I was recently running up a new CentOS6.4 64-bit minimal install on VMware vCenter v5  & vSphere client v5, and during the install of CentOS you can configure the networking manually, which I usually do for servers.  This VM server has 2 VNICs, so I configured both manually and plugged in all the usual settings, static IP, default gateway etc., all very straight forward.  On rebooting I noticed I had no networking at all, that’s odd I think.

I look at /etc/sysconfig/network-scripts/ifcfg-eth0 and eth1 and notice that the line ONBOOT is set at “NO”, so no wonder it wasn’t working, so simply change it to “YES” and you are good to go.

DEVICE=eth0
TYPE=Ethernet
UUID=dfe0f2f3-ff34-41c4-b634-c06b32c4567
ONBOOT=yes <==== change to YES
NM_CONTROLLED=no 
BOOTPROTO=none
HWADDR=00:55:36:AF:52:15
IPADDR=192.168.1.50
PREFIX=16
GATEWAY=1.1.1.1
DNS1=123.34.5.6
DNS2=123.34.5.6
DOMAIN="local"
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"