Imagine you live in a very large apartment building with several dozen self-contained housing units. Even though the apartment building has its own address, you can’t really use the address alone to receive mail because the mail carrier wouldn’t know which apartment should get it. What you really need is the address of the apartment building in combination with the number of your apartment.
Private IP addresses are sort of like apartment numbers. They allow multiple internet-connected devices to share a single IP address (just like multiple people can live in the same apartment building) and thus address the shortage of IPv4 address.
There are three ranges of private IP addresses:
As you can see, the 192.168.0.0 IP address belongs to the 16-bit block of private IP addresses, along with 65,535 other private IP addresses.
In practice, private IP addresses work something like this:
A router with a public IP address sends and receives data to and from the internet. The router then uses a private IP address for communication with devices in the local network, which are also assigned private IP addresses. That’s how it’s possible for many devices to share a single public IP address.
Private IP addresses have become especially important with the emergence of the Internet of Things. When you use a network analyzer such as NetSpot visualize, manage, troubleshoot, audit, plan, and deploy wireless networks, you can expect to see anywhere from a few to several dozen wireless networks. In reality, each network you find likely contains many different internet-connected devices that all share the same public IP address.
All public IP addresses are completely unique. That means that each public IP address is directly assigned to just one device. If that device is a router, it becomes possible for other devices to become part of the same private network and connected to the internet via the same public IP address, but that doesn’t change the fact that each public IP address is directly assigned to just one device.
With private IP addresses, things are slightly different. Because there can be an infinite number of private networks, there can also be an infinite number of devices with the same private IP address. However, multiple devices on the same private network can’t share a single private IP address.
We’ve already established that the 16-bit block of private IP addresses contains 65,536 different private IP addresses. It’s important to specify that the number of available private IP addresses within a single block also depends on the network mask chosen. For example:
The number following the IP address is the abbreviation for the subnet mask, and the number of ones in the subnet mask when expressed in the binary notation is equal to the number of the abbreviation. For example, the /16 subnet would have 16 ones in a row, and the rest of the numbers being zeros: 11111111.11111111.00000000.00000000, which equals to 255.255.0.0 when converted from binary into decimal.
If all this sounds somewhat confusing, don’t worry. The good news is that your router handles all of this automatically so there’s absolutely no reason to learn how to convert binary numbers into decimal numbers — unless, of course, you want to.
IPv6 is the most recent version of the Internet Protocol, and it contains 340,282, 366,920,938,463,463,374,607,431,768,211,456 addresses. Researchers estimate that there are approximately 7 * 1027 atoms in the human body, which means that there are 4.86 * 1010 IPv6 address for every atom in the human body. How come there are so many IPv6 addresses? Because IPv6 uses a 128-bit address.
Theoretically, it should be possible for every single internet-connected device to get its own public IPv6 address. But just because every single internet-connected device can get its own public IPv6 address doesn’t make private IP addresses obsolete.
There are many reasons why someone might want to use a private IP address instead of a public one, and it goes without saying that the Internet Engineering Task Force (IETF), which is responsible for the development of IPv6, understands this.
There’s, for example, fc00::/7, which is reserved for local use (and you can think of it as an alternative to spaces like 220.127.116.11/16). To learn more about private IPv6 addresses, we recommend you visit this page, which explains the anatomy of a private IPv6 address in much more detail than we could possibly do here.
192.168.0.0 is a private IPv4 address belonging to the 16-bit block of private IP addresses. Without private IP addresses such as 192.168.0.0, it wouldn’t be possible for 25 billion devices to connect to the internet because the fourth version of the Internet Protocol uses 32-bit addresses, limiting the address space to 4,294,967,296 addresses.
When you visualize wireless networks using a network analyzer, there’s a strong chance that more than one wireless network will use the 192.168.0.0 IP address to make it possible for multiple devices to connect to the internet using a single public IP address.