IPv4 vs IPv6
Two address families that run the internet
Understand capacity, notation, and how they impact DNS results
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Quick summary
IPv4 uses 32-bit addresses (example: 192.0.2.10) and is widely supported but limited in total address space. IPv6 uses 128-bit addresses (example: 2001:db8::10) and provides a vastly larger pool.
Key differences
- Address size: IPv4 = 32-bit, IPv6 = 128-bit.
- Notation: IPv4 uses dotted decimal, IPv6 uses hexadecimal with colons.
- Availability: IPv4 is still common, IPv6 adoption continues to rise.
- Network design: IPv6 reduces reliance on NAT for large networks.
Quick example
A domain can publish both record types: an A record for IPv4 and an AAAA record for IPv6. Clients choose the best path available. If you only publish A, IPv6-only users cannot reach the site.
example.com A 203.0.113.10
example.com AAAA 2001:db8::10
example.com AAAA 2001:db8::10
Common use cases
- Checking if a domain is reachable on IPv6-only networks.
- Diagnosing performance or routing differences between IPv4 and IPv6.
- Ensuring DNS records include A and AAAA where needed.
FAQ
Do I need both IPv4 and IPv6?
Dual-stack (A and AAAA) gives the best reach today. IPv4-only can block IPv6-only users.
Will IPv6 replace IPv4 soon?
IPv6 adoption is growing, but IPv4 is still required for broad compatibility.
Why are IPv6 addresses longer?
The larger space prevents exhaustion and enables more flexible network design.