If you have a missing default gateway on your Redhat system you can add new route as per network interface or globally. Defining default gateway using ifcfg files, that is, defining it as per network interface basis takes a precedence over global system wide default gateway configuration defined by /etc/sysconfig/network configuration file.
This is a companion discussion topic for the original entry at https://linuxconfig.org/configuring-default-gateway-on-redhat-enterprise-linux