* A POE injector is a device that provides power and data over a single Ethernet cable to a POE device, such as a VoIP phone, a wireless access point, or a security camera12.
* A POE injector is needed when the switch or router that connects to the POE device does not support POE or does not have enough POE ports available12.
* A POE injector can be installed between the switch or router and the POE device, using two Ethernet cables: one from the switch or router to the injector, and another from the injector to the POE device12.
* A POE injector can supply up to 30W of power per port, depending on the POE standard it supports (802.3af or 802.3at)12.
* B. Enable MDIX is not a correct answer because MDIX is a feature that allows a switch or router to automatically detect the type of cable (straight-through or crossover) and adjust the pin assignments accordingly34.
* MDIX is not related to providing power to a POE device, and it is usually enabled by default on modern switches and routers34.
* C. Use a crossover cable is not a correct answer because a crossover cable is a type of Ethernet cable that swaps the transmit and receive pairs of wires, allowing two devices of the same type (such as two switches or two computers) to communicate directly56.
* A crossover cable is not needed to connect a VoIP phone to a switch or router, as they are different types of devices that use different pin assignments56.
* A crossover cable also does not provide power to a POE device, and it may not work with gigabit Ethernet or auto-MDIX devices56.
* D. Reconfigure the port is not a correct answer because reconfiguring the port on the switch or router that connects to the VoIP phone does not address the issue of providing power to the phone78.
* Reconfiguring the port may involve changing the speed, duplex, VLAN, or security settings, but none of these affect the power delivery to the POE device78.
* Reconfiguring the port may also cause network connectivity or performance issues if the settings are not compatible with the VoIP phone or the network78.
References:
* What Is a PoE Injector and How to Use It? | FS Community
* Power Injector for PoE Networks | Eaton
* CCNA / CCENT / Network+ Tutorial: Crossover Cables And Auto MDI-X
* Straight-Through and Crossover Cables - N10-008 CompTIA Network+ : 2.3
* Straight-Through, Crossover, and Rollover Cables - CompTIA Network+ N10-006 - 1.5
* CompTIA Network+ Cheat Sheet (Updated for Latest Exam) - StationX
* CompTIA Network+ : Common TCP And UDP Default Ports - Tutorialsweb.Com
* A Guide to Network Troubleshooting - CompTIA