CentOS ifcfg-eth0 config file deleted. Utility to recreate it

You will also need to add this to your /etc/sysctl.conf:

net.ipv4.ip_forward = 1

and then run:

sysctl -p /etc/sysctl.conf

The default behavior for Red Hat is not to forward packets, but just to be an end point.

You are also going to want to accept traffic going through the box (or it won't work very well as a router)

iptables -A FORWARD -i eth1 -j ACCEPT

You'll also want to add postrouting masquerade rules for the traffic.

BTW, in your ifcfg-eth1 file, change the device name to eth1, otherwise you may have problems.

DNS is there to provide domain name <=> ip addressing, you might need to have your own DNS server if you have servers inside the 192.168.3.X network, so you do not have to remember IP addresses, though you will want to configure those machines with static IPs or set up DHCP to always assign them the same IP. If however you do not have a need for internal DNS, use the ones your ISP provides, or Google's (8.8.8.8).

Don't use these old deprecated alias interfaces. Instead, add all the IP addresses to eth0.

Edit /etc/sysconfig/network-scripts/ifcfg-eth0 and add the addresses:

IPADDR2="xx.x.xxx.202"
NETMASK2="255.255.255.192"
IPADDR3="..."

and so on.