Net

_$: route add -net 192.168.1.0 netmask 255.255.255.0 dev eth0
_$: route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
...
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0

_$: route del -net 192.168.1.0 netmask 255.255.255.0 dev eth0

Host

_$: route add -host 192.168.1.105 dev eth0
_$: route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
...
192.168.1.105   0.0.0.0         255.255.255.255 UH    0      0        0 eth0

_$: route del -host 192.168.1.105 dev eth0

Gateway

_$: route add default gw 192.168.1.1 dev eth0
_$: route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 eth0

_$: route del default gateway 192.168.1.1