Public and Private IP Addresses

Just like an Aadhaar card identifies a citizen nationwide, a Public IP address identifies your device on the internet, making it reachable from anywhere in the world. In contrast, a Private IP address is used by routers within home or office networks to recognize and communicate with your device locally. Together, public and private IP addresses work together to ensure that information is transmitted accurately across the internet to the correct device. This dual-layer system helps the internet support billions of connected devices, without requiring each one to have a globally unique address. In this article, we will understand the public and private IP address ranges and the difference between the two, which will bring you closer to how the internet works.

Table of Contents:

• What is an IP Address?
• Why Do Devices Need IP Addresses?
• What is a Private IP Address?
• What is a Public IP Address?
• Difference Between Public IP Address and Private IP Address
  • IP Address Visibility
  • Scope and Accessibility
  • Communication
  • Provider
  • IP Address Ranges
  • Security and Privacy
  • Cost and Configuration
  • Address Availability
  • NAT Dependency
• How to Identify Public vs Private IP Ranges
• Conclusion

What is an IP Address?

An IP Address (Internet Protocol Address) is a numerical value assigned to a device on a network that uses the Internet Protocol for communication. It is through this number that your device is recognized in a computer network. It can be thought of as a street address that helps the postman find your home. An IP address has two functions:

• It identifies the network interface (like a Wi-Fi card or Ethernet port) of your device on a network. Network interface identification is one of the primary functions of the IP Address.
• It also provides the location of that device within the network, enabling data to be routed to the correct destination.

There are two types of IP Addresses, IPv4 and IPv6, and they are typically represented as a string of numbers separated by periods, like 192.168.1.1 for IPv4, or a combination of hexadecimal digits and colons, like 2001:0db8:85a3:0000:0000:8a2e:0370:7334 for IPv6.

Why Do Devices Need IP Addresses?

Devices need IP addresses primarily for communication and identification, but there are other important reasons as well. Let us look at them one by one in detail.

• Identification: An IP address provides a unique identifier for each device, allowing them to be distinguished from one another. Without this unique ID, it would be impossible to know which device is sending or receiving data.
• Communication: When you request a website, send an email, or stream a video, your device sends out data packets. Each packet includes both the sender’s and the recipient’s IP addresses. Therefore, having an IP address is important for a device to send or receive data, i.e., communicate.
• Routing: Having IP addresses for every device makes it easier to route the data packets to the correct device. Network routers use IP addresses to guide data packets through the most appropriate path to their destination.
• Organization and Management: Attaching an IP address to each device makes organizing and managing a complex network easier. They help cluster similar network devices into smaller subnets, improving performance and security.

IP addresses are categorized in a way other than IPv4 and IPv6. These are Private IP addresses and Public IP Addresses.

Step into the World of Cybersecurity – Build a Secure Career!

Enroll Now and secure your future in one of the world’s fastest-growing tech domains!

Explore Program

What is a Private IP Address?

A private IP address is the numeric label assigned inside a local network. It may be your home network or your office network, as both are considered a LAN, one of the most basic types of computer networks. The private IP address allows a device to communicate with other devices on the same network but prevents direct access from the public internet. The private IP address can be thought of as the room number in a house. It is different from the street address (the home address). If a postal service has to deliver your mail, it would not be concerned with which person the mail has to reach (or the room number).

• Private IP address ranges are not routable on the Internet. This means data packets addressed to a private IP cannot travel on the Internet. Instead, when a device with a private IP needs to communicate with the internet, its local network’s router performs a process called Network Address Translation (NAT). It translates the private IP address to the public IP address so that the device can communicate with the internet.
• The Internet Assigned Numbers Authority (IANA) has reserved the following IPv4 address ranges as private IP address ranges:
  • Class A supports large networks and ranges from 10.0.0.0 to 10.255.255.255
  • Class B is for medium-sized networks and ranges from 172.16.0.0 to 172.31.255.255
  • Class C is commonly used for home networks with the range of 192.168.0.0 to 192.168.255.255

IPv6 also has a reserved range for private addresses, known as Unique Local Addresses (ULAs), starting with fc00::/7.

Can a Private IP Address Be Traced?

Yes, a private IP address can be traced, but only inside a local network. Outside the local network, it has no identity or traceability.

Only the router knows which IP address was assigned to which device on its local network; routers keep logs and routing tables that map private IPs to specific devices. Everyone, including an IT expert, can check to see which device is using which private IP address using the router’s administration interface or the monitoring tool for the network.

But, no, a private IP address cannot be directly traced from the public internet. These are designed not to be routed across the internet and are not unique globally. They add a layer of network security to your device.

As such, a private IP address offers a good deal of privacy and security since there is no way to trace access or connections externally across the public internet.

What is a Public IP Address?

A public IP Address is a unique numerical identifier given to any device connected to the internet and is globally routable. Public IP addresses are visible and accessible from anywhere on the internet. When your device needs to access a server, it will utilize the public IP address as its identification so that the server knows where to send the data. Public IP addresses are assigned by your Internet Service Provider (ISP). All devices connected to your local area network share an IP address. Your router acts as a gateway to the internet on behalf of the connected devices, and uses NAT to convert private addresses to public addresses and vice versa.

Public IP addresses are also dynamic and static.

• Dynamic public IP addresses: These are mostly used by home users. When you sign up for an ISP, the ISP uses a public IP from its pool of public IPs assigned to the company and issues you a public dynamic IP address. Every so often, the ISP will change your public IP address.
• Static public IP addresses: These are IP addresses that do not change. Static public IP addresses are used mostly by businesses or for specific applications requiring a consistent address (typically to host a web server and run dedicated game servers). Static public IPs usually come at an additional cost from your ISP.

Can You Track a Public IP Address?

Yes, a public IP address can be tracked to a certain extent. Below is a list of what can be tracked using the public IP and by whom:

• Geographic Location: Online IP lookup tools can use your public IP to identify your country, region/state, city, and your ISP. It gives the address of your ISP office or its main hub. Websites use this to tailor content and display regional ads.
• Internet Service Provider (ISP): Your public IP directly reveals the name of your ISP.
• Online Activities: This is logged by your website or the service that you are using. Whenever you visit a website, send an email, or interact with an online service, your public IP address is typically logged by that website or service. This is how they know where to send data back to you.

Public IP addresses cannot reveal your street address or your personal information, or your browsing history.

Difference Between Public IP Address and Private IP Address

Let us now compare the public IP address and private IP address to better understand them both.

1. IP Address Visibility

• Private IP Address: Private IP addresses remain hidden from the global internet and are only visible to devices within the same local network.
• Public IP Address: Public IP addresses are shown to any device connected to the internet, and are traceable internally by ISPs to the approximate geographical location.

2. Scope and Accessibility

• Private IP Address: A private IP address is used within local networks (e.g., homes, schools, offices), allowing devices to communicate internally but preventing any access via the internet to help maintain a sense of network privacy and security.
• Public IP Address: A public IP address is assigned by an ISP and allows everyone to identify the device from anywhere across the globe, and helps any device to access websites, servers, and online services.

3. Communication

• Private IP Address: Private IP address ranges enable communication within the same local network, for example, a printer or a laptop.
• Public IP Address: A Public IP address is used for sending and receiving data across the internet, like accessing websites.

4. Provider

• Private IP Address: A private IP address is assigned by the internal network management device, usually a router.
• Public IP Address: On the other hand, a public IP address is provided by Internet Service Providers (ISPs).

5. IP Address Ranges

• Private IP Address: The IANA (Internet Assigned Numbers Authority) has assigned a particular range of IP addresses as private IP addresses. These are
  • Class A: 10.0.0.0 – 10.255.255.255
  • Class B: 172.16.0.0 – 172.31.255.255
  • Class C: 192.168.0.0 – 192.168.255.255
• Public IP Address: All the IP addresses outside the private IP ranges are used as public IP addresses.

6. Security and Privacy

• Private IP Address: They are more secure from external attacks and cannot be targeted directly from the internet since they are not visible to the public.
• Public IP Address: They are highly exposed to threats unless protected by firewalls or NAT (Network Address Translation).

7. Cost and Configuration

• Private IP Address: These are free and are assigned by the router using the DHCP protocol.
• Public IP Address: In India, ISPs charge a fee for accessing the internet and often require manual setup or port forwarding.

8. Address Availability

• Private IP Address: The private IP address ranges are abundant because they are reused across different networks.
• Public IP Address: Public IP addresses, on the other hand, have a limited pool that is governed by IANA. Due to the IPv4 scarcity, IPv6 has been introduced.

9. NAT Dependency

• Private IP Address: Private IP addresses are highly dependent on NAT to communicate with the internet.
• Public IP Address: Since the Public IP address directly routes the traffic, there is no need for NAT, and they are not dependent on it.

How to Identify Public vs Private IP Ranges

The Internet Assigned Numbers Authority (IANA) has reserved specific IPv4 and IPv6 ranges for private use. If an IP address falls in one of the following ranges, it is a private IP, and the rest are generally considered public IPs, except the ones that are reserved for other special purposes.

Private IPv4 Address Ranges:

• Class A: 10.0.0.0 to 10.255.255.255
• Class B: 172.16.0.0 to 172.31.255.255
• Class C: 192.168.0.0 to 192.168.255.255

Private IPv6 Address Range:

IP addresses starting from fc00::/7 are private addresses. This means any IPv6 address starting with fd in the first octet is in the private IP address ranges.

Now, let us look at ways to identify the Public and Private IP ranges.

1. Using Command Line Tools

Open your command line tool and follow these steps to check and know your private IP address and public IP address.

a. To find your Private IP address (on your local machine):

• Windows:
  1. Open Command Prompt (search for ‘cmd’ in the Start menu).
  2. Type ipconfig and press Enter.
  3. Look for your active network adapter (e.g., “Wireless LAN adapter Wi-Fi” or “Ethernet adapter”). Your private IPv4 address will be listed next to “IPv4 Address.”
• macOS / Linux:
  1. Open Terminal.
  2. Type “ip addr show” or “ifconfig” (though ifconfig is deprecated on many modern Linux distributions, ip addr show is preferred).
  3. Look for your active network interface (e.g., eth0, wlan0, or en0). Your private IPv4 address will be listed next to inet. For IPv6, look for inet6.

b. To find your Public IP Address (from your local machine):

You cannot directly get your public IP from your local machine’s network settings because it’s the IP address of your router’s external interface. However, you can use command-line tools that query external services:

• Using curl or wget
  These commands are basic to Linux/macOS and often available on Windows via Git. These commands send a request to a public service (ifconfig.me) that then reports back the public IP address from which it received the request.

curl ifconfig.me
or
wget -qO- ifconfig.me

• Using dig
  This is again for Linux/macOS, and to use it on Windows, use the BIND tools. This command queries OpenDNS’s resolver for your public IP.

dig +short myip.opendns.com @resolver1.opendns.com

2. Online Tools to Check IP Type

An online tool is the easiest way to determine both your own public IP address and to check whether it is public or private. Here is a list of online websites to find your IP address and check the type.

• WhatIsMyIP.com
• IPinfo.io
• NordVPN IP Checker
• IPstack
• DNS Checker IP WHOIS Lookup

You can input an IP address, and the tool will tell you if it is a private IP or a public IP.

If it is a public IP, it will often provide additional details like the ISP, approximate geographic location, and sometimes even the organization that owns the IP block.

Conclusion

To conclude, private IP address ranges are equally important as public IP addresses, even if they are not visible on the internet. We discussed the importance of the two and how they collaborate to form a system that modern devices can rely on. They together facilitate seamless communication, enhance network security, and also provide a solution to the problem of a limited pool of public IP addresses.

Ready to test your knowledge or prepare for your next big interview? Explore our comprehensive collection of computer network interview questions and answers to deepen your understanding!

Public and Private IP Addresses – FAQs