What is a function of a firewall on an enterprise network?

The fundamental and defining function of a firewall is to act as a security barrier, inspecting and controlling network traffic to enforce access control policies by permitting or blocking packets based on predefined rules for both incoming (ingress) and outgoing (egress) connections.

While a firewall may be configured as a default gateway for internal hosts, its primary function is traffic filtering and security enforcement, not solely acting as a routing point.

Modern enterprise firewalls predominantly use stateful inspection, which tracks the state of active connections, rather than stateless inspection, which examines each packet independently without context.

This describes the common placement of a firewall at the network perimeter, but not its core function, which is to filter traffic at that strategic location.