In most consumer networks, IP addresses are assigned dynamically as needed, just as external IP addresses are assigned by an ISP, ensuring that every device has a unique address and allowing for addresses to be recycled and reused as devices come and go from the network. Once inside your network, a router, either standalone like an AirPort Extreme or one built in to a cable or DSL modem, handles the IP addresses of the devices that connect to it. That address can be dynamic, in that it changes based on the needs of the ISP, or static, meaning that it never changes once it’s assigned (static IP addresses are often available only for an extra fee). In most situations, an internet service provider (ISP) assigns a single external IP address to a customer. The series of numbers and periods allows network traffic to be routed to and from individual devices, just like a home’s street address allows mail and packages to arrive at the correct destination.
All network devices, from computers, to smartphones, to printers, to televisions, need a unique IP address.
