Poodle, what's that offering you something like a Rouda, you, Terada?
I think it's a survey.
Isurava, what's a server?
A server.
We're going to learn about servers in this video.
What's that over there behind us?
A laptop, a laptop.
Which one do you use?
Oh, I love Kopra.
You use a laptop rather than a server.
Now, in a previous video, which I've linked here and below, I explained a little bit about servers
and clients.
But Poodle, don't you think it'll be better if we practically demonstrate what those are in a network?
And to do that, we're going to use a skip tracer that did this.
OK, let's do that then.
Now, analogies are OK, but it's much better to demonstrate this practically using a tracer.
So let's actually build a network together and I'll show you how clients and servers can work together.
And I'll show you that a client can also become a server.
You could have two laptops, one providing a service to another laptop so the laptop can be a server
in some cases or it can be a client in other cases.
OK, so in packet trace, I'm going to go to end devices and I'm going to select a server.
And added to my apology, I'll select a traditional PC and add it to the topology.
Now, these are symbols or representations of devices physically.
This is a server physically, that's a laptop.
But logically, that's what they look like.
These are once again, just symbols in an application like packet tracer.
In networking, we use network diagrams to explain what a network looks like.
Another example would be here where I'm using an application called Jeunesse three.
So here's a window server and here's a PC.
Notice different symbols for different types of devices.
I could change the symbol if I wanted to.
So in this application, I simply select a change symbol and then I could specify another type of symbol
to represent a device and noticed there are many types of devices shown here.
But as an example, I could say this is a server cluster if it was a cluster of servers.
The point is, is that a symbol is simply a logical representation for a physical device in packets.
So if I click on this server, there's a physical representation of the server and then I could once
again change the symbol or icon used to represent that server.
He has the physical representation of the PC notice Ethernet port right over there.
So, again, this is a logical representation of a device.
Now, these two devices can't communicate with each other.
We either need to communicate using a physical cable or we need to communicate using the air.
So what I'm going to do is select connections and I'll select what's called a cross over cable.
A cross over cable allows two PCs to talk directly to each other.
In the old days, we had to use what was called a cross over cable to allow PC to talk to PC.
Now, today, we don't have to do that.
I'll talk later about or to medics.
This used to be a problem in the old days.
It's not such a problem these days.
Notice the interfaces have gone green, but in pectoris, if I delete that cable and then use just a
standard Ethernet cable.
Notice the interface is down because packets are still expects you to use the right cable.
So once again, I'll delete that cable and I'll select a cross over cable, copper, cross over cable
and connect first Ethernet on the PC to first Ethernet on the server.
So there you go.
I've built a network that's an example of a network.
It's a logical representation of a physical network.
OK, but to allow these two devices to communicate with each other, we need to have two things.
We need to have an Ethernet address or Mac address that's built into network interface codes so a manufacturer
will burn a Mac address onto a network interface card.
You can change Mac addresses, but generally you don't have to.
They are globally unique.
There have been cases where they've been duplicate MAC addresses, but in general that isn't a problem.
Every device has its own Mac address.
So if I look at this PC and go to config, go to first Ethernet zero.
Here is the Mac address of the PC.
You can see your Mac address on a Windows computer as an example by going to control panel.
Network and Internet network and sharing center, have a look at your adapter settings, so as an example,
this Wi-Fi network adapter has this Mac address.
That's its physical address or Mac address.
You'll see something similar on an iPhone or other devices.
Every device that communicates on physical Ethernet or communicates on Wi-Fi is going to have a Mac
address.
We don't have to configure that.
Again, that's configured by default by the manufacturer on the server.
First Ethernet zero, Noticias, the Mac address of the server.
But what I'll do is change that, so I'll change the Mac address.
This is a 12 digit number in hexadecimal and I'll discuss hexadecimal and the details of this later
in the course.
But for the moment, just notice, they are 12 numbers.
They're hexadecimal numbers.
So that's the Mac address now of the server.
On the PC, I'll change the Mac address as well.
And I'll make this a bunch of ones, so triple zero one followed by eight ones.
Now, again, you don't have to change the Mac address.
I'm just doing that to make things simple.
Now, the second thing we need is an IP address.
Typically in networks, a server, which could be a home router, will be allocating IP addresses to
your PCs using a protocol called Dynamic Host Configuration Protocol, or DHP.
So DHS is allocating IP addresses to your PC.
I can see that here by opening up a command prompt.
And if I type IP config, an IP address, in this case, IP version four is configured on my Windows
laptop.
So those Windows laptop has received an IP address automatically from a server or it could be configured
statically.
You can configure IP addresses statically in our little network.
We don't have a router or another type of device, so we have to manually configure the IP addresses.
So on this first PC, I'm going to give it an IP address of 10.1 wandered one.
And a subnet mask of 2.5 to five, five, not too far, 5.0.
Now, don't worry too much about IP addresses for the moment.
Just understand that we've configured a Mac address.
You don't have to do that.
And I've configured an IP address.
You don't have to do that.
If you've got two Windows laptops, they can automatically communicate with one another here because
we're using packet tracer.
I'm configuring the IP addresses manually.
OK, so if I go to desktop and open up a command prompt, I'll make this a bit bigger and top the command
IP config.
What you'll notice is this PC has an IP address.
I'll do something similar on the server.
Let's give the server.
IP address of 10 dot wandered one to two and a subnet mask of two four five to four five two five zero.
So on the PC, now I can use a special application called Ping to verify connectivity to the server.
Ping is basically sending a message saying, Hello, are you there?
And then the servers replying back, Yes, I'm here.
And the PC is saying, Hello, are you there?
And the server replies back, Yes, I'm here.
So basically, it sends the PC sends a message to the server saying, please reply if you're there.
And the server replies back saying, yes, I'm here.
And it's used just to verify that the server is up.
Is it there?
Is it working?
Is it turned on?
So on the PC, I can use the command ping 10 one one.
And as you can see there, we are getting a reply from 10 one, one, two.
The IP addresses this, the servers IP address.
Use the common IP conflict to see it make this bigger is 10 one, one two.
OK, but that doesn't really prove anything except that my PC can ping the server, that I've got IP
connectivity to the server.
I basically send a message to the server saying, are you there?
And the server reply back saying, yes, I'm here.
So this server.
Is there, but that doesn't really help us, what we want to do is have a look at the services running
on the server and notice here are a whole bunch of services.
We've got HTP as an example.
We've got DNS, which is a domain name system, basically allows me to resolve domain names such as
Google dot com or Facebook dot com to an IP address.
We've got other types of services here, like email, FTP and various other services, so on the service
I'm going to leave this is on that's the default on the PC if I close this command prompt down.
And open up a Web browser.
And let bra's using HDP hypertext transfer protocol to the IP address of the server.
What you'll notice is a Web page displays, I can see a small Web page here which says, hello, world.
I can go back.
I can go look at an image page and he has a Cisco logo.
Now, that doesn't really do much, but that's an example of a network.
We've got a client on the left, a server on the right.
The server is configured with the service and it's serving a Web page to the client when the client
requested the Web page.
If I turn the service off so I've turned it off now for HP, but it's on for https is once again just
an encrypted version of.
Hypertext transfer protocol, which is used for web browsing, I'll close this down, open it up again,
try and go to HTP 10.1.
Good one, too.
Now, what will happen?
And it might take it a while, is it time out?
And there you go.
Notice it says request timed out, and that's because the server is no longer listening on Port Portelli.
It's not listening.
So it just basically drops the traffic that you send to it.
So if you send a request saying show me a Web page on Portelli, it just basically drops the request.
Ignores what you what you asking if I go.
However, notice we get to the Web page because the server is listening on Port 443 three now, which
is the port number used for https.
I'll enable HDP once again and let's try and go to the server on Port 80, and that's worked.
So just to prove it, because that wasn't very clear.
I'll open up a Web browser again and manually type HTP 10.1 or one to two and notice the Web page displays.
Now, another great thing about Packet Tresser is we've got the simulation mode.
If I select simulation mode, I can actually see what's going on.
So on the PC and I'll just move this around so we can see what's going on.
I'm going to click go now.
And what you'll notice is a packet has been sent into the network.
Now there's a lot of information here and I'll go through this in more detail when we talk about the
outside model and the TCP IP model.
But what I'd like you to see is we've got a Mac address, which is the Mac address of the PC, sending
traffic to the Mac address of the server.
And we've got an IP address, which is the IP address of the PC going to the IP address of the server
source.
IP address is PC destination IP address is the server Atalay it to here we've got an Ethernet header
source.
Mac addresses the PC destination.
Mac address is the server.
Notice here we've got Port 80, Port 80 once again is the port number that the server is listening on.
If we look at that in more detail and don't get scared by this, this is just an example of the kind
of data that's sent into the network.
Wireshark will show you this in more detail than this, but this gives you an idea of what's going on.
Sauce Mac address is the PC destination, Mac address is the server, we've got sauce, IP address,
PC destination, IP address of the server.
We're using IP version four here.
We also using a protocol called TCP or Transfer Control Protocol that basically just gives us reliability
in a network transmission.
So if you send something to a server and it gets lost, it'll be reset retransmitted.
So it gives us reliability.
Destination port number is 80.
So when we send that into the network that will be sent to the server and the server will receive that.
And then what it will do is send something back to the PC.
So a packet gets sent back from the server to the PC with information, notice the source port for the
reverse traffic from the server to the PC is 80.
Basically the client talks to serve on port and then the server replies back from Port Eighty to a port
number that your client has randomly decided to use.
Now, that's a lot of information, and I'm hoping it's not too overwhelming.
The best thing you can do is install pack a tracer and bold a topology yourself and follow what I'm
doing.
There's no better way to learn than to do things yourself.
One of my favorite analogies is riding a bicycle.
I can talk about riding a bicycle.
I can show you pictures, videos, etc, but until you yourself ride a bicycle, fall off a few times,
struggle a bit, you'll never learn to ride a bicycle.
Best way to learn is to just do it so bold as yourself and try it yourself.