Symptom

When a GLC-LH-SMD 1G SFP transceiver inside a CVR-QSFP-SFP10G (QSA) QSFP+ transceiver is inserted in a 40G QSFP+ interface of a Nexus 3100 device, the link may not reliably come up/up as expected when the GLC-LH-SMD transceiver is removed, then re-inserted inside the CVR-QSFP-SFP10G. Furthermore, DOM information for the GLC-LH-SMD may not appear as expected. Specifically, the transceiver's "Current" reading may show as 0.00mA, the "Tx Power" reading may shows as N/A, and the transceiver's type may show as "Unknown Type-(unknown)". N3K# show interface Ethernet1/51/1 transceiver details Ethernet1/51/1 transceiver is present type is Unknown Type-(unknown) <<< name is CISCO part number is SFCT-5716PZ revision is 001 serial number is XXX nominal bitrate is 1300 MBit/sec Link length supported for 9/125um fiber is 10 km cisco id is 3 cisco extended id number is 4 cisco part number is 10-2625-01 cisco product id is GLC-LH-SMD cisco vendor id is V01 SFP Detail Diagnostics Information (internal calibration) ---------------------------------------------------------------------------- Current Alarms Warnings Measurement High Low High Low ---------------------------------------------------------------------------- Temperature 35.76 C 90.00 C -10.00 C 85.00 C -5.00 C Voltage 3.34 V 3.63 V 2.97 V 3.47 V 3.14 V Current 0.00 mA -- 65.09 mA 2.40 mA 61.00 mA 3.00 mA <<< Tx Power N/A 0.00 dBm -13.01 dBm -3.00 dBm -9.50 dBm <<< Rx Power -5.71 dBm 0.00 dBm -23.01 dBm -3.00 dBm -19.20 dBm Transmit Fault Count = 0 ---------------------------------------------------------------------------- Note: ++ high-alarm; + high-warning; -- low-alarm; - low-warning

Conditions

1. Nexus 3100 device connected to a link. 2. Nexus 3100 has a GLC-LH-SMD 1G SFP transceiver inside of a CVR-QSFP-SFP10G (QSA) QSFP+ transceiver inserted in a 40G QSFP+ interface. 3. During the switch's uptime, the GLC-LH-SMD was removed, then re-inserted inside the CVR-QSFP-SFP10G.

Workaround

To proactively avoid encountering this issue, avoid removing and re-inserting the GLC-LH-SMD transceiver from the CVR-QSFP-SFP10G. To work around this issue after it has been encountered, remove the CVR-QSFP-SFP10G while the GLC-LH-SMD is still inside, then re-insert the CVR-QSFP-SFP10G while the GLC-LH-SMD is still inside. Then, administratively bounce the link as shown below: N3K# configure terminal N3K(config)# interface Ethernet1/51/1 N3K(config-if)# shutdown N3K(config-if)# no shutdown

Further Problem Description