Static vs Dynamic IP: Which One Do You Actually Have

A static IP stays the same. A dynamic IP changes — sometimes after every reboot, sometimes after weeks, sometimes never in practice. The distinction matters more than most casual internet users realise, and your ISP's answer to 'which do I have?' is usually some version of 'dynamic, unless you pay more.'

How Dynamic IPs Work

When your router connects to your ISP, it requests an IP address using DHCP. The ISP's DHCP server assigns one from a pool, with a lease time — typically 24 to 72 hours for residential connections. When the lease expires, the router requests a renewal. Usually it gets the same IP back. Sometimes it doesn't.

In practice, many residential customers keep the same dynamic IP for months or years, simply because the DHCP server keeps handing them the same address. But unplug your router for long enough, and you might come back with a different IP. The ISP needs the flexibility to reassign addresses efficiently across their customer base.

Why Static IPs Exist

If you're running a server — web server, mail server, game server — you need people to be able to reach it at a consistent address. A changing IP means DNS records go stale, incoming connections fail, and whatever you're hosting becomes intermittently unreachable. Businesses running their own infrastructure buy static IPs from their ISP specifically to avoid this problem.

Remote access is another use case. If you want to SSH into your home network from anywhere, a static IP means you always know the address. With a dynamic IP you need a dynamic DNS service — something that continuously updates a domain name with your current IP address.

The Privacy Angle

A static IP is a persistent identity. Every connection you make, every server log that records your IP, every ad network that tracks it — they can link all of it to you indefinitely. A dynamic IP at least provides some degree of pseudonymous churn. Not much, practically speaking, because ISP records link dynamic IPs to subscribers at any given time anyway. But it's something.

Wait — this matters. Static IP addresses also accumulate reputation. If your static IP ends up on blacklists or in threat intelligence feeds, that reputation follows your address permanently. Dynamic IPs reset that association when they change hands.