: The TFTP server responds with a "File Not Found" error for the specific config, forcing the phone to the default file, which might also be missing or inaccessible. TFTP Server Issues
The log indicates the feature is activating. The phone is using the default configuration to forcibly downgrade or change its internal software build to match what the TFTP server dictates as the "default." cisco ip phone downloading xmldefault cnf xml repack
He opened a second terminal and ran a packet capture. Every time a phone requested its MAC config, he replied with a custom-built XML payload injected from a Python script. : The TFTP server responds with a "File
<device> <line instance="1"> <callerId>WRONG NUMBER</callerId> <voicemail>999</voicemail> </line> </device> Every time a phone requested its MAC config,
CUCM 12.5, 200 phones (mostly 8845). Symptom: Every morning at 8 AM, 30 phones reboot and fail to register, logs show "repack XMLDefault.cnf.xml". Investigation: TFTP server CPU was 100% due to a backup job running simultaneously. Root cause: TFTP service timed out while reading phone-specific files → served fallback → found default file outdated → repacked. Resolution: Rescheduled backup, increased TFTP cache timeout, and synced all configs. The repack messages disappeared.
Earlier that day, his lazy coworker, Mark, had tried to “optimize” the TFTP server. To save space, Mark had deleted all the individual phone configs and created a single “repack” of the default XML file, thinking the phones would just “figure it out.”