another networking puzzle

Dave has a network problem as he’s just bought a second DSL line. I’ve also got two DSL lines but haven’t bothered to connect the two together. I did think about it, running two IP networks on the same LAN and assigning default routes manually. But the hassle wasn’t worth it. It just means the switch over if one line goes down is a few minutes longer. The complexitity versus the benefit doesn’t stack up. Besides one of my DSL lines should disappear soon, but it hasn’t.