IP address

An IP address (Internet Protocol address) is a distinct numerical identifier allocated to any device connected to a network, such as a computer, smartphone, or server. It serves as a digital identifier for your equipment, facilitating the accurate transmission and reception of data over the internet or within a local network, analogous to a postal address for physical correspondence.

Categories of IP addresses

Based on how they function and are assigned, several types of IP addresses exist, each serving a distinct purpose in network communication. Here’s a breakdown of the common types with examples:

1. IPv4 and IPv6

• IPv4 (Internet Protocol Version 4): The most common type, it uses 32-bit addresses and is expressed as four sets of numbers (octets), each ranging from 0 to 255, separated by periods.
  • Example: 192.168.1.1
• IPv6 (Internet Protocol Version 6): A newer version with 128-bit addresses, designed to handle the increasing number of internet-connected devices. It uses hexadecimal numbers separated by colons.
  • Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334 

2. Public and private IP addresses

• Public IP Addresses: Visible and accessible on the global internet, they facilitate communication between devices across the internet. Your Internet Service Provider (ISP) assigns a public IP address to your network’s router.
  • Example: 24.156.99.202
• Private IP Addresses: Used within local networks (LANs), these addresses enable internal communication between devices like computers, printers, and servers without direct internet access. They are assigned by a router using DHCP. IANA has reserved specific IP address ranges for private networks.
  • Example: 192.168.1.100 (often used for devices within a private network) 

The terms Public IP Address and External IP Address are often used interchangeably because, in most home and office networks, they refer to the same thing — the IP address that the outside world sees when your device accesses the internet. You can learn how to find your external IP address to see what address is visible to websites and online services.

In contrast, devices within your local network — like your phone, laptop, or smart TV — are usually assigned private IP addresses. These addresses are only valid inside your network and cannot be accessed directly from the internet. They help organize internal traffic and allow multiple devices to share one public IP through NAT. For more details, check out what is a private IP address.

3. Dynamic and static IP addresses

• Dynamic IP Addresses: These IP addresses change periodically and are assigned by DHCP servers. They are common for home networks and devices that frequently connect and disconnect.
  • Example: Your laptop getting a different IP address every time you connect to a public Wi-Fi network.
• Static IP Addresses: These are fixed, manually configured addresses that remain constant. Businesses often use them for servers or services requiring a consistent address, such as web servers or remote access.
  • Example: A web server consistently using the IP address 192.168.1.100. 

It’s also useful to understand whether an IP address is dynamic or static. A dynamic IP is automatically assigned by your ISP and may change over time, while a static IP stays constant and is often used for servers, remote access, or networked devices requiring stable addresses. Learn more about the differences in this guide: Dynamic vs Static IP.

4. Special types of IP addresses

• Loopback IP Address: A special address (127.0.0.1 for IPv4 or ::1/128 for IPv6) used by a device to refer to itself, often for testing network services.
• Default Gateway IP: The router’s IP address that connects a local network to the internet.
• Multicast IP Addresses: Used for sending data packets from a single source to multiple recipients, commonly used in video streaming and online gaming.
• Broadcast IP Addresses: Used to send a message to all devices on a local network. 

How IP addresses work

Here’s a simplified explanation of how IP addresses work, focusing on the steps involved in sending and receiving data across networks. Every device connected to the internet has a unique IP address, which functions like a mailing address for data. When you request a webpage, your device sends a request through your router, which forwards it to the internet. The response data travels back using your IP address as the destination.

If you’re curious, you can learn how to find your IP address on Windows, Mac, or iPhone. This can be useful for troubleshooting network issues or configuring access.

Separately, if you want to change settings on your home network, it’s helpful to know how to find your router’s IP address — that’s the gateway through which all your traffic flows.

1. Connecting to a network

• Your device (computer, smartphone, etc.) connects to a network, which could be your home Wi-Fi, a public Wi-Fi hotspot, or a cellular network.
• When connecting, your device is assigned a unique IP address by the network’s router or a DHCP (Dynamic Host Configuration Protocol) server. DHCP is a protocol that simplifies network configuration and IP address assignment.
• At home, your router acts as a DHCP server, assigning private IP addresses to the devices connected to your network (e.g., your laptop, printer, smart TV).
• Your router also receives a public IP address from your Internet Service Provider (ISP), which is the address visible to the outside world

2. Preparing and sending data packets

• When you access a website or send an email, your device converts the information into smaller units called data packets.
• Each packet includes a header with crucial information, such as the source IP address (your device’s IP) and the destination IP address (the website’s server IP).
• If you’ve entered a domain name like “example.com”, a process called DNS (Domain Name System) resolution translates that human-readable domain name into the numerical IP address that devices use to locate each other on the network

While it’s difficult to pinpoint a single inventor for the entire internet, the creation of the Internet Protocol (IP), along with the Transmission Control Protocol (TCP), is largely credited to Vint Cerf and Robert Kahn. 

Working in the early 1970s, their contributions enabled different computer networks to communicate with each other, forming the foundational architecture of the Internet.

3. Network address translation (NAT)

• If your device has a private IP address, the packets are sent to your router.
• Your router performs Network Address Translation (NAT) and replaces the private IP address in the packet headers with the router’s public IP address.
• This allows multiple devices on your private network to share a single public IP address when communicating with the internet.

If needed, there are ways to trace activity back to a specific device inside your network — for example, you can learn how to find a device by IP address to pinpoint which machine is using a certain IP internally.

If you’re working with a network-attached storage (NAS) system, identifying its IP address is often necessary to access it from other devices on your network. You can follow this guide on how to find the IP address of a NAS to quickly locate it and manage your shared storage.

4. Routing

• The data packets are then forwarded across the internet through various routers and networks.
• Routers analyze the destination IP address in each packet header and determine the most efficient path for the packet to reach its destination.
• Routing protocols, such as BGP, help guide packets across the vast network of interconnected systems, ensuring they travel through the appropriate networks (Autonomous Systems or AS) until they reach one responsible for the destination IP address.

5. Delivery and response

• The packets arrive at the destination device or server, identified by its IP address.
• If the destination is a website, the server processes the request and sends a response (e.g., the webpage content) back to your public IP address using the same process in reverse.
• Your router receives the response, performs reverse NAT to translate the public IP address back to your device’s private IP, and delivers the data to your device