The Cisco AIR-PI21AG-A-K9 is an Aironet Power Injector. It’s designed to provide Power over Ethernet (PoE) to Cisco Aironet access points or other PoE-compatible devices. Specifically, the “21AG” likely refers to its support for 802.3af and 802.3at PoE standards. The “A-K9” indicates a specific regulatory domain and feature set. Essentially, this injector allows you to power a device over an Ethernet cable, eliminating the need for a separate power source.
