Setting multiple IPs on Linux or in this case Debian is rather straight forward… All the network info is stored in the file /etc/network/interfaces and you just need to add the info to the file…
Before making changes to this file, I recommend you check your values at least 3 times! If you have made a mistake and trying to do it from a remote location, YOU WILL LOCK YOURSELF OUT!
This is a sample configuration with device eth0 having the IP address of 192.168.1.2 on a Class C Network with 192.168.1.1 as the default gateway.
/etc/network/interfaces – configuration file for ifup(8), ifdown(8)
# /etc/init.d/networking restart