It's the fault of the DHCP-client. Everytime the Lease-Time is over (which might happen in the interval ofjust a few minutes) a DHCP-Renew ist done. The tablet's DHCP-client is somehow broken, because it always sets the default route supplied by the DHCP-Server, even if there is a different default route active . I have not found a "clean" solution for that problem, yet. I personally edited /etc/udhcpc/udhcpc.script so that it doesn't do anything on RENEWs, just on BOUNDs.