Why Are IP Addresses Called Logical Addresses?

You may already know that IP addresses are unique identifiers that are assigned to devices that access computer networks. An IP address is a string of numbers separated by periods, which looks like this: 192.168.1.1. 

But IP addresses are actually abstract, logical identifiers, not physical locations. Unlike MAC addresses, which are permanently attached to a specific NIC chip in a device, IP addresses can change. This is what makes them “logical addresses,” as opposed to “physical addresses.” 

Let’s take a look at the logical nature of IP addresses – and a few important details about how IP addresses work. 

IP Addresses Can Change and Be Reassigned

IP addresses are not permanently tied to any specific computer or device. Rather they can be assigned to different devices, as needed by the network, and these numbers can be changed. 

Some examples of these reassignments: 

• Your home internet service provider (ISP) may periodically assign your router a new public IP address, which allows them to reconfigure their network while still successfully routing traffic to you. 
• If you move a virtual machine (AKA: a software-based computer) from one physical server to another, it will get a new IP address on the new network. 
• When you connect your laptop to different WiFi networks, such as home, work, or a coffee shop, it gets assigned a new logical IP address on each network. This allows traffic to be routed properly, regardless of your physical location. 

The IP address is simply an abstract identifier. Networks use IP addresses to communicate, and those IP addresses can change as you move from one network to another.

IP Addresses Follow a Structured Numbering Scheme

Let’s talk about that string of numbers that makes up an IP address. Is it random? Not really!

The format of an IP address contains both network and host identifiers. Let’s say your IP address is 192.168.1.5. 

This means that 192.168.1 is the network ID, and 5 is the host ID on that network. 

This number scheme reflects the logical network topology and allows IP addresses to be structured hierarchically. Devices on the same network share the same network ID, but they need to be differentiated from another nonetheless. 

This numbering system helps to efficiently route traffic between network segments. 

IP Addresses Operate at the Network Software Layer

Network communication models like TCP/IP and OSI are structured in layers, and each layer has a specific role. 

IP operates at the network layer in these models. The network layer focuses on logical communication between devices, and it determines how to route data based on IP addresses. The lower layer (AKA: the physical layer) in these models deal with physically transmitting data over cables, wireless signals, and hardware. 

The network layer can operate independently from the lower layers by using logical IP addresses to communicate in abstraction. 

This separation of concerns that is provided by the layered structure is what allows the network layer of TCP/IP and OSI models route data without worrying about the physical connections. 

IP Addresses Work with Common Networking Protocols

There are many fundamental networking protocols (TCP, UDP, and ICMP, for example) that work in conjunction with IP addresses. 

Here’s how: 

• TCP (Transmission Control Protocol) uses IP addresses to logically connect and exchange data between two endpoints. 
• UDP (User Datagram Protocol) uses IP to efficiently send messages between devices without establishing an ongoing connection. Unlike TCP, UDP does not perform extensive error-checking and acknowledgements. This makes UDP faster, but it also means that data delivery is not guaranteed to the same extent as with TCP. 
• ICMP (Internet Control Message Protocol) uses IP addresses to send error messages and diagnostics when errors occur. 

Thanks to IP addresses, these standards are able to function and communicate at the network layer, independently of physical transmission details. Again, this is part of why IP addresses are called logical, as opposed to physical. 

Understanding IP Addresses vs MAC Addresses

Let’s take a look at the differences between IP addresses and MAC addresses. Specifically, IP addresses are logical, whereas MAC addresses are physical. 

MAC stands for Media Access Control, and they are the physical hardware identifiers assigned to network adapters and devices. More precisely, they are assigned to a chip within those adapters and devices. In contrast to IP addresses that can change, MAC addresses are permanently associated with their chips.

This is because MAC addresses are hardcoded. They are programmed into the network interface controller (NIC) chip of a device. This occurs at the point of manufacture; MAC addresses provide a unique physical identifier for each network adapter, and it remains fixed for the device’s entire lifetime. 

Other Permanent Addresses

There are a handful of other permanent addresses: 

• Serial Number: Most hardware components have a unique serial number assigned and printed on the device itself. Serial numbers identify a specific physical unit and do not change.
• Universally Unique Identifier (UUID): A UUID is a 128-bit number used to uniquely identify information in computer systems. They are generated based on unique values from a system’s hardware, software, or timestamp and remain consistent.
• Hostname: While hostnames can sometimes be changed, they are often intended to remain permanent identifiers for systems. Changing a hostname arbitrarily can break connectivity in some cases.
• Bluetooth and WiFi Device Addresses: In addition to MAC addresses for ethernet, Bluetooth and WiFi devices also have their own permanent device addresses assigned to them.

IMEI Number: The IMEI (International Mobile Equipment Identity) number uniquely identifies a specific mobile phone handset. It is factory-assigned and permanent.

Guidelines for IP Address Management 

You have a few options for how your IP address may be assigned.

First, DHCP stands for Dynamic Host Configuration Protocol. In this case, it dynamically assigns an IP address from a pool as a device joins a network. This is often used for home networks and WiFi. 

Second, “static allocation” is a specific and permanent IP address that is manually configured to a device. This is used for servers, printers, etc. 

The DNS (Domain Name System) helps to map domain names to IPs and can be updated as addresses change. 

The Takeaway: IP Addresses Are Logical Because They Aren’t Physical

IP addresses are “logical” because they are software-based identifiers, not physical identifiers that are tied to physical hardware. 

Their abstract and configurable nature allows networks great flexibility and efficiency. As a review: 

• IP addresses can be reassigned as needed to route traffic successfully. 
• Their hierarchical structure reflects network topology and enables effective routing. 
• At the network layer, IP addresses communicate logically between endpoints, regardless of the physical transmission details. 
• They also work hand-in-hand with core networking protocols to allow seamless communication. 

Although physical limitations still exist, the logical nature of IP addressing enables the automated, versatile networking infrastructure we rely on today!