AIR-PWRINJ3 802.3af?

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May 8th, 2007
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Is the AIR-PWRINJ3 power injector that ships with the 1130s 802.3af compliant? The literature says that the 1130 is 802.3af but I cant find anything that says the injector is...

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Rob Huffman Tue, 05/08/2007 - 07:57
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Hi Jeff,


The Power Injector would not be considered in the 802.3af discussion as it applies to PoE (Power over Ethernet Switches)only. So what this is saying is that the 1130 can be powered by PoE or by the Power Injector. Have a look at this description of the 802.3af Standard;


Due to the rapid acceptance of IP telephony solutions, the IEEE 802.3af Power over Ethernet committee, of which Cisco is a leading contributor, led efforts to standardize Power over Ethernet. The IEEE 802.3af-2003 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access method and Physical Layer Specification. Amendment: Data Terminal Equipment (DTE) Power via media Dependent Interface standard that was approved June 12, 2003 defines how power may be delivered to 10BASE-T, 100BASE-T or 1000BASE-T attached devices.


With the announcement of IEEE 802.3af-2003 compliant 10/100/1000BASE-T support for Cisco Catalyst multiservice switches, Cisco delivers standards based Power over Ethernet that is backward compatible with the installed base of Cisco prestandard Power over Ethernet capable switches. This announcement underlines the commitment by Cisco Systems to deliver standards based solutions and investment protection to enterprises that have deployed Cisco Power over Ethernet solutions.


Although Power over Ethernet was originally intended to support power to Cisco IP phones, development of other Power over Ethernet capable devices has driven the expansion and value of this technology including extending Power over Ethernet support to Cisco 802.11wireless access points. These developments have required that greater power delivery be considered as Power over Ethernet is extended to support more complex applications.


The IEEE 802.3af-2003 Power over Ethernet standard defines terminology to describe a port that acts as a power source (PSE) to a powered device (PD), defines how a powered device is detected and also defines two (2) methods of delivering Power over Ethernet to the discovered powered device. IEEE 802.3af power may be delivered using a Power over Ethernet capable Ethernet port, which is referred to as an End-Point PSE or by a mid-span PSE that can be used to deliver Power over Ethernet in the event an existing non-Power over Ethernet capable Ethernet switch is used.


The IEEE 802.3af standard states that power may be delivered by an end-point PSE, using either the active data wires of an Ethernet port or the spare wires, to a powered device. An end-point PSE, such as a Power over Ethernet capable Ethernet switch, may implement either scheme. If a mid-span PSE is used, then the mid-span PSE can only implement power delivery over the spare pairs of the copper cabling and cannot be used to deliver Power over Ethernet over 1000BASE-T connections. It should be noted that even if a device supports both methods of providing power, only one mechanism may be used to deliver power to a powered device.


From this doc;


http://www.cisco.com/en/US/netsol/ns340/ns394/ns147/ns412/networking_solutions_white_paper09186a008026641c.shtml


Hope this helps!

Rob

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