Try running as root in command line:
netconfig
Answer all questions correctly (hostname is your machine) and make sure you have all the necessary information (primary and secondary DNS IPs, domain name, DHCP server name if needed, and DHCP server IP if needed).
For RedHat, it might be config-redhat-network but I'm not 100% on that. A RedHat user will most certainly correct me if I'm wrong.