Certified Network Defender (CND) — Question 121

Which firewall technology can be implemented in all (application, session, transport, network, and presentation) layers of the OSI model?

Answer options

• A. Circuit-level gateway
• B. Packet filtering
• C. VPN
• D. Network address translation

Correct answer: C

Explanation

The correct answer is C, VPN, as it operates at multiple layers of the OSI model, providing secure communication over various protocols. The other options, such as circuit-level gateways and packet filtering, primarily function at specific layers and do not encompass the entire OSI model.