Choose Apple menu > System Preferences, then click Network.
Select your service that uses DHCP (such as Ethernet or Wi-Fi) in the network connection services list.
Click Advanced, click TCP/IP, then click Renew DHCP Lease.
Windows → Open a command prompt, click Start, point to All programs, point to Accessories, and then click Command prompt.
ipconfig /release
ipconfig /renew
Errigal Server (Atlas, Comeragh, Hyperion) under the .err zone
ExteNet Servers (QAEXT, EXT) under the .ext zone