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Can someone help me understand PoE and what I need?

edited June 2014 in SecuritySpy
Hello all this is my first post as I am narrowing down my new system. I will be using SecuritySpy with Dahua PoE cameras on a late 2012 iMac. I went ahead with PoE (Power over Ethernet) not really thinking too much about it, just assumed Id plug them in the ethernet ports. I have two different type of wireless router/switches in my home network. The Fios-supplied actiontec modem/router and two add-on Cisco EA3500s each with 4 gigabit ports.

I made the assumption I would plug the cameras into these gigabit ports but now I am getting the feeling that I will need addtional hardware to handle PoE (which I prefer to use regardless if my cameras have a power cord). I cant find any mention of PoE in the basic router manuals.

Do I need some sort of additional hardware to use PoE? What is teh common setup from a network HW standpoint?

Thanks all!


  • Your hardware doesn't have POE built in. You will need to use a POE injector. Search Amazon for POE injector and you will see them... usually around 15 to 20 dollars. This will take the output of your Cisco ports and inject onto the cat5 the power. You plug in the CAT5 to the camera as well... It will have a external power supply that will provide the voltage that will be sent down to the camera. Your other option is to buy a ethernet switch that provides POE.... but for one or two cameras this would not be cost effective. Basically you will have the ethernet from your Cisco running a cable to the input data side of the injector, a power supply that plugs into the injector and then the cat5 data and power cable running from the injector to the device that requires POE. The upside to having a ethernet switch that supports POE built in is that you avoid having the external power supply ... you can configure the port on the switch for POE ( some let you chose between the standard POE of 48 volts - which is what your particular camera requires ) and passive POE of 24 volts that some devices like Ubiquiti Wireless AP's require.
  • Thanks so much doodah - I can see having the multiple power supply plugs becoming unmanagable if I scale my system...Im assuming I would need one injector for each camera if i dont get a switch...which I hope I do I am just setting up one to see how it all works.
  • One thing to keep in mind with POE switches is that you have to make sure that they are able to supply power to to all the ports simultaneously. Some POE switches work fine if you plug in 1 or 2 POE devices, but might not able to supply enough power on all the ports simultaneously. Also, if possible buy a managed switch. This would allow you to toggle the power to the camera via the POE switch (say to reset a crashed camera) instead of manually playing with the camera/cabling which might be inconvenient or hard to reach.
  • All good information by doodah and DeanL. I would say going for a dedicated PoE switch is the best option, especially if you're planning to scale your system up in the future. As DeanL says though, make sure to read the specs of the switch carefully, as some supply power only to a subset of their ports.

    If you do decide to use PoE injectors though, note that there exist multi-port versions of such devices, so that you don't necessarily need an injector plus power supply for each camera, which would quickly become very messy and unmanageable.
  • Thanks so much all. I hunted down most of my options yesterday - all mentioned above. Since I am essentially "testing" with one camera, then scaling from there if IM happy with it, I just picked up a simple 48v $12 PoE injector.

    I saw the multi port injectors which look like a good way to go (was immediately concerned with individual injectors and plugs because I'll be looking at 4-6 cameras) but had a hard time finding a reasonably priced 6+ port gigabit injector. Also, it seemed that many I found on Amazon did not come with power supplies for some reason (one more thing to be concerned about getting "right"). I did pay attention to the specs, ensuring 48v delivery to all ports (up to certain watts usually 60 which should be fine I believe).

    Having said all that, I assumed it would be best to use gigabit injector(s) since my router port is gigabit?

    On the PoE switch issue, I thought I would run into problems with my router handing out DHCP IPs to the there an issue there?

    Thanks Again
  • The 802.3af PoE specification was designed to work the same way over ethernet networks of different speeds - it's the same standard whether the data rate is megabit or gigabit. After all it's just injecting power into an ethernet cable so it should't have any effect on the data transmission itself. Having said that, it might be best to get PoE injectors that are rated for gigabit speed, just to be sure there will be no problems.

    The ideal network topology will be all devices, including the router, connected into a single PoE switch. The DHCP service in the router will work perfectly well handing out IP addresses to any device connected to such a network - it doesn't care if a device is connected directly to one of its ports, or if it's connected to a switch that's connected to one of its ports.

    The switch will have an IP address itself only if it's a managed switch (mentioned by DeanL above). In this case the switch will have a web interface that you can connect to (via its IP address) in order to change settings and get information about its functions. A standard unmanaged switch doesn't itself have an IP address; it simply routes ethernet data packets around the network.

    Therefore, managed switches are more expensive but more configurable and flexible; unmanaged switches are simpler and cheaper, but still perfectly good for small to medium networks.

    Hope this helps!
  • edited June 2014
    Thanks Ben this is really good information and hopefully helpful to others searching this topic for purposes of ip camera setup.

    One followup on the switches...managed vs. unmanaged: would it make any difference when it comes to accessing the cameras (in my case the Dahua) and changing their ip? or accessing their settings? One thought is will I see the cameras as client devices from my router config page in either scenario?

    ..and on the gigabit I was only concerned about data transfer maximization i.e. having a weak link in the chain...
  • It won't really help with setting up the Dahua cameras - the switch would be able to tell you that a device is connected on a particular port and give you some information about the communication with that device (e.g. port speed, MAC address, packets sent/received) but it won't show you information such as the IP address of the device, because the switch operates at a lower level than this.

    The trick with the Dahua cameras is to work out what the default IP address is (which should be stated in the user manual), and then use the "Cameras with a fixed address by default" procedure on our Setting up Network Cameras manual page.

    Re gigabit PoE injectors: yes you're right, it's sensible to be concerned about avoiding weak links.
  • Hey Ben just an update here and some information you and others may find usefull. I received the Dahua IPC-HFW4300 3MP bullet today (from amazon there were several mine was sold by HD security) along with a TP-LINK gigabit PoE injector (forget where but the return label just says amazon fulfillment). Based on my readings here I was prepared to do an IP dance to recognize the camera knowing that my router and DHCP is ip 10.213.1.x.

    First I tested the PoE by plugging the the ethernet and power cables in it was quite simple and intuitive for someone who has never dealt with it. I noticed the IR lights blink so I felt confident the camera had power and there is also a status indicator on this PoE Injector that, as the instructions said, turned solid green once it was delivering 48c power to a device.

    The camera came with a basic manual that someone not familiar with networks at all would be terrified of. There was also a CD that apparently has other instructions and a scan tool to locate the camera.

    Turns out I never needed the CD. After connecting, I took a chance and dialed up my router at its default In the client table I immediately noticed an unfamiliar device (no name just a dot) with the .111 ip. I hit that in the browser and viola! It was the camera. I did the web plugin download as instructed and I was rolling perfectly on both Safari and Chrome.

    I was amazed at how easy it was. I am now going to download security spy and get that hooked in.

  • Hi Mike, great to hear the setup was easy! Thanks for letting us know about your experiences.
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