Automatic Private IP Addressing (APIPA)

Automatic Private IP Addressing (APIPA), supported by Microsoft Windows OS, comes into action when the DHCP on a network is not functional, either permanently or temporarily. APIPA is a private IP address range of 169.254.0.0 - 169.254.255.255, which has been designed for small non-routable networks. It is an autoconfiguration address, as shown in Figure 2.15, which means that as soon as a DHCP client cannot discover a DHCP server on a given network, Windows automatically assigns an APIPA address to a computer's network interface.

As soon as a DHCP server becomes available, the APIPA address is replaced by the one assigned from the DHCP server: