Every pluggable optical transceiver (SFP, SFP+, QSFP, QSFP28, etc. ) ships with a small EEPROM that stores two kinds of information: a fixed Serial-ID block (vendor, part number, serial number, capabilities) and—when provided—a diagnostics area (real-time temperature, voltage, TX/RX power, etc. Optical transceivers can be used on switches, routers and network adapters (fiber network cards). For network engineers, knowing how to view and interpret SFP information from the Cisco command-line interface (CLI) is essential.