While that in theory should work, you may be running into problems because you have overlapping routes for a large part of the IP address space if you have another internet connection up at the same time.

Instead of 111... try using the private IP space of 192.168.x.x which aren't routable and supposed to be used for internal networks and keep the netmasks a bit more reasonable perhaps... That may work out better, or it might not help at all.

Matthew