APIPA

Automatic Private IP Addressing (APIPA)
Okay, so what happens if you have a few hosts connected together with a switch or hub and you don’t
have a DHCP server? You can add IP information by hand (this is called static IP addressing), but
Windows provides what is called Automatic Private IP Addressing (APIPA), a feature of later
Windows operating systems. With APIPA, clients can automatically self-configure an IP address and
subnet mask (basic IP information that hosts use to communicate) when a DHCP server isn’t
available. The IP address range for APIPA is 169.254.0.1 through 169.254.255.254. The client also
configures itself with a default Class B subnet mask of 255.255.0.0.
However, when you’re in your corporate network working and you have a DHCP server running,
and your host shows that it is using this IP address range, this means that either your DHCP client on
the host is not working or the server is down or can’t be reached because of a network issue. I don’t
know anyone who’s seen a host in this address range and has been happy about it!


CCNA Data Center - Introducing Cisco 2013.