I've got a linux server with two possible connections to the net: one is a slow, high-latency cellular modem (ppp0), and the other is through fast wifi->broadband (wlan0).
The problem is that the broadband connection sometimes goes down. However, because the wifi is still there, wicd leaves the default route through wlan0. (If the wifi signal disappeared, then wicd would remove wlan0 from the routing tables and the default route would fail over to ppp0, but, in this case, the wifi, itself, looks fine).
What I need is a tool which will actually test for connectivity all the way to some selected servers and, if they are unreachable, set the default routing interface to be ppp0 for a time.
I can probably hack together a script which can do this, but it seems like something which other people would have needed to do. Is there not already a tool or script which does this?