Cisco ONS 15400 Series

February 13, 2004

Products Affected

Problem Description

Under certain conditions, the transmitter of an ML-100 Fast Ethernet interface might stop transmitting and raise the EQPT alarm.

Background

Ethernet interfaces support the ability to briefly pause transmit in response to pause flow control frames. These pause frames are sometimes sent by a switch or router during network congestion.

An issue has been discovered in the flow control subsystem of ML-100 Ethernet interfaces which may cause a 10/100 Ethernet interface to become permanently stuck in a transmit pause state. Once transmit is stuck in this way, transmit can only be resumed by a reset of the card.

This issue is most likely to occur as a result of flow control on the Ethernet link, but may also be triggered by corrupted frames.

Problem Symptoms

The interface receives traffic but does not transmit traffic, and transmit counts on the ML-100 Fast Ethernet interface do not increment. No immediate alarms will be raised when the transmit lockup occurs. The EQPT "Equipment Failure" alarm may be raised for the card several hours after the issue occurs.

Workaround/Solution

A card reset is required to restore traffic. To prevent this issue, enable auto-negotiation and disable flow control on both ends of each Fast Ethernet link. Use the following ML-100 interface commands:

speed auto

flowcontrol send off

If auto-negotiation is undesirable, the chance of the issue occurring can be reduced by disabling flow control on the device at the other end of the ML-100 FastEthernet link. This issue is resolved in Release 4.6 and Maintenance Release 4.1.3.

DDTS

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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:

• Open a service request on Cisco.com
• By email
• By telephone

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