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.
Whoa, whoa, whoa, whoa, whoa, whoa, 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 Iana, 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 reserved 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 LANs.
Private IP address.
Spaces were originally defined in an effort to delay IPv4 address exhaustion.
But there are also a feature of IPv6 where exhaustion is not an issue.
Bear with me.
Packets.
Addresses in these ranges are not routable 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 Nat 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.
172.16.99.222 and a web application is served in your host.
Now in that machine you can use the web address.
HP Colon slash slash 127.0.0.1 to access the web app as well as Http colon slash slash.
172.16.99.222.
Both IP addresses point to the same machine, which is your host.
Generally an IP address that starts with 169 means that your computer wasn't able to obtain an IP address
from your Dhcp 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 subnets from the above ranges.
If an administrator decides to use the IP range.
192.168.0.0 slash 16 and then decides to have a single subnetwork assigning 255.255.0.0 as a subnet
mask.
Then he or she will have a subnet with a max of 65,536 devices.
Make sense.