Ethernet Configuration Activate NIC card at boot time

If in your server NIC card is not getting up while reboot the server, in this case you need to login and start manually. To make network interface up at the time of boot we need to set ONBOOT option in ifcfg-eth0  config file. name ifcfg-eth0 can be different if you have multiple NIC card, this you can verify using ifconfig -a command.

edit the  file /etc/sysconfig/network-scripts/ifcfg-eth0

#vi /etc/sysconfig/network-scripts/ifcfg-eth0

make an entry ONBOOT="yes" if not present 

This will enable NIC interface available on boot time.

If still not working make below entry on file /etc/rc.local

#vi /etc/rc.local

ifconfig eth0 up