Adding IP’s to your linux machine can be a hard task at first but it can be broken down to these few steps.
To implement a temporary solution you can execute the command
Command: ifconfig eth0:1 IP.ADDRESS.HERE. (Note IP.ADDRESS.HERE is the additional IP you want linked to your machine.)
Main IP: eth0:0
Secondary IP: eth0:1
Third IP: eth0:2
Fourth IP: eth0:3
Further note that computers start counting at 0 being a element number and up. Meaning 1 = 0 2=1 3=2 etc.
To make these changes Permit we will have to configuration the networking files to reflect these actions.
Starting out make sure that the ifcfg-eth0 file does not consist of any gateway=parameter. If it does remove this statement. The root to find this file is as following: etc/sysconfig/network-scripts/ifcfg-eth0
Next, copy the file ifcfg-eth0 and name it ifcfg-eth0:1
Command: cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:1
Once you have copied the file edit the ifcfg-eth0:1 and change the statement Device=eth0 to device eth0:1 and change the IPAddr= to the addon IP you want, that is assigned to your machine. Start the Secondary interface with: ifup eth0:1
Repeat this step to add as many IP addresses as you desire.