Nexus 93108TC-FX3P: QSFP-100G-CU1M link only comes up when speed is set before inserting the cable
Two Cisco Nexus 93108TC-FX3P switches on NX-OS 9.3(11) are connected with genuine QSFP-100G-CU1M DACs but the link never comes up. The compatibility matrix says the cable is supported from NX-OS 9.3.5. The port config is a plain 'switchport mode trunk' / 'no shutdown', and 'show interface eth1/54 transceiver details' identifies the cable correctly: 'type is QSFP-100G-CR4', 'name is CISCO-LEONI', 'part number is L45593-D218-D10', 'cisco product id is QSFP-100G-CU1M', 'cisco part number is 37-1666-01', 'DOM is not supported'. Four different cables were tried and FEC was disabled, without success. When trying to hard-code the port, the poster found that the speed/duplex/negotiation commands are not even available while the cable is inserted.
- Hardware: Cisco Nexus 93108TC-FX3P
- Transceivers: QSFP-100G-CU1M (CISCO-LEONI L45593-D218-D10)
- Form factor: QSFP28, DAC
Symptoms / messages:
link down on QSFP-100G-CU1M between two Nexus 93108TC-FX3P
DOM is not supported
speed/duplex/negotiation commands not available while the cable is inserted
disabling FEC did not help
Comments 2
Accepted solution: set speed and duplex manually under the interfaces. Because the speed command is rejected while the DAC is plugged in, the poster removed the cable, configured 'speed' on the port first, then reinserted the cable, and the 100G link came up.
A respondent checked the Cisco TMG compatibility matrix (supported since NX-OS 9.3.5) and asked whether the cable might be bad, whether the ports were admin down and whether the switch recognizes the cable.