Symptom

A Catalyst 9500HP switch may observe the stackwise-virtual link remaining down/down when the optic used for the stackwise-virtual link is 100G and the link goes down. Expected behavior is that the link will recover on its own either when the optic is replaced or the layer 1 issue is remediated. In the broken scenario the transmit power on the optic will show as -40.0dBm. Example output from "show interface transceiver detail" for a port experiencing the issue: Optical High Alarm High Warn Low Warn Low Alarm Transmit Power Threshold Threshold Threshold Threshold Port Lane (dBm) (dBm) (dBm) (dBm) (dBm) --------- ---- --------------- ---------- --------- --------- --------- Hu2/0/1 1 -40.04 7.00 4.00 -2.90 -6.90 <<<<<<< Optical High Alarm High Warn Low Warn Low Alarm Receive Power Threshold Threshold Threshold Threshold Port Lane (dBm) (dBm) (dBm) (dBm) (dBm) --------- ---- --------------- ---------- --------- --------- --------- Hu2/0/1 1 -1.27 7.00 4.00 -6.90 -10.91 A full reload of the stackwise-virtual system is required to recover.

Conditions

This has been observed on C9500-32C platforms with 17.15.1 using QSFP-100G-FR-S and QSFP-100G-LR optics for stackwise-virtual links. This behavior is not seen if the link is used for non-SVL ports.

Workaround

The issue is not seen when using 40G optics in place of 100G optics

Further Problem Description