Simple LAN-to-Internet Firewall

The simplest possible design is a protected LAN connected to the public IP network (for example, the Internet) through a firewall. No publicly accessible servers reside in the protected LAN (which means, for example, that the users connected to the LAN have to download their e-mails from somewhere else—for example, from their Yahoo! or Hotmail accounts). Figure 2-1 shows a simple firewall design.