You can always make the change permanent by adding the commands you type to your /etc/rc.d/rc.local script.

Alternatively, you can set up a virtual IP interface by creating a file
called ifcfg-eth0:1 in your /etc/sysconfig/network-scripts directory. This file should look something like this:

DEVICE=eth0:1
USERCTL=no
ONBOOT=yes
BOOTPROTO=none
BROADCAST=<your broadcast IP address>
NETWORK=<your subnet address>
NETMASK=<your netmask>
IPADDR=172.16.3.10

This should automatically add the eth0:1 interface each time the network
service is started.

Have you taken the time to update all your server software with the latest patches? RH6.2 has several known security issues.