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‫Up to now, all the networks that we mentioned were assumed to be a public network and all of the IP

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‫addresses were public IP addresses, right?

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‫In the internet, addressing architecture, a private network is a network that uses private IP address

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‫space.

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‫Wait, wait, wait.

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‫I'll try to explain an unknown with another one.

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‫But first, I should explain what the private IP address space is.

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‫Tell you what?

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‫Let's take a break here, and I'll talk about the special use IP addresses, including the private IP

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‫address space.

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‫So the authorities, IETF and AIA, Anna, please don't ask you can Google it if you really want to

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‫know who they are.

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‫But they've restricted from general use various reserved IP addresses for special purposes.

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‫So that means you cannot use any IP address in these reserved blocks as the public IP addresses of your

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‫devices.

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‫So here we have some of these reserve blocks.

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‫Now, these are the most important blocks for us to know, because pretty much anybody who's not familiar

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‫with the networking concept gets confused about the difference between public and private IP addresses.

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‫So these IP blocks are reserved for private networks.

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‫They're commonly used for home office and enterprise, local area networks or land.

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‫Private IP address spaces were originally defined in an effort to delay IPv4 address exhaustion, but

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‫they're also a feature of IPv6, where exhaustion is not an issue.

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‫Bear with me.

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‫Packets addresses in these ranges are not readable in the public internet because they are ignored by

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‫all public routers.

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‫Therefore, private hosts cannot directly communicate with public networks but require network address

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‫translation or NAT at a routing gateway for this purpose.

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‫But no worries.

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‫We'll talk about that coming up next.

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‫So without getting too deep, the only thing about the loopback is that 127.0.0.1 is the most common

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‫IPv4 address, which is mapped to the local host.

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‫So let me give you an example.

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‫The IP address of your host machine is one seven two one six nine nine two two two, and a web application

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‫is served in your host.

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‫Now in that machine, you can use a web address.

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‫H h p colon slash slash 127.0.0.1.

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‫To access the web app, as well as a call and slash one seven two eight one six nine nine two two two

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‫both IP addresses going to the same machine, which is your host.

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‫Generally, an IP address, it starts with one, six nine means that your computer wasn't able to obtain

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‫an IP address from your server.

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‫Usually that means that your router is wedged and needs to be rebooted or that your Wi-Fi isn't working

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‫at all.

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‫So now let's have a look at the private IP address blocks closely.

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‫As I mentioned a few minutes ago, a private network is a network that uses private IP address space.

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‫Administrators of private networks can assign networks and subnet from the above ranges if an administrator

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‫decides to use the IP range one nine two one six eight zero zero slash 16 and then decide you have a

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‫single sub network, assigning 255 down to 55 dot 0.0 as a subnet mask.

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‫Then he or she will have a subnet where a max of 65000 536 devices.

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‫Makes sense.