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.
Reference:
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