Comment 6 for bug 556831

> Just connect your machine to a router not connected to the net.
> You will then see the problem.

Does the router advertise a default route to the system being installed? Does the *router* have a default route?

ubiquity (or probably, apt) should certainly handle a "no route to host" (EHOSTUNREACH) error gracefully; if, however, the network is configured in such a way that it *claims* to have a public Internet route when it doesn't, ubiquity cannot usefully distinguish this case from the case where the network is just Very, Very Slow, and would normally fall back to the TCP protocol-level timeouts.