We use RHEL7.6, and are trying to configure a dummy adapter. We use a minimal install, and apply Centre for Internet Security Benchmark hardening.
As part of the build, we stick with using network manager, but change the host based firewall back from firewalld to iptables. Network manager is cumbersome, but understand the functionality it provides to other services, and the fact that the raw config files cannot be edited once they are network manager managed.
herein lies the problem.
Unexpectedly, when using nmtui, you cant use it to create a new interface of type "dummy". To do this, you need to use nmcli. This isn't a big deal, and I've followed, among others, the instructions laid out in https://access.redhat.com/solutions/4878391.
The problem is though, that the /etc/sysconfig/network-scripts/ifconfig-dummy file never gets created - even if forcing the "save" option (which is default behaviour anyway) in the mncli command.
If I reboot the server, then the configuration is back OK, but the adapter is down, and no longer network manager managed - I need to manually claim the device by network manager again and it then springs into life.
What am I doing wrong? as this doesn't seem to be working as documented.