Cisco BPX 8600 Series Switches

Field Notice: ATM Service Interface (ASI) Card Y-Redundant Switch Causes Data Traffic Delays and Discards on the BPX

December 9, 1998

Products Affected


Problem Description

After a Y-Redundant switch-over on an ASI card set, traffic experiences excessive delays on available bit rate (ABR) connections, and QBin full-discards on constant bit rate (CBR) connections.


This problem is a result of the stand-by card of an ASI Y-Redundant pair not being programmed correctly prior to a Y-Redundant switch.

Problem Symptoms

Switching to Y-Redundant backup causes the connection's performance to be reduced. The problem manifests itself as excess delay on ABR connections, to discards due to Qbin full and Tx EFCI cells on CBR connections.


With ABR connections, the delay seen by the end device increases from 200msec to approximately 2 seconds. With CBR connections, the Qbin full-discards. To get out of this condition, delete Y-Redundant and reset the cards.

The following procedure should be performed on all stand-by cards of ASI Y-Redundant pairs to ensure that they are programmed correctly prior to a Y-Redundant switch. This procedure must be performed on stand-by ASI cards after an addyred, resetcd slot of a stand-by ASI card or insertion of a stand-by ASI card. This procedure does not need to be performed following a switchcc. You must have Service level access or higher to perform this procedure.

  1. Build the following control packet:

    • scp1

    • The UI will prompt "Enter Function Code". Enter 4.

    • The UI will prompt "Enter Operator Code". Enter 0.

    • The UI will prompt "Enter Data Byte 0". Enter . This terminates the packet.

  2. Down the card by entering:

    dncd slot

  3. Send the control packet by entering:

    xcp1 slot 1

  4. The UI should display an acknowledgement message. If not, send the control packet again.

  5. Up the card by entering:

    upcd slotM

Because this workaround activates the stand-by card, the active LED on the front panel of the stand-by card will be green, making it difficult to distinguish which card of the Y-Redundant pair is active. In other words, the active LED on the active and standby cards will both be green.

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: