PoE (or inline power) is 48 Volt DC power provided over standard Ethernet unshielded twisted-pair (UTP) cable. Instead of using wall power, IP phone sand other inline powered devices (PDs) such as the Aironet Wireless Access Points can receive power provided by inline power-capable Catalyst Ethernet switches or other inline power source equipment (PSE).Inline power is enabled by default on all inline power-capable Catalyst switches. Deploying inline power-capable switches with uninterruptable power supplies (UPS) ensures that IP phones continue to receive power during power failure situations. Provided the rest of the telephony network is available during these periods of power failure, then IP phones should be able to continue making and receiving calls. You should deploy inline power-capable switches at the campus access layer within wiring closets to provide inline-powered Ethernet ports for IP phones, thus eliminating the need for wall power. Cisco PoE is delivered on the same wire pairs used for data connectivity (pins 1, 2, 3, and 6). If existing access switch ports are not capable of inline power, you can use a power patch panel to inject power into the cabling. (In this case pins 4, 5, 7, and 8 are used.) Additionally, power injectors may be used for specific deployment needs. In addition to Cisco PoE inline power, we now support the IEEE 802.3af PoE standard. Not all access switches and phones comply with 802.3af. The Cisco Catalyst 6500, Cisco Catalyst 4500, and Cisco Catalyst 3750 are capable of supporting 802.3af.
The use of Category 3 cabling is supported for IP Communications under the following conditions:
- Phones with a PC port and a PC attached to it (Cisco Unified IP Phone 7970, Cisco Unified IP Phone 7960, Cisco Unified IP Phone 7940, and Cisco Unified IP Phone 7910+SW) should be set to 10 Mbps, full-duplex.
This setting requires hard-coding the upstream switch port, the phone switch and PC ports, and the PC NIC port to 10 Mbps, full-duplex. No ports should be set to AUTO negotiate. If desired, you can hard-code the phone’s PC port to 10 Mbps half-duplex, thereby forcing the PC’s NIC to negotiate to 10 Mbps half-duplex (assuming the PC’s NIC is configured to AUTO negotiate). This configuration is acceptable as long as the uplink between the phone and the upstream switch port is set to 10 Mbps full-duplex.