how to use the google DNS servers with an O2 Wireless box

Steps:

1. telnet into the router: telnet 192.168.1.254 (you will need a telnet client. Windows, MacOS and Linux all come with them)
2. login as SuperUser, with a password of O2Br0ad64nd (this is public knowledge BTW, but only useful INSIDE your network. This works in the web UI too)
3. run the following commands:
   dns server route flush
   dns server route add dns=8.8.8.8 metric=0 intf=O2_ADSL
   dns server route add dns=8.8.4.4 metric=0 intf=O2_ADSL
   dns server route list
   saveall
   exit
4. If you make a mistake on a line, press CTRL-C to cancel. dns server route list will show the list at any time.
5. If you want to use the O2 servers as a backup, omit the first line (dns server route flush) which removes O2′s DNS servers (which at the time of writing are 87.194.255.155 and 87.194.255.154).
6. If you want to use Google as a backup DNS server, not the primary, change the metric to 20 (O2′s ones are 10)
7. Enjoy!

As pointed out by Antonio Lulić, you will most likely need to restart your wireless box / router once you have done this. I don’t recall having to do it, but it’s not a bad idea from time to time anyway :)