Hi my name is she had from teach ethics.
Welcome you all to Cisco five's race course in this video.
We will cover the topic of what we call a network address translation or net by the end of this video.
You will be able to understand what exactly is net and why we need it and how to deploy it and also
what are the different deployment modes of Net.
So let's start as the name implies network address translation means you translate private IP addresses
to public IP addresses to use on the Internet.
As we all know in our private networks we use private IP addresses which actually not routing all anywhere.
You cannot use those private IP addresses to browse the internet.
So we need to translate those private IP addresses to public ip addresses legal IP addresses who assigned
this IP addresses your ISP your Internet service provider.
OK.
So it's as simple as this translate private IP addresses to public IP addresses to be used on the Internet.
Let's review quickly what are the private IP addresses you use internally on your network on the 10
subnet 10 0 0 0 0 2 10 2 5 5 2 5 5 5 5 172 16 0 0 2 1 7 2 31 2 5 5 5 5 and 1 92 168 0 0 2 1 9 3 2 1
6 2 8 2 5 5.
The last one is the most commonly used private IP addresses used in a new local land.
The last one most of the local lands use this range actually.
OK so as we sit here you go.
You have here this Walter which is what we call a natural Tower or the translator.
It translates the private addresses in your local land to public IP addresses to be used on the Internet.
OK so private eyepiece are converted into public eyepiece right.
And again who assigned those IP addresses.
Your local ISP let's move to the next slide.
How networks.
Here you go.
You have here and that's routing or a firewall in between the inside which is the local land and the
outside which is the Internet this firewall or net router translates the inside private IP is to the
outside it maintains a table which we call a net table this net table actually saves the inside local
IP addresses to the global IP addresses.
So for example if your local IP address is standard 0 0 1 it will be mapped to a public IP address of
2 1 2 0 9 1 6 5 0 1 10 which is the public IP address that can be used on the OK.
So there is a table here that the natural order or that is a firewall.
As we'll discuss right later consider this as an ace a firewall it's considered a net dropped it or
a net translator it translates private IP from the inside to a public IP on the outside.
OK
so here is the table inside.
We call it inside local.
And here in on this side we call inside global OK.
Don't be confused.
This is the outside but this is the actually naming scheme of Cisco this interface ip is called Inside
looking.
This interface which is connected to the outside world is called Inside global.
OK.
Yes this is an outside zone.
But the name is inside global which is this IP address of this interface.
OK.
This is the naming acronym of Cisco inside look an inside look.
OK let's move forward.
What are the different types of net or net deployment moves.
Net has three types.
Static dynamic dynamic port translation.
Let's see each type of those nets static nets means you map one private IP to one public IP which means
if you have one static ip of 10 to zero the 10 to one this one this one it will be mapped to one equivalent
outside or global IP if you have another private IP and the one between the two.
It will be mapped to another IP address.
So mainly each private IP address is mapped to a unique public IP address.
OK dynamic net which is the second type this type of net.
Multiple multiple private IP addresses are maps to a pool of public IP addresses which means you have
here your inside IP addresses okay
you map the inside to approve appointments arrange like for example if you have an inside range from
10 to 1 to the 10 until 10 to 20 to 27.
This range is mapped to a pool of global IP addresses.
For example here from 2 0 9 1 6 5 2 or 1 to 3 until 2 0 9 1 6 5 2 1 to 10.
So 7 global IP public addresses.
OK so there is a point here.
The ISP assigns you a point of public addresses to your local network.
So what does that mean.
If you have 10 private IP addresses they wouldn't be mapped to attend public global IP addresses OK.
All right.
So remember static net means 1 to 1 permanent mapping one private to public OK.
So if you have 100 Internet users you will need 100 global addresses.
This is not actually very practical here or possible because public IP addresses are actually limited
okay.
So say you have 1000 Internet users you cannot you can't actually like get from your ISP 1000 public
IP addresses.
It's impractical because public IP addresses are actually limited.
They are actually finished they are already IP V4 or vision for already finished we use now IP v 6 version
6.
So that is the limitation of the dynamic net that if you have too many internal private IP addresses
you cannot assign actually one global IP address for each internal private IP.
So what is the solution for this.
Here you go let's sort of see the static nothing.
You just go to the previous slide here which is the third type of off the net which is dynamic Perth
at this transformation or pat to solve the problem of actually having too many private IP addresses
Cisco or also many of the vendors most of them invented this type of network address demonstration which
is me which is called Pat or Perth address translation if you have to do many private IP addresses and
the ISP cannot assign too many global IP addresses for you.
What is the solution here.
The solution here is to use Perth numbers which means if you have 10 okay say 20 private IP addresses
and ISP can only assign to you.
Five global IP addresses.
What's the solution.
How you how you will work how you connect to the Internet.
The solution is to assign a unique Perth number for the public IP addresses to be used to distinguish
between the original private IP address.
So here the port number serves the problem of the private IP addresses are more or have more numbers
than the public IP addresses.
So here you go static nothing.
1 to 1 translation
OK so static nothing.
1 to 1 translation one private one public.
Here is that one private IP translated to 1 public.
Very easy.
You can check on this link if you need more information next.
The dynamic assigns a range of IP addresses from the inside say from 1 to 2 to 1 to 10 to a poll of
a public IP addresses which is safe from this range two hundred the one to two hundred nine okay.
So arrange of inside or private IP addresses mapped to a pool of public or outside IP addresses.
What is the advantage of this.
This adventure is if the mapped pool has fewer addresses than the rain group.
If this public IP is are less than the inside private IP you will have a problem.
You will need a solution.
What is the solution to use this solution.
The PAC or the network address translation you release.
You will use here a number as you can see.
Here is the inside.
It is the outside and in between he is the ace.
If I run over the Net server as you can see some IP address in the inside but different port number
they translate also to the same public IP but different port number
Okay so the port number here is the solution.
Twenty twenty twenty twenty one twenty Twenty twenty twenty one two the same I be private so the same
private IP address translated to the same public IP but with a different port number so path number
here is the solution.
OK so go.
Why do we need to spread.
Because the Internet internal private IP is are more than the assigned public IP addresses.
What is the advantage of using the dynamic at actually to reserve or concerns the public ip addresses
because public IP V4 are limited so dynamic part or dynamic port.
Understand summation is the most common method of conserving IP address space so you can have hundreds
of internal hosts sharing one public IP address but of course with a different port number no okay that's
also with you in the next view.
We will cover the topic of configuring Cisco as a firearm as a net server.
Thank you very much for watching and see you on the next video.