Route

route is the command to view and edit the routing table. With route you can see what is the routing for IP-packets coming from a network interface for a specified destination is. A default gateway may be listed for non-routable packets.

Example
Show your routing table: Kernel IP routing table Destination    Gateway         Genmask         Flags Metric Ref    Use Iface 10.0.0.0       0.0.0.0         255.255.255.0   U     0      0        0 eth1 192.168.1.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0 0.0.0.0        10.0.0.138      0.0.0.0         UG    0      0        0 eth1
 * 1) route -n

Options
-n show numerical addresses instead of hostnames

Typical pc
For a pc with typical network access, to add a gateway issue route add default gw 192.168.1.1 (where 192.168.1.1 is the address of your gateway)

Adding a network
To tell your Linux to send packages for the network 192.168.0.0/24 to the network device eth3: route add -net 192.168.0.0 netmask 255.255.255.0 eth3 The same with a default gateway of 192.168.0.1: route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1 eth3

Deleting an entry
$ route -n Kernel IP routing table Destination    Gateway         Genmask         Flags Metric Ref    Use Iface 192.168.0.0    0.0.0.0         255.255.255.0   U     0      0        0 rausb0 127.0.0.0      0.0.0.0         255.0.0.0       U     0      0        0 lo 0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        0 rausb0 $ route delete -net 0.0.0.0 $ route -n Kernel IP routing table Destination    Gateway         Genmask         Flags Metric Ref    Use Iface 192.168.0.0    0.0.0.0         255.255.255.0   U     0      0        0 rausb0 127.0.0.0      0.0.0.0         255.0.0.0       U     0      0        0 lo $ Strange error messages should not hold you back: $ route Kernel IP routing table Destination    Gateway         Genmask         Flags Metric Ref    Use Iface 192.168.0.0    *               255.255.255.0   U     0      0        0 eth1 link-local     *               255.255.0.0     U     0      0        0 eth1 loopback       *               255.0.0.0       U     0      0        0 lo default         192.168.0.1     0.0.0.0         UG    0      0        0 eth1 $ route del -host 192.168.0.0 SIOCDELRT: No such process $ route del -net 192.168.0.0 SIOCDELRT: Invalid argument $ route del -net 192.168.0.0 netmask 255.255.255.0 eth1 $ route Kernel IP routing table Destination    Gateway         Genmask         Flags Metric Ref    Use Iface link-local     *               255.255.0.0     U     0      0        0 eth1 loopback       *               255.0.0.0       U     0      0        0 lo default         192.168.0.1     0.0.0.0         UG    0      0        0 eth1 $