Use the Network pane in System Preferences to deactivate then activate the network interface. This allows you to renew or acquire a new DHCP lease.
1. Choose Location from the Apple menu, and Network Preferences from the submenu.
2. Choose Network Port Configurations from the Show pop-up menu.
3. Deselect the checkbox for the network interface for which you need to renew the DHCP lease.
4. Click Apply.
5. Reselect the checkbox for the network interface.
6. Click Apply.
7. Quit System Preferences.
Note: If you use locations, you can automate these steps by simply toggling between locations. Create a location in which the affected network interface is inactive, then toggle between it and your normal location. For more information, see technical document 106653, "
Mac OS X: How to Use Locations".