Connecting any device to the internet starts with an IP address, but not all IP addresses serve the same purpose. You may have noticed your home computers or mobile devices showing an internal IP address like 192.168.1.101 that differs from the public IP on internet speed tests.
So what‘s the difference and why does it matter?
This guide will break it down in simple terms to help explain the distinct roles of internal vs external IPs for networking, privacy, and security.
A Brief History of IP Addressing
To understand the split between internal and external IPs, we need to step back to the origins of the internet.
In the early days of computer networking, machines connected directly to each other with simple point-to-point links. This evolved in the 1960s to the earliest wide area networks like ARPANET, which connected university research computers across the US.
Each host computer on these networks needed a unique identifier so packets could be properly routed to them. The initial method was simple host tables mapping names to address numbers – but this approach became unmanageable as the network grew.
To solve this, RFC 760 introduced the concept of internet protocol (IP) addresses in January 1980. The first IP specification defined IPv4 addresses as 32-bit numbers like 192.0.2.9. This allowed over 4 billion possible address combinations – more than enough for the networks of the day!
With IP addresses assigned in a structured manner, it allowed efficient routing and enabled the explosive growth of the internet we‘ve seen over subsequent decades.
So where do internal IPs come into play? Early IP addresses were ALL public since the networks were relatively small. But as more private business and home networks came online, changes were needed to accommodate local addressing.
This gave rise to Network Address Translation and the system we have today of both internal and external IP addresses playing important but distinct roles.
IP Addressing Today – Public vs Private
Fast forward to today, and IP addresses are an integral part of how modern networks operate. Any time you connect a device like a PC, smartphone, or even an IoT refrigerator to WiFi or ethernet, it‘s assigned an IP address.
There are now two broad categories of IP address:
Public IP addresses – Also referred to as external or internet-routable addresses. Think of these like public phone numbers – they uniquely identify your network out on the broader internet.
Private IP addresses – Also known as internal or non-routable addresses. These identify devices locally on your home or business network. Like unlisted phone numbers, they are not visible or accessible from the public internet.
This distinction between public and private IP addresses is key to providing security and allowing the continued growth of the internet.
The challenge early on was that available IPv4 addresses were being rapidly exhausted with all the new networks coming online. Network Address Translation (NAT) provided a solution by allowing many private devices to share a single public IP to access the internet.
When your home router connects to your ISP, it‘s assigned a public IP address. But all your PCs, smartphones, etc get private addresses from the router‘s internal network. NAT handles seamlessly translating between the two.
Let‘s look more closely at how these public and private IP addresses work:
Public IP Addresses
Public IP addresses are assigned by your internet service provider. These uniquely identify your network on the broader internet, similar to a home address. Some key points:
IPv4 format with 32 bits – e.g. 184.108.40.206
Globally unique across the whole internet
Can be geo-located back to service provider and general region
Allows direct communication between public networks
Firewalls and NAT determine what inbound traffic to allow
Commonly dynamic (changing) for home users and static for business
Total IPv4 space has been exhausted, driving shift to IPv6
Private IP Addresses
Private IP addresses are used internally within a local network:
Reserved IPv4 ranges like 192.168.x.x, 10.x.x.x, and 172.16.x.x
Recycled internally – so your friend may have the same 192.168.1.102 address
Managed by your router‘s DHCP server, not the ISP
Used for communication between devices on same local network
Not accessible directly from public internet
Can be either static (fixed) or dynamic (changing)
This separation of public and private IP spaces helps segment broader internet routing from local networks. It provides essentially unlimited room for continued growth despite IPv4 address exhaustion.
Now let‘s look at why the internal vs external IP distinction matters both for privacy and for troubleshooting home network issues.
Implications of Your Public vs Private IP Address
Understanding the difference between public and private IP addresses is important for several reasons:
Privacy and Security
Your public IP address can provide information about your general location and ISP. It could potentially be logged by sites you access and tracked for profiling purposes.
Using a VPN allows changing your public outward-facing IP address to enhance privacy. This prevents the sites you visit and even your own ISP from viewing your home IP address and tying activity back to your network.
Leaking an internal private IP address could open up potential attack avenues from the public internet into your local network. Obscuring private IPs is recommended as a best practice.
Knowing the internal IP landscape is critical for diagnosing and fixing connectivity problems between devices on your home or office network. Issues like two devices showing the same IP address can prevent communication.
Understanding internal IPs is also essential to configure port forwarding and Network Address Translation rules on routers to enable selective inbound traffic.
Public internet traffic depends on public IP addresses for proper routing across the network. Local network traffic relies solely on internal private IP addresses not visible to the outside world.
The vast private IP space allows continued growth of local networks independently from the limited public IPv4 space. This has helped forestall IPv4 address exhaustion issues as networks gradually transition to IPv6.
Now that we‘ve covered the key differences and importance of public vs private IP addresses, let‘s run through how to find them.
How To Check Your Public and Private IP Addresses
Finding your home network‘s public IP address is straightforward from any internet connected device:
Windows – Open command prompt and run
ipconfigto see your "IPv4 Address"
Mac OS – Click the Apple logo and choose System Preferences > Network. Your "IP Address" is shown.
iPhone or Android – Open Settings > WiFi and tap the "i" next to your network. Scroll down to view your IP address.
Fire TV or Firestick – From Settings go to My Fire TV > About > Network. Check your IP address here.
Web Browser – Just search Google or Bing for "what is my IP address" to reveal your public IP.
You can also log into your router‘s admin interface at 192.168.1.1 or check your account dashboard on your ISP‘s website.
For privacy, use a trusted VPN provider to change your IP and mask your physical location and ISP identity.
Finding your private IP takes a bit more work but can be vital for troubleshooting home network issues.
Windows – Go to Settings > Network & Internet > Wi-Fi > Hardware Properties
Mac – Apple Menu > System Preferences > Network
iPhone and Android – On the WiFi settings screen, tap your network name then view IP address
On Router – Check router admin interface for DHCP client lists to see issued private IPs
Knowing the difference here can prevent confusion around why your IP doesn‘t seem to change even using a VPN. Viewing your private IP on a Windows PC or iPhone will always show your local network address – you need to check the public IP seen by the outside world.
Public vs Private IP Addresses – Conclusion
Understanding the distinction between public vs private IP addresses is key to properly troubleshooting connectivity and getting the most privacy from a VPN.
Here are some key points:
Public IP addresses uniquely identify your network on the broader internet. Private IP addresses only work locally on your home or business network.
Masking your public IP behind a VPN provides increased privacy by hiding your location and ISP information.
Public IPs are assigned by your ISP. Private IPs are allocated by your router‘s DHCP server.
IPv4 public IP addresses have become scarce, while private address space continues growing through recycled use locally.
Knowing both your public and private IP schemes is important for configuring port forwarding, diagnosing network issues, and overall connectivity.
I hope this guide has helped demystify the critical yet often misunderstood differences between internal vs external IP addressing! Let me know if you have any other questions.