Cisco Unified IP Phone 7900 Series

Field Notice: CP-7935 Unrecoverable After Failed Upgrade

May 7, 2004

Products Affected

CP-7935 IP Phone

Problem Description

If a firmware upgrade for a Cisco IP Phone 7935 fails due to timeout from a TFTP server or other network disruption, the device is left in an unrecoverable state.

Under normal circumstances, the CP-7935 is notified that a phoneload should be downloaded from the TFTP server. The CP-7935 then requests the phoneload from the server and saves it to memory. There are timeout and retry counters that account for normally expected network latency and server utilization. However, when both the retry counter and timeouts are exceeded, the device continues the reboot sequence. Because the complete phoneload failed to be downloaded and saved to memory, the phone fails to reboot. Currently there is no field available recovery from this type of failure.


The root cause has been identified in the CP-7935 upgrade logic. An available flag was not being set at the initiation of the phoneload download. This flag identifies to the device that the load is not either complete or confirmed. The bit should have been set and then removed once a complete phoneload was downloaded.

This logical failure had not been discovered previously due to the default settings of the timeout timers and retry counters. The combination of these two mechanisms have accounted for the large majority of customer networks and TFTP infrastructure.

The development team has completed the logic change needed to address properly setting the upgrade flag. This load is currently undergoing final testing and will be made available on the Software Center (registered customers only) .

Problem Symptoms

When powered up, the display shows the Cisco Systems logo, disappears for a brief period (a second or two), then returns to the Cisco Systems logo screen and stays in that state. No other activity is displayed on the screen. Sniffer traces show very little and erratic behavior from the affected CP-7935.


Workaround Options:

Give the 7935 firmware upgrades every chance to succeed in upgrading their firmware by performing either one of the proposed workarounds below:

Workaround Option 1:




Identify which firmware is present in the CallManager version to be upgraded to.


Acquire the desired 7935 firmware from CCO and install. Validate that the firmware image is downloadable from the cluster's TFTP server:

a) Open a CMD prompt

b) Enter the command: tftp -i get <7935_FIRMWARE> where 'tftp': is the IP address of the cluster's TFTP server, and '<7935_FIRMWARE>' is the file name of the 7935's firmware image.


Configure the 7935 firmware in the Device Defaults page to that of the desired version.


Reset (Reset/Reset, which is a power-cycle) no more than 20 7935s at a time. This will help prevent TFTP-based timeouts. Validate that the individual 7935 firmware upgrades are successful as you proceed.


Upgrade the CallManager servers.

Workaround Option 2:




Before the CallManager upgrade, power-down the 7935s.


Perform the CallManager upgrade.


Wait for all other devices to upgrade their firmware.


Power-up the 7935s, no more than 20 at a time. This will help prevent TFTP-based timeouts. Validate that the individual 7935 firmware upgrades are successful as you proceed.


To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.



CSCee08148 (registered customers only)

7935 Will Not Boot

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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