How To Configure Network Setting on CentOS 6.3

بسم الله الرحمن الرحيم

In the Name of Allah. The Most gracious, The Most Merciful

Synopsis:

A short tutorial on how to configure network settings on CentOS 6.3 machine.

Assumptions and Prerequisites:

• OS: CentOS 6.3 x64
• Server Name: mujahid
• Subnet: 192.168.1.0/24
• Server IP: 192.168.1.20
• Subnet Mask: 255.255.255.0
• DNS IP: 192.168.1.15
• Gateway IP: 192.168.1.1
• Domain: houseofjaleel.com.au
• Network Device/Interface: eth0 
• Text Editor: vi
• Firewall (IPTables) is disabled.
• SELinux is disabled.
• '#' - Script Comment.
• This machine is a Server; therefore has a fixed IP settings. It is not assigned any network settings from any DHCP or BOOTP service.

Step-by-Step Instructions:

1. Create the network configuration file /etc/sysconfig/network-scripts/ifcfg-eth0 with the following configurations and save it.

DEVICE="eth0"       # Device name
HWADDR="00:0C:29:7D:A0:62"    # eth0's MAC address. This may be different on your machine.  
NM_CONTROLLED="no"   # Settings are not controlled by the Network Manager service. 
BOOTPROTO="none"   # This device does not receive network settings from any dhcp service on the network.
ONBOOT="yes"            # Service starts at boot time.
TYPE="Ethernet"    # Device type is of Ethernet.
IPADDR="192.168.1.20"               # IP Address of this Network device.
NETMASK="255.255.255.0"     # Subnet Mask
GATEWAY="192.168.1.1"         # IP Address to access the Internet (usually it's a Router).
DNS1="192.168.1.15"       # IP Address of the machine hosting the DNS on the LAN.
DOMAIN="houseofjaleel.com.au"     # Name of the Domain this server belongs to. Omit if no domain configured on Network.
IPV6INIT="no"    # ipv6 is not enabled on this server machine.
USERCTL="no"   # Except for root user, users can't alter network setting for this device.


Clean (without comments) version of the file /etc/sysconfig/network-scripts/ifcfg-eth0


DEVICE="eth0"
HWADDR="00:0C:29:7D:A0:62"  
NM_CONTROLLED="no"  
BOOTPROTO="none"  
ONBOOT="yes" 
TYPE="Ethernet"
IPADDR="192.168.1.20" 
NETMASK="255.255.255.0" 
GATEWAY="192.168.1.1" 
DNS1="192.168.1.15" 
DOMAIN="houseofjaleel.com.au" 
IPV6INIT="no" 
USERCTL="no"


2. Restart Network service.
# /etc/rc.d/init.d/network restart

3. Enable Network Service to start at boot time.
# chkconfig network on

4. Check to see if network settings have been loaded from the configuration file for 'eth0'.
# ifconfig

5. Disable ipv6 device driver on this server machine from loading at boot time.
# echo "install ipv6 /bin/true" > /etc/modprobe.d/disable-ipv6.conf 

6. Restart server.
# reboot

 7. Login as root and check network settings. It should show that there is no "inet6" setting anymore.
# ifconfig

Conclusion:

Change the "DNS1" configuration to "127.0.0.1" or "192.168.1.20", if DNS is configured on the local machine.

Use 'DNS2' to add a secondary DNS host (eg. DNS2="192.168.1.16").

IPV6 is outside of the scope of this tutorial.