Ifconfig
From Noah.org
Set static IP
These settings are lost on reboot. This is just for a temporary config.
# ip route add default via 192.168.0.1 # ifconfig eth0 192.168.0.2 netmask 255.255.255.0
Virtual Interfaces
Adding virtual interfaces is easy in Linux. Just add a number to a real interface name. In this example, I assume 'eth0' is the real interface name, so I will configure 'eth0:1' (you can pick any free number after the 'eth0:'). The netmask defaults to 255.255.255.0.
ifconfig eth0:1 192.168.0.3
If you need to specify the netmask, this is easy:
ifconfig eth0:1 192.168.0.3 netmask 255.255.255.128
Delete an interface
Use the 'down' command:
# ifconfig eth0:1 down