Subnetting a network

One of the things that I have trouble with when setting up networks is the subnetting part. On digg.com today they an article that talks about how to setup a subnet for schools. This could be interesting part to talk about when doing the networking unit at school or the hacker high school.

http://www.learn-networking.com/design-basics/how-to-subnet-a-network.php

Denial of service attacks and how to prevent them
http://www.learn-networking.com/network-security/how-to-prevent-denial-of-service-attacks.php

Now one of the things I like about the learn-networking is that they have is a quiz at the end of each.