In the newer distros within the RHEL / CentOS / Fedora family,
ifconfig is usually missing. Instead they try to get you to use
ip instead.
The utility
ifconfig was old and easy to use. Thus it has been replaced by a new and exceedingly complex utility instead.
You'll have to look through the manual page for "ip" to get an idea of the options. Do you have a specific task in mind? If so, how was it expressed using "ifconfig"?