Change DNS server in Bbox 2

Connect to your Bbox2 using telnet (example: telnet 192.168.1.1) Login with admin and password, the default password is the serial number of your bbox2

To see the currently served DNS address: 

rg_conf_print /dev/br0/dhcps/dns/0/ (output example:  (0(192.168.1.1))
Change the address like so: 
rg_conf_set /dev/br0/dhcps/dns/0/ 8.8.8.8
Save the configuration by issuing the command: save