In which MAC Authentication Bypass phase does the switch accept a single packet to learn the MAC address of the endpoint?

In the MAC Authentication Bypass (MAB) process, the phase where the switch accepts a single packet to learn the MAC address of the endpoint is during the MAC address learning phase. This phase is crucial because it enables the switch to identify un-authenticated devices based on their MAC addresses.

During this phase, when a device sends its first request to the network, the switch captures this packet and logs the MAC address. This action is essential as it allows the switch to link the MAC address to the specific port it is connected to. Subsequently, the switch uses this information to determine the necessary access privileges for that device during the authorization phase, which follows the learning phase. In essence, the device's MAC address must be learned first before any further authentication steps can take place, making this phase foundational to successful network access control.

The other phases play distinct roles, such as initiation, where requests are made, authorization, where access is granted based on identity, and accounting, which deals with logging session information. However, it is the MAC address learning phase that specifically involves the switch learning the MAC address from the initial packet sent by the endpoint.