What is an IP address?

What is an IP address? Every device within a network is assigned a distinct identifier. Much like how you address a letter for postal delivery, computers use this identifier to direct data to the correct device in the network.

Today, most networks, including the internet, rely on the TCP/IP protocol for communication. Within this system, each device’s unique identifier is referred to as its IP address.

There are two main types of IP addresses: IPv4 (Internet Protocol Version 4) and IPv6 (Internet Protocol Version 6). Every computer has an IPv4 address, and many also use the newer IPv6 system. Here are the key differences between these two types of addresses:

In the early days of IPv4, the internet was not the vast global network it is today. Most networks were private, isolated from others. As the internet grew rapidly, there were concerns about running out of IP addresses, since only 32 bits were available for a unique address.

IPv4 provides 232 possible unique combinations, offering just under 4.3 billion unique addresses. With IPv6, that number expands dramatically to 2^128 possible addresses, alleviating concerns about address shortages. We'll explore later how to check your computer’s IPv4 or IPv6 addresses.

How Computers Obtain IP Addresses

An IP address can either be static or dynamic. A static IP address is a fixed address that is permanently assigned. While it’s uncommon for internet service providers to assign static IPs, you can manually assign static IP addresses to devices within your local network. However, doing so without a good understanding of TCP/IP may lead to network issues.

Dynamic IP addresses are far more common. They are allocated by the Dynamic Host Configuration Protocol (DHCP), which is a service operating on the network. Typically, DHCP is managed by network devices like routers or dedicated DHCP servers.

A dynamic IP address is assigned through a leasing process, meaning the address is only valid for a certain period. When the lease ends, the computer automatically requests a new lease. If the device was disconnected from the network during the lease period, it may receive a new IP address.

This process is generally seamless, and the user may not notice unless there is an IP address conflict on the network (when two devices have the same IP address). Such conflicts are rare, and modern technology usually resolves them automatically.

Now, let’s take a closer look at the key components of an IP address and the distinct roles of specific addresses.

IP Classes

As previously mentioned, IPv4 addresses are composed of four sets of eight-digit binary numbers. This means each set can range from 00000000 to 11111111 in binary, or from 0 to 255 in decimal. Essentially, this gives the address range from 0.0.0.0 to 255.255.255.255.

However, certain numbers within this range are reserved for specific uses in TCP/IP networks. These reserved ranges are regulated by the Internet Assigned Numbers Authority (IANA), the governing body of TCP/IP addressing. Among these, four particular ranges are reserved for special functions.

Other reserved IP addresses are allocated for subnets. A subnet is a smaller network of computers connected to a larger network via a router, with its own addressing system to enable quicker communication within the subnet without traversing the larger network.

A router within a TCP/IP network, including the internet, is designed to recognize various subnets and appropriately direct traffic. Below are the IP address ranges designated for subnetting:

The first three address ranges (Classes A, B, and C) are most commonly used for subnet creation. Later, we will explore how subnets use these ranges. The IANA has designated specific uses for multicast addresses in its RFC 5771 document, but it has yet to assign a purpose for Class E addresses, which it reserved in the RFC 1112 document from 1989. Prior to IPv6, there was much debate regarding whether IANA should release Class E for general use on the internet.

Now, let's take a look at how subnets function and explore who owns those unreserved IP addresses on the internet.

Internet Addresses and Subnets

Here's an example of a subnet IP address that you may find on your home computer when using a router (either wired or wireless) between your ISP connection and your device:

In addition to IP address reservations, the IANA also allocates blocks of IP addresses to various entities, often large commercial or government bodies. Your internet service provider (ISP) might be one of these entities or it could be a smaller part of a broader block managed by such organizations. When you connect to the internet, your ISP assigns you one of these addresses. A comprehensive list of IANA’s IPv4 address assignments and reservations can be found on IANA's website [source: IANA].

If you have only one computer connected to the internet, that device can use the IP address provided by your ISP. However, many households today use routers to share a single internet connection among multiple devices.

When using a router to share an internet connection, the router obtains the IP address directly from the ISP. It then creates and manages a subnet for all devices connected to that router. If your computer’s address falls within one of the previously mentioned reserved subnet ranges, it means your connection is routed, not a direct link to the internet.

IP addresses within a subnet consist of two components: the network and the node. The network part identifies the subnet itself, while the node, also referred to as the host, is a specific device that requires a unique address on the network. Computers differentiate between the two parts of the IP address using a subnet mask. Though it resembles an IP address, a subnet mask functions as a filter to determine which portion of the IP address identifies the network and which part identifies the node [source: Solarwinds].

A subnet mask is composed of a sequence of 1 bits followed by 0 bits. The 1 bits mask the network part of the IP address, leaving only the unique node identifiers visible. In IPv4, the most commonly used subnet masks have complete octets of 1s and 0s, as shown below:

When configuring large networks, administrators choose the appropriate subnet mask based on how many subnets or nodes are needed. To create more subnets, more bits are allocated for the network; to allow more nodes per subnet, more bits are reserved for the nodes. This can even require using custom, non-standard subnet mask values. For example, if you need 10 bits for networks and 22 for nodes, the subnet mask would be represented as 255.192.0.0, which is created by using 11000000 in the second octet.

It’s essential to remember that in every subnet, both the first and the last addresses are reserved. The first address designates the subnet itself, while the last address serves as the broadcast address for all devices on that subnet.

Understanding Private and Public IP Addresses

It's also crucial to learn the difference between private and public IP addresses. These two types serve distinct roles, both of which are essential for devices to communicate across the internet and within local networks [source: Mitchell].

Allocation and Registration

Public IP addresses are unique across the globe and need to be registered with the Internet Assigned Numbers Authority (IANA) or a local internet registry. This ensures that each public address is distinct and can be reached across the internet.

In contrast, private IP addresses are not registered or managed by any central authority. They are intended for use within private networks, such as those in homes, schools, and businesses.

Accessibility and Scope

As mentioned earlier, public IP addresses are accessible over the internet, making them crucial for external communications. They are assigned to devices that need to be directly reachable from outside their local network, such as web servers, email servers, and routers that connect a local network to the global internet.

A private IP address enables several devices within the same network to interact with each other, but it cannot be accessed directly from outside the network.

Security and Cost

Given that public IP addresses are accessible from anywhere on the internet, they require careful management. To safeguard devices with public IP addresses from unauthorized access and security threats, firewalls, intrusion detection systems, and additional security measures are often implemented.

On the other hand, private IP addresses operate within a closed network, which provides a layer of isolation and security. Additionally, since private IP addresses can be reused in various networks, they help conserve the limited pool of public IP addresses, reducing costs for both individuals and organizations.

The Role of IP Addresses in Digital Communication

Few concepts are as integral to modern communication as the internet protocol address. IP addresses allow devices from across the world to locate and interact with each other in an instant! Despite the rapid advancements of the internet, IP addresses remain essential components that keep the digital world in motion.

As you've discovered, an IP address is a core building block that supports the connectivity and functionality of our digital universe. By understanding the nature and role of IP addresses, we not only gain a greater understanding of the underlying systems but also enhance our ability to engage with and shape the communication landscape more effectively.