I am trying to get a Nortel phone to authenticate using 802.1x and MDA. The phone will authenticate fine when using multi-host mode. When I change to MDA, the phone says "EAP Not Authenticated" however the ACS server see's a passed authentication and showing the dot1x switchport interface detail command, I see the Voice domain authenticated and I see spanning-tree forwarding for the Voice Vlan on that port. The phone gets to the DHCP request and stops there. It appears that it falls back to the guest-vlan and gets an IP address from there. I have the required Cisco attribute configured in ACS. Has anyone else experienced this problem or have any ideas what could be wrong?