the interface configuration. MAB stands for MAC Authentication Bypass, which is a feature that allows devices that do not support 802.1X, such as printers and video cameras, to bypass the authentication process and gain network access based on their MAC addresses1. By adding mab to the interface configuration, the Cisco ISE administrator can enable MAB as a fallback method after 802.1X fails or times out. This way, the devices that support 802.1X can use their machine certificate credentials, while the devices that do not support
802.1X can use their MAC addresses to authenticate with Cisco ISE2. The other options are not correct because they either compromise the security controls or do not address the problem. Changing the default policy in Cisco ISE to allow all devices not using machine authentication would weaken the security posture and expose the network to unauthorized access. Enabling insecure protocols within Cisco ISE in the allowed protocols configuration would also reduce the security level and increase the risk of attacks. Configuring authentication event fail retry 2 action authorize vlan 41 on the interface would only apply to the devices that fail authentication twice, and would not solve the issue for the devices that do not support 802.1X at all3. References:
* 1: MAC Authentication Bypass Deployment Guide
* 2: Configuring MAC Authentication Bypass
* 3: Cisco Identity Services Engine Administrator Guide, Release 3.1 - Segmentation