Dynamic IP address

It depends on the network far more than on the word. Four providers with at least 25 home probes changed no address at all in 30 days. They were Free in France, KPN in the Netherlands, Init7 in Switzerland and Andrews & Arnold in the UK. Comcast, AT&T and Verizon changed fewer than one in ten. At the other end, 1&1 Versatel in Germany and Starlink changed almost every address within a week.

The pattern has moved. A study of RIPE Atlas probes in 2015 found Deutsche Telekom reassigning addresses every 24 hours and Orange every 168 hours. In September 2026, 39.6 percent of Telekom home lines had a new address within a week, so most no longer change daily. Orange France changed 4.8 percent in the same week.

The best-known mechanism is DHCP. Its standard of March 1997 calls it dynamic allocation: the server assigns an address "for a limited period of time". The router renews that lease before it ends, so a DHCP address can stay the same for months while the line stays up.

Some DSL providers do not use DHCP at all. They open a PPPoE session and set the address per session. One large European provider told the 2016 study that it changed addresses after 24 hours "as a privacy feature". The same study found that outages count too: in 2015, Orange changed a line's address even after the shortest outage.

Carrier-grade NAT adds a third case. Starlink's default IPv4 setup gives each dish an address from 100.64.0.0/10 and translates it to a shared public one; a public address is an option on its Priority plans. Its home probes showed a new public address nearly every week.

In two ways. The provider delegates a prefix to the home network, and that prefix can change like an IPv4 address. Among home probes with IPv6, 12.4 percent had a new /64 within a week and 22.3 percent within 30 days.

A RIPE guide for operators, published in October 2017, advises against this. It calls non-persistent prefixes "considered harmful" and recommends persistent ones by default, while asking providers in countries with "specific legal environments" to offer changing, privacy-oriented prefixes as an option.

Inside the network, each device also rotates its own temporary address. Since February 2021 the standard default is a new preferred address every day, valid for two days. The 2007 version had allowed seven.

A static IP address is one the provider does not change. It is often an extra, for example on business lines. It matters when other people need to find you at the same address: a mail server, a camera you reach from outside, or an IP allowlist.

Spamhaus, for example, expects a mail server to sit on a static address with matching reverse DNS. BT says a dynamic address "is not suitable if you want a computer to be permanently visible on the internet".

A residential proxy borrows home connections, so it inherits their addresses and their changes. Residential lines are sold as a rotating proxy by default, and a sticky session can hold an exit only as long as the household keeps its address.

Your own address matters too. If a proxy account lets you in by IP whitelisting and your home line is dynamic, access stops the day the address changes. Proxy authentication with a username and password does not depend on your address at all.

Blocklists face the same problem from the other side. The authors of the 2016 study pointed out that a ban on a dynamic address can outlive the person it was meant for. On some networks, a user could get a new address simply by restarting the router.

Early networks set addresses by hand or from a fixed table. BOOTP, published in September 1985, looked each machine up in a database "relating hardware address to IP address", so a machine always got the same one. Dial-up changed that. From May 1992 a PPP link could ask the other side for an address each time it connected, so every call could bring a different one.

DHCP, first published in October 1993 and revised in March 1997, made the idea general. It is based on BOOTP but adds "automatic allocation of reusable network addresses". PPPoE, published in February 1999, kept the dial-up session for broadband lines, for providers that wanted to "maintain the session abstraction associated with PPP".

IPv6 added privacy to the reasons for change. A standard of January 2001 gave devices temporary addresses that rotate, and the current version, of February 2021, makes them change every day by default.