After installing RHEL 6 you may not be able to get network connection up on booting the machine.
This is a reported bug in RHEL 6.
Follow below steps to solve the issue.
Edit /etc/sysconfig/network-scripts/ifcfg-eth0 file, which is your default first NIC configuration file.
If you are using DHCP server:
Edit below file and change as given below
#vi /etc/sysconfig/network-scripts/ifcfg-eth0
ONBOOT="yes"
BOOTPROTO="dhcp"
Save & restart networking service,
#service network restart
If you are providing manual IP:
Edit below file and change as given below
#vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
IPADDR=192.10.110.10
NETMASK=255.255.255.0
NETWORK=10.10.10.0
GATEWAY=192.9.110.253
ONBOOT=yes
BOOTPROTO=none
USERCTL=no
Save & restart networking service,
#service network restart
