I have 802.1x authenticating back to an ACS server with MAC authentication bypass configured for a voice VLAN port. I also have a guest VLAN configured on the port, however when I disable the certificate authentication on a Windows XP host and plug it in behind the phone, it doesn't get put into the guest VLAN.
Any special configuration I need on a voice VLAN port?
When connected directly into the port it seems to functions properly.. it authenticates to ACS when the certificate is present and it gets pushed into the guest VLAN when the certificate is not present.