I've done this with Soekris and Cisco. The tricky part is getting a router that will take a cable modem module (not sure if either Soekris or Cisco will), plus

I've done this with Soekris and Cisco. The tricky part is getting a router that will take a cable modem module (not sure if either Soekris or Cisco will), plus a DSL terminator (both Soekris and Cisco will). These are not consumer tech, and they're not cheap. Then you have to get or guess the configs for both WAN links, possibly with unhelpful residential support techs. Cisco 2600 class routers are power hungry and loud too, so no win there. Soekris is smaller and more efficient, and runs BSD, so it's awesome in other ways...but it is a pain in the neck to set up. Several hours of prep plus work for your first time. But if you are most concerned about DNS, I can think of two quick options: put your own router (ideally running Tomato or DD-WRT) behind your existing mess and serve DHCP from there to your network(s), or take DHCP from your provider, but hardcode the DNS settings on each host. Edit: and Aside: less than a minute after posting this, I decided to check google to see if Soekris supported cable modem cards, and my post (this comment) came up on the first page of results. I had no idea google could turn crawls into results that quickly. But it appears that Soekris does not support cable modem cards, from a cursory investigation.