say there was a
 network administrator over here.

0:20:40.380000 --> 0:20:45.140000
 And I want him to have an IP address
 in his network, which is let's say

0:20:45.140000 --> 0:20:49.300000
 seventy seven dot one two zero.

0:20:49.300000 --> 0:20:52.400000
 Let's say that's their network.

0:20:52.400000 --> 0:20:57.420000
 Then I would need to provide
 an IP address over here.

0:20:57.420000 --> 0:21:00.540000
 And guess what? I would do
 the exact same procedure.

0:21:00.540000 --> 0:21:03.580000
 I've already got an interface
 VLAN eight.

0:21:03.580000 --> 0:21:10.860000
 But that interface VLAN eight is not
 useful for managing the switch unless

0:21:10.860000 --> 0:21:13.140000
 you are in VLAN eight.

0:21:13.140000 --> 0:21:17.180000
 I need an interface
 VLAN seventy seven.

0:21:17.180000 --> 0:21:22.040000
 So I can talk to so that people in VLAN
 seventy seven can manage the switch.

0:21:22.040000 --> 0:21:27.220000
 So that is the concept of creating and
 using a switch virtual interface

0:21:27.220000 --> 0:21:30.600000
 for the management plane
 for management purposes.

0:21:30.600000 --> 0:21:33.880000
 Now a lot of times at the CCNA level,
 that's how they first introduced

0:21:33.880000 --> 0:21:38.560000
 this concept of a switched virtual
 interface also called an interface

0:21:38.560000 --> 0:21:43.920000
 VLAN. They say, look, and a lot of times
 the way they'll do it is they'll

0:21:43.920000 --> 0:21:45.800000
 just focus on VLAN one.

0:21:45.800000 --> 0:21:51.720000
 They'll say, hey, because actually
 VLAN one contains a switch virtual

0:21:51.720000 --> 0:21:53.500000
 interface already by default.

0:21:53.500000 --> 0:21:55.180000
 You don't have to create it.

0:21:55.180000 --> 0:21:58.880000
 So if you go into any switch, any brand
 new Cisco switch, turn on and

0:21:58.880000 --> 0:22:00.320000
 you do a show run.

0:22:00.320000 --> 0:22:04.000000
 You'll see that you have an interface
 VLAN one that already exists.

0:22:04.000000 --> 0:22:07.100000
 Now that interface VLAN one does
 not have an IP address on it.

0:22:07.100000 --> 0:22:09.560000
 So you have to put the
 IP address on there.

0:22:09.560000 --> 0:22:12.660000
 And then a lot of CCNA materials will
 say, look, just put an interface,

0:22:12.660000 --> 0:22:16.440000
 put an IP address on
 interface VLAN one.

0:22:16.440000 --> 0:22:20.000000
 Interface VLAN one.

0:22:20.000000 --> 0:22:22.140000
 Put an IP address on that.

0:22:22.140000 --> 0:22:27.960000
 That's appropriate with two that's similar
 to all the other IP addresses

0:22:27.960000 --> 0:22:30.020000
 you have of hosts in VLAN one.

0:22:30.020000 --> 0:22:33.280000
 So let's say in VLAN one,
 all my hosts are 1.1.1.

0:22:33.280000 --> 0:22:39.800000
 Something. I'll give
 this guy 1.1.1.20.

0:22:39.800000 --> 0:22:44.840000
 Do a no shutdown because this
 is a layer three interface.

0:22:44.840000 --> 0:22:47.700000
 You see layer two interfaces connect,
 you know, switch ports.

0:22:47.700000 --> 0:22:49.580000
 Those are up by default.

0:22:49.580000 --> 0:22:52.300000
 Layer three interfaces are not
 necessarily up by default.

0:22:52.300000 --> 0:22:54.080000
 So you have to do a no shutdown.

0:22:54.080000 --> 0:22:57.380000
 So now you've got a switch virtual interface
 that you can use to manage

0:22:57.380000 --> 0:23:03.680000
 the switch. Well, that's true if your
 network administrators are in VLAN

0:23:03.680000 --> 0:23:07.840000
 one. What if your network administrator's
 PC is in VLAN eight?

0:23:07.840000 --> 0:23:11.540000
 If your network administrator is in
 VLAN eight, he or she can't reach

0:23:11.540000 --> 0:23:13.100000
 that IP address.

0:23:13.100000 --> 0:23:17.740000
 Because that IP address is only reachable
 within the broadcast domain

0:23:17.740000 --> 0:23:19.300000
 known as VLAN one.

0:23:19.300000 --> 0:23:22.900000
 So I would have to create
 another interface VLAN.

0:23:22.900000 --> 0:23:28.340000
 Put another IP address on it that's
 suitable for VLAN eight.

0:23:28.340000 --> 0:23:34.220000
 Make sure I do no
 shutdown on that.

0:23:34.220000 --> 0:23:39.680000
 And now anybody in that broadcast domain
 can reach the switch via this

0:23:39.680000 --> 0:23:45.920000
 IP address. So that is using a switch virtual
 interface purely for management

0:23:45.920000 --> 0:23:50.780000
 purposes. Just so I have something
 I can ping or tell not to or SSH on

0:23:50.780000 --> 0:23:54.420000
 the switch. But this video
 series is not about that.

0:23:54.420000 --> 0:23:57.800000
 This video series is about
 inter VLAN routing.

0:23:57.800000 --> 0:24:01.940000
 And this exact same concept of a switch
 virtual interface can be used

0:24:01.940000 --> 0:24:04.080000
 for that as well.

0:24:04.080000 --> 0:24:07.080000
 Let's take a look at that.

0:24:07.080000 --> 0:24:13.300000
 So previously you learned that back
 in the old days when all switches

0:24:13.300000 --> 0:24:16.540000
 could do were look at MAC addresses
 and compared against a MAC address

0:24:16.540000 --> 0:24:20.200000
 table. We're talking about layer two
 switches that in order to do inter

0:24:20.200000 --> 0:24:24.980000
 VLAN routing, you need to have a physical
 router like this circle right

0:24:24.980000 --> 0:24:27.000000
 here. And we talked about that.

0:24:27.000000 --> 0:24:32.220000
 We said that well, you know, you could
 run two, if I have two VLANs, I

0:24:32.220000 --> 0:24:36.280000
 could run two physical cables to the
 router and then put each cable on

0:24:36.280000 --> 0:24:38.220000
 the router into a
 different subnet.

0:24:38.220000 --> 0:24:44.180000
 We said or using the router on a stick
 method, I could just do 802.1Q

0:24:44.180000 --> 0:24:49.280000
 trunking here and then use sub interfaces
 on the router to route back

0:24:49.280000 --> 0:24:51.820000
 and forth between the VLANs.

0:24:51.820000 --> 0:24:57.460000
 But in today's networks, we'll scroll
 down here, most switches today are

0:24:57.460000 --> 0:25:00.440000
 capable of routing as
 well as switching.

0:25:00.440000 --> 0:25:02.740000
 Not all of them, but most of them.


0:25:02.740000 --> 0:25:06.940000
 So here's where we can reuse this concept
 of a switch virtual interface

0:25:06.940000 --> 0:25:09.600000
 for routing purposes.

0:25:09.600000 --> 0:25:14.280000
 All right, so let's go back to
 management for just a second.

0:25:14.280000 --> 0:25:18.600000
 Let's say that I wanted to create a
 layer three switch virtual interface

0:25:18.600000 --> 0:25:22.260000
 for VLAN two, so these two people could
 ping it and they could tell not

0:25:22.260000 --> 0:25:25.460000
 to it. All right,
 so let's do that.

0:25:25.460000 --> 0:25:29.640000
 I'm going to first create an interface
 VLAN two because actually I already

0:25:29.640000 --> 0:25:32.140000
 have my VLAN two configured here.

0:25:32.140000 --> 0:25:37.900000
 So I would say interface VLAN two,
 put an IP address on there that's a

0:25:37.900000 --> 0:25:41.180000
 auto-vac, host address that's not currently
 allocated to anything else,

0:25:41.180000 --> 0:25:44.340000
 like maybe that one.

0:25:44.340000 --> 0:25:48.020000
 And a subnet mass that's the same as
 all the hosts, don't forget about

0:25:48.020000 --> 0:25:50.480000
 your no shutdown command.

0:25:50.480000 --> 0:25:53.780000
 And then I'm going to create a switch
 virtual interface for VLAN three,

0:25:53.780000 --> 0:25:56.100000
 just like we did previously.

0:25:56.100000 --> 0:26:01.840000
 Interface VLAN three, IP address, let's
 use an unused address in that

0:26:01.840000 --> 0:26:11.320000
 subnet. No shutdown.

0:26:11.320000 --> 0:26:16.780000
 All right, and we also know that these
 two switched virtual interfaces

0:26:16.780000 --> 0:26:21.040000
 are going to dynamically be
 allocated MAC addresses.

0:26:21.040000 --> 0:26:24.520000
 It's not part of my running
 config, but it is there.

0:26:24.520000 --> 0:26:27.400000
 It is viewable with
 another command.

0:26:27.400000 --> 0:26:31.640000
 So let's just say the MAC address here
 was zero, zero, zero, two, and

0:26:31.640000 --> 0:26:36.340000
 then just make it
 a bunch of threes.

0:26:36.340000 --> 0:26:40.060000
 All right, so that's the MAC address
 of that switched virtual interface,

0:26:40.060000 --> 0:26:46.240000
 that SVI, and let's just give
 a MAC address to this one.

0:26:46.240000 --> 0:26:58.240000
 Okay, now with what I've configured
 right here so far, my hosts in VLAN

0:26:58.240000 --> 0:27:08.420000
 two have an IP address on the switch
 that they can use to telnet to, to

0:27:08.420000 --> 0:27:11.420000
 SSH to, to to to to.50.

0:27:11.420000 --> 0:27:15.460000
 My hosts in VLAN three also have an
 IP address on the switch that they

0:27:15.460000 --> 0:27:17.420000
 can use to telnet to.

0:27:17.420000 --> 0:27:25.380000
 Now, if I want to interview land routing,
 two more steps I have to do.

0:27:25.380000 --> 0:27:28.340000
 First step is not on
 the switch at all.

0:27:28.340000 --> 0:27:32.380000
 I have to go to my DHCP server because
 remember these hosts are most likely

0:27:32.380000 --> 0:27:33.840000
 getting their IP addresses
 via DHCP.

0:27:33.840000 --> 0:27:37.660000
 I have to go to that DHCP server and
 I have to configure the server to

0:27:37.660000 --> 0:27:42.540000
 say, hey, when you have a DHCP pool
 for VLAN two, which is the two to

0:27:42.540000 --> 0:27:46.040000
 two network, I need to configure the server
 to allocate the default gateway

0:27:46.040000 --> 0:27:49.260000
 of two to two 50.

0:27:49.260000 --> 0:27:53.900000
 I'm going to give that my SVI's IP
 address as the default gateway.

0:27:53.900000 --> 0:27:55.500000
 Same thing for VLAN three.

0:27:55.500000 --> 0:27:56.460000
 So that's step number one.

0:27:56.460000 --> 0:28:00.560000
 You have to do something so that the
 users in the VLANs learn that their

0:28:00.560000 --> 0:28:04.300000
 default gateways IP address is actually
 what you've configured on your

0:28:04.300000 --> 0:28:06.820000
 switched virtual interfaces.

0:28:06.820000 --> 0:28:09.440000
 And that's not really something you
 do in the switch that you do that

0:28:09.440000 --> 0:28:13.700000
 on the DHCP server, or if any of your
 hosts have static IP addresses,

0:28:13.700000 --> 0:28:15.960000
 you do it right within
 the host itself.

0:28:15.960000 --> 0:28:23.880000
 Second step. You see, when we had a
 router, if I have a router that has

0:28:23.880000 --> 0:28:29.760000
 two interfaces, whether it be two physical
 interfaces or two sub interfaces,

0:28:29.760000 --> 0:28:35.060000
 and let's say it's like this, right
 there, and let's say this is fast

0:28:35.060000 --> 0:28:37.680000
 ethernet zero slash one.

0:28:37.680000 --> 0:28:42.120000
 And up here, we have fast ethernet zero
 slash zero, which is two to two,

0:28:42.120000 --> 0:28:46.400000
 just to say three for
 the sake of argument.

0:28:46.400000 --> 0:28:52.760000
 Without doing anything on our part
 as a network administrator, just by

0:28:52.760000 --> 0:28:56.920000
 putting an IP address on a functional
 interface on a router, that creates

0:28:56.920000 --> 0:29:00.720000
 a connected route in
 the routing table.

0:29:00.720000 --> 0:29:16.580000
 So here we would have two connected
 routes, which means that if a packet

0:29:16.580000 --> 0:29:26.660000
 comes into the router and the destination
 IP address, let's say the packet

0:29:26.660000 --> 0:29:30.280000
 comes in on fast ethernet
 zero zero.

0:29:30.280000 --> 0:29:33.240000
 So the packet was received
 right here.

0:29:33.240000 --> 0:29:40.080000
 And the destination IP address is
 three, three, three, anything.

0:29:40.080000 --> 0:29:41.840000
 It doesn't really
 matter what it is.

0:29:41.840000 --> 0:29:48.300000
 Well, that will match a route
 in our routing table.

0:29:48.300000 --> 0:29:51.120000
 They'll match this one.

0:29:51.120000 --> 0:29:55.440000
 And so now that packing can be routed
 out, this interface right here.

0:29:55.440000 --> 0:30:00.560000
 That's because IP version four
 routing is enabled by default.

0:30:00.560000 --> 0:30:03.320000
 The moment that connected routes are
 put in the routing table, because

0:30:03.320000 --> 0:30:06.620000
 all you did was put an IP address on
 interface, that router can route

0:30:06.620000 --> 0:30:09.580000
 back and forth between
 those interfaces.

0:30:09.580000 --> 0:30:13.200000
 That's not the case with switched
 virtual interfaces.

0:30:13.200000 --> 0:30:19.000000
 When you create switched virtual interfaces,
 yes, you have two logical

0:30:19.000000 --> 0:30:21.940000
 interfaces here that are
 known in software.

0:30:21.940000 --> 0:30:25.880000
 They have two different IP addresses,
 but this switch will not allow you

0:30:25.880000 --> 0:30:27.520000
 to route between them.

0:30:27.520000 --> 0:30:31.640000
 In other words, if a layer three packet
 comes in going to two, two, two,

0:30:31.640000 --> 0:30:37.220000
 50, he can respond, but he can't route
 a packet that came in on VLAN two

0:30:37.220000 --> 0:30:39.540000
 and route it out VLAN three.

0:30:39.540000 --> 0:30:42.700000
 And just the same, he can't route a
 packet that came in on VLAN three

0:30:42.700000 --> 0:30:44.780000
 and route it out on VLAN two.

0:30:44.780000 --> 0:30:50.280000
 Inter-VLAN routing or just IP routing
 in general is not enabled by default.

0:30:50.280000 --> 0:30:52.680000
 So we have to turn it on.

0:30:52.680000 --> 0:30:58.140000
 At the global configuration level,
 we simply type IP routing.

0:30:58.140000 --> 0:31:03.880000
 Just with that one command, we've basically
 turned our switch into a router.

0:31:03.880000 --> 0:31:07.600000
 Now we would see in the routing table
 that we have two connected routes.

0:31:07.600000 --> 0:31:12.360000
 We have a route to the two, two, two
 network that's connected via VLAN

0:31:12.360000 --> 0:31:18.480000
 two and another connected route in
 the three, three, three network via

0:31:18.480000 --> 0:31:24.920000
 VLAN three. And now my switch virtual
 interfaces, if my laptops are pointing

0:31:24.920000 --> 0:31:29.800000
 to those as their default gateways,
 those switch virtual interfaces can

0:31:29.800000 --> 0:31:32.900000
 be used to route packets
 back and forth.

0:31:32.900000 --> 0:31:35.220000
 I don't need an external
 router to do it.

0:31:35.220000 --> 0:31:40.520000
 For every VLAN I've got on here, if
 I've got 200 VLANs, I could create

0:31:40.520000 --> 0:31:45.200000
 200 switched virtual interfaces,
 one per VLAN.

0:31:45.200000 --> 0:31:52.120000
 And once I enable IP routing, I can
 route between all those VLANs and

0:31:52.120000 --> 0:31:56.600000
 switch virtual interfaces.

0:31:56.600000 --> 0:31:58.660000
 So that concludes this
 particular video.

0:31:58.660000 --> 0:32:01.700000
 In the next video, I'm actually going
 to configure this on a switch and

0:32:01.700000 --> 0:32:05.400000
 we'll see how it works and we'll verify
 that it actually can be used for