Public IP Addresses: Everything You Need to Know
A public IP address is an IP address that your home or business router receives from your ISP. Public IP addresses are required for any publicly accessible network hardware, like for your home router as well as for the servers that host websites.
Public IP addresses are what differentiate all devices that are plugged into the public internet. Each and every device that's accessing the internet is using a unique IP address. In fact, a public IP address is sometimes called an Internet IP.
It's this address that each Internet Service Provider uses to forward internet requests to a specific home or business, much like how a delivery vehicle uses your physical address to forward packages to your house.
Think of your public IP address as any other address you have. For example, your email address and your home address are both completely unique to you, which is why sending mail to those addresses ensures that they actually get to you and not someone else.
The same exclusivity is applied to your IP address so your digital requests are sent to your network...and not someone else's.
Private vs Public IP Addresses
A private IP address is, in most ways, the same thing as a public IP address. It's a unique identifier for all the devices behind a router or other device that serves out IP addresses.
However, unlike with public IP addresses, the devices in your home can have the exact same private IP addresses as your neighbor's devices, or anyone else's all around the world. This is because private addresses are non-routable — hardware devices on the internet are programmed to prevent devices with a private IP address from communicating directly with any other IP beyond the router that they're connected to.
Because these private addresses are restrained from reaching the internet, you need an address that can reach the rest of the world, which is why a public IP address is needed. This type of setup enables all the devices in your home network to relay information back and forth between your router and ISP using just a single address (a public IP address).
Another way to look at this is to think of the router in your home as your own Internet Service Provider. While your router serves out private IP addresses to the devices privately connected behind your router, your ISP delivers public IP addresses to the devices that are publicly connected to the internet.
Both private and public addresses are used for communication, but the range of that communication is limited based on the address that's used.
When you try opening a website from your computer, the request is sent from your computer to your router as a private IP address, after which your router requests the website from your ISP using the public IP address assigned to your network. Once the request has been made, the operations are reversed — the ISP sends the address of the website to your router, which forwards the address to the computer that asked for it.
Range of Public IP Addresses
Certain IP addresses are reserved for public use and others for private use. This is what makes private IP addresses unable to reach the public internet, because they aren't even able to communicate properly unless they exist behind a router.
The following ranges are reserved by the Internet Assigned Numbers Authority(IANA) for use as private IP addresses:
- 10.0.0.0 to 10.255.255.255
- 172.16.0.0 to 172.31.255.255
- 192.168.0.0 to 192.168.255.255
Excluding the addresses above, public IP addresses range from "1..." to "191...".
All of the "192..." addresses are not registered publicly, which means they can only be used behind a router as private IP addresses. This range is where most private IP addresses fall, which is why the default IP address for most Linksys, D-Link, Cisco, and NETGEAR routers is an IP within this set.
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