route delete/add

Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.2.1 0.0.0.0 UG 100 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 wlan0
localnet * 255.255.255.0 U 0 0 0 eth0

sudo route del -net 192.168.1.0 netmask 255.255.255.0 dev wlan0

For example if your router IP address is 192.168.1.254 type the following command as the root user:
# route add default gw 192.168.1.254 eth0
OR use hostname such as dsl-router:
# route add default gw dsl-router eth0