Last updated: October 29, 2025
Internet Protocol (IP) addresses are numerical labels that identify devices on a network. IPv4 is the original widely deployed version, while IPv6 is its successor designed to solve address exhaustion and improve efficiency. Modern networks are commonly dual-stack, meaning both protocols operate side-by-side. Your device, browser, and the websites you visit negotiate which version to use automatically. Understanding both protocols helps you troubleshoot connectivity issues, interpret diagnostics, and configure services properly.
| Property | IPv4 | IPv6 |
|---|---|---|
| Length | 32-bit | 128-bit |
| Notation | Decimal dotted quad (e.g., 203.0.113.42) | Hexadecimal colon-separated (e.g., 2001:0db8:85a3::8a2e:0370:7334) |
| Total addresses | ~4.3 billion | ~3.4×1038 (virtually inexhaustible) |
| Private ranges | 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 | fc00::/7 (Unique Local Addresses), fe80::/10 (Link-Local) |
| Loopback | 127.0.0.1 | ::1 |
| Broadcast | Supported (e.g., 255.255.255.255) | Not used; relies on multicast |
::. Example: 2001:0db8:0000:0000:0000:ff00:0042:8329 → 2001:db8::ff00:42:8329.
IPv4’s finite address space could not keep pace with the explosive growth of the internet—smartphones, IoT devices, cloud servers, and home networks all needed unique addresses. Workarounds like Network Address Translation (NAT) extended IPv4’s life, but added complexity and broke true end-to-end connectivity. IPv6 restores end-to-end principles, simplifies routing, and enables massive scaling with built-in features such as stateless address autoconfiguration (SLAAC) and pervasive multicast.
IPv4: Typically uses NAT so many private devices share one public address. This complicates inbound connections and some peer-to-peer apps.
IPv6: No NAT by design. Every device can have a globally routable address, which simplifies direct connectivity (while firewalls still enforce security).
IPv6 uses a streamlined header and extension headers for optional features, improving router performance. Aggregated addressing simplifies global routing tables and can reduce latency by enabling more efficient path selection.
IPv4 commonly uses DHCPv4. IPv6 supports SLAAC (automatic addressing from router advertisements) and DHCPv6. Many networks deploy a mix for flexibility.
While IPsec exists for both, it was architecturally mandatory in IPv6’s design era and remains a first-class citizen. Regardless of protocol, endpoint and application-layer security practices remain essential.
IPv4 addresses are published in A records; IPv6 in AAAA records. Dual-stack sites publish both so clients can choose the best path.
Most client systems today follow Happy Eyeballs (RFC 8305) logic—attempting IPv6 and IPv4 in parallel and using whichever connects faster. If your network has partial IPv6 misconfiguration, sites could feel slow or intermittent. Tools like Ping, Traceroute, and Dig on this site help identify whether IPv6 paths are healthy compared to IPv4.
You don’t need to configure anything as an end-user—if your ISP and router support IPv6, your devices will typically use it automatically. For hosting and businesses, enabling IPv6 improves reachability and future-proofs services.
Often due to firewall rules, missing AAAA records, or provider networks that have asymmetric IPv6 routing. Compare ping and traceroute results for each protocol to isolate the fault.
You still need proper firewall policy. The lack of NAT is not inherently less secure—stateful firewalls and sane defaults maintain protection while preserving end-to-end connectivity.
For hands-on testing, explore our Dig guide, Ping guide, Traceroute guide, and Whois guide.