Static and dynamic IP addresses

Most home and mobile connections have a dynamic address that changes now and then. A static address stays the same until you ask for a change.

What the two words mean

Dynamic means the address is lent to you for a while. Your internet provider keeps a pool of addresses and hands one to your router each time it connects, with a time limit called a lease. When the lease ends, or the router restarts, you may get the same address again or a different one.

Static means one address is reserved for you and does not change. Providers usually charge extra for it and offer it mainly on business plans.

The same two words are used inside your home network. Your router lends dynamic private addresses to phones and laptops, and you can tell it to always give one device, such as a printer, the same private address. That is free and is set in the router; it is often called "DHCP reservation" or "address binding".

How to tell which you have

1. Note the public address on our home page.
2. Switch the router off for five minutes and switch it on again. On mobile data, turn flight mode on and off.
3. Look again. If the address changed, it is dynamic.

If it did not change, it may still be dynamic: many providers give the same address back for weeks. Your plan or bill normally says "static IP" if you are paying for one.

Who needs a static public address

• Someone hosting a website, mail server or game server at home or in an office.
• An office whose staff connect in from outside through a VPN.
• A business whose bank, supplier or software allows logins only from an approved address.
• Owners of security cameras and recorders who want to view them directly from outside, without the maker's cloud service.

For ordinary browsing, video, calls and online games, a dynamic address is completely fine.

What a dynamic address is better at

• A little privacy. A site that remembers you only by address loses track when it changes.
• Cost. It is included in every plan.
• Less attention. A fixed address that runs services is scanned by automated attack tools all day. That happens to every address, but a changing one gives them less to hold on to.

If you need to be reachable but have no static address

• Dynamic DNS (DDNS): a service gives you a name such as myhome.example.net and a small program in your router keeps the name pointing at your current address. Many routers have this built in.
• A tunnel or relay service: your device makes an outgoing connection to a service on the internet, and visitors reach you through it. This also works when your provider shares addresses.

Both fail in one case if used alone: when your provider uses carrier-grade NAT, the public address is not yours alone, so DDNS and port forwarding cannot work. A tunnel service, or a static address from the provider, is then the only way.