Cisco IGX 8400 Series Switches

Field Notice: Echo Cancellation on UVM Fails

Updated May 11, 1999

April 1, 1999

Products Affected




Model A with Firmware Version A


Model B with Firmware Version A


Model C with Firmware Version A


Model D with Firmware Version A


Model E with Firmware Version A

Problem Description

In some instances, the UVM Echo Canceller ceases to cancel echo on some voice channels. The result is echo during phone calls. In extreme cases, the echo renders the channel unusable.


This problem has been observed only on channels configured for G.164 Tone Disabler. Once a channel is in this state, the echo is constant. Experience is that one channel in 100 (configured for G.164 tone disabler) will enter this state over a three day period in a noisy office environment.

Problem Symptoms

The user will notice echo on all calls across affevted UVM channels. Once the channel is in the no-echo state, it remains in this state until the workaround is applied.



If G.164 tone disabler is configured, change it to G.165 (cnfecparm) to clear the stuck channel and prevent future occurrences.

If G.165 tone disabler is configured, changing this setting to G.164 and then back to G.165 will clear the stuck channel.


Currently, there is no solution to this anomaly. Bug CSCdk76161 has been opened to track this problem and its resolution. Please use the Bugwatcher feature available in CCO Bug Toolkit to track this bug.


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



CSCdk76161 (registered customers only)

Echo persists on a channel until UVM EC is reset.

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: