Tenda D810R ADSL2+ User Manual page 49

You can check this
option.
a. Primary DNS server
b. Secondary DNS server
Caution: In the IPoA mode,
DHCP is not supported,
so you need to manually
enter the WAN IP
address, subnet mask,
default gateway, DNS
server and other settings.
D810R ADSL2+ Router User Guide
43