I have read people taking about passive switches.
DO they exist?
I think you can get a passive switch if you use optic fiber, but not with ethernet cabling.
With ethernet even a simple hub has to be powered.
Am I wrong?
If you mean "unpowered ethernet switch", then the answer is "no, it does not exist".
If you mean "unpowered ethernet hub", then the answer is "yes, but you probably do not want one".
If you mean "PoE-powered ethernet switch", then the answer is "yes, for small devices".
If you mean "PoE-passive ethernet switch", then the answer is "yes, but that is not standard".
If you mean something else, then I am out of ideas...
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Well yes I was asking by un powered swiches of hubs (ethernet).
I know there are un powered fiber optic switches.
But as you say I had the idea than an unpowered ethernet switch does noe exit.
Unpowred ethernet hub, I was not sure about their existance.
Not a general solution, but may be a they are a good solution when you run out of ethernet connections, don't have power near the place (or don't want more power consumption) and the devices that connect to them do not consume to much bandwith.
For example some IOT devices, if yo want to add a temperarute measurement devices in the exterior an other sensors (movement for example) and do not have enough ethernet connections in that place.
You could add a passive hub and connect all sensors to a single ethernet cable.
Am I wrong?
I plan to use switches in the main cabinet with POe for some of the connections.
What is then a PoE-passive ethernet switch?
"Passive" is one that does not negotiate voltage for the PoE, it expects a particular voltage to be present on the line at all times. An "active" switch has logic that negotiates the voltage and power levels with the connected device.
Note also that there's direction involved, a switch can be either powered-by (PoE-in) another device, or supply power to another device (PoE-out, which is almost always what is meant by just "PoE", but beware!).
As an example, here is a switch https://mikrotik.com/product/RB260GS that can be powered by a passive PoE-in connection, but has no PoE-out capability
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Thanks a lot for the explanations.
Now it is clear for me.
I would need an active switch with some slots with PoE to provide power to some devices.
It is good to know that there can be some PoE powered switches, just in case the need arrive.
They are not very common, I do not think many people really uses them:
https://www.eeweb.com/building-a-passive-ethernet-hub/
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Thank you they are interesting for connecting some devices like IOT devices (low bandwidth) when you get out of connections.
Now that I remember, I thinkg that early hubs where like that.
The old ehternet 10-Base T was interesting for that kind of use as it was very easy to expand (with lots of other problemes, one of then where electric outgages).
It can work only for 10 Mb. Early 10 Mb Ethernet was bus oriented using tee connections to a single coaxial cable.
100 and 1000 Mb links constantly transmit an "idle" bit sequence when there is no packet traffic. That means the link must be one point to one point.
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Existing hubs will only work up to 100 Mbps ethernet at best if I recall correctly... wikipedia seems to confirm that gigabit ethernet hubs never materialized
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Thanks.
A pity, they wouldnbe usegill in some situations.
Transmiting continuously seems like a power waste, but may be they justo are holfing linebdownnand there is no power consumption to transmit a 0.
@moeller0 your anserr semms to be angainst @mk24 .
Do 100 passive hubs existe? It implies that line is not hola in 0 state when idle.
For some uses like iot devices sharing 100 Mb among everal would be more thank enough.
Even 10 would di, but It sounds less interesting.
I am talking about powered hubs here, with hub meaning that all connected stations act upon a shared ethernet segment with the need for collision detection, as compared to switches which will give each station their own individual ethernet segment without the possibility of collisions.
I would only use a hub for very specific purposes (like being able to snoop all traffic from one connected station) and generally use switches.
Yes, perhaps in a very specific and rare use case, they can be a viable alternative... but, in general, this is a bad idea.
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Yes of course, not a good way to plan for the future or to connect your computers to internet.
But the problem today with ethernet is its star design which make dificult to grow the net without a carefull planning (being logically a shared bus network).
To much investment in infraestructure that probably won't never be used, and to many cable runs.
There are other cable buses that support variable speeds communication (i.e RS485)
But they have not been developed to the extent of ethernet and are not in widespread use).
So at the end that protocols are slower than even 10Mb ethernet and finding devices for them is difficult, son they are reduced to some specifical use cases.
But here is the rub, if you have a bunch of IoT devices in one room, just aggregate them onto one cheap gigabit switch and use a single cable to uplink this to your main switch... or if you have multiple such IoT "nests" give each of them their own switch and use a single uplink...
Yes, but you have to power the switch and it has to be on all the time, with more power consumption.
Not a big problem most of the time.
I had heard of passive switches and it sounded interesting (but I suspected you could not do intelligent switching with no poser), even passive hub would be but there are many drawbacks.
Maybe have a look at energy efficient ethernet that might allow to reduce the idle powerdraw.
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Thank you I was not aware of that standard.
I have read a bit about it.
I remember that my small switch had a Green energy logo, so at least the switch will not be dragging energy continuously (but my IS router and the openwrg router and AP will, and my QNAP system...).
I will take that into account when I buy the new 1GB switch with PoE for the new home under construction (in a year or two I hope).
I will try to buy efficient equipment with low consumption, a simple fiber to ethernet ONT from the ISP (not easy to get, most of them just provide a router for residences) a good switch and a router running in a nano RS4 or similar.