All language subtitles for 20 - Routing - Practical Routing - Enhancing VLANs-eng

>> I'm so looking forward to this nugget.

And it ties together the concepts of routing
which we just talked about with the concept

of VLANs which we just talked about previously.

So, here's the idea.

VLANs are a layer two features, that's really
low in the OSI model in terms of things.

So, when they separate something at layer two
and the only way that you're going to beat

that is by doing layer one
separation and that would look

like taking those two computers there connect
to that switch and physically plugging them

into different switches and then you could
say, "Okay, see I'm even more separate

than I could be at level-- at layer two
because I'm now-- not even on the same switch.

I'm physically separate, physical separation."

So, layer two separation is, I mean, it's
really separate, it's as low as you can get

without physically separating your devices.

So, your devices when they are put
on different VLANs truly cannot talk.

You know, even if we were to do
something like this and let's say the one

on the left we give him 10.1.1.50
as the IP address,

the one on the right in the right is 10.1.1.51.

Even if they're in the same IP subnet
and now, you can think of that,

you're okay well that's layer three,
that's above the above the VLAN.

Well, it's kind of like layer three,
everything works its way down, right?

Layer three is great as long as
it has a layer two to stand on.

I mean, what's the first thing that happens
when this guy try-- tries to access this guy?

He sends a broadcast, right?

He's saying, "Hello, I'm
trying to reach 10.1.1.51.

ARP, what is your MAC address?"

And the ARP goes nowhere.

It comes out the two red ports and there is no
10.1.1.51 on those red ports so, he is cut off.

Even if we manually could type in the MAC
address of this guy and somehow associate it.

So, this guy wouldn't have the ARP,
the VLANS would still separate it.

It would still say, "No, you cannot go there.

You are not authorized.

This is a layer two separation."

So, we've got these guys
that are saying, "Help us.

We can't talk."

So, the host can't speak
directly even if they need too.

Even if, you know, the one on the right is,
you know, accounting server nine or something

like that the one on the
left is accounting user one.

So they need some kind of layer
three assistant to make it happen.

Enter stage left, [inaudible], the router.

[Laugh] My weird mind, I was trying figure out
a way to have a router come dancing on the scene

and capes and all, it didn't work out.

Now as you saw from the opening slide, I'm going
to show you two different options of routing

between VLANs, this one being the
first using separate interfaces.

Now, I know it may seem kind of
silly but I still remember back

to when I was first learning Cisco when I was
looking at CCNA and all I saw was diagrams

like this to where we'll
they weren't even that nice.

See, they're just kind of like, you
know, in a textbook black and white.

You know, I just saw this
logical view of the network.

And while I was like, okay I kind
of get it like I never really get it

until I started seeing physically.

I'm looking at the rack, I'm tracing cables and
I'm like, oh, oh that's how it's plugged in.

So, I tried to represent what we see in this
logical view with what it actually looks

like physically doing this kind of thing.

So let's look at the physical and
then we'll jump back over there.

Physically, I have a router this is get old
60 just because clip art guy made the guts.

You know the same, same router
we saw previously.

We've got one interface we'll say Fast Ethernet
0/1 plugged in to we'll just say port two.

That's what it looks like, Fa0/1.

Another interface is plugged in to, I'll put
F0/0 is plugged in to I don't know it's looks

like about port 10 or something
like that that's over there.

Now, these ports as you can see from
the logical view are in different VLANs.

So maybe this, this port is a sign to VLAN 10.

And let me switch colors.

This port right here is assigned to VLAN 20.

Now these computers right here, they'll
be assigned to the VLANs as well.

Let's go back, go purple, we'll say this
one right here connected port 12 is assigned

to VLAN 10.

And the computer on the right,
this one-- now don't you love--

I've tried to find that old sputnik
kind of computer that I could.

The computer on the right, he's
going to be in the VLAN 20.

So, these ports right are assigned
to the appropriate VLANs, right?

So, what that means is this guy, if
we are to follow his packet flow,

we would go into this interface we'll say, "Fast
Ethernet 0/-- let me write in the red F0/0."

He'll be assigned an IP address
from this guy's subnet.

So we'll make him 10.1.20.1.

This guy over here, this computer might
be 10.1.20.20 and this is his IP address.

And he has a default gateway,
well what is default gateway be?

10.1.20.1, right?

So, what that saying is, he-- and these
are all /24, so a Class C subnet mask.

So, to get off of his network he's going
to come in here ARP for his default gateway

which is on the same VLAN come in here.

This guy, let's say he's
trying to ping the purple guys.

Let's fill in the purple players.

Purple guy number one is 10.1.10.20.

Let's give him that IP address.

His default gateway is 10.1.10.1 and that's
his port right here 10.1.10.1 is the IP address

we'll assign to this interface.

So, when this guy, when the
guy on the right pings the guy

on the left his packet flow is going to go wooh,
you know, coming in down here, hit this guy,

he's going to look at his routing table and
go, "Oh, great you're right over there."

He's going to come in to this port on the switch
of VLAN and then come out and reach this guy.

By the way, you'll often see
routers that are connected this way.

And actually, the way I'm showing
you right now is very, very uncommon.

It's just kind of to learn the concept.

I'll show you the most common way, coming up.

The commonly called routers that are
connected like this a router on a stick.

I kid you not like a corn dog or something.

You know it's a-- yeah, Google it,
and you type in router on a Stick

and you'll see this exact diagram.

So, from a logical view, this
is kind of what it looks like.

So that's physically, this is what it looks
like from the logical view, two computers,

two different VLANs, router one
interface in each one of those VLANs.

Now what I just did was pause
the recording so I could go in

and label all of the different ports.

Now, forgive me I did-- just
to how I put things in.

The ports physically on this view
I don't reflect the actual orders.

So, this is my computer that's what I'm working
on right now plugged in to Fast Ethernet0/5.

This is my Dell laptop.

I actually have a little tiny laptop
I used to test and play around with.

I've got that plugged in to Fast Ethernet 0/6.

Now I'm already going in but
actually when I paused it I went in

and assigned these guys the correct IP address.

So you can see these guys got 10.1.20.50.

And well, you can't see the laptop but it's
got 10.1.10.50 [inaudible] there we go.

So, it's got the 10.1.10.50 [inaudible]
me and this is this is my laptop.

So, they each have their
default gateway set to 10.1.20.1.

And this guy has his default gateway
set to 10.1.10.1 which is going

to be how we configure this router.

Now this router you can see is
plugged in to Fast Ethernet 0/3 and 4.

So, the first thing I haven't even
done any of this config 'cause I want

to show it all to you on the switch.

All I did was going in and I kind of turned
on the ports 'cause they were all shutdown.

So, let's go in and create first
off the two VLANs on CBT switch.

Let's do a quick show VLAN first.

This is from-- we still have some VLANs hanging
around from the previous Nugget that we did

and that's fine they're not going to causing
any harm there's no ports assigned to them.

So, I'll go VLAN 10 named blue
exit, VLAN 20 named red exit.

Okay, so we've got the two VLANS created
let's go start assigning some ports.

I'm going to go into interface
Fast Ethernet 0/5.

Just to make sure, switch port mode
access that should all be that way but

and I was-- I want to double check.

Then we will do a switch port access VLAN.

And we are in the red so that'll be VLAN 20.

Hit the up arrow and that's
shoot over to Fast Ethernet 0/4.

Yet, there's some other ports that are red

but they're just logical and
not assigned to any thing.

So, you are VLAN 20.

And if you were being thorough
you could do a description

and put router VLAN 20 interface
and so on and so forth.

We don't need to do that though.

So, I exit back out and let's go into interface
Fast Ethernet 0/3 through him on VLAN 10 as well

as Fast Ethernet 0/6 which is the
PC put him on VLAN 10 as well.

Okay, good.

So, let's go back in to a show-- show VLAN.

I saw my VLAN once.

See how these messages are valuable.

VLAN one just went down.

Why? Because there's no active ports left

in VLAN one I just moved all the active
ports out into these other VLANs.

So now I have VLAN blue and VLAN red with
the correct ports assigned that kind of match

that diagram that you see on the screen.

Now I'll do a show IP interface brief.

These are these are the four ports right
here that they're all plugged in to.

So we're kind of seeing in the config
what's reflected there on the diagram.

Okay. Now what?

Now I need to go over to the router.

So I've got the VLANs setup,
everybody is separated even if I wanted

to at this point my happy
computer could not reach

over here 'cause they are not only
different IP subnets but they are

on completely different VLAN,
so they're not talking.

So I'm now going to go to my router
and give this guy the IP Address.

So, on the blue VLAN, he'll be
10.1.10.1 let's add those in there.

On the red VLAN, he will be 10.1.20.1, right?

So this guy is going to kind
a do this, this sort of thing

and then loop back here to communicate with him.

So, that's going to be the
flow of the chain of events.

On the red VLAN, he will be 10.1.1.20.1, right?

So this guy is going to kind
of do this, this sort of thing

and then loop back here to communicate with him.

So, that's going to be the
flow of the chain of events.

So, let me keep those and then
let's jump over the router.

Reach down, move my console cable up.

Sometimes I'm-- sometimes I'm glad there's
no camera to show just how wacky it was set

up this-- 'cause I've got--
I like standing when I teach

but I don't have a standing desk anymore.

So I literally have packing boxes where I
put my keyboard up, my-- like it's funny.

So, and now, I moved over to the router.

So, show IP interface brief.

Now this, we just did the base
config in the last nugget,

so we just I think demonstrate putting an IP
address on there but that's no longer relevant.

So let's go into interface Fast
Ethernet, interface Fast Ethernet 0/0.

And let's give it the IP address
IP 10.1.10.1, 255.255.255.0, enter.

Oh, what am I doing?

IP space address.

So, that's now accurate to meet this.

I'm looking, double checking,
Fast Ethernet 0.0.10.1.1.

We're good.

Good. Let's go into interface Fast Ethernet 0/1.

We'll do IP address 10.1.20.1, right?

Put that in there.

Every-- and then they were both powered up just

from the base configuration
Nugget that we did before.

So, that's good.

Good, good.

So in this one, let me do
a show IP interface brief.

And I see 10.1.10.1.

It's good, looks up 10.1.20.1.

Okay, so let's test it.

I'm going to see if this guy
can actually ping 10.1.20.1.

They should be on the same VLAN.

So, well, let's-- let me bring it up.

Ping 10-- well let me just IP config first.

IP config and you know I want to get this--
let me get that guy out of there, there.

You are disabled.

And just-- and this-- that's
going to cause confusion I think.

So, LAN1 is gone 'cause we
won't know which default gateway

to use since you had two of them.

So, now we just have the LAN2.

Okay. So, we've got 10.1.20.50 so
let's see if we can ping 10.1.20.1.

And look at that, over there.

And then now, great.

I've severed my network connections
I'm getting all these errors.

So, great, where there-- but it's
kind of like, well wait a sec,

prove to me that that's the actual
Cisco router let's telnet there.

10.1.20.1, this-- I'd never even realized a
mistake that-- this a secure Cisco router.

So we're in there, enable Cisco.

So this is indeed the same exact Cisco router.

So, that proves to me now that I can move
from this computer into this interface.

Now, my laptop I can't really
show you 'cause it's right there.

But that I've already configured with this IP
address so let's see if we can ping that far.

Exit out of here and let's do ping
10.1.-- well, first let's ping 10.1.10.1.

That's good.

Okay, what that proves is I'm going out here,
hit in this and then I'm able to reach this side

and that tells me the interface is up.

I haven't really gone too much further but
let's now go the rest of the way 10.1.10.50.

Okay, there we go.

So, we've got 10.1.10.50 which now replies
which tells me, "I'm going through this router,

back out this interface and
then hitting this guy."

Now, we can actually prove
it a little differently.

I can do trace route, trace
rt in the windows world.

Trace route-D, that says,
"Don't try to resolve host."

And otherwise, this command just takes forever

because it's always trying to
figure out what name is that.

It'll look at the IP address you typed in and
trying do what's call the reverse DNS to try

and figure out what host name that is.

Well I do that, it takes too long.

So I'll do trace route 10.1.10.50 which is
saying, "Show me the path to that laptop."

And what this shows is my computer which is
it's this happy computer over on the left.

My computer 10.1.20.50 goes
through the router at 10.1.20.1.

So we're routing now and the
router spits it out here and that's

when it ends up reaching 10.1.50.

Now, a trace route if this
is your first time seeing it,

it actually does three pings for each hop.

That allows you to see if there's
ever a slow link in the chain.

You'll be able to be like, oh,
looks like this one is really slow.

But in this case, it's verified for us the
actual path that we're going through the router.

Now, let's look at option two.

Most people don't use the scenario I just gave
you other than maybe to learn how to route

and things like that because
it's just inefficient.

The more VLANs you have and people have lots of
VLANs you know 10, 20, 30 that kind of thing.

The more VLANs that you have the more interfaces
it's going to end up taking on a router.

And routers honestly don't have
that mini Ethernet interfaces.

Usually routers will have, you
know, a few maybe two, three, four,

five at most, but routers are also expensive.

So the more interface users start adding in
there you just start maxing out the route.

It's just, just inefficient.

In the end, you're eating up
extra switch ports for that.

And I mean, if every single router
connection needs a switch port then--

or every single VLAN needs a switch
port you're eating up just a lot

of your ports just to connect to the router.

So, you probably have been staring
at this picture for a second.

What do we do?

We use a trunk port.

Now, remind me again, scream in out
loud and people think you're crazy.

What VLANs are carried by a trunk port?

And we all scream, "All of them.

All VLANs are carried by a trunk port."

Absolutely.

So if a trunk carries all VLANs then nothing
is to stop us from setting up this router

and connecting it to a trunk port.

So, all the VLANs that's all the blue traffic,
all the red traffic that are needed come

down here to this router and
it's able to do the routing.

Okay. So, what's that mean to me what--
so, let's go back to the scenario.

We have at this computer 10.1.20.50, right?

And then, this computer 10.1.20.50
or wait a second, 10.1.10.50.

Okay, so we have these IP addresses.

So, if that's the case, then I mean, these guys
needed default gateway on their network, right?

One needs 10.1.10.1 the other needs 10.1.20.1.

So now, we're just plugged
into one interface here.

So what IP address do we give that interface?

Well the answer is actually both of them.

Let me introduce to you to
the concept of subinterfaces.

Oh, that's a weird one.

So, here's-- we've got and
we'll say, "Fast Ethernet 0/0?

Now, right now I want to know.

What-- I think yeah this is
definitely Fast Ethernet 0/0.

So physically, a Fast Ethernet 0/0
plugged into the Fast Ethernet 0/2.

That interface is the physical interface
it actually gets nothing assigned to it.

There's no IP address at all.

What we'll do though is create
Fast Ethernet 0/0.10 for VLAN 10.

We'll create Fast Ethernet 0/0.20 for VLAN 20

and then we can give them the IP
addresses 10.1.20.1 gets assigned

to that subinterface 10.1.10.1
gets assigned to that one.

So what are those?

How-- I mean, how did those work?

They are virtual interfaces.

We're going to get use to
this word virtual, right?

They don't really exist but
what it does is accept tags.

Remember, did I say remember?

Remember, the trunk port keeps
the tag on the interface.

So, when this guy says, "I need
to reach my default gateway."

The trunk port will say, "Okay, this is request
from we'll just say client one" and I'm going

to put the tag of VLAN 10 on there.

So when it's received on
here, this router will need

to know okay VLAN 10 tags
all go this subinterface.

So, that one will respond to it.

And this one, you know, it'll come in
and it'll be tagged and we got to go red.

It will be tagged VLAN 20 right there so we
need to configure this subinterface to respond

to those tags for VLAN 20, just try it out.

I still have the same configuration
on there so let's first off empty it

to where it's back the way it
should be for this kind of config.

I'm going to go in to Fast Ethernet 0/1
and do no IP address and shut it down.

We'll not going to need it
anymore because we're going

to just connect Fast Ethernet
0/0 to the trunk port.

Likewise, I'm going back out and go

into interface Fast Ethernet
0/0 and do no IP address.

Because like I said, there's not
going to be anything assigned

to that individual interface
the physical interface.

I'm going to start creating the subinterfaces.

So, let's look at it.

I'll do a show IP interface brief and it feels
like we've taken a step backwards in our config

because now it's like there's nothing there.

Well, before I do the router config,
I'm going to hop down and do the tru--

do the switch because the switch needs to
know that I'm going to set up the port going

to the router as a trunk nor or view, right?

So I'm in CBT switch, I'm looking here
on the diagram this is Fast Ethernet 0/2.

We'll do switch port trunk encapsulation
dot1q turn on 802.1q protocol

and then I'll do a switch port mode trunk.

That's it.

And it-- oh, wait a sec.

Did I write down the wrong port?

I did, that's why CDP is so valuable.

This-- sorry scratch that it
should be Fast Ethernet 0/3.

Great, more practice.

And so, we'll get back in there.

Config T interface Fast Ethernet 0/3.

Switch port trunk and encapsulation.1q.

Switch port mode trunk.

There we go.

That now, we're good.

Okay, so it's saying, "Okay, wait a sec, I'm
resetting that interface, change down back up.

So now it's configured as a trunk port.

And remind me to show you a command
about trunking, just thought of.

I'll show you that in a second.

I can hear you.

I know what you're thinking.

All right.

So I'm sitting on-- I'm sitting on the router.

I'm going to do-- okay, so
here's the subinterface.

I'm going to go into interface
Fast Ethernet 0/0.

And you might be wondering.

Well, I mean how many of these can you create?

How many subinterfaces are supported by CSCO?

There it is.

That was somewhere around
4,294, 967, 000 [inaudible].

I mean it's-- no, no, no, no don't go and create

that many sub interfaces I'm sure
the router would explode before then.

He's just saying, "You have the
flexibility to create a lot of them."

There's no feasible limit to
the number that you can create.

But the nice thing about this is you can use
whatever, you know, normal number you want to.

So, I'm going to come in here and
let me say, "Fast Ethernet 0/0.10.

Now, to make this happen, first off
the subinterface number does not--

does not mean that this now magically
responds to things for VLAN 10.

The subinterface number is just unidentified.

Let me do a show IP interface brief and you
see new magic interface has popped up out

of nowhere this .10 which it doesn't do
anything until I typed in encapsulation dot 1q

and follow it up with what VLAN it responds to.

That's the key.

That's the one that says, "Okay, subinterface
0/0.10 any packets that you see tagged

with the number 10 on it remember 'cause
this is a trunk that's a good thing.

Any thing that you see tagged with
VLAN 10 you will grab, you grab those."

And that's such required command.

So you could and I don't know why you would,
you could make this subinterface number 1,292

and then say encapsulation.1q10
and it would do the same thing.

But why would you do that?

It's just not logical.

So, usually, usually, you will match the
subinterface number to the VLAN number.

Now, let's give it the IP address.

[ Pause ]

Good. Now, let me show you something else.

I'm going to do interface.

Usually, one thing you'll find in Cisco is that
it doesn't really matter what order you typed

to commands in like if I go
in and do a no shut first

and then assign the IP address that's fine.

I could also go in and do the IP
address and then do a no show.

I mean, the order it's not really
order dependent but some commands will.

Like watch this.

I'll do, let me just set the up arrow.

IP address 10.0.20.1, watch what it tells me.

It's like sorry you can't give
this subinterface an IP address

until you tell me what VLAN it belongs to.

And if you think about it make sense that the
router is trying to convey you it's like, "Hey,

I don't know when to use this subinterface."

There's nothing telling me when
this subinterface should jump in

and be like I got you, you
know, and grab the packet so.

So, we have to tell it, "Okay,
okay, sorry about that."

Encapsulation, and so you're going to grab the
packet when it is VLAN 20 and now I hit the

up arrow, takes the IP address
no problem, right?

So, now I can do a show IP interface brief.

That's looking cool.

So we've got now the two sub
interfaces 10.1.10.1 and 10.1.20.1.

Every thing else is the same and now
our computers can do their pings just

with out any problem.

Well, with out any problem.

I actually went in and disable it 'cause I
had to save the last recording and it blew up.

So now, let me flip it back it over.

So now I've got LAN2 we should.

We should have-- we should have--
yep, there we go the IP address.

So, let's if it works.

Ping 10.1.10.1.

Dot 10-- Oh, wait no, or scratch that
10.1.20.1, that's the IP address I'm in.

Destination host, oh, there yo go.

Oh, okay, okay.

Thank you Window 7.

See Window 7, it fix you out like Windows
XP, when you disable and enable an interface

like that, it'll just hang there.

It's like I'm just sitting here and you're
like what's wrong with you Windows and as fell

as I go gamed on like 30 seconds later.

Window 7 is like ha, ha I'm so fast

but really behind the scenes it
takes with the same 30 seconds.

It's just doesn't make it and he sent it away.

So, it just took some time and there we go.

We now have my interface, my interface active.

And now, what I'm doing is I'm
coming in over that trunk port.

Let's do a show interface Fast Ethernet 0/0.10.

That didn't show me too much.

So, well, I guess we'll only see the
statistics on the parent interface.

So I can see-- you know, this guy is not
much but he's receiving some data for these

and now I should be able to
ping through to the other side.

So, the same exact result 10.50, right?

Ping 10.1.10.50, there we go.

Same exact results as before.

However, this one using-- this is truly a router

on a stick this one using the
trunk configuration to do this.

Now, let me mention one more thing.

I'm really debating, adding a third
option in here and I think I'm going to.

I want to mention one more thing and that
is the validity of router on a stick.

You will find a way, if you get in
the real world and some one is like,

"Hey, did-- so I heard you took CCNA?

Did you learn routing through VLANs, you know."

"Like, oh yeah, using the router on the
stick" and they'll be like, wa-ha-ha, nobody,

uses router on a stick blah, blah, blah."

You know it's like they have this thing-- I
will say router on a stick is designed typically

for smaller environments, but
it is used all of the time.

And you know, the reason they say people
don't use it is because it's a bottleneck

and that that is absolutely correct.

Because literally, for this guy to get to
this guy, he's got to go do this little thing.

Da, da, da, da kind of you know,
hopping back and forth that's the--

that word yo-yo effect you get on the, the
router on a stick because you're going out

and back in, in and out and back in.

You're going-- and see that kind of thing.

So, it will slow you down but
I'm telling you for small,

sometimes even maybe mid-sized
business, it works great.

I mean if you can't afford a layer three
switch which is option number three,

there's no replacing a router on a stick.

All right.

So, let me show you-- oh, oh, oh wait,
wait, before I do that before I see--

I almost forgot somebody who reminded me.

I heard him, I wanted to show
you one more command on trunking.

Well it's kind of a nice one.

We've configured a number of
trunk interfaces now, right?

On our CBT switch, there is a
quick command that you can use

to show what interfaces are trunking.

You can do a show interface trunk.

This is handy because I can go in
there and I can say, "Oh well, now,

there are more trunks but they're not active."

I can see Fast Ethernet 0/3 it's on 802.1q
is its encapsulation and it says, "Okay,

VLANs allowed or all of them as it"-- now, we
can restrict it, we can go in and say, "Well,

not that VLAN, not this VLAN, not that."

You know we can trim it down.

But it's saying normally a trunk allows
all VLANs so everything is allowed

and then these are the ones
that are actually active.

So, even though on this example we
only use VLAN 10 and 20 to switch

because it is a trunk is allowing me
to send all these VLANs to the router.

So, all that traffic is going to the router.

Now you might say, "Oh, wait a
second, that doesn't feel efficient.

Can I trim that down?

Can I like-- can I just say VLANs 10 and 20
are allowed to cross that trunk to the router?"

Answer is, "Sure."

Go into interface Fast Ethernet 0/3
and you can do a switch port trunk

and the command is actually allowed.

Do you see that?

Allowed VLANs and you can say,
"I want to allow all of them.

Well, I want to allow a few of
them, add a few of VLANs to them

or I want to remove the current ones.

Now, you've got to be careful because
you might say, "Okay, allowed VLAN 10."

And I won't allow it ''cause it's, you know,
it just says word that's why it hit VLAN 10.

And says, "Okay, what I'm going to do is now
trim that down you can see that kind of takes

down a VLAN one 'cause nothing
else is active there now.

So, I'm going to do a show
interface trunk again.

Now you can see the out port and it
says, "Allowed VLANs are active now."

You've got to be careful here, be very careful.

In production, it's very bad
to just cut off VLANs on a whim

and it's sometimes you'll be
like, "Okay, well I want to do--

okay, I've added 10 let's add 20 now."

I will tell you, everybody
makes that mistake once.

It's like the matrix, right?

Everybody falls the first time Neo.

That can be a painful fall because
what that does is and let me go back,

is notice it just replaced VLAN 10.

So, let me talk to you about
a production environment.

You've got switches, you know, they're doing
their thing with trunking and you've got all

of these hundreds of devices
connected, you know, 50 different VLANs.

You know like oh, I just
need to add VLAN 50 here.

So you go in and type the command that I just
showed you and say, "You know, allowed VLAN 50"

and what happens is all the other 50
VLANs or 20 VLANs or whatever that around

that thing get stripped and
replaced by just to VLAN 50.

If you've got some experience in this field,
and you done that, you know that pain.

That's a complete outage, and that
a few phone calls and that's sent

down in the manager's office saying,
now why did you do that again?

So you got to be careful,
this is a replace command.

So, if you want to use the
switch for trunk-allowed VLAN,

then I will do 10 comma 20 that will do that.

Now, what if you've got a whole bunch of VLANs,
you don't want to retype them all, right?

So what you can do is that-- let
me go back and let's just say,

allowed VLAN 10 so we're
back down to just 10, right?

And so now, I'm going-- let say, I
want to add in 20, so I can do switch

for trunk-allowed VLAN add, you know,
instead of just typing in VLAN I'm saying,

add to the current list of
VLANs that are there VLAN 20.

And that trims it down, and that's pretty cool,
because that allows you to be really efficient

to only send the VLANs towards
the router that belong there.

Now, one of the things that you'll notice
is it says, VLANs allowed, VLANs active,

VLANs forwarding and not pruned only 10 it takes
some time, it takes usually 5 to 10 seconds

for the VLANs to come up once you've
added them in there, maybe 30 seconds.

It just takes time now before the VLANS are
actually added to the trunk, but if I stand here

and there we go, and hit the [inaudible]
enough times it will pop, and pop in there,

so that's the one that I want to show you.

Now, let me talk about option number 3.

I wasn't originally going to show
this, but it's so valuable and it's

so easy that I've just got to do it.

Option number 3 is essentially that.

There is no router, or I guess more
specifically there's no external router.

Option number 3 is what just about every
large network will use and that is setting

up a system of layer three switching.

Now the 3550 happens to be a layer 3 switch,

and what that does is really integrate
routing inside of the switching device.

So instead of needing a router outside here
which you run into environments where you have

to have that, but they actually include routing
capabilities and the way that we do it is

through those VLAN interfaces that we
were setting up way back in the VLANs.

Remember I said, when you create VLAN 10,
you're actually creating the layer two VLAN.

That was the command where we
went in-- we run the switch.

We go into global config and we type in
VLAN 10 that creates the layer two VLAN.

But then I said, okay, but what
if you wanted a routed interface

for that VLAN or a logical interface?

We can do interface VLAN 10, and
that will create an interface

that everybody in VLAN 10 can reach.

Now check this out.

I can give an IP address to that interface
10.1.10.1 the same IP address we were using

for that now that phantom router here as
a default gateway, so here's the concept.

Instead of this guy ARP-ing and finding this
outside router that will do the routing for it.

He will send an ARP and he'll find, you
know, think of it like back here somewhere.

You know, he'll find the router inside of
the switch which responds to the ARP messages

and he goes oh yeah, I'll take care of
you, I'll switch you between the VLANs.

I'll get you off the-- your
VLAN that's no problem.

And so we create that and we go in,

we create interface VLAN 20 give
it the IP address 10.1.20.1,

the same IP address-- wait a second.

I keep flipping those.

The same IP address this guy was using as
his default gateway, so that the other one is

that guy using his default gateway.

So let me show you "oh."

Let me show you.

I'm going to go into global
config mode, so I created VLAN 10.

VLAN 10 has always been there.

Now, I'm going type in Interface VLAN 10, IP
address 10.1.10.1, Interface VLAN-- "ops."

Let me unplug that router which is saying, I've
got that IP address, what are do you doing?

He's gone.

So IP address interface VLAN 20, IP
address 10.1.20.1, 255.255.255.0, okay?

So now we've got, and I'm
wondering why did VLAN 20--

oh, because there's nothing active in VLAN
20, because I disabled my network card.

So let's bring him backup.

We should see VLAN 20 resurrected itself.

So now, let's go back.

And I see that we've got VLAN 10 which
is no-- we've got VLAN 1 as well.

So this guy is like, got arms every direction.

VLAN 1 was what we did when
we put the base configuration.

VLAN 10 took the 1 IP address of the router.

VLAN 20 took the other IP address.

Now that VLAN 20 is going to come up
any second to where that's now active,

but now I'm able to on my computer
and this is something I want to do.

There's VLAN 20 just when active down there.

I'm going to do first often ARP-a.

I want to make sure.

Let just make sure 10.1.20.1.

I don't-- see, here's the problem.

My computer remembers the IP address-- sorry the
IP address to Mac address mapping for 5 minutes.

So I'm going to clear the ARP table.

ARP-D star as a command.

That actually wipes out the whole ARP Table.

So the next time I try to ping, it's going
to make sure I'm checking the Mac address

because previously, that duplicate
Mac address thing alerted me to that.

Previously, this guy had the IP addresses and
he had a different Mac address than the switch.

So if this guy remembers his Mac address he's
not even going to send out the ARP for minutes,

and we're going to not be able to
communicate so, let's jump back there.

So now, I'm going to get on my command prompt

and let's do a ping 10.1.20.1 is the
IP address of the now the switch.

It's not replying which is great.

And I can ping through now, ping.10.1.10.1.

I hope-- actually, you know what?

Probably not going to be able
ping to through, because I have--

this is an annoying thing--
all right there we go.

It's now back in place.

There we go.

As soon as I did that, it's like, now I can.

Now I've only got one-- one interface to
default gateway, so now I'm pinging through.

And you notice that, both of
the IP addresses are own by.

Oop, I forgot that we put a
username on that what was it?

Germany, there we go.

They're owned now by the CBT switch, the
router is out of the picture, in large network.

In, you know what, layer 3 switches
are no longer a out of reach commodity.

The price has come down on them
significantly and recently here so.

This is really starting to take hold
then we're trying to see a lot of layer

through switches all over the place.

That's your option 3.

That's the one that businesses normally use.

The biggest advantage of using
a layer 3 switch is the speed,

because as soon as you get a
layer 3 switch that has the--

man I thought I can do it
right while I'm talking, nope.

Layer 3 switch.

The layers 3 switch that-- or a switch.

Okay, I'm done writing.

Switch as the layer 3 capabilities
will have A6 to support it.

So a layer3 switch will always be faster
than the router because it can actually route

at wider speed, that's the biggest advantage.

In addition to all of the other ones to
where you don't have to have an extra router,

you don't have tie up a [inaudible], you don't
have configure trunk, you don't have bottleneck.

I mean there's just so many
advantages to using a layer 3 switch.

So that is kind of your intense
jump into the water of routing.

We went from what is a router to routing
between VLANs tying together all those concepts.

We saw, using separate interfaces which, not a
recommended method anymore, although it works.

Using sub interfaces by connecting a router
interface to a trunk port and then number 3

by using no router at all,
by using a layer 3 switch,

and using all the internal logical interfaces
inside of there we can move our data,

we can route our data between VLANs.

I hope this has been informative for you,
and I'd like to thank you for viewing.