I recently created a new Centos VM. When it booted, I noticed it did not have a working ethernet connection. So, I started playing with things, and got it working. Here are my notes:
To view connections
To bring up the connection was simple:
nmcli c eth0 up
To make it persist across boots required the autoconnect value:
nmcli c mod eth0 connection.autoconnect yes
This last one reflects the ONBOOT value in the file /etc/sysconfig/network-scripts/ifcfg-eth0
Setting it changed ONBOOT from no to yes.
Rebooting the machine and ip addr shows the connection up.