A portmapper is a tool that dynamically distributes/maps TCP/IP port usage. There are sending ports (in NW also known as Connection Ports) and receiving ports (listening ports, in NW aka: Service Ports). Service Ports are the ones you usually restrict by firewall rules. For interoperability, specific port ranges are restricted worldwide to allow communication between all computers. So at least one portmapper must be provided by an OS which supports TCP/IP, additional portmappers may be provided by the application. Now - NW (already the NC client package) of course uses both port types And it provides an extra portmapper. there are at least 4 service ports involved but by default 2000 are enabled. Unfortunately, 2 ports are fixed: 7937 & 7938. And this is obviously the problem. I think, these conflicts will be corrected if you let NW make the firewall adjustments during installation but I am not completely sure as I never ran into this problem.  To change these settings, please read my recent thread [URL] BTW - the advice to modify the hosts table is not wrong but the effect applies more to name resolution. And if you want to verify the port usage, use netstat -a .    
[IMAGE] I install the rpm packages without any erro but after systemctl start networker nsrexecd starts but after that no other deamons are starting.  
networker 18.1 setup problem