The , which specifies the required software version the phone should run. Downloading the XMLDefault File
Cisco IP phones follow a strict "hunt algorithm" to boot. If it can't find its primary configuration, it requests XMLDefault.cnf.xml . If this file is also missing, or if it points to a firmware version (load) that the phone cannot find or "understand," the phone will restart and try again, creating a loop. Common causes include: cisco ip phone downloading xmldefault cnf xml repack
When a Cisco IP phone boots, it follows a specific hierarchy to obtain its configuration: The , which specifies the required software version