Our Cisco 8851 aren't able to reconnect and sing on at CUCM just cuz they are un- and then replugged to network!
We had to move them in the office and as we reconnected, even to same switch port, they are unable to reconnect to CUCM and are since rebooting again and again! If we take new device, change the MAC at CUCM that new device works instantly! What could be the reason for that behaviour?