APIPA

The term APIPA is actually abbreviation of Automatic Private Internet Protocol Addressing. This is a property of the recent operating systems of Microsoft Windows. While using the APIPA, the DHCP client may by itself configure to an Internet Protocols Address (IP Address) in the event server (DHCP) is not available.  However, when the DHCP client is booted, it primarily checks for a DHCP server so as to have the IP (Internet Protocol) address as well as the SUBNET Mask. If the client does not find this information, it then utilizes the APIPA in order to develop a configuration with the IP (Internet Protocol) address from the already specified typical range set for Microsoft Systems. Such Microsoft IP Address ranges from 169254.o.1 to 169.254.255.254.

Moreover the client machines can develop a configuration by themselves with the default Class-B SUBNET Mask i.e. 255.255.0.0. Thus the client normally uses such self-monitored/configured IP (Internet Protocols) addresses in absence of DHCP server.

Thus an APIPA use to check for availability of DHCP server at regular intervals (usually after 5 minutes). So whenever the DHCP is found on the Network, the APIPA suspends and a DHCP server is replaced by the APIPA network path with the help of assigned (dynamically) address.  The APIPA is useful for small networking environments.