It was 3:47 AM in the server room. The only light came from the blinking port LEDs and the pale glow of a laptop screen. Jake, the night-shift voice engineer, had been staring at the same error for four hours.
“Phone is downloading xmldefault.cnf.xml.”
He slammed his coffee cup down. For the uninitiated, that message was boring. For Jake, it was the sound of a silent apocalypse.
Every Cisco IP Phone in the corporate HQ—all 1,200 of them—was ignoring their specific configurations. Instead of pulling SEPABCD123456.cnf.xml (their unique file), they were all falling back to the generic xmldefault.cnf.xml.
The result? Receptionists had the CEO’s direct line. The CFO’s phone was showing the breakroom extension. And the IT helpdesk number just routed to the vending machine on floor 3.
“The repack,” Jake whispered.
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.”
They did not figure it out.
Jake cracked his knuckles. He opened WinSCP and navigated to /tftpboot/. There it was: xmlDefault.cnf.xml. He right-clicked. Edit.
Inside was Mark’s “efficient” script:
<device>
<line instance="1">
<callerId>WRONG NUMBER</callerId>
<voicemail>999</voicemail>
</line>
</device>
“Idiot,” Jake muttered. He didn’t have the original backup. The RAID had failed last Tuesday, and Mark “forgot” to check the logs. cisco ip phone downloading xmldefault cnf xml repack
So Jake did the unthinkable. He performed a manual 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.
Phone by phone. Office by office.
At 5:00 AM, the night janitor watched as Jake ran down the hallway, laptop in hand, Ethernet cable trailing behind him like a tail. He plugged directly into a Cisco 7965 that was blinking “Config Failed.”
He hit Enter.
The phone screen flickered. For three seconds, it showed “Contacting DHCP.” Then, a miracle.
It rebooted. The line buttons lit up green. The display read: Jake S. – Ext. 1042.
He didn’t stop. He ran to the next floor.
By 7:55 AM, just as the first executives arrived, the last phone—the lobby concierge—dinged cheerfully.
Jake slumped against the wall. On his screen, the TFTP log showed the final success: It was 3:47 AM in the server room
FILE REQUEST: SEP006B8E5C2A12.cnf.xml – STATUS: REPACK SUCCESS
Mark walked in at 8:02 AM with a latte.
“Hey, did you fix that little XML thing?”
Jake looked up. He smiled, unplugged his laptop, and walked to HR.
The phones never downloaded xmldefault.cnf.xml again. Because Jake repacked his resume instead.
The message "Downloading XMLDefault.cnf.xml" on a Cisco IP phone represents a critical stage in its boot sequence where the device attempts to find a baseline configuration and instructions for its next steps, such as firmware upgrades or server registration. The Role of XMLDefault.cnf.xml
When a Cisco IP phone boots up, it follows a specific hierarchy to obtain configuration data:
Device-Specific Configuration: The phone first requests a unique configuration file based on its hardware address, typically named SEP.
Fallback to Default: If the TFTP server returns a "File Not Found" error for the unique MAC-based file, the phone falls back to requesting the XMLDefault.cnf.xml.
Auto-Registration and Firmware: This default file is primarily used for phones that have not yet been registered to a Cisco Unified Communications Manager (CUCM) or are configured for auto-registration. It contains essential information, including the IP addresses of the CallManager cluster and the specific firmware load the phone should be running. Understanding the "Repack" Context “Idiot,” Jake muttered
While "repack" is not a standard status message in the Cisco boot cycle, it often refers to how administrators handle the firmware and configuration packaging when using third-party TFTP servers (like Asterisk or TFTPd64).
Firmware Extraction: Firmware is often downloaded as a .ZIP or .TAR archive. To "repack" or properly place these files, they must be extracted into the TFTP root directory.
Editing the Load Information: Administrators must often manually edit the XMLDefault.cnf.xml file to point the phone toward the specific firmware version they wish to install. Troubleshooting Boot Loops
If a phone is stuck "Downloading XMLDefault.cnf.xml," it usually indicates a breakdown in the TFTP communication or a configuration mismatch: IP Phone, SCCP & SIP Phone Registration Process with CUCM
The xmldefault.cnf.xml file acts as a baseline configuration. When a phone powers on, it requests its specific SEP<MAC>.cnf.xml. If the TFTP server (usually CUCM) cannot find that unique file (because the phone is unprovisioned, the MAC address is wrong, or the file is missing), the phone falls back to requesting xmldefault.cnf.xml.
If you’ve ever spent more than 15 minutes watching a Cisco IP phone cycle through the "Configuring IP," "Contacting DHCP," and then hanging on "Downloading xmldefault.cnf.xml," you know the frustration. Usually, this indicates a TFTP configuration file mismatch, corrupt download, or a phone that is looking for a specific file that your Call Manager isn't serving correctly.
In this post, we’ll break down what XMLDefault.cnf.xml actually is, why the phone demands it, and how to repack or reconstruct this file to get your phone back online.
When a Cisco IP phone boots up, it requests a specific configuration file named after its MAC address (e.g., SEP001122334455.cnf.xml).
XMLDefault.cnf.xml. This file tells the phone which firmware version it should load by default.The Issue: The phone has no entry in the Cisco Unified Communications Manager (CUCM). It asks for its specific file, fails, and falls back to XMLDefault.cnf.xml. If this file is missing or misconfigured on the TFTP server, the phone hangs.
Solution:
SEP[MAC].cnf.xml file.Modern Cisco IP Phones (8800/7800 series) have moved to a more robust system. They use HTTPS for configuration download, signed XML files, and Device Enrollment over HTTP. The xmldefault.cnf.xml legacy has been replaced by ITL (Initial Trust List) and CTL (Certificate Trust List) files.
However, thousands of legacy 7900-series phones still run in warehouses, schools, and home labs. For those, the "repack" remains a lifeline.