I have been thinking of teaching myself the basics of Linux-Fedora networking. I am in the process of getting a few old pcs, 4 of them to be precise for this purpose only. Now I want to learn all types of servers that exist. Be it e-mail server, web server, file server, FTP server etc. Out of the 4 pcs one will a server and one would be a firewall. Please correct me if I am wrong to assume that a physical pc can't be configured to act as a firewall. Can you please suggest me something by giving a few practical tips. Links to sites/tutorials/books etc? Please also add other types of servers that I have not mentioned here. I am also aware of this tutorial that exists as a good place to start in the Servers sub-forum on this site itself.