What is a dynamic IP address?

A dynamic IP address is an IP address that can change every time you connect to the Internet. A dynamic IP address is generally assigned by a router that has been configured to distribute IP addresses. A network that is configured to assign dynamic IP addresses does so every time a network device is connected, without any setup required by a person.

Dynamic IP addresses expire after a certain period of time has elapsed, usually configured when the network is setup.  It is common to have dynamic IP addresses expire after a few days.  When a dynamic IP address expires, a router will assign a new dynamic IP address.  This can be the same IP address the network device previously had, or a new IP address.  For this reason it is preferable for certain network devices to have static IP addresses assigned by a network administrator.