I've been Googling around for a while and can't find any good utilities (command line or GUI, don't mind too much) for configuring iptables routing.
Part of the trouble is that 'iptables configuration' mostly means firewall set up and I don't want/need to do that as it's in my ADSL router. What I want is to configure routing tables in a Linux 'server' box on my network.
It *may* be that some of the firewall utilities will do what I want but it's difficult to penetrate the mass of information about firewall set up. I think Smoothwall can probably do what I want but is possibly overkill. Quagga maybe too but it is definitely overkill, I don't have complex requirements, just slightly non-standard ones.
There are sites like http://lartc.org/howto/lartc.rpdb.multiple-links.html which tell you how to do some of what I want but they're very old and I wonder if they're still the right way to do things. They're mostly four or five years old and the kernel and routing have probably moved on somewhat since then. They don't really handle failover either.