HP J8168A, J8165A, J8164A, J8161A User Manual
PoE planning and
implementation guide
hp procurve
www.hp.com/go/hpprocurve
PoE
Power over Ethernet Devices
HP ProCurve
PoE Planning and
Implementation Guide
© Copyright 2003 Hewlett-Packard Development Company,
L.P. The information contained herein is subject to change
without notice.
This document contains proprietary information, which is
protected by copyright. No part of this document may be
photocopied, reproduced, or translation into another language
without the prior written consent of Hewlett-Packard.
Publication Number
5990-6045
November 2003
Edition 1
Applicable Products
HP ProCurve Switch 2626-PWR (J8164A)
HP ProCurve Switch 2650-PWR (J8165A)
HP ProCurve Switch xl PoE Module (J8161A)
HP ProCurve 600 Redundant and
External Power Supply (J8168A)
Trademark Credits
Windows NT®, Windows®, and MS Windows® are US
registered trademarks of Microsoft Corporation.
Disclaimer
HEWLETT-PACKARD COMPANY MAKES NO WARRANTY
OF ANY KIND WITH REGARD TO THIS MATERIAL,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE. Hewlett-Packard shall not be
liable for errors contained herein or for incidental or consequential
damages in connection with the furnishing, performance, or use
of this material.
The only warranties for HP products and services are set forth in
the express warranty statements accompanying such products and
services. Nothing herein should be construed as constituting an
additional warranty. HP shall not be liable for technical or editorial
errors or omissions contained herein.
Hewlett-Packard assumes no responsibility for the use or
reliability of its software on equipment that is not furnished by
Hewlett-Packard.
Warranty
See the Customer Support/Warranty booklet included with the
product.
A copy of the specific warranty terms applicable to your HewlettPackard products and replacement parts can be obtained from your
HP Sales and Service Office or authorized dealer.
Contents
1 Introduction
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Power Through the Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
PoE Capabilities of the Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2 Operating Rules
HP 600 RPS/EPS Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Redundant Switch Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
External Switch Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
EPS Power Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Maximum PoE Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
PoE Power With and Without EPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Switch Port Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Switch Priority Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Line Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
PD Power Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
3 Planning
PD Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Supported Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Number of PDs per Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Planning Your PoE Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
HP ProCurve 2626-PWR Configurations . . . . . . . . . . . . . . . . . . . . . . . . 3-3
With an HP 600 RPS/EPS Powering One Switch . . . . . . . . . . . . . . 3-3
With an HP 600 RPS/EPS Powering Two Switches . . . . . . . . . . . . 3-4
HP ProCurve 2650-PWR Configurations . . . . . . . . . . . . . . . . . . . . . . . . 3-5
With an HP 600 RPS/EPS Powering One Switch . . . . . . . . . . . . . . 3-6
With an HP 600 RPS/EPS Powering Two Switches . . . . . . . . . . . . 3-7
i
HP ProCurve Switch xl PoE Module Configurations . . . . . . . . . . . . . . 3-8
With an HP 600 RPS/EPS Powering One Module . . . . . . . . . . . . . . 3-8
With an HP 600 RPS/EPS Powering Two Modules . . . . . . . . . . . . 3-9
Infrastructure Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Glossary
Index
ii
1
Introduction
This chapter provides an overview of Power over Ethernet (PoE) and a list of
reasons why a user might want to implement PoE in their environment. It
discusses how PoE transmits power over twisted pair cable and the capabilities of the devices used to provide PoE.
Overview
Power over Ethernet technology allows IP telephones, wireless LAN Access
Points and other appliances to receive power as well as data over existing LAN
cabling, without needing to modify the existing Ethernet infrastructure.
IEEE 802.3af is an extension to the existing Ethernet standards. Power Over
Ethernet is likely to become a standard feature of ethernet switches in a few
years, as the cost of adding power supplies to the Ethernet switches is going
to be small. It offers the first truly international standard for power distribution (consider how many different AC power plugs exist worldwide).
Almost all appliances require both data connectivity and a power supply. Just
as telephones are powered from the telephone exchange through the same
twisted pair that carries the voice, we can now do the same thing with Ethernet
devices.
Introduction
The technology is bound to make a big impact in the world of embedded
computing. In the realm of embedded computers, where the systems are
increasingly connected to LANs and the internet, the advantages of providing
power and data through a single cable should be obvious. Consider a typical
application: a system for a car park that includes security cameras, information signs, call-for-help telephones and vehicle sensors. Such a system is
distributed over a significant area, where mains power is not easily available.
A single link to a PoE Ethernet Switch makes implementing this system less
expensive and faster than using a non-PoE switch.
1-1
Introduction
Overview
Power Over Ethernet connections to embedded computers will allow much
cheaper installation (no AC cabling, lower labor costs), facilitate updating the
installation and repositioning of sensors without electricians, while maintaining full control over every node through the Internet, with VoIP and
webcam telephony. Functionality can be changed by downloading new software through the network.
Introduction
Figure 1 shows a typical system implemented to power telephones. The PoE
Ethernet switches are installed to supply power over the twisted pair LAN
cables to run phones or other appliances as required.
Mitel 3300 IP PBX
5300xl
HP PoE switch
Figure 1-1. Example of a Typical Implementation
Here are some reasons why you might want to do this:
■ Only one set of wires to bring to your appliance - simplifies installation
and saves space.
■ There is no need to pay for additional electrical power runs or to delay
your installation schedule to make them- saves time and money.
■ The appliance can be easily moved, to wherever you can lay a LAN cable
- minimal disruption to the workplace.
■ Safer - no AC voltages need to be added for additional network devices.
■ As well as the data transfer to and from the appliance, you can use SNMP
network management infrastructure to monitor and control the
appliances.
■ Appliances can be shut down or reset remotely - no need for a reset button
or power switch.
■ When implementing wireless LAN systems it simplifies the RF survey task,
as the access point can easily be moved and wired in.
HP PoE switch
1-2
Power Through the Cable
Introduction
Overview
A standard CAT5 Ethernet cable has four twisted pairs, but only two of these
pairs are used for 10Base-T and 100Base-TX data. The specification allows
two options for using these cables for power:
■ The spare pairs are used. The pair on pins 4 and 5 are connected
together and form the positive supply, and the pair on pins 7 and 8 are
connected and form the negative supply.
■ The data pairs are used. Since Ethernet pairs are transformer coupled
at each end, it is possible to apply DC power to the center tap of the
isolation transformer without upsetting the data transfer. In this mode of
operation the pair on pins 3 and 6 and the pair on pins 1 and 2 can be of
either polarity.
The standard does not allow both pairs (spare and data) to be used - a choice
must be made. The Power Sourcing Equipment (PSE) applies power to either
set of wires. Hewlett-Packard has chosen to supply PoE power over the data
pair. The Powered Device (PD) must be able to accept power from both
options.
An obvious requirement of the specification is to prevent damage to existing
Ethernet equipment. A discovery process, run from the PSE, examines the
Ethernet cables, looking for devices that comply with the specification. It does
this by applying a small current-limited voltage to the cable and checks for the
presence of a 25k ohm resistor in the remote device. Only if the resistor is
present, will the full wattage be applied, but this is still current-limited to
prevent damage to cables and equipment in fault conditions.
Introduction
The Powered Device must continue to draw a minimum current. If it does not
(for example, when the device is unplugged) then the PSE removes the power
and the discovery process begins again.
PoE Capabilities of the Products
The HP ProCurve PoE switch devices are multiport switches that can be used
to build high-performance switched workgroup networks with PoE. These
switches are store-and-forward devices that offers low latency for high-speed
networking. The HP ProCurve PoE switch devices are designed to support
Redundant Power Supply and Power over Ethernet (PoE) technologies.
The 2650-PWR and 2626-PWR switches have 48 and 24 auto-sensing 10/
100Base-TX RJ-45 ports, respectively, and two dual-personality ports—either
auto-sensing 10/100/1000Base-T RJ-45, or mini-GBIC. The dual-personality
ports do not support PoE.
1-3
Introduction
Overview
The HP ProCurve Switch xl PoE Module (J8161A) is a module for the HP
ProCurve 5300 xl Switch and has 24 auto-sensing 10/100-TX RJ-45 ports. All
24 ports are capable of supplying PoE power. However, for the module itself
to be able to supply PoE power it first must be connected to an EPS port on
an HP ProCurve 600 Redundant and External Power Supply (J8168A), hereafter referred to as the HP 600 RPS/EPS.
Introduction
The Switch 2600-PWR Series devices can be connected to an HP 600 RPS/EPS
and receive full redundant power from the RPS part of the unit for switch
operation, if the internal power supply in the switch fails. If multiple switches
are connected to the RPS ports and several switches lose power at the same
time, the switch attached to the lowest RPS port number receives power. The
HP 600 RPS/EPS unit can provide all the power necessary to keep the switch
running.
EPS power from the HP 600 RPS/EPS device is the PoE capability of the device
and supplies backup and additional power for the ports of the 2626-PWR,
2650-PWR switch devices. It also provides PoE power to the HP ProCurve
Switch xl PoE Module.
These switch devices are designed to be used primarily as high-density wiring
closet or desktop switches. With these switches you can directly connect
computers, printers, and servers to provide dedicated bandwidth to those
devices, and you can build a switched network infrastructure by connecting
the switch to hubs, other switches, or routers. In addition, they support the
PoE standard, IEEE 802.3af, and can supply power over a twisted-pair cable
to power devices such as telephones and wireless access points.
1-4
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