2026-09-16 · IPV4 Scanner
Your internet connection has one of two arrangements: an address that stays put, or one that can change. Most people have the second and never notice. The moment it starts to matter is usually the moment you try to run something other people need to reach.
A dynamic address is leased. Your provider keeps a pool and hands one out when your router connects, for a fixed period, renewed automatically. In practice you often keep the same address for months, because renewals usually return what you already had. But nothing guarantees it, and a long outage or equipment change can move you.
A static address is assigned to you and does not change until someone changes it deliberately.
The reason dynamic addressing exists is economics. IPv4 addresses are scarce and expensive, and a provider with 50,000 customers does not need 50,000 addresses, because they are not all connected at once. Pooling is how the shortage was managed for twenty years.
You are hosting something. A mail server, a VPN endpoint, a game server, a site on your own hardware. Other machines need to find you at a fixed location, and DNS records pointing at an address that moves are broken records.
Somebody is allowlisting you. Remote access to an office network, a client's database, an API restricted by source address. The allowlist entry becomes wrong the moment your address changes, and the failure is confusing: everything worked yesterday and nothing has changed on your side.
You are running a mail server. This is the strongest case. Mail from dynamic address ranges is treated as spam almost universally, because the overwhelming majority of it is. Reputable delivery also requires a matching reverse DNS record, and providers will not set one for an address they may reassign.
For ordinary browsing, streaming, gaming and video calls, a static address gains you nothing. Those are all outbound connections, and outbound connections work identically either way.
Remote access to your own home is the case people most often get wrong. It sounds like it needs a static address, and it usually doesn't — dynamic DNS solves it, as below.
Dynamic DNS is a small client on your router or a machine at home that notices your address changing and updates a DNS record to match. You get a stable name pointing at a moving address. For remote access to a home network, a camera, or a NAS, this is genuinely sufficient, and it is usually free.
Its limits: a short delay between change and update, during which the name points at somebody else's connection; and it does nothing for mail reputation or for an allowlist that takes addresses rather than names.
A cloud server sidesteps the question. Any small VPS comes with a static address included, and for anything genuinely public that is usually cheaper and more reliable than hosting at home on a residential line with asymmetric upload speeds.
A tunnel service exposes a local service publicly without any inbound connection at all. Your machine connects out, and traffic arrives back through that connection. This works behind carrier-grade NAT, where nothing else will.
Worth knowing about, because it produces symptoms that look like a broken router. Some providers, particularly mobile and newer fixed-line networks, no longer give each customer even a dynamic public address. Instead, many customers share one, translated at the provider's own equipment.
Under it, inbound connections are impossible. Port forwarding on your router does nothing, because the port is not yours to forward. If you have configured everything correctly and inbound connections still never arrive, compare the address your router reports with the one the IP lookup tool sees. If they differ, you are behind carrier-grade NAT, and no amount of router configuration will change that — you need to ask your provider for a real public address, usually as a paid option.
How do I know which I have?
Note your public address, reboot your router, wait a few minutes and check again. If it changed, it is dynamic. If it did not, it may still be dynamic with a long lease — your provider's account portal or support will confirm.
Is a static IP more secure?
No, and mildly the reverse. A fixed address is a fixed target, easier for automated scanning to catalogue over time. The security of what you expose matters enormously more than whether the address moves.
Does a static IP make my connection faster?
No. Speed is determined by the line and the network, not by how the address was assigned.
Can I make my dynamic address stay the same?
Not reliably. Keeping the router powered on tends to preserve it, since renewals usually return the same address, but nothing guarantees it. If you need certainty, you need a static address or dynamic DNS.
Why does my IP change when I reboot the router?
Because reconnecting requests a fresh lease, and the pool may hand back a different address. Some providers key the lease to your equipment and return the same one; others do not.