When you start a Windows Vista-based computer, you may notice the following:
The computer first uses an Automatic Private IP Addressing (APIPA) IP address.
Later, the computer acquires an IP address from a Dynamic Host Configuration Protocol (DHCP) server.
This behavior occurs if Windows Vista cannot immediately contact a DHCP server. In this situation, Windows Vista tries for only six seconds to contact a DHCP server and then uses an APIPA IP address. Then, Windows Vista continues trying to acquire an IP address from a DHCP server.
This behavior differs from earlier versions of Windows. For example, when you start a Microsoft Windows XP-based computer, Windows XP tries for a full three minutes to contact a DHCP server before it uses an APIPA IP address.