I have configured an ATA186 using SIP connecting to my centralized CUCM 7.1.3 cluster. Everything is fine except for one problem; Only one port on the ATA will register at a time. When I power it up, one port registers, while the other shows up as 'Unknown' in CallManager. If I reset the registered port, the 'Unknown' port registers, but the first port doesn't come back from 'Unregistered'. That is until I reset the second port, when port 1 is 'Registered' and port 2 is 'Unregistered'.
When I look at the Status page of the ATA's web interface, I can see the SIP Reg(0/1) value is either "ON,OFF" or "OFF,ON", depending on if the first port or second port is currently registerd.