Home > Articles > Networking > Network Administration & Management

Using 802.3af (Power Over Ethernet) as a Sysadmin Tool

  • Print
  • + Share This
By using Power over Ethernet (802.3af) to provide power for devices such as WiFi Access Points, VoIP desktop phones, and webcams, companies can save on A/C wiring costs and UPS provisioning. Daniel P. Dern tells you how you can gain additional sysadmin capabilities, including remote off/on/reboot and power provisioning management.

Although we're used to thinking of Ethernet cabling as a medium for data, the wires can also be used to deliver a useful amount of DC power to connected devices. This is called Power over Ethernet (PoE). In addition to saving money on installation, PoE can sometimes be a useful tool for sysadmins. Here's how.

Power Over Ethernet: A Little Bit Of Background

Similar in principle to the way that the wire pair that carries your POTS (Plain Old Telephone System) telephone signals into your house also carries enough juice to power the phone's core innards of headset, dial, and ringer, PoE delivers DC power (up to about 15 watts per wire) over standard Ethernet cabling (CAT5 and better, and some CAT3)—enough to power a growing number of commonly-used useful devices.

PoE has been around for a number of years, with proprietary (and often noninteroperable) implementations from Cisco, PowerDsine, and others. In June 2003, however, the IEEE ratified its 802.3af Power over Ethernet standard, which has, in turn, spurred standard-compliant 802.3af products.

In addition to powering WiFi Access Points (APs) and Voice over IP (VoIP) phones, PoE is also seen as a way to power things such as networked security webcams and smoke/fire detectors; along with RFID scanners, keyless entry and time card systems, "smart signs," audio/video jukeboxes, EPOS and retail Point of Information systems, vending and gaming machines, switch and display panels, and so on. PoE can also be used to recharge PDAs and cell/mobile phones (through docking stations or chargers), and partially recharge notebooks. (There's also a PoE electric razor and a PoE electric guitar, FYI.)

Power is "injected" into the cabling at the wire-closet side. This can be done either through "end-span" LAN/WAN switches, which incorporate the power supply circuitry, or (if you don't want to replace existing LAN switches or only want to power some segments) "mid-span" power patch panels or injectors, which are connected in-between the switch and the segment. The 802.3af standard defines details such as which wire pairs are used, signaled to the device to determine its power needs, and so on. And, of course, the end devices have to support PoE.

NOTE

Pre-standard PoE devices may be incompatible with 802.3af equipment.

Sending power over the Ethernet cables avoids the need to install A/C wiring and outlets; for example, for hard-to-reach Access Points (often located in ceilings or otherwise hard-to-reach places, or in areas in which you'd rather not be running electrical cabling). Doing the wiring can also be far less expensive—no power cabling or jack needed, and running power cables often requires union electricians (Ethernet cabling may not).

Powering devices such as Access Points, VoIP phones, and security cameras also simplifies provisioning backup power because a single UPS can be located in the wiring closet, rather than needing one at each device location.

In case you're wondering, Power over Fiber (PoF?) is on its way—still a few years out. But for now, there's an interesting hack approach for runs too long to use Ethernet for data: running Ethernet cabling in parallel to the fiber, just to provide power to the fiber-connected remote device.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020