I am trying to use my Pi 3 as RADIUS server and TACACS+ server because im trying to practice for the CCNA is it possible to configure the pi as a radius or TACACS+
The Raspberry Pi is a normal (small) computer running Raspbian what's just Debian compiled for the ARM processor and with some firmware for the RasPi. You find freeradius and tacacs+ in its repository. So just install and run it.
Look at it and install it with:
rpi ~$ apt show freeradius rpi ~$ apt show tacacs+ rpi ~$ sudo apt install freeradius rpi ~$ sudo apt install tacacs+