Wireless Access

Hello all, 

I went through the different community article for IPM and I'm still getting confused how IPM works, hopefully, I can get a resolution in this discussion. 

 

I'm using a Cisco switch to provide to power up a couple of AP-315.

from the controller side, I enabled IPM with the following priorities

 

IPM enabled (applied to a specific AP for testing)

show ap debug system-status ap-name B1F1AP01 | begin "Power Status"

**********

Power Status
------------
Item Value
---- -----
Power Supply: POE-AF
LLDP Power: Successfully negotiated at 20.8W
Current Operational State: 2.4GHz radio: No restrictions, 5GHz radio: No restrictions (Overridden by LLDP)

**********

 

IPM Disabled 

**********

Power Status
------------
Item Value
---- -----
Power Supply: POE-AF
LLDP Power: Successfully negotiated at 20.8W
Current Operational State: No restrictions (Overridden by LLDP)

**********

 

as you can see I got the same results with/without IPM, 

my question now is simple, how/when IPM will take effect?

 

Additional output from Switch side (overview about PoE budget)

SW_B1F1#show power inline
Available:1400(w) Used:1292(w) Remaining:108(w)

If the AP is succesful in reserving the full POE budget it needs from the switch for unrestricted operation, IPM does not do anything.

If the switch can only deliver 802.3af POE, IPM can be used to minimize and specify/prioritize the restrictions the AP will apply when actual consumption reaches the limit of what's available.

show AP debug shows the following
.....
Power Supply: POE-AF
.....
as far as I understand here that Poe source is ''af'' standard, I'm I right?

can you please give me more details about
"AP will apply when actual consumption reaches the limit of what's available."

thank you anno!!

Please review the attached

Your AP negotiated 802.3at power, thus IPM is not needed.

 

"LLDP Power: Successfully negotiated at 20.8W"

 

---

@MandP wrote:
show AP debug shows the following
.....
Power Supply: POE-AF
.....
as far as I understand here that Poe source is ''af'' standard, I'm I right?

can you please give me more details about
"AP will apply when actual consumption reaches the limit of what's available."

thank you anno!!

---

 

Thanks for the feedback,

Briefly speaking now, IPM will play a role only if the switch provides 802.3af PoE standard.

from debug output command:
show ap debug system-status ap-name B1F1AP01 | begin "Power Status"
Why controller showing:
Power Supply: POE-AF
?

802.3at POE negotiation is completed with LLDP in addition to the 802.3af signaling. That's why the debug output immediately below what you quoted is important for determining the current power draw negotiated by the AP.

 

https://en.wikipedia.org/wiki/Power_over_Ethernet

 

---

@MandP wrote:
Thanks for the feedback,

Briefly speaking now, IPM will play a role only if the switch provides 802.3af PoE standard.

from debug output command:
show ap debug system-status ap-name B1F1AP01 | begin "Power Status"
Why controller showing:
Power Supply: POE-AF
?

---

 

sorry, not totally convinced =)
Prefered if the controller can show up the actual power supply type as the wich is at as the AP end up by negotiating 21w. I'll assume that AF is showing for

apart of that, we mentionned that IPM will play role if switch provide AF PoE standard,

based on the document attached in the previous post by @jhoward, i saw this:
The primary goal of IPM is that, when customers need to run APs that may require 802.3at/bt but
only have 802.3af/at switches or PSEs, if the default power-save settings outlined on the data sheet
are not acceptable, then a custom IPM policy can be defined, which can allow those APs to run on
802.3af/at power in a configuration that is required per the config, and gives the admin more
granular control over how the IPM policies impact overall performance.

what do you think?

Not sure what to convince you of, your output above shows 20W, which is not AF possible, so your switch is providing at least 20W (more actually once the cable losses are accounted for) 

 

What model of Cisco switch are you using? Cisco used non-standard POE+ (which is NOT 802.3at) so the AP could be signaling off the voltage as AF but getting more power because the PSE is providing more than 15W. 

 

At any rate, IPM is as outlined in the doc. With an explicit policy, you can control what type of power saving measures the AP will take. Without it, the AP will use the default settings outlined in the DS when AF power is present.

cclemmer, jhoward
Thanks for your inputs, feel more comfortable as I understand now that Cisco switch can provide an AF standard that can go up to 30w and named under PoE+.

as I have In my environment, Cisco 4500 with different PoE modules and controller showing AF ==> PoE modules are PoE+ and not AT.

Thus APs won't decrease power with priority order I provided. (Please correct me if I'm wrong).

@cclemmer, I have a plan based on the idea you said of disabling LLDP.
I'm thinking of disabling LLDP so AP will draw 15.4w (neg.cable loss) and with that way IPM will take effect and disable feature based on my list of priority. What do you think? this should do the trick.

Yes, that should work for testing. That's what I do on my Cat3560 at home to test lower power draw.

 

---

@MandP wrote:
@cclemmer, I have a plan based on the idea you said of disabling LLDP.
I'm thinking of disabling LLDP so AP will draw 15.4w (neg.cable loss) and with that way IPM will take effect and disable feature based on my list of priority. What do you think? this should do the trick.

---

 

Awesome ! I'll test that and see.

Is there a way to disable LLDP for a specific AP from the controller side?

To some degree yes, but note that much of the early part of the LLDP happens before the AP will receive the config, and outside of lab testing is not really a viable/recommended config change to make. Doing so could lead to odd behavior and logic on the AP after bootup and applying the config, so YMMV.

 

Far better to disable on the switch, or limit the power, to force AF power on the AP, to do your testing.

 

I ended up using "ap-poe-power-optimization", I saved 6.2w
Personally, I think, IPM isn't the best option for an AP connected to cisco PoE+ switch

That command is an early precursor to IPM and is more heavy handed and less flexible (it disables USB and ENET1). IPM is incredibly valuable for those customers that wish to tailor how the APs save power, as well as provide more control to the end user on exactly which power saving measures to take (in your example, 'ap-poe-power-optimization' would not be viable if the USB port or second ethernet port was needed).

 

802.3at POE negotiation is completed with LLDP in addition to the 802.3af signaling.

 

The AP debug is showing you the results from both signalling methods. 802.3af POE power was available on the connection, and LLDP was able to negotiate higher wattage requested.

 

To test this in the lab, disable LLDP on your cisco switch and the APs will only pull 802.3af and without negotiating the additional 802.3at power and will react accordingly.