NAT, Non-Routable Address Space and the Limits of IPv4

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The Bits and Bytes of Computer Networking

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Google

The Bits and Bytes of Computer Networking

3037 ratings

Curso 2 de 5 em Specialization Google IT Support Professional Certificate

This course is designed to provide a full overview of computer networking. In this course, we’ll cover everything from the fundamentals of modern networking technologies and protocols to practical applications and network troubleshooting. By the end of this course, you’ll be able to: - describe computer networks in terms of a five-layer model. - understand all of the standard protocols involved with TCP/IP communications. - grasp powerful network troubleshooting tools and techniques. - learn network services like DNS and DHCP that help make computer networks run. Except as otherwise noted, the contents on this site are licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

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Networking Services

In the fourth week of this course, we'll explore networking services. We'll learn about why we need DNS and how it works. We'll also show you why DHCP makes network administration a simpler task. By the end of this module, you'll be able to do describe how DNS and DHCP work, how NAT technologies help keep networks secure, and how VPNs and proxies help users connect and stay secured.

Basics of NAT4:14

NAT and the Transport Layer4:15

NAT, Non-Routable Address Space and the Limits of IPv43:44

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The IANA has been in charge of distributing IP addresses since 1988.

Since that time, the internet has expanded at an incredible rate.

The 4.2 billion possible IPv4 addresses have been predicted to run out for

a long time and they almost have.

For some time now, the IANA has primarily been responsible with assigning address

blocks to the five regional internet registries or RIRs.

The five RIRs are AFRINIC, which serves the continent of Africa,

ARIN which serves the United States, Canada and parts of the Caribbean.

APNIC, which is responsible for

most of Asia, Australia and New Zealand and Pacific Island nations.

LACNIC which covers Central and South America and

any parts of the Caribbean not covered by ARIN.

And finally RIPE, which serves Europe, Russia and

the Middle East and portions of Central Asia.

These five RIRs have been responsible for assigning IP address blocks

to organizations within their geographic areas and most have already run out.

The IANA assigned the last unallocated slash eight network blocks

to various RIRs on February 3rd, 2011.

Then in April 2011, APNIC ran out of addresses.

RIPE was next, in September of 2012.

LACNIC ran out of addresses to assign in June 2014.

And ARIN did the same in September 2015.

Only AFNIC has some IPs left, but those are predicted to be depleted by 2018.

Wikipedia has a great article all about IPv4 exhaustion and

the timelines involved.

I've added a link to it in the reading just after this video.

This is of course, a major crisis for the internet.

IPv6 will eventually resolve these problems and

we'll covered in more detail later in this course.

But implementing IPv6 worldwide is going to take some time.

For now, we wanted to continue to grow and we want more people and devices

to connect to it but without IP addresses to assign, a workaround is needed.

Spoiler alert, you already know about the major components of this workaround.

NAT and non-routable address space.

Remember that non-routable address space was defined in RFC1918 and

consists of several different IP ranges that anyone can use.

And unlimited number of networks can use non-routable address space internally

because internet routers won't forward traffic to it.

This means there's never any global collision of IP addresses

when people use those address spaces.

Non-routable address space is largely usable today

because of technologies like NAT.

With NAT,

you can have hundreds even thousands of machines using non-routable address space.

Yet, with just a single public IP,

all those computers can still send traffic to and receive traffic from the internet.

All you need is one single IPv4 address and via NAT,

a router with that IP can represent lots and lots of computers behind it.

It's not a perfect solution, but until IPv6 becomes more globally available,

non-routable address space and NAT will have to do

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