‫Up to now, all the networks that we mentioned were assumed to be a public network and all of the IP
‫addresses were public IP addresses, right?
‫In the internet, addressing architecture, a private network is a network that uses private IP address
‫space.
‫Wait, wait, wait.
‫I'll try to explain an unknown with another one.
‫But first, I should explain what the private IP address space is.
‫Tell you what?
‫Let's take a break here, and I'll talk about the special use IP addresses, including the private IP
‫address space.
‫So the authorities, IETF and AIA, Anna, please don't ask you can Google it if you really want to
‫know who they are.
‫But they've restricted from general use various reserved IP addresses for special purposes.
‫So that means you cannot use any IP address in these reserved blocks as the public IP addresses of your
‫devices.
‫So here we have some of these reserve blocks.
‫Now, these are the most important blocks for us to know, because pretty much anybody who's not familiar
‫with the networking concept gets confused about the difference between public and private IP addresses.
‫So these IP blocks are reserved for private networks.
‫They're commonly used for home office and enterprise, local area networks or land.
‫Private IP address spaces were originally defined in an effort to delay IPv4 address exhaustion, but
‫they're also a feature of IPv6, where exhaustion is not an issue.
‫Bear with me.
‫Packets addresses in these ranges are not readable in the public internet because they are ignored by
‫all public routers.
‫Therefore, private hosts cannot directly communicate with public networks but require network address
‫translation or NAT at a routing gateway for this purpose.
‫But no worries.
‫We'll talk about that coming up next.
‫So without getting too deep, the only thing about the loopback is that 127.0.0.1 is the most common
‫IPv4 address, which is mapped to the local host.
‫So let me give you an example.
‫The IP address of your host machine is one seven two one six nine nine two two two, and a web application
‫is served in your host.
‫Now in that machine, you can use a web address.
‫H h p colon slash slash 127.0.0.1.
‫To access the web app, as well as a call and slash one seven two eight one six nine nine two two two
‫both IP addresses going to the same machine, which is your host.
‫Generally, an IP address, it starts with one, six nine means that your computer wasn't able to obtain
‫an IP address from your server.
‫Usually that means that your router is wedged and needs to be rebooted or that your Wi-Fi isn't working
‫at all.
‫So now let's have a look at the private IP address blocks closely.
‫As I mentioned a few minutes ago, a private network is a network that uses private IP address space.
‫Administrators of private networks can assign networks and subnet from the above ranges if an administrator
‫decides to use the IP range one nine two one six eight zero zero slash 16 and then decide you have a
‫single sub network, assigning 255 down to 55 dot 0.0 as a subnet mask.
‫Then he or she will have a subnet where a max of 65000 536 devices.
‫Makes sense.