Definition
of APIPA: A feature of Microsoft Windows, APIPA allows a computer configured as a DHCP client to obtain
an IP address even in cases where the DHCP server cannot provide one.
APIPA functions as a DHCP server failover mechanism as follows. If the client cannot obtain an address from the server, it
obtains an address from the built-in, reserved address range of 169.254.0.1 through 169.254.255.254. The client
verifies this address is not already in use on the LAN using ARP. Whenever the DHCP server become able to service requests, the
client updates its address information accordingly.
The 169.254.xxx.xxx address range is reserved for private nodes, not for computers directly connected to the Internet. In
APIPA, all nodes in this range utilize the same default network mask, 255.255.0.0, and thus all reside on the same subnet. With
these restrictions, APIPA works well only on home or small business networks. Though part of Windows 98, Windows ME, Windows
2000, and newer flavors, APIPA does not exist in Windows NT.
APIPA is automatically enabled for all DHCP clients in Windows unless the computer's Registry is modified to disable it.
APIPA can be disabled for each network adapter individually or on the entire computer.
Also Known As: Automatic Private IP Addressing; AutoNet
