Can a Cisco switch be forced to provide pre-standard PoE to an 802.3af-compliant IP phone?
A. There is no way to force the switch to provide pre-standard PoE, because the power allocation is done automatically through negotiation. Cisco switches with PoE capability automatically supply power to connected pre-standard powered devices, such as Cisco IP phones and Cisco Aironet access points, and to IEEE 802.3af-compliant powered devices if the switch senses that there is no power on the circuit. This means the switch supplies power to any non-Cisco device that does not have Cisco Discovery Protocol (CDP), as long as it is an IEEE 802.3af-compliant powered device. In conclusion, Cisco pre-standard PoE devices and 802.3af-compliant devices work accordingly, and the switch cannot provide either pre-standard PoE to an 802.3af device or 802.3af power to a Cisco pre-standard device.
