Configure the network card on CentOS on VirtualBox

Show the name network interface:# ifconfig -a

Modify eth0's configuration file:
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.1.212
NETMASK=255.255.255.0

Note: if you want to use DHCP, change BOOTPROTO=dhcp

Define default gateway (router IP) and hostname:
# vi /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=centos64.local
GATEWAY=192.168.1.1

Make sure you have correct DNS server defined:
# vi /etc/resolv.conf
nameserver 8.8.8.8

Restart networking:
# /etc/init.d/network restart