Cisco Certified Network Associate (CCNA) 2026 – 400 Free Practice Questions to Pass the Exam

The correct answer is indeed 50. The IPsec Encapsulation Security Payload (ESP) is utilized for providing confidentiality, integrity, and authenticity of data in transit. In the context of IPsec protocols, ESP specifically operates directly over the Internet Protocol and employs the port number 50 for its function. This port is defined for the encapsulation of the entire data packet, enabling the protection of IP packets through encryption and additional security measures.

Port 51 is used by the Authentication Header (AH), another protocol within IPsec that provides integrity and authenticity but does not perform encryption. The significance of identifying the correct port associated with ESP lies in understanding how IPsec protocols are structured within network security measures, ensuring that systems can properly recognize and handle different types of IPsec traffic accordingly.

Understanding the specific roles of these port numbers is fundamental for configuring firewalls, routers, and other network devices to allow or restrict the appropriate traffic types associated with IPsec.