Automatic Private IP Addressing, also known as APIPA or Auto IP, is a method of automatically assigning IP addresses to networked computers and printers.
A networked device configured to use Auto IP first makes a request to a DHCP server for an address. If the device does not receive an IP address, which happens when there is no DHCP server on the network or when the DHCP server is not responding, the device assigns itself an address. Auto IP addresses always follow this pattern:, where and are any two numbers between 0 and 255. Unlike DHCP, Auto IP does not require a router or a separate server to assign an IP address.
If a network is configured with IP addresses for a different network than, devices with Auto IP addresses will not be able to communicate properly.
Unless a network is intentionally configured using Auto IP addresses, a device with an Auto IP address is a sign that there is a problem with the network. Most networks using automatic IP address configuration for new devices use DHCP, not Auto IP. Devices with Auto IP addresses that should not have them can be a sign that there is an issue with the router or DHCP server, or with cabling. On a wireless network, Auto IP addresses can also indicate that interference or an obstacle is preventing normal network communications.