Why no power over ethernet ?

[duan]

Hi, just a little question, why do you use USB 5v as power input since it could be done by the ethernet ? (better way for standalone)

[Foxtrot]

Size and Cost.

[biob]

Wouldnt that depend on the infrastructure enabling POE for the port your connected too?

[Just_a_User]

3 minutes ago, biob said:

Wouldnt that depend on the infrastructure enabling POE for the port your connected too?

From the little i know, the POE switch first uses a low power non harmful signal to both non POE and POE devices and await a response before providing full power down the line. This is to allow a mix of POE and non POE on the same switch. I'm not sure if all POE switches do this or some.

As the PacketSquirrel is an in-line LAN tap, for POE to be enabled the squirrel would need to request power when offered by the switch and then pass it through to the end device.  As it is, I think it might (I really don't know) be possible to make a patch cable to pass power around the PacketSquirrel while putting the Ethernet through the squirrel but no idea if that would work as I really don't understand the finer details of POE.

[biob]

We have to request POE to be enabled on a port. Once enabled, it works pretty much as you described.

[HeavyVin]

30 minutes ago, biob said:

We have to request POE

That's dependent on the switch and its setup. There are even some POE only switches I have heard about. This is why I would connect a tester to the line first if I was connecting a squirrel to someone else's network. I wouldn't want voltage going into a data only line.

37 minutes ago, Just_a_User said:

possible to make a patch cable to pass power around the PacketSquirrel

I am looking at the standards for POE so I can make the aforementioned cable. I won't know if I can till I try, though I know it should be possible. 

[biob]

The switches support it, but We have to request POE as it is deliberately disabled until required. Couple of places I’ve worked have been the same.

[HeavyVin]

I know of far too many people that buy a box, plug it in, and leave the site if it starts working. Many even leave default passwords in place. I guess its different for organizations that care enough about security to hire testers. The switches I have used have POE enabled by default with the operation as described by @Just_a_User The nice thing about POE is that it is another option for power. If in a situation where it does not work then one could still use the micro USB port. I would like it even if just for testing so I don't need the USB cable when I finally set up a testing environment for my squirrel.  

[telot]

You can roll your own POE for the squirrel.  It's quite hacky, but I've done it with my pineapples before.  Nothing fancy, just broke out two unused ethernet wires from the plug and ran them to a USB plug.  So my laptop would have two plugs (eth and usb only for power), one cable going down to the pineapple in my bag, where its split out again into ethernet and power (barrel plug in the case of the pineapple, microusb for the squirrel obviously.  

 

 

 

telot

[barry99705]

3 hours ago, telot said:

You can roll your own POE for the squirrel.  It's quite hacky, but I've done it with my pineapples before.  Nothing fancy, just broke out two unused ethernet wires from the plug and ran them to a USB plug.  So my laptop would have two plugs (eth and usb only for power), one cable going down to the pineapple in my bag, where its split out again into ethernet and power (barrel plug in the case of the pineapple, microusb for the squirrel obviously.  

 

 

 

telot

Yea, that works, for yourself.  You'd need access to the wiring closet on "location", which you probably aren't going to have.

[Darren Kitchen]

These work pretty well too

 

[Just_a_User]

2 hours ago, Darren Kitchen said:

These work pretty well too

Nice, If they had a 3rd lead that injected incoming power to continue on past the squirrel to the target that would be perfect!

Im guessing that one would only be good for unplugging a POE device (or find an unused cable) and checking out the switch its connected to?

[Irukandji]

1 hour ago, Just_a_User said:

Nice, If they had a 3rd lead that injected incoming power to continue on past the squirrel to the target that would be perfect!

Im guessing that one would only be good for unplugging a POE device (or an unused cable) and checking out the switch its connected to?

Yeah, that would be a problem.

[lowk3y]

7 hours ago, Darren Kitchen said:

These work pretty well too

 

@Darren Kitchen where to get one of those?

[Just_a_User]

40 minutes ago, lowk3y said:

@Darren Kitchen where to get one of those?

http://a.co/1WXIUQS

 

 

[Niceday]

Having had a good look at PoE, I have a problem - the use of PoE/PoE+ mode A by PoE switches. 

I wired up some RJ45 breakout boards to check and verify the voltages put on each wire with various setups.

PoE powered devices are referred to as PD.  Equipment providing PoE is referred to as Power Sourcing Equipment (PSE).

I'm assuming standard 802.3.af/at 48v active PoE/PoE+ coming from a PoE switch or injector, as they are the most common setup (and mostly PoE switches these days).  I'm ignoring bespoke PoE setups using 12v/24v as I doubt I'd ever come across one.

When equipment is plugged into an active PSE, hardware negotiation takes place using low voltages to see if the high voltage power is needed.  If its a PD, then the answer is yes and around 50v is sent down the wires to power it.  If not (e.g. PC or Packet Squirrel), it isn't, so your stuff doesn't get fried by the high voltage it doesn't want or need.

Now to the problem. 

PoE switches are Endspan devices and those look to use PoE mode A, where the power is sent over wires 1,2,3 and 6 along with data - the very 100Mb data wires the PS needs to get its data from.  The PS wants those wires to get the packets, but it doesn't want the 50v that's sent down them.

PoE injectors are Midspan devices and those look to use mode B, where the power is sent over wires 4,5,7 and 8, leaving 1,2,3 and 6 just for data.  That setup would be fine, and there it should be easy to make up a cable sending wires 1,2,3 and 6 via the PS plus wires 4,5,7 and 8 around the PS and straight to the PD device.

SO :

If I put the PS in the way of the PD, the power negotiation with the PSE ends up not asking for power, and the PD I want to get the traffic for, doesn't power up.

If I double-jumper wires 1,2,3 and 6 so the PD comes up and the PS can get a copy of all the data, I take it I'll fry the PS with the 50v.

@Sebkinne - does the PS need voltage regulators to drop the 50v down to protect it ?   how much voltage can the PS take ?

Other than that, I think I'm pretty much stuck as far as putting a PS in line with a PoE powered device unless I use local power after the PS to bring it up.

Any and all help appreciated.

[HeavyVin]

12 hours ago, Niceday said:

the very 100Mb data wires the PS needs to get its data from

Just when I thought I had something. I no longer have a clue how to get poe support. We have to make sure we can supply the voltage out also or the device we are intercepting won't be giving us anything. 

How does the Packet Squirrel run off of different voltages? I know some USB jacks supply 2.4v while some supply 5v. Also, how do we respond to the switch saying we need power?

I feel like this is one of those things where with every answer I find I end up with more questions.

[RazerBlade]

1 hour ago, HeavyVin said:

Just when I thought I had something. I no longer have a clue how to get poe support. We have to make sure we can supply the voltage out also or the device we are intercepting won't be giving us anything. 

How does the Packet Squirrel run off of different voltages? I know some USB jacks supply 2.4v while some supply 5v. Also, how do we respond to the switch saying we need power?

I feel like this is one of those things where with every answer I find I end up with more questions.

What USB does not supply 5v?

[HeavyVin]

I thought some wall adaptors used 2.4v

[Just_a_User]

2 minutes ago, HeavyVin said:

I thought some wall adaptors used 2.4v

that's most likely 2.4A @ 5V

[Niceday]

The Packet Squirrel uses 5v via micro USB to power it. 

To capture packets, the Packet Squirrel will use RJ45 wires 1,2,3 and 6 to get the packet data, as all 10/100 devices do.  For PCs and printers and other non-PoE devices, that's fine as the voltages sent down those wires for the data packets are small (maybe 2 or 3 volts).

When PoE devices are used, as well as the data packets, you can get around 50v coming down those same RJ45 wires to power the PoE device.  That means the RJ45 connectors of the Packet Squirrel could get 50v sent to them and that might be too much for them to cope with - I haven't seen anything yet to say what the limit is before they could suffer damage.

The Packet Squirrel won't use that 50v to power itself, as it isn't a PoE device - it uses the 5v on the micro USB connector for power.  It just needs to cope with a 50v voltage level without damage or have the level reduced, while letting the 50v get to the PoE device.

I'm looking into whether a PoE splitter would drop the RJ45 voltages down to a safe level (they should, or I don't see the point of them).  Even so, if the PoE device runs at a Gig and the Packet Squirrel doesn't, the splitter might solve the voltage problem and still not help if the PoE device and the switch negotiate a Gig speed that the Packet Squirrel can't keep up with. 

Just not sure that you can capture PoE device packets without powering the PoE device after the Packet Squirrel.  That is, by connecting the Packet Squirrel RJ45 input to the PoE switch (reducing the speed to 100Mb and rejecting the offer of PoE power at the same time) and then connecting the Packet Squirrel RJ45 output into a separate mains powered PoE injector to power the PoE device.  Even that setup is OK for sys admins, as they just want to troubleshoot data issues and aren't trying to be covert about it.

Just a shame the Packet Squirrel doesn't do PoE passthrough.  Maybe in the next version.

[killergeek]

If you want to use POE you want to focus on the  802.3at (poe+ ~30W) and 802.3af (poe ~15w) standard.
There are some other earlier standards but those are vendor specific, like the early cisco POE.

Poe PSE (Power Sourcing Equipment) will only apply power to the wires if it "see" a PD (Powered Device) device according to the POE standard.
There are some cheap injectors/switches that will apply always the power. but you want to avoid if possible because not all ethernet transformers like the DC power.
A switch is classified as a "End Point" and a injector is classified as a "Midspan" in the standard. both are PSE equipment.
A endpoint will apply its power in mode A which means that it will put power on the same pair as the 10/100mb datalines 1,2,3,6 . a midspan will apply power in mode B to the spare pare of the 10/100mb 4,5,7,8.
But this also apply to a 1000mb line. but here the spare pair is also used for data.

The system can use 2 pairs (mode A or B) or 4 pairs (both mode A and B) to supply power. but this depends on the POE implementation by the manufacture and the used POE chipset.

It does not make out if you use a 100mb or 1000mb POE switch/injector if you plug in a PS you always get the 100mb connection. that is just the standard ethernet working.

The POE PSE is not using any type of ethernet packet. it is checking the resistance of the PD to check what kind of power it needs. and does this with a DC voltage.
The ethernet signals are AC couple on top of the DC and they will not interfere with each other. 
If you want to really understand how this is working you will need to read some datasheets on how this is handled.
Some good reads can be found by linear and maxim.
http://www.linear.com/products/power-over-ethernet_(poe)_interface_controllers
https://www.maximintegrated.com/en/products/power/power-over-ethernet.html

So capturing any POE communications with the packet squirrel is not possible.

If you want to power your PS with POE get one of the active POE splitter that is linked earlier here.
@Niceday yes those devices drop down the 50v to 5v (in the case of usb) for supplying power to a device.

To power a POE device after the PS get a POE injector or switch.



You can use a setup like this to get POE power to the packet squirrel and to the device (example a POE ipcam).

[Just_a_User]

That's really good info, thanks!

8 hours ago, killergeek said:

To power a POE device after the PS get a POE injector or switch.

I was thinking/hoping to be able to use somethin like this thats passive (power in = power out) and just tap the data lines. Running the PacketSquirrel from USB port or Powerbank.

So imagine this if you connected the barrel connectors directly together

[killergeek]

@Just_a_User That may work.

You need a pse that supplys in mode B. Most of those are 100mb and use the spare pairs for the power.

The only problem may be with the used transformers for the Ethernet signal in the switch en target device that will not like something in between.

But it's worth a try.

[PoSHMagiC0de]

Why no built in POE?  Lets see what that entails with a similar project using our favorite alternative device, the Raspberry Pi Zero.  The extra hardware for the power would increase the size of the unit.  I imagine you will need diodes too since the POE power and the USB power will terminate in the same spot so you want diodes to prevent one from going down the path of the other perspective.  Needless the say the size would go up (I know it will not be the size of the below project but still another piece or 2 of more hardware is needed like POE board and step down for the actual PS micro board power), the cost would rise also.

But if you really want it and feel adventurous, maybe this will give you ideas to break your own PS if you want it internal.  :-P

 

Using an external solution like Darren shows looks a lot more appeasing to me.  But if you ask enough, maybe they will make a special edition just for those who want it. :-D  I do not see many POE networks at sites I visit except for those dedicated to VoIP or powering IP cameras so POE isn't high on my list for features.