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Networking Fundamentals · Foundational

Stateful Firewall

A firewall that tracks the state of connections and automatically allows return traffic for sessions initiated from trusted networks.

Definition

A stateful firewall records each session's five-tuple and TCP state in a state table, so administrators need rules only for the initiating direction. Stateless packet filters examine each packet in isolation and need explicit rules for both directions.

Example

An internal user's HTTPS request creates a state entry, so the server's response is allowed back in.

Exam tip

Stateful = remembers sessions; stateless ACLs need explicit return rules or the established keyword.

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