configure a system to use two different networks

Question: 

How we can configure a system to use two different networks.

Requirements:

Red Hat Enterprise Linux or *nix OS

A system with two Network Interface Cards (NICs)

Two different networks

Solution:

• Edit the file  /etc/sysconfig/network and fill in the values of the variables:

NETWORKING=yes

HOSTNAME=myhost.example.com

Note: If necessary, remove or comment out the variable GATEWAY. Each NIC will have it's own gateway.

• Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 and add the following variables with their corresponding values:

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
NM_CONTROLLED=no
USERCTL=no
IPADDR=
NETMASK=
GATEWAY=
PEERDNS=yes
DNS1=
DNS2=

• Do the same for the file /etc/sysconfig/network-scripts/ifcfg-eth1:

DEVICE=eth1
BOOTPROTO=none
ONBOOT=yes
NM_CONTROLLED=no
USERCTL=no
IPADDR=
NETMASK=
GATEWAY=
PEERDNS=yes
DNS1=
DNS2=

The values between '<' and '>' are dependent on your network.

The variables PEERDNS, DNS1 and DNS2 are optional. If you have the same DNS servers for both networks, you should put the nameservers IPs in the file /etc/resolv.conf, and in both ifcfg-eth?files remove the variables DNS1 and DNS2 and setPEERDNS=no.

• Restart the network service:

# service network restart

Thanks!