If you have:
ip route:
10.200.64.0/20 dev eth0 proto kernel scope link src 10.200.65.12
10.200.64.0/20 dev wlan0 proto kernel scope link src 10.200.65.12
default via 10.200.16.1 dev eth0
default via 10.200.16.1 dev wlan0
You could do:
ip route del default via 10.200.16.1 dev eth0
ip route del 10.200.64.0/20 dev eth0 proto kernel scope link src 10.200.65.12
If the link comes back on eth0, you could then do
ip route add 10.200.64.0/20 dev eth0 proto kernel scope link src 10.200.65.12
ip route add default via 10.200.16.1 dev eth0
Similar for the wlan0 one.
The ip command is extremely useful and much more powerful than route and
ifconfig ever were. A lot more options are available, and the syntax
is a lot nicer too.