So why do we need net or network address translation.
The major reason is IP version 4 address exhaustion.
For years there's been a worry that IP version for addresses would run out and the heavy essentially
run out today is the drive to move to IP version 6 because of IP version for address exhaustion.
However it's probably more than likely that he's still using an IP version for dress and in a lot of
networks today engineers still need to make the move to IP version 6.
One of the reasons for that is because of RAFC 1918 RAFC 1918 was drafted in February 1996.
So in other words it's been around for a long time.
This discusses the address allocation for private internets.
I'm not going to bore you going through the entire document.
But notice in section 3 they talk about private address space.
The Internet assigned numbers of 30 or I honor has reserved the following three blocks of IP address
space for private internets 10.00 at zero up to 10 or 255 255 255.
In other words a 10 slash a Prefect's 172 to a 0.0 up to 1 7 2 3 1 2 5 5 2 5 5.
This is a 1 7 2 door 16 slash 12 Prefect's and then we have 1 1 2 1 6 8 0 2 0 2 1 2 1 6 8 255 255.
This is a 1 9 2 1 6 8 slash 16 Prefect's in my example here.
I'm using a 1 9 2 1 6 8 189 address internally.
What are you using on your PC.
More than likely if you're at home using one of these our provision for addresses in companies as mentioned
such as Apple or HP you may be using a public IP address.
So RAFC 19:18 was drafted to try and conserve IP addresses.
The idea here is that rather than allocating public IP addresses to every device in the Internet devices
within companies could be allocated these addresses and they could be enacted or translated when they
needed to access the Internet with port address translation or pat.
The idea is is that you overloading an IP address hence the term that Cisco uses.
We could have one public IP address used by 500 internal devices.
These are FC 19:18 addresses are non ratable on the Internet.
In other words Internet service providers will block or drop traffic going to or coming from these address
ranges.
Well that's assuming that they've configured they Rajahs correctly but they should have access lists
blocking those addresses so that they non-radical on the Internet.
These are YSI 19:18 addresses are used internally within organizations and hence we have the term private
addresses used within private networks and public addresses used on the global public internet now.
Technically there's nothing stopping private IP addresses from being routed across the Internet.
The reason they non-radical is because ISP are blocking traffic to or from those address ranges.
So the issue is if private IP addresses are non-profitable how do we get on to the Internet.
Well that's way network address translation Knecht comes in that allows us to translate a private IP
address to a public IP address your Internet service provider or ISP will allocate you an IP address
or a range of IP addresses a router.
Another type of device will translate to your internal private IP addresses to that globally readable
public IP address.
Now the terminology that uska use can be confusing and it's something that people often struggle with
Siska use the terms inside a local address inside global address outside local address and outside global
address.