9.3. OpenSolaris As a Router or Firewall

In addition to behaving as a network client and server, OpenSolaris can also serve as a network router and firewall. Many organizations purchase dedicated special-purpose hardware to perform these functions, but OpenSolaris' functionality might be suitable for your environment.

9.3.1. Routing

When computer systems are attached to the same physical network, they can communicate with each other directly by sending packets on the network medium, whether it's wired or wireless. When the systems are attached to different networks, an intermediate system, called a router, must be used to forward data from one network to another. On the Internet, there can be several, perhaps dozens, of routers along the path from one system to another. In order for your system to exchange data with other networks across a router, it must be aware that the router exists, and know for which networks the router can accept traffic for forwarding, as not all routers can accept traffic for all destinations. You must configure routing in some way, regardless of whether your system will operate as a router—otherwise, it can only contact systems on the same network. In addition, if your system is to operate as a router, it must be configured to forward packets; otherwise, any traffic directed to it by systems for routing will be discarded.