This button appears on the administrator's main page, if Quadro performs as a DHCP client and gets its IP address automatically. The corresponding settings are configured from the System Configuration Wizard. If this radio button is selected, Quadro is turned into a DHCP client.
The button Renew WAN IP Address is used to get a new WAN IP address very quickly if Quadro moves to another network for example. Certainly Quadro as a DHCP client will get its new IP address automatically anyway - but it may last up to 15 minutes. So, press the button if you don't want to wait.