edc: I've read the replies, thank you.
How do I set Ubuntu up, with two NICs, to connect to Vodafone UFB please?
The answer is don't do it.
Set up a machine dedicated to being the router and nothing else, possibly a firewall distro like www.pfsense.org would do the trick. Its designed to be secure from the start and based on FreeBSD so its more secure than linux already. A Ubuntu install will not give you a secure firewall.