Alternate Configuration is useful if you use the same computer on more than one network and at least one of the networks does not have a DHCP server, for example, laptop users can use Alternate Configuration to automatically assign IP addresses on both office and home networks without having to manually reconfigure the TCP/IP settings.
Alternate Configuration provides two methods of automatically assigning an IP address: user configured Alternate Configuration, and APIPA.
User configured Alternate Configuration provides more detailed parameters than APIPA. If you need a specific IP address and subnet mask for a client, or access to a default gateway, a DNS server, or a WINS server, you should use user configured Alternate Configuration supply the required information.
If you’re happy with a reserved IP address in the 169.254.0.1 to 169.254.255.254 range and you don’t need access to a default gateway, a DNS server or a WINS server, then you can use APIPA.