Xtra now gives out routers to new customers. These are D-Link models (502, 504T), which can lead to connection problems. (This is a D-Link issue). The DNS will intermittently not work correctly, and IP addresses will resolve to a different website. These models use an old version of Linux with a prehistoric DNS proxy server which is known to be faulty and abandoned upstream. IanMcDonald managed to get D-Link to release latest version of firmware as they were violating GPL. In theory you could fix this problem as the DNS proxy is only a very small package but the solution below is easier.
My solution was to edit resolv.conf, and then lock the file. This will cause problems if you want to switch networks, but the file can always be unlocked and changed. I was also suggested an alternative method which I have not tried.
Open your /etc/resolv.conf and set valid DNS-servers
sudo gedit /etc/resolv.conf
For Xtra they are (at 19/04/07) 22.214.171.124 126.96.36.199
Now save the file.
Lock it with
sudo chattr +i /etc/resolv.conf
This will permanently lock your DNS-values. (to unlock, use chattr -i)
When testing a 733MHz Compaq with 384MB RAM, running Ubuntu 8.10 (reasonably acceptable performance!), I ran into problems trying to get it to connect to Xtra via an external modem. For some reason, which I haven't worked out yet, both gnome-ppp and kppp refused to talk to the modem. wvdial worked fine, except the login always failed - wvdial responded to Xtra's 3rd prompt "Login/Network User:" by replying with the username instead of "PPP".
I succeeded by running pppconfig, and then changing the last few lines of the chat script in /etc/chatscripts as follows:-
# ispname ogin: your_username # isppassword ssword: your_password # postlogin User: PPP '' \d\c # end of pppconfig stuff