PoE+ on former 3Com Gigabit PWR Switches

[lorn10]

Hi there!

Here follows a new topic regarding the former 3Com PWR gigabit switches and their PoE+ capability.

PoE+ becomes more and more important, a new factor is the upcoming Wi-Fi standard 802.11ax aka Wi-Fi 6. For example, the Aruba 5x0 access point series requires 802.3at (PoE+) support. It works with 802.3af (PoE) only when the PoE IPM feature is available. Well, I was not able to find regarding the original 3Com PWR switch models any PoE IPM related information so it looks that the Aruba 802.11ax access points are incompatible.

In our company we use a 3Com 4800G PoE (JD011A) switch. This model is very similar to the HP A5500-EI PoE+ (JG240) gigabit switch. They share the same software and almost the same hardware.

One difference it that the later HP JG240 model has PoE+ while the original 3Com only had PoE non-plus. This is most likely because the HP switch has a much stronger power supply which results in a higher PoE output of 740W versus 370W.

So what are my options to use PoE+ devices at the 3Com 4800G gigabit switch?

There seems to exist a way through an additional external power supply. That one will be connected to the DC-input of the switch. With that configuration the PoE output can be increased. For the original 3Com 4800G PoE series there was available the external H3C RPS 800 power supply. That model was later available as HPE RPS 800 Redundant Power Supply (JD183A). Additionally HP has released some larger even more powerful external RPS models which should also work with the earlier 3Com PWR switch models.

So is this the only possible path to add higher power consuming PoE devices to these older 3Com switches?

What’s about a nonofficial PSU upgrade of the internal 3Com 4800G power supply? Because of the similarity between the HP A5500-EI and the 3Com 4800G switch models it should be theoretically possible to replace the internal PSU unit.

In detail, the idea is to buy a defunct HP A5500-EI (JG240) switch, dissemble it, and replace the weaker 3Com PSU unit with that one out the HP.

Because these switches are all EOL and out of warranty this shouldn’t become a problem. Well, this may work easy at any standard ATX based personal computer but it may be somewhat more complex at professional network devices like these switches.

[Ivan_B]

Hello!

Being on official HPE representative, I have to warn you that any unauthorized modification of PSUs can cause electrical and fire hazard to the people who will use such modified devices. 

But that warning is not the whole story - in all your assumptions and plans you miss one very important fact - PoE+ is not just a PoE with more power, it's a different protocol (IEEE 802.3at) and except more powerful PSUs you need appropriate PSE that can "speak" PoE+ and can negotiate more than 15W power to its endpoints. I am afraid that your plans will fail at this particular step.

Please, if you need PoE+, just consider buying appropriate device - it will be a wise and safe choice.

[FalconSez]

Both models are well past EOL; hence not recomended.

So the correct answer at this point is switch replacement; especially if we're talking about a production environment. 

HP 5130 HiPoE (JH326A) might be what you're looking for; but I'm not aware of any EOS announcements regarding it.

https://h50146.www5.hpe.com/products/networking/datasheet/HPE_FlexNetwork_5130_HI_Switch_Series.pdf

-Frankie

[lorn10]

Thanks for the fast answers.

Well, the first mentioned option with an external DC power supply is officially supported and absolutely applicable without any restrictions. However, in this example here it seems that a larger model is needed. PWR models of the 3Com 4800G switch range needs at least an H3C RPS 1000 class PSU. (I must agree that this option is not really cost effective.)

Regarding my second mentioned unofficial PSU replacement idea it looks as follows. I was able to get some more detailed information. To my big surprise the newer HP POE+ A5500 switches share the same power supply, model PD67024. This is true at least for the HP A5500 models with 370W PoE+ support. These PSE have just a much higher revision; version 15 compared with version 1 at my 3Com 4800G.

But the most interesting thing is the PSE software level. It looks that my 3Com 4800G has with version 612 compared to 413 the newer PSE software version. This is because my 3Com 4800G switch has the newer firmware release (5500EI-R2222P08) installed.

For me this is really a reason to try it.

<3Com 4800G>display poe pse
 PSE ID                           : 4
 PSE Slot No                      : 1
 PSE SubSlot No                   : 0
 PSE Model                        : PD67024
 PSE Power Enabled                : enabled
 PSE Power Priority               : -
 PSE Current Power                : 104      W
 PSE Average Power                : 104      W
 PSE Peak Power                   : 137      W
 PSE Max Power                    : 370      W
 PSE Remaining Guaranteed         : 370      W
 PSE CPLD Version                 : -
 PSE Software Version             : 612
 PSE Hardware Version             : 1
 PSE Legacy Detection             : enabled
 PSE Utilization-threshold        : 80
 PSE Pd-policy Mode               : disable
 PSE PD Disconnect Detect Mode    : AC

<HP A5500> display poe pse
 PSE ID                           : 4
 PSE Slot No                      : 1
 PSE SubSlot No                   : 0
 PSE Model                        : PD67024
 PSE Power Enabled                : enabled
 PSE Power Priority               : -
 PSE Current Power                : 0        W
 PSE Average Power                : 0        W
 PSE Peak Power                   : 0        W
 PSE Max Power                    : 370      W
 PSE Remaining Guaranteed         : 370      W
 PSE CPLD Version                 : -
 PSE Software Version             : 413
 PSE Hardware Version             : 15
 PSE Legacy Detection             : enabled
 PSE Utilization-threshold        : 80
 PSE Pd-policy Mode               : disable
 PSE PD Disconnect Detect Mode    : AC

[lorn10 · Accepted solution]

Here follows a last little update. The problem has been solved now in a different way.

As mentioned in my first post, in conjunction with the first 802.3af PoE standard, Aruba requires for their 802.11ax access points a feature called PoE IPM. The definition of that IPM feature is as follows:

Intelligent Power Monitoring (IPM) is a feature that actively measures the power utilization of an AP and dynamically adapts to the power budget. The static power management method, in contrast to IPM, limits the operation and performance of an AP based on the worst case power usage model.

Source:
https://www.arubanetworks.com/techdocs/ArubaOS_651x_Web_Help/Content/ArubaFrameStyles/AP_Config/IPM.htm

Now I have compared this to the H3C / 3Com PSE functionality:

PSE—A power sourcing equipment (PSE) detects and classifies powered devices (PDs), supplies power to PDs, and monitors the PD power and connection status. PSEs include endpoint PSEs and midspan PSEs.

Source:
http://download.h3c.com/download.do?id=2411039

That has now brought me to the conclusion that the Aruba PoE IPM feature is basically the same as the H3C / 3Com PoE PSE.

So finally, it seems that the newest Aruba 802.11ax access points are compatible also to quite old 3Com PoE non-plus switches as long as they provide a PSE mechanism.

Update 02.05.2021:
I can confirm meanwhile also practically that the 802.11ax PoE+ Aruba 510 Series works perfectly well with the mentioned old 3Com 4800G PWR switch series. It is just strongly recommended to use the most recent Comware Switch firmware. Five Aruba AP-515 are currently in use and they operate absolutely fine. Also here it is recommended to use a current firmware version. An other quite important point in conjunction with PoE+ seems to be the network cabling, especially on longer distances. Because I am at a Cat. 7a infrastructure (Dätwyler Uninet 7702 flex) there exist in my case absolutely no problems also on longer distances.