Try to configure ASA8.0(4) phone proxy feature with Callmanager 6.1(x) as per the documentation http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/unified_comm.html#wp1144829
I assigned TFTP server ip address on the remote IP phone with ASA proxy address, and the remote IP Phone can successfully register to CallManager.
But from remote IP Phone, the phone directory and phone service button are not working:"Host not found". I think this is because the ip phone still get the phone service internal ip address of CallManager?
Or I missed something?