If you've ever plugged in a DAC (direct attach copper) or an SFP/SFP+ Transceiver that was not made by Cisco into a Cisco device, you know that there is a slight chance that it'll actually turn on and work. Most of the time, the transceiver is not supported and the port will refuse to come up.
With NX-OS devices, you can run a command to allow unsupported transceivers. Obviously, Cisco does not recommend this but it can help when you're in a pinch and need to order more Cisco branded SFPs or DACs. The funny thing is - this command cannot be found in the help so no tab-to-complete!
conf t service unsupported-transceiver
Some devices require you to execute this command on a port (as shown below). For most use cases, you can execute the command above and it'll be device-wide.
conf t int e 100/1/1 service unsupported-transceiver