Cisco 7920 causing HAVOC

I have three voice servers running; Asterisk on debian, A@H, and Callmanager 4.12. Whenever I boot up a 7920 registered to CM - all other phones unregister and start "Configuring IP’. They never recover until I shut down the 7920. Any help appreciated

You might want to re-image the 7920 with the latest image to clear any commands it might be sending out.

it is a known bug

Method 1:
turn off CDP on the 7920

Method 2:
use a cisco switch