D-Link DWR-961 User Manual page 12

Section 4 - Configuration
NAT disable:
Enabling this option will disable the NAT firewall function of the
DWR-961, exposing all connected devices directly to the Internet.
This is an advanced feature and not recommended for normal use.
Click Apply to save your settings, or Refresh to revert to your
previous settings.
D-Link DWR-961 User Manual 14