In previous Red Hat Enterprise Linux releases, the default way to configure networking was using network scripts. The term network scripts is commonly used for the script /etc/init.d/network and any other installed scripts it calls. The user supplied files are typically viewed as configuration, but can also be interpreted as an amendment to the scripts.
Although NetworkManager provides the default networking service, Red Hat developers have worked hard to ensure that scripts and NetworkManager cooperate with each other. Administrators who are used to the scripts can certainly continue to use them. We expect both systems to be able to run in parallel and work well together. It is expected that most user shell scripts from previous releases will still work. Red Hat recommends that you test them first.
It is recommended that NetworkManager and network scripts not be used together.
In addition, it is observed that when configured with two gateways in ifcfg-teamX files, NetworkManager would load two default gateways, which would introduce connection issues with different subnet, while network scripts will only load ONE default gateway.