Outside Network 2

The outside network is also referred to as the external or public network. The outside area, or untrusted area, is considered to be all devices and networks beyond the direct control of the organization’s administration and security policies. The outside area typically includes everything beyond the external interface of the perimeter router, the ISP, and the Internet and all networks attached to it.

The outside network wouldn’t normally be attached directly to a firewall device because of media and data framing issues. A firewall device like the Cisco PIX devices have LAN interfaces only requiring another device between the firewall and the serial WAN connection. The perimeter router, possibly a lower-end model, provides the media conversion, framing transition, and any first-line security services.