Cisco 6100 Series IP DSL Switches

Field Notice: 6100 Series DSLAM with Software Release 2.4.x: System Reset Can Cause Subscriber Configuration Loss

March 20, 2000

Products Affected



6100 Series DSLAM

Software release 2.4.0 and 2.4.1

Problem Description

Cisco engineering has discovered an issue with system software release 2.4.0 and 2.4.1: a possibility exists for subscriber configuration corruption to occur after a system reset. This issue can occur if you are utilizing both of the subtend ports. When this issue occurs, subtended connections on the second subtend port will not come up and subtending (transit) traffic through those connections will not flow.

Note:?This problem can occur only following a system reset.


The current system controller code has a multi-dimensional bit array to keep track of the availability of subtending circuits; entries in this bit array are accessed using the subtend port ID and internal circuit ID. The bit array is then used when transit (subtending) circuits are created. Because of the way these arrays are accessed and verified during a system reset, it becomes possible for a rare condition to occur and configuration information to be lost. The DDTS number CSCdp52757 (registered customers only) was issued regarding this problem.

Problem Symptoms

Configuration information for subtending systems can be lost following a reset of a 2.4.0 or 2.4.1 parent node. After this issue occurs, only one branch of the subtending tree, terminated at that node, will be working. All user traffic on the effected branch will stop.


This issue has been resolved in system software 3.0, which is available on CCO to registered CCO users.

The following workaround is also available to customers not wanting to upgrade:

  1. Before resetting a 2.4.0 or 2.4.1 node that has subtended DSLAMs, perform a configuration save using ViewRunner.

  2. Following a system reset, perform a restore using the saved configuration data from ViewRunner.


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




Subtended system with transit subscribers hangs during 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: