Hello and welcome back. Dicey Anyone interconnecting Cisco Network devices. Part one. This is Episode 2 to 3. Mac learning and frame flooding.
I am frightened, everyone. I'm being instructed for this course. Last video went over a little bit How the swish learns the back and a little bit how it avoids broad storms. And,
um, this episode of recovering a little more demonstration based of Mac learning and frame flooding.
So, in the objectives for today, we're gonna look at, you know, CASS and broadcast, freeing, flooding, the Mac address learning on a switch.
We're gonna do a live demo off how the entries get put into the Mac address table.
Quick. Pre assessment for begin. How many dynamic entries are in the Mac address table at the switch? Start up. Give you a few seconds.
All right. It should be 00 dynamic entries.
All right. So, again, house, which learns the mac so
it's get first. It's gonna in the
frame. Comes into the switch from a host. It's gonna look at the
sore sport and see Okay,
I'm gonna put this sore sport in my Mac address table saying
I have an entry for this host number one. I have the Mac address going to this interface. You know,
um and then it's gonna look at it and say, OK, do I have a destination for this? No, I don't have a destination of host to, So I'm gonna flood this frame out every port that
out, every interface that I have, except for the one that it just came in on.
So that unique cast frame the 11 frame is also called unknown. Unique as frame the frame whose destination Mac addresses not known a switch. So it'll actually flood that out. All interfaces, except for that one it came in on.
So broadcast frame is used for two different things you'll see sometimes use AARP, but has the Mac it the destination? Mac, address off.
All right, so we'll get into a quick demonstration here of it.
Go and get the pen out.
I'll say B B wants to send a frame to Hey, hey. Here is gonna come in.
He says, Okay, I'm gonna put your
Mac and here
to f a 01
And then it says, Okay, I don't have a address for a so I'm gonna send it out this address on the Senate out here
and I send it up here
so he's gonna get it up here, but then
states the TCP so he responds because that three way handshake and he's OK. Now I know where a is,
say, f a zero to.
Meanwhile, these ports
are going to say, OK, we now have an entry for B B B because the source
So it's C f A
and he also is going to come in and say Okay, now I have I can populate BBB on here
on f A 0 24 Let's say
those can continue this process until it fills up this Mac table.
one thing you're going to see, though, is how is does it avoid loops?
Uh, I was saying no one has the Mac for CCC yet. Even a switch,
if he comes in for CCC, is gonna go at this port which goes in here, he says, Okay, I don't have one for CCC, so he's gonna flood it out this way
back down here, he says, Okay, I don't have one for CCC back up to here.
Let's hear it Meanwhile, this one
came out here
is gonna be going up this way. So they're just gonna crossing paths like this.
So the way that spanning tree works
is this actually going to take the one of these links here
and completely get rid of it? So
crossing paths like this
So the way that spanning tree works
Is this actually going to take the one of these links here?
It's gonna take this one and draw big extra. It's gonna block that link
this way. When a friend comes in for CCC from over here at de,
it's gonna come in and say, OK, I need to go to sea. Sea, Sea he says, Oh, I can't go out this way is blocked.
So now we're gonna go out here, he's gonna go CCC and down to here.
This way, it stops that loop. And then if he doesn't know where CCC is, he can't send it back this way.
So it'll discarded because it can't go out the same
There's a little bit of STP. I'll show you a live demonstration of STP
in just a moment.
All right, so now we got plenty up here I'm gonna do another
show. Mac. Address table
dynamic will just give you the
So here I have the
I have these ah, switches set up in cereal here. So switch one to switch to to switch three. They're all in line,
so there should be no loops
switch. I'm gonna set up with one device off each one. Someone go ahead and plug in the
host device here and we'll see how long it takes.
So you see the protocol and link going up and up
so it could just do a
So if we look at Port one, we're not connected.
Do a show, Mac. Address table
dynamic. Now we have to switch it or to ports there.
So I'm gonna go ahead and plug in the r two
devices and CR two switches. So one device in the switch to one device in a sweet story
so you won't see the line protocol messages go up because around other switches. Now, if we had the council poor hooked up into the r two switches, you would see down.
We're gonna give it about 15 seconds for them to determine whether it's an access port or a trunk port, and we should see them pop up in the Mac address table here.
All right, so I'm gonna go ahead and hit dynamic. And also remember, you can use the a barrel to go to your previous command.
so now we have the other devices.
both of these devices are here,
so f a 0 24 is the one connecting to the switch to
and switched to connects it to switch three.
So, by default, these these were the only thing I've changed on these switches was changing. Host name.
So these were these cannon
four packets all day long, right out of the box.
So here, what I'm gonna do here is
I'm just gonna show you a quick example of what spanning tree does. So right now we have
the route port.
Don't worry about to roll too much.
I'll just show you how it works. So I'm gonna set up these.
So which is kind of in that triangle that we just saw in the previous example. So I'm gonna go ahead and connect, switch. Want to switch three now and we'll show you
about how long it takes to actually block that port.
So see, here
it's an hour and listening and blocking,
So when I see Andy to now is learning
and again. And I see me too. I'll actually show you
what this all means. What the report is, what the alternate ports are, what the costs are,
um, and how it's actually determined
that actually work. So now it's actually blocked the port 24 support 24
is being blocked. So that way it will stop a loop.
So we have looked at the Mac address table,
and Sean, you well, let me get to beckon to dynamic.
So now we can see the different devices. Um,
So we've seen what happens about how long it takes to pie plate.
We've seen the entries,
all right. So I'm gonna go and take a party out,
and we will continue on. So post assessment here with this Mac address table. Where do you think A frame? What's the destination? Mac for Steve's PC would go
give me a few seconds to think about it here.
All right. If you guessed fast Ethernet 03 you would be correct.
All right, So the next time, so they're gonna be looking at the Mac address table.
Some different ways to use the show commands how to clear it out. The aging timer works.
Look at a few other things.
And as always, if you guys have questions, need some help Shoot me. Message. I'll be glad to help you out. All right. Thank you for watching this video. Look forward to teaching the rest of it. Thank you.