You'll now learn how to properly do networking. There are Good Tools ™ you can use, and Bad Tools ™ you should try to avoid. Good Tools are those that either aid you in debugging network problems or those that are secure. Bad Tools are tools that are either insecure, or known to be wrongly used.
Add text to cover ifconfig, route, ppp (also PPP over serial cross-cable) and radvd for IPv6 networking.
Add text about tcpdump, ettercap, ethereal, nc (also known as netcat) and telnet (but only for connecting and testing SMTP/HTTP/..., not for logging in, because it's one of the Bad Tools).