Removing old NICS from your virtual machines is typical when moving virtual machines to different hyper visors. Ie, moving a VMware Virtual Machine to to Hyper-V or VirtualBox.
Using your favorite editor, edit the following
/etc/udev/rules.d/70-persistent-net.rules (CentOS 6 only)
The first device will be the old NIC, comment it out with a # and change the name=””
to your old NIC value, typically eth0
then save the file and restart networking. This in most cases will solve the issue.
For CentOS / RHEL 5.X
remove the following
#reboot -t now
Then run system-config-network
This will allow the creation of the new device with the network settings you provide.
finally restart networking.