Watchguard SOHO User Manual page 19

How does a firewall work?
these dangers. As is illustrated in the image below, the SOHO
physically seperates your trusted network from the Internet.
Using rules we will discuss in Chapter 3: "Configuring Incoming
and Outgoing Services" on page 63, the WatchGuard SOHO
evaluates all traffic between the external network (the Internet)
and the trusted network (your computers) and blocks any
suspicious activity. In order for this to work as described, you
must configure both the external and trusted networks to work
together and to talk to one another as well as the rest of the world.
User Guide 5.0 19