Change DNS server in Bbox 2

Connect to your Bbox2 using telnet (example: telnet 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(
Change the address like so:
rg_conf_set /dev/br0/dhcps/dns/0/
Save the configuration by issuing the command: save