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jasongt
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GPER usage questions

Tue Aug 20, 2019 9:06 pm

We have a job coming up in a warehouse with some long Ethernet runs for access points. We will be using CAT6 cabling.

If we use standard 802.3af POE switches and access points that are powered 802.3af, my understanding is that the GPER can go in between and the switch should power the GPER and the access point.

Is that correct?

Do they pass VLANs?

Any reason not to use them?

Thanks
Jason
 
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normis
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Re: GPER usage questions

Wed Aug 21, 2019 10:18 am

Yes, it will effectively extend your cable and will pass any data you transmit and also will power the device at the other end. It's like putting a switch in between. There will be a minimal voltage drop, below one Volt, see table at the second page of this file; https://i.mt.lv/cdn/rb_files/GPeR-1565848659.pdf
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marekm
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Re: GPER usage questions

Mon Aug 26, 2019 1:48 am

Does it learn MAC addresses (SVL or IVL?), drop bad frames and add some delay (store and forward), auto-negotiate (possibly different speeds to both ends) like a switch? Or is it a true layer 1 repeater, nothing more?
Also, does it allow 802.3af/at PoE detection/classification with the device at the other end? For this you must draw almost no current at low voltages, so that 25k resistance is still correctly measured.
 
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floaty
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Re: GPER usage questions

Wed Sep 11, 2019 12:34 am

It's like putting a switch in between
mmh, thats a delphi-oracle term ...
a switch learns mac-adresses ... a switch ages mac-adresses !?
so question is: is this a switch, like a two-port-bridge or is it just like patch-port in OVS which says "<->" ?
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r00t
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Re: GPER usage questions

Wed Sep 11, 2019 1:27 am

Does it learn MAC addresses (SVL or IVL?), drop bad frames and add some delay (store and forward), auto-negotiate (possibly different speeds to both ends) like a switch? Or is it a true layer 1 repeater, nothing more?
Also, does it allow 802.3af/at PoE detection/classification with the device at the other end? For this you must draw almost no current at low voltages, so that 25k resistance is still correctly measured.
Good questions...
Also what about MTU it can do?
 
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doneware
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Re: GPER usage questions

Wed Sep 11, 2019 2:11 am

It's like putting a switch in between
a switch learns mac-adresses ... a switch ages mac-adresses !?
a switch with 2 ports doesn't need to learn no MAC addresses and henceforth not responsible for any aging procedures. it neither runs no loop prevention algorythm. whatever is received from port A will be sent out to port B. it is basically a more expensive piece of wire that is manageable :-)

if it would support different speeds on both ports, it sould then also have buffering to mitigate drops from congestions due to different bitrate frames arrive and leave.
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Re: GPER usage questions

Wed Sep 11, 2019 2:57 am

i think its a 2port switch with Poe in to power it and Poe pass-through

a great device

gper1.jpg
gper2.jpg
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floaty
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Re: GPER usage questions

Fri Sep 13, 2019 12:57 am

a switch with 2 ports doesn't need to learn no MAC addresses
of cause there would be no need, neither would be a need for that in a linux-bridge which contains two logical interfaces by my command or a 24-port switch where I only plugged two cables in ...
... but they do ! ... threrefore my question.
There are Access-Points in the field which communicates power-requirements over LLDP-MED ... more questions ... !? How would a GPER behave ?

Expecting a pair of GPER ... (what is it ... ... kleine racker : ) ? ... tomorrow.
... or how Gertrud would say:
" a field-test is a field-test is a field-test"
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floaty
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Re: GPER usage questions

Fri Sep 13, 2019 1:21 am

"Yes, it will effectively extend your cable and will pass any data you transmit"

data ... yep, data is a lot ...

so let us concatenate which questions:

- ether-speed negotiation bursts (and the results ... we all now: it's standard ... but it's not golden in functionality ... nowhere )
- lldp-behaviour (lldp-med ...etc. ... etc.)
- mtu (max_es ? no max_es ?
- multicast

studied "https://i.mt.lv/cdn/rb_files/GPeR-1565848659.pdf" thoughtfully ... but ... I've ... still ... some questions left
... so let's fill the voids
\Yii
~~
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r00t
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Re: GPER usage questions

Fri Sep 13, 2019 2:01 am

What chip is that? Marvell 88e8041? It's hard to read from the image...
But that's a huge chip for such simple device, probably have like 4 ports or even MII interface...

If it does have more ports, maybe there could be GPER version with more than two connectors? So you could branch off cable to the device, like AP... just like you did in the old days of coaxial cable with the T...

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