Network testing

There are many kinds of networking appliances and applications that need testing.

Firewalls will normally need 3 computers - one on each side of the firewall. One would configure the firewall and then send packets from one side to the other side. Then check if the packets got through or not.

Routers or switches might need more computers connected to the device under testing.

Proxies can be tested in a way similar to firewalls.