IPv4 vs IPv6 – explained simply

IPv4 is limited and relies on NAT, while IPv6 offers a massive address space and direct connectivity. This article explains how both protocols work, how addresses are structured, and what it means in practice.

IP addresses are the foundation of all network communication. Without them, devices would not be able to find each other.

Today, two versions exist side by side: IPv4 and IPv6.

But what is the real difference? How are these addresses structured, and why does it matter in practice?

In this article, we take a deeper look at IPv4 and IPv6 – still easy to understand, but with more technical depth.

IPv4 structure

An IPv4 address consists of 32 bits and is written as four octets:

192.168.1.1

Each octet represents 8 bits and can range from 0 to 255.

This results in:

2^32 = 4,294,967,296 possible addresses

However, many of these addresses are reserved (for example private networks or special purposes).

Private IPv4 ranges

10.0.0.0/8
172.16.0.0/12
192.168.0.0/16

These are commonly used in local networks and are not directly reachable from the internet.

IPv6 structure

An IPv6 address consists of 128 bits and is written in eight groups:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

Each group represents 16 bits and is written in hexadecimal.

The address space is enormous:

2^128 ≈ 3.4 × 10^38

This allows for practically unlimited unique addresses.

Overview graphic of an IPv4 and an IPv6 address. (Picture: AI)

Short notation

IPv6 allows abbreviations:

leading zeros can be omitted
consecutive zero blocks can be replaced with ::

2001:db8::1

Prefix and interface identifier

IPv6 addresses are typically divided into:

network prefix (e.g. /64)
interface identifier (host part)

A typical network might look like this:

2001:db8:abcd:0012::/64

The host portion is often generated automatically.

Address assignment (DHCP and autoconfiguration)

IPv4

IPv4 usually relies on DHCP to assign:

IP address
gateway
DNS servers

IPv6

IPv6 supports multiple methods:

SLAAC (stateless autoconfiguration)
DHCPv6
a combination of both

Devices can generate their own addresses automatically.

DNS records

IPv4 uses A records:

example.com → 192.168.1.1

IPv6 uses AAAA records:

example.com → 2001:db8::1

Modern systems usually support both.

NAT and connectivity

IPv4 commonly uses NAT (Network Address Translation).

Multiple devices share a single public IP address.

IPv6 does not require NAT, since there are enough addresses available.

This enables direct communication between devices.

Prefixes and dynamic addressing

Internet providers often assign dynamic IPv6 prefixes.

Typical sizes are /56 or /64.

This means:

the network part is assigned by the provider
the host part is generated automatically

The prefix may change over time, depending on the connection.

QoS and traffic handling

IPv6 includes built-in fields for traffic prioritization:

Traffic Class
Flow Label

In practice, QoS is still mostly implemented at the network level.

Address size and performance

IPv6 addresses are significantly longer than IPv4 addresses.

This results in slightly larger packet headers.

In modern networks, this has little to no noticeable impact.

Stable and secure infrastructure is no coincidence. With Catarix IT, I help implement setups like this in a clean and reliable way.

Conclusion

IPv4 is simple and widely used, but limited.

IPv6 provides a massive address space and new capabilities, but adds complexity.

Both protocols will continue to coexist for a long time.

Understanding their differences is essential for anyone working with networks.