IPv4 vs IPv6

IPv4 vs IPv6 is simply the older 32-bit address format versus the newer 128-bit one. IPv4 is still what most people type and what a lot of mail and allow-lists expect. IPv6 is longer, and on our VPS plans it is enabled by default. Dual-stack means your site answers on both. If you publish an AAAA record, many phones will use IPv6 first, so a leftover AAAA after a move can send mobile visitors to the old server while office Wi-Fi on IPv4 still looks fine.

What you get on shared hosting and VPS

On a LogicWeb VPS you receive IPv4 and IPv6 together, with IPv6 on by default. Shared hosting always includes IPv4; whether IPv6 appears for your site depends on the stack in front of the vhost. Mail reputation, PTR records, HELO names, and many allow-lists are still built around IPv4. You can send mail over IPv6, but receivers often still weigh the IPv4 path they also see. Turning IPv6 off only to keep things simple can hide a second live path that shows up on LTE. Turning IPv4 off on a public web server still leaves some visitors stranded, so plan to run both on purpose.

How to test IPv4 and IPv6 for your domain

Ask DNS for both record types, then request the site over each stack. That tells you whether phones and IPv6 networks will hit the same place as your IPv4 checks.

dig A example.com +short
dig AAAA example.com +short
curl -4sI https://example.com | head -n 5
curl -6sI https://example.com | head -n 5

Replace example.com with your domain. If AAAA is empty, you are IPv4-only, either by choice or by accident. If AAAA points at a different server than A, you effectively have two productions. A broken or stale AAAA is a common reason only phones fail after a migration. ping6 can mislead the same way ping can, so prefer dig and curl against the name you actually serve.

Cut over both stacks, or stay IPv4-only on purpose

Before a move, write down the old and new IPv4 and IPv6 addresses. If the new host has IPv6, publish AAAA only when the vhost and certificate are ready. If the new host has no IPv6, remove the old AAAA so it does not keep answering. A dangling AAAA is still production traffic. When you open a ticket, paste dig A, dig AAAA, and both curl headers. If only phones fail, say so clearly—that pattern often means a leftover AAAA still pointing at the previous host.