POE switch, explain it to me

[Anthony5]

Gonna buy some new security cameras and found that POE is quite common these days.

Then looked up for a POE switch and they are quite affordable on Ebay, not so in Thailand of course.

http://www.ebay.com/itm/NEW-6-Port-IEEE802-3af-PoE-Switch-Power-Adapter-For-CCTV-Network-POE-IP-Cameras-/151730078541?hash=item2353d1434d

So some questions that come up my mind, which I hope someone knowledgeable can answer.

Let's say I have a POE switch, from which 1 port goes to an area where there are more than one POE enabled camera installed, which are connected via additional switch installed in that area.

That switch is of course a regular 10/100 switch.

Is this possible?

Does a POE switch give a fixed output, or is this dependable on the power supply you connect to it?

For example if I connect a 12A power supply to 6 port POE switch, will I have 6 ports x 2A or 1 port x 12A output?

[IMHO]

You can only have one POE powered device per port on a POE switch. If you run an ethernet cable from a port on a POE switch to a non-POE switch, you're just wasting a POE port - the power-over-ethernet part will just be lost.

Be careful when shopping - many POE switches actually only have POE on a limited number of ports - e.g. a 16 port switch might only support POE on 4 ports, with 12 non-powered ports. Also pay attention to total power budgets - some cheap switches might have a bunch of POE ports, and each port might have a decent max. power rating, but the overall power budget means you just can't use all ports at once.

To make it even trickier, some of the Chinese POE IP Camera vendors use non-standard POE voltages, meaning you're locked into using their own proprietary POE switches - make sure you buy cameras supporting the normal standards: 802.3af (POE) or 802.3at (POE+)

Edited August 25, 2015 by IMHO

[Anthony5]

You can only have one POE powered device per port on a POE switch. If you run an ethernet cable from a port on a POE switch to a non-POE switch, you're just wasting a POE port - the power-over-ethernet part will just be lost.

Be careful when shopping - many POE switches actually only have POE on a limited number of ports - e.g. a 16 port switch might only support POE on 4 ports, with 12 non-powered ports. Also pay attention to total power budgets - some cheap switches might have a bunch of POE ports, and each port might have a decent max. power rating, but the overall power budget means you just can't use all ports at once.

To make it even trickier, some of the Chinese POE IP Camera vendors use non-standard POE voltages, meaning you're locked into using their own proprietary POE switches - make sure you buy cameras supporting the normal standards: 802.3af (POE) or 802.3at (POE+)

Thanks for the explanation, especially the mention of the standards, of which I wasn't aware.

I think I will go for the normal power supply option, since power at those location is in place already anyway, and as it is not possible to extend the POE function over a normal switch to much re-cabling would be involved.

[RichCor]

I think I will go for the normal power supply option, since power at those location is in place already anyway, and as it is not possible to extend the POE function over a normal switch to much re-cabling would be involved.

POE usually just involves inserting an Ethernet "POE Coupler" (actually a powerblock / power injector wired to a wallwart AC/DC power supply) on the individual Ethernet lines going to each IP Camera (or POE enabled Ethernet device). Looks a right mess when you have a number of cameras.

A POE Powered switch just helps clean up the mess, as all the connections and power supplies are internal in the POE Switch.

[IMHO]

You can only have one POE powered device per port on a POE switch. If you run an ethernet cable from a port on a POE switch to a non-POE switch, you're just wasting a POE port - the power-over-ethernet part will just be lost.

Be careful when shopping - many POE switches actually only have POE on a limited number of ports - e.g. a 16 port switch might only support POE on 4 ports, with 12 non-powered ports. Also pay attention to total power budgets - some cheap switches might have a bunch of POE ports, and each port might have a decent max. power rating, but the overall power budget means you just can't use all ports at once.

To make it even trickier, some of the Chinese POE IP Camera vendors use non-standard POE voltages, meaning you're locked into using their own proprietary POE switches - make sure you buy cameras supporting the normal standards: 802.3af (POE) or 802.3at (POE+)

Thanks for the explanation, especially the mention of the standards, of which I wasn't aware.

I think I will go for the normal power supply option, since power at those location is in place already anyway, and as it is not possible to extend the POE function over a normal switch to much re-cabling would be involved.

Any reason you can't just piggyback a small 4-8 port POE switch on top of that 2nd switch you're talking about?

[Anthony5]

You can only have one POE powered device per port on a POE switch. If you run an ethernet cable from a port on a POE switch to a non-POE switch, you're just wasting a POE port - the power-over-ethernet part will just be lost.

Be careful when shopping - many POE switches actually only have POE on a limited number of ports - e.g. a 16 port switch might only support POE on 4 ports, with 12 non-powered ports. Also pay attention to total power budgets - some cheap switches might have a bunch of POE ports, and each port might have a decent max. power rating, but the overall power budget means you just can't use all ports at once.

To make it even trickier, some of the Chinese POE IP Camera vendors use non-standard POE voltages, meaning you're locked into using their own proprietary POE switches - make sure you buy cameras supporting the normal standards: 802.3af (POE) or 802.3at (POE+)

Thanks for the explanation, especially the mention of the standards, of which I wasn't aware.

I think I will go for the normal power supply option, since power at those location is in place already anyway, and as it is not possible to extend the POE function over a normal switch to much re-cabling would be involved.

Any reason you can't just piggyback a small 4-8 port POE switch on top of that 2nd switch you're talking about?

Of course I could, but that would mean that I would need 3 POE switches, one where all the Ethernet cables start and then another 2 at locations where more than 1 camera is connected to a locally installed switch.

Guess would make it expensive at the end, and your remark that there are different standards makes me a bit wary.

[IMHO]

Of course I could, but that would mean that I would need 3 POE switches, one where all the Ethernet cables start and then another 2 at locations where more than 1 camera is connected to a locally installed switch.

Guess would make it expensive at the end, and your remark that there are different standards makes me a bit wary.

POE switches do not need to be "fed" by another POE switch.. i.e. it's totally fine to have something like this:

WAN > Router > Ethernet > Gigabit switch > Ethernet > POE Switch > Ethernet > IP Cameras

Indeed it's the way you'll want to set it up if using cheaper POE switches, as they are normally only Fast Ethernet speeds (10/100mbps) - if you put them too high up the signal chain, they're just going to limit your overall LAN speed.