D-Link DSL-2640U Quick Installation Manual page 24

DSL-2640U
11. For connection of Static IP type: in the IP section, fill in the IP
Address, Netmask, Gateway IP address, and Primary DNS
server fields.
12. For connection of Dynamic IP type: if your ISP has provided the address
of the DNS server, in the IP section, deselect the Obtain DNS server
addresses automatically checkbox and fill in the Primary DNS
server field.
Quick Installation Guide
24