It must be like this:
Code:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# This is a list of hotpluggable network interfaces.
# They will be activated automatically by the hotplug subsystem.
mapping hotplug
script grep
map eth0
# The primary network interface
iface eth0 inet static
address 10.100.100.102
netmask 255.0.0.0
gateway 10.100.100.1
auto eth0
auto lo:0
iface lo:0 inet static
address 10.100.100.105
netmask 255.0.0.0
gateway 10.100.100.1
pre-up sysctl -p > /dev/null
Take care about the leading spaces!