Wireless router is LAN’s default gateway and acts as the DHCP server.
Most router act as a DNS server.
The default DNS should be the same as the Default Gateway.
For example, if your router
IP Address is 192.168.1.1
Default Gateway is 192.168.1.1
DNS1 Server should be 192.168.1.1
DNS2 Server could be 126.96.36.199 or your ISP provided DNS