Yes, but this still switches the default route from the first ethernet card inserted to the second. Basically, whichever card is added last becomes default route.
My main trouble is that the second ethernet card is a wireless card, so that if I am not near an access point, dhcp fails and shouldn't change any route. This preserves my wired ethernet card as default. In general, though, I think I want to be able to select an interface to be preferred default route (because the default should be the wired card if that's active).
Is there a better solution to this (perhaps) more general problem of picking an interface to be default route?
Let me know if I've confused anyone terribly. (Besides myself.)