IPv4 Public and Private Addresses
In this video from ITFreeTraining I will look at the different types of IPv4 addresses that are available and how they can be used on the internet and inside your company.
Access the video on ITFreeTraining http://itfreetraining.com/ipv4/public-private
Access the rest of the course http://ITFreeTraining.com/ipv4
Download the PDF handout http://ITFreeTraining.com/handouts/ipv4/public-private.pdf
IPv4 Address
0:12 – IPv4 uses a 32bit 4 byte address, which gives over 4 billion addresses. Not all of these are useable and some were originally poorly allocated. When the internet was first created, no one thought that it would take off the way it did and thus some wasteful allocation of IP Addresses occurred. In February 2011 the Internet Assigned Numbers Authority, the organization tasked with allocating IP Addresses, allocated the last free block of IPv4 addresses. Some of these blocks of addresses were allocated to ISPs but have not yet been allocated to customers. Also, there are a number of IP Address space saving technologies that have been developed to help get the most use out of an available IP Address space. For these reasons, IPv4 is not here to stay permanently, however it will certainly be here for quite a while longer. Let’s now have a look at how these addresses are allocated.
Public and Private Addresses
1:13 – The first main split of addresses is public and private. Public addresses are required to access the Internet. Just like a telephone number, it must be unique. Since all public IP Addresses are unique, any router on the internet will route them to where they need to go. To ensure this process is correctly managed, Public IP Addresses are assigned by the Internet Assigned Number Authority and Regional Internet registries. These organizations are responsible for managing the IP Addresses globally and allocating them to regions, ISPs and organizations.
The second split of addresses is private addresses. With these addresses, an administrator is free to assign them as they wish to their own network entirely under their own control. Since there is no central control with these IP Addresses, they are not routable on the Internet. However, a private IP Address can be translated to access the Internet. For example, 100 computers in a company could be allocated private IP Addresses and use the one public IP Address to access the internet. The process from converting the private IP Address to a public IP Address is known as translating, more specifically Network Address Translation (NAT). It is one of the ways that IPv4 has been able to continue to be used when all the IP Addresses have been used. I will now have a closer look at how Public IP Addresses are allocated.
Public IP Addresses
2:42 – As stated, IANA is responsible for allocating public IP Addresses. It does this with blocks. These blocks of IP Addresses are allocated to Regional Internet Registries. The regional internet registry is then free to allocate IP Addresses to ISPs and organizations according to their internal policies. You can see that despite the fact that the IANA has run out of IP Addresses, there still may be free IP Addresses with the Regional Internet Registries and ISPs. The important point to remember is that if you are allocated a public IP Address, it is routable to all other public IP Addresses on the internet. When you connect to an ISP, the ISP will give you a public IP Address that you can use to access all of the public internet. Next, I will have a closer look at the Private IP Addresses.
Private IP Addresses
3:37 – Shown here are the private IP Addresses. An administrator is free to configure these private IP Addresses on their network as they see fit. The point to remember with these IP Addresses is that they are not routable on the internet. If an internet router receives traffic with a destination of a private IP Address, it will simply drop the traffic. There are also some other groups of IP Addresses that you should be aware of.
This description is too long for YouTube. Be sure to check out http://itfreetraining.com/ipv4/public-private for the full explanation.
References
“Installing and Configuring Windows Server 2012 R2 Exam Ref 70-410” pg 201
“IPv4 Address exhaustion” https://en.wikipedia.org/wiki/IPv4_address_exhaustion
“Link-Local address” https://en.wikipedia.org/wiki/Link-local_address
“Regional Internet Registries world map” https://commons.wikimedia.org/wiki/File:Regional_Internet_Registries_world_map.svg#/media/File:Regional_Internet_Registries_world_map.svg
Credits
Trainer: Austin Mason http://ITFreeTraining.com
Voice Talent: HP Lewis http://hplewis.com
Companion Document: Phillip Guld https://philguld.com
Video Production: Kevin Luttman http://www.KevinLuttman.com
Quality Assurance: Brett Batson http://www.pbb-proofreading.uk
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