What is Alternate Configuration?
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.
By default, a computer running Windows Server 2003 tries initially to contact a DHCP server on the network to dynamically configure each installed network connection. If a DHCP server is found and the leased configuration is successful, then TCP/IP configuration is completed. Otherwise, the computer uses either APIPA or a user configured alternate configuration to automatically configure TCP/IP.
The Alternate Configuration tab is only visible if Obtain an IP address automatically is selected on the General tab of the Internet Protocol (TCP/IP) Properties dialog box.
If APIPA has been selected as the mode of alternate configuration, then Windows Server 2003 selects an address in the reserved IP-addressing class that ranges from 169.254.0.1 to 169.254.255.254. This range of IP addresses is reserved by the Internet Assigned Numbers Authority (IANA) for APIPA use and none of the IP addresses in this range are used on the Internet.