Subnet and PortsIPv4 and IPv6 compared: why both exist and what changes for you
IPv6 was created because IPv4 addresses ran short. Both are in use together today.
The size difference
IPv4 addresses have 32 bits, about 4.3 billion in all. IPv6 addresses have 128 bits, which is about 3.4 x 10^38. Addresses are so many that every subnet can be a /64 with room for 2^64 devices.
Side by side
| IPv4 | IPv6 | |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Written as | Four decimal numbers: 192.0.2.1 | Eight groups of hex digits: 2001:db8::1 |
| Typical LAN subnet | /24 | /64 |
| Broadcast | Yes | No (multicast is used) |
| NAT | Very common | Usually not needed |
| Configuration | Manual or DHCP | Automatic (SLAAC) or DHCPv6 |
| Header | Variable, with options | Fixed size |
Why NAT matters less in IPv6
In IPv4, one public address is shared by a whole home through NAT, which hides the devices and makes it hard for outsiders to reach them. In IPv6, each device can have a globally reachable address, and the router's firewall decides what may come in. Plan firewall rules with that in mind.
What changes for users
For most people nothing: websites work over both. Your provider may give you IPv6 addresses along with IPv4. Some services (some games, some office tools) still work only over IPv4.
What changes for administrators
- Subnets are /64. Do not try to save addresses.
- You need firewall rules for both families.
- Logs and allow lists now contain IPv6 addresses, which are written differently. Use the standard short form from RFC 5952 for comparing.
- DNS has separate records: A for IPv4 and AAAA for IPv6.
How the two live together
Most networks run both ("dual stack"): a device has an IPv4 and an IPv6 address and uses either. There are also translation methods between them. The IANA registry reserves blocks for such uses, such as 64:ff9b::/96 for translation.
Which to use now
If your provider offers IPv6, turn it on and test. If you manage servers, make sure services listen on both. For learning, practise IPv4 subnetting first, then IPv6.
Will IPv4 stop working?
There is no date at which it will. The two will be used side by side for a long time.
Is IPv6 faster?
Not by itself. Speed depends on the network and the routes.
This is an independent guide. It is not connected with IANA, the IETF or any network equipment maker. Address and port data come from the IANA registries as fetched on 14 November 2026; RFC texts were read from rfc-editor.org. Check the originals for anything you rely on.