MAB authentication problem, MAC addresses not registered on switch

[iancresswell]

We run 3850 switch stack to support our users, we run MAB authentication on the switch to authorize devices, they run IOS version 16.3.6

We see some scenarios where people connect a network dongle to the switch but cannot gain access to the network.

When we check the switch often we simply see no MAC address registered on the port.

Occasionally we see an "Authentication failed" message for the MAC address on the switch but then do not see a matching denied log on the NPS server, in fact we often see an accept message on the NPS server for the same MAC address and the same time and the port is in an authorized state.

Has anyone any insight on why the MAC address of the dongle is not being picked up by the switch when the dongle is connected?

[PaulSmith]

I am not quite sure what you mean by dongle but could another protocol be blocking the traffic like Dynamic ARP Inspection or IP Source Guard?

[iancresswell]

New laptops do not have an onboard NIC so have a "dongle" that connects to the laptop that has the NIC in it.

Some dongles work immediately, however, some do not register a MAC address on the switch and have to be repeatedly reconnected or moved to different ports several times before they register.