Connection activation failed device not managed by NetworkManager

Connection Activation
Failed device not managed by NetworkManager

There are two services in the system in the management network, so you need to stop one,

1. Remove network manager from startup services.
Chkconfig NetworkManager off

2. Add default net manager
Chkconfig network on

Stop NetworkManager first
Service NetworkManager stop

And then start default Manager
Service Network restart

Or you can change it easy:

System-config-network
Uncheck the box that sets the eth0 as managed by NetworkManager and set IP info from there.

System-config-services
Stop and disable NetworkManager, start and enable Network

You have problem because both of NetworkManager and network using same network driver and default network blocking access for NetworkManager. If you disable NetworkManager your problem will disappeared after restart.