Original subtitles

Okay so I'm going to set this to real time to end this simulation.

Let's run another simulation.

And what I'm going to do on the P.C. is open up a different application.

You can see the web server has displayed the website on that server.

I'll close this down now.

So that was just a built in web server running on that internal server.

What I'll do here is let's start.

Email Let's compose an e-mail.

In this example the only email address used is Peter at Cisco dot com going to our server again you

can see that we're running multiple services on the server.

We've got HDP TFT IP FCP package.

We've got an e-mail server.

The only user account I've configured on the server is Peter.

You could create a different one if you wanted to.

So you could add another user for yourself.

We've got two e-mail services running here simple mail transfer protocol is empty P and pop three pop

three is an older protocol that allows us to retrieve e-mail from an email server is empty.

He allows us to transmit e-mail these protocols use different port numbers.

So let's actually show that practically.

So test e-mail test e-mail

showing port numbers before I click send.

I want to make sure that I'm running simulation mode which I am and now I'll click send S.M. T.P. users

TTP looking at that TTP message inbound Peter you we have our source and destination MAC addresses.

P.S. talking to the server PCI IP address talking to the server ip address.

So layer to layer 3 this is IP version 4.

Again just to recap make sure that you know this stuff at least to the type field indicates that the

protocol at least three is IP version for IP version 6 has a different protocol number.

We know the protocol at layer four because of this number DCP.

So that indicates TTP at leave for destination port number is 25 what is 25 looking at the eye on a

Web site port 25 is simple mail transfer it's empty.

So random port number we femoral port number going to port 25.

So we are sending an email to the server using S.M. T.P. so push that along.

So we've got our TTP what's called the three way handshake that takes place so we have to use what are

called synchronization bits and it has to be an acknowledgement.

I'll talk about that in a separate video but notice here we've got our inbound PDA going to the server

once again source port number destination port number at layer four.

You can see S.M. teepee data.

So we are sending data to the server this will be our actual email going to the server.

And now the server replies back looking at that.

The message to the P.S. notice port 25 talking to the agreed port number of 1027 SMP B data.

Another reason we have the TCB handshake is we have to agree what port numbers we're going to be talking

on.

If you choose a random port number to talk to me how will I know what your random port number is.

You need to tell me that or your ephemeral port number you need to tell me what that is.

Notice also we have sequence numbers and acknowledgements in the messages so that takes place.

And now suddenly we've got some more TTP let's have a look at that TTP message inbound PD you still

using port 25 so a bunch of TTP messages

a run out of space there

for my packet tracer has locked up so I'm going to restart it.

This may happen sometimes with packet tracer.

Now you may encounter problems like this and Packet Tracer.

Just bear with the application it's not perfect but it's well worth the trouble because you'll learn

a lot to using this application case.

I didn't get my email.

Let's try that again someone to send it to Peter at Cisco dot com test to test to send my email now

to retrieve my email.

I'm going to go to simulation mode and I'm going to click retrieve to get my email from the server.

So what have we got.

Share what message is this notice.

This is T C P but the port number is 1 1 0 what is 1 1 0 on the eye on a website.

We can see that this is post office Protocol Version 3 or pop 3.

So this is the protocol used to retrieve the message from the server.

So here's the actual POP 3 message.

Let's have a look at that inbound means it's inbound to the switch.

So it will be the same inbound and outbound on the switch.

Source MAC address is P.C. destination MAC addresses server type is 800 telling us that it's IP version

4 source and destination ip addresses PCI and server protocol use it Layer 4 is TTP we can see that

here.

Source port number used by the PCI is this destination port number is 110.

This is pop 3 data so that will go to the server message goes back to the P.C. we've got some TTP messages

I'll clear my event list it's got a real time and then hopefully on my P.C. what you can see is I've

received my messages Now see here's my original message.

Actually that's been retrieved from the server and here's has my test to message that was received from

the server.

Now I can spend a long time showing you different protocols here as an example you could open up a command

prompt and then open up FCP to the server and log in as Cisco Cisco username Cisco password Cisco and

use the command D.R. to see the files on the server if you ran simulation mode you'd be able to see

those messages to the server.

So spend some time having a look at the different protocols use email use HDP use FCP to see the messages

and the protocols simulation mode in packet traces.

Great to actually see what's going on.

So fantastic way to actually learn the protocols.