Cisco Certified Network Professional 2026 – 400 Free Practice Questions to Pass the Exam

In an 802.1X setup, the feature that blocks port access until a device is authenticated is known as AAA, which stands for Authentication, Authorization, and Accounting. This protocol framework is essential for managing who can access network resources, how they can access them, and keeping track of their activities.

With respect to 802.1X, when a device connects to the network, it initially cannot access any data until its identity is verified through an authentication process managed by AAA. The authentication typically involves the device supplying credentials, such as username and password, which are then validated against a centralized server (like a RADIUS server). Only after successful authentication does the network device grant access to the port.

This approach enhances network security by ensuring that only authorized devices are granted access to the network, effectively blocking any unauthorized attempt to use the network resources until explicit validation has taken place. Other features like port security and MAC filtering can help control access but don't inherently perform authentication as required in an 802.1X scenario. Dynamic ARP Inspection, on the other hand, relates more to protecting against ARP spoofing and does not directly manage port access guidelines under authentication protocols.