We saw in this chapter some pretty complicated networks. We also saw that building firewalls and QoS for such networks is not so complicated. However, it is very important to draw the network and identify security breakpoints to be able to create a firewall that will protect your network.

In my opinion, the most important things about security are knowing your network, building it in an intelligent manner and with security in mind, and most of all, understanding how packets flow in your network.

Understanding the flow of the packets in the network is essential for people who want to build good firewalls and intelligent QoS. I've seen simpler networks than the ones presented here with very complicated firewalls, which had rules that didn't belong there or that could be reduced to much simpler ones.

I've also seen some networks that were badly thought out from the beginning. For instance, think about the second example of this chapter and how it would be if we place one server on the...