dynamic routing in linux?

[inetd]

If I have 2 broadband lines from 2 different ISP and these lines are connected to a single linux gateway. All my clients behide the linux box will uses these two lines to access the internet. Now I want to have a more statable internet connection for my clients such that if one of the broadband becomes fail, then all the internet access are routed through the other broadband.

How can I do that in linux?
What tools should I use?

Thanks.

 

[lgarner]

I haven't done it with Linux myself, but zebra might be what you're looking for.