Have a problem whereby we can't get a mab endpoint to get network access behind a Cisco 7940. If I reboot the phone, then both the phone and mabendpoint get network access. In the switch logs we can see where dot1x started fro both, no response so mab was started and mab authentication was successful for both on the switch. Both get network access. If the phone is already registered and on the network and the mab endpoint behind it is now rebooted, the switch log says "starting 'dot1x' for client (5448.10bc.21f9)" but switch never says that it didn't get a dot1x response or that dot1x failed or that it is starting mab. Switch is a 3560V2 15.02SE10a code. Not sure why the switch is not reporting no further information about the mab endpoint after starting dot1x.
Behind another type of Cisco Phone, a 7821, there is no problem. You can reboot the mab endpoint and it gets access. Swithport priority order is default i.e dot1x then mab.