Cisco WAN Switching Modules

Cisco/StrataCom Field Notice: BTM or AIT Trunk Errors

December 23, 1997


IGX Broadband Trunk Module (BTM) trunks or IPX Asynchronous Transfer Mode (ATM) Internetworking Trunks (AITs) cause anomalous errors after switchcc command.

RCN Number

Not applicable.

Products Affected

IGX or IPX with BTM or AIT trunk cards installed.

Bug Details

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

View CSCdj30587 (registered customers only)

View CSCdj34216 (registered customers only)


AIT or BTM trunks may corrupt data after the processor cards switch in the node where the AIT or BTM is installed. The anomalous errors are caused by misprogramming on the trunk card. Although the net result is the same, there are two ways in which the AIT or BTM trunk becomes misprogrammed. One way is caused by firmware (CSCdj30587) the other is caused by software (CSCdj34216).

There are two symptoms to look for with either type of bug;

  • The first and more obvious is that the trunk card will start dropping packets, usually Complex GateWay (CGW) packets.

  • Second, the Frame Relay PVCs in transit on the trunk have random frame drops resulting from the trunk packet drops.

The trunk packet drops can be observed using the command:

dsptrkerrs <slot>

where the slot value is the slot where the trunk card resides.

The frame drops can be observed using the commands:

dspchstats <slot.port.dlci>,dspchstats <slot.port.vpi.vci>

(for the ATM end of a Frame Relay to ATM connection), or

dspportstats <slot.port>

where the slot is the slot number of the frame relay card and the port is the logical port number where the data link connection identifier (DLCI) or virtual path identifier/virtual channel identifier (VPI.VCI) is terminated.


The solution for the firmware-caused problem is to upgrade the firmware on the AIT or BTM to "IBL" or "IDA" or later. This operation is the easiest to execute as it affects only the single trunk card being upgraded.

If upgrading the firmware to "IBL" or "IDA" does not clear up the problem, the next procedure involves upgrading the network software; this is a much more extensive task. The maintenance releases of software with the fix for CSCdj34216 are: All versions of 8.5, 8.4.09 or later 8.4 versions, and 8.2.56 or later 8.2.5X versions.

Note: The firmware and the software maintenance releases containing the fix may be obtained from the CCO Software Center at


Reset the AIT or BTM trunk card. This can be done by either issuing the resetcd <slot> h command or by physically reseating the card.


It is recommended to first upgrade the AIT or BTM firmware, as this is the quickest fix. Be aware that the upgrade procedure is intrusive on the trunk card being upgraded. Also note that the burnfwrev command takes three to five minutes to execute, during which time the card will be out of operation. After the firmware is burned, the card resets automatically, which causes the workaround to be implemented, and which can clear up the problem.

In order to test whether the new "IBL" or "IDA" or later firmware fixes the problem, the switchcc command should be executed during a scheduled maintenance window. If the processor switch results in the trunk errors and frame drops, the software should be upgraded. The switch software upgrade involves upgrading all nodes in the network to the same version and should not be attempted without extensive research and planning. Consult the Release Notes for the version of software to be loaded, or call the Cisco TAC for help. Cisco provides the services of Program Engineers who specialize in researching, planning, and executing network upgrades.

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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