ipconfig (internet protocol configuration) in Microsoft Windows is a console application that displays all current TCP/IP network configuration values and can modify Dynamic Host Configuration Protocol DHCP and Domain Name System DNS settings.
Forced release & renew
An important additional feature of ipconfig is to allow system admins to force refreshing of the DHCP ip address of the host computer to request a different ip address. This is done using two commands in sequence. First, ipconfig /release is executed to force the client to immediately give up its lease by sending the server a DHCP release notification which updates the server's status information and marks the old client's ip address as "Available". Then, the command ipconfig /renew is executed to request a new ip address which is usually a different ip address than the original ip address. In the case where your computer is connected to a Cable or DSL modem, you may need to plug directly into the modem network port bypassing your router and issue ipconfig /release followed by turning off your power for a period of time to ensure that your old ip address is taken by another computer.
Mac OS X ipconfig
ipconfig in Mac OS X serves as a wrapper to the IPConfiguration agent, and can be used to control the BootP and DHCP client from the command line interface. Like most UNIX-based operating systems, Mac OS X also uses ifconfig for more direct control over network interfaces, such as configuring static IP addresses.