Cisco Versatile Interface Processors

Field Notice: Port Flapping, Output Stuck, VIP Crash, or Performance Issues with Multichannel Port Adapters

Revised May 6, 1999

Products Affected











Problem Description

Various issues have been identified that may affect normal operation of the multichannel T1 or E1 port adapters. These issues are related to the software drivers for the port adapters. New drivers are available that resolve these issues. Under certain circumstances, behavior such as port flapping, output stuck conditions, performance issues, and inability to maintain output levels at or near line rate may be seen. Rarely, a VIP2 controller may crash when used with a multichannel E1 or T1 port adapter.


Several issues have been reported against the multichannel T1 and E1 port adapters.

Problem Symptoms

Depending on the traffic mix and patterns, one or more of the following symptoms may occur in a system using a multichannel port adapter.

  • Interface resets (ports flapping)

  • Poor performance

  • Output stuck condition

  • Loss of data

  • TX output rate not near line rate

  • VIP crash


Resolutions have been incorporated into Cisco IOS software releases 11.1(25)CC and 12.0(4)T.

The Cisco IOS 11.1(25)CC image is currently available on CCO. The Cisco 12.0(4)T images are scheduled to be available on CCO in early May 1999.

Until customers can upgrade to one of these images, the following steps can be used as a workaround:

  1. Turning off keepalives may reduce the amount of port flapping.

  2. Shutting the interface down before making configuration changes may prevent a crash.

  3. Shutting down a T1 or E1 controller only when there is no traffic may prevent a VIP crash.


If you are a registered CCO user and you have logged in, you can view the bug details.



CSCdk76520 (registered customers only)

VIP2 Crash with PA-MC-8E1/120 in vip_enable_tx_polling

CSCdk82659 (registered customers only)

7200 with PA-MC-4/8T1: heavy traffic causes interface flap

CSCdm02847 (registered customers only)

POTENT: VIP crash when shut down T1 or E1 with ISP Mix traffic

CSCdm03079 (registered customers only)

POTENT: Interfaces flapping after changing crc on one interface

CSCdm06312 (registered customers only)

POTENT: Unable to bring up serial interface

CSCdm06792 (registered customers only)

POTENT: (found to be a duplicate of CSCdm06312)

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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