[falko]

I hope your file looks rather like this:

# 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

# The primary network interface
# allow-hotplug eth1
auto eth1
iface eth1 inet static
    address 192.168.1.75
    netmask 255.255.255.0
    network 192.168.1.0
    broadcast 192.168.1.255
    gateway 192.168.1.50

The leading spaces are important - they mean that the address, netmask, etc. settings still belong to eth1.