Your public IP address is:
What is this public IP?
Public or external IP addresses are those addresses that are routed on the internet. It can be IPv4 or IPv6. And it is a unique address assigned by the internet service providers. And most internet users are connected behind a single public IP address except for some enterprise users who require multiple IP addresses for different services they offer. And mostly for home users, it is always a single public IP address. In conjunction with private IP addresses, many users can connect behind a single public IP address.
But how can many users connect to the internet using a single public IP? The IP address should be unique right ?
That’s where private or local IP addresses can come to your rescue.
How do you tell if an IP address is public or private?
If you check the IP address at your home or even at the office from your machine by doing ipconfig or ifconfig, you would most likely get an IP address from the private IP address range that is 10.0. 0.0/8, 172.16. 0.0/12, 192.168. 0.0/16, also known as RFC 1918 addresses. Those Private IP addresses cannot be routed across the internet. Instead, your router would convert those Private IP addresses to Public IP addresses with a feature called NAT. This means each user on the internet will have unique public IP addresses.
So If you see an IP address in the RFC1918 range, it is a private range, and the rest are public IP addresses. There are some IP addresses between 224.0. 0.0 to 239.255. 255.255 those are called multicast addresses which are used for special network purposes and protocols.
One of the benefits of using the private IP address range is that it provides flexibility in IP assignments. You could have the same private IP addresses used by the other users. E.g., You can have IP address 192.168.1.10/24 in your network, and your neighbor next to your block can have the same subnet. However, each user will have unique public IP addresses.
What happens if you try to route the private IP address to the internet?
Most of the ISP’s by default, would block the RFC1918 addresses entering into their routing table. There were instances in the past that some part of the internet went down when some users started to advertise the private IP address to the internet. Currently, ISP’s are blocking them, so even if you advertise private range, it would block at the ISP level.
Will my public IP change?
It depends on how your internet service provider has set up your internet IP configuration. Most of the household broadband networks use DHCP for IP assignment. Hence you would see the public IP addresses keep changing. However, they mostly use static public IP addresses in an enterprise network so that the public IP address will remain.
If you want to stop your IP address from changing, you can reach out to your local ISP and request static IP addresses. After you get the static IP addresses from the ISP, they would configure them for you. Afterward, your public IP would never change. There are many use cases when you can use your own static IP from the ISP. One such example is hosting a web service from home.
There would be some charges involved for getting those static IPs though.
Does IP address change with location?
You might also wonder, every time I move from one location to another, my IP addresses are changing; why is that. Since the public IP addresses are unique, each block of those public IPs is assigned to each geo-location by the Internet Assigned Numbers Authority (IANA). And these IP addresses are then again split as separate subnets by the internet service providers.
Not only just the location, you can even try to switch between your mobile internet and the home broadband, and you will notice your public IP address changes.
What is the purpose of IPv6?
When the IPv4 works perfectly fine, what is the need for an IPv6, you might be thinking. As you may know, when the internet initially came out, no one ever thought it would grow so big. As the internet has become huge and popular, and that increased the usage of the public IPv4 over time. The exhaustion of IPv4 addresses also started, and we started running out of public IPv4 addresses. That’s when IPv6 was released.
The internet comprises both IPv4 and IPv6 traffic, and moving out of IPv4 is still a challenging task for many internet users. Some enterprise users are still using only IPv4, and some are planning to migrate and using dual-stack, meaning running both IPv4 and IPv6 on the environment. Eventually, we will move out of IPv4 and migrate to IPv6. And IPv4 will be the thing in the past!