Insufficient Power for PoE?

[jlhainy]

I have an interesting issue.  I am running a 4500 with 1300W power supplies.  We have IP Cameras and Cisco APs being powered by this switch.  I have one AP that will not power up.  It powers up with an A/C adapter just fine.  I took the AP to another POE switch and it powered up just fine.  So, I was thinking it was a PoE issue.

Checking the syslogs, I found the following:

Interface Gi5/36: inline power denied. Reason: Insufficient inline power, requested(17303) available(10018)

So this syslog basically is telling me that there isn't enough power, which is fine, I do have 50 devices being powered.  They are a mix of Cisco and non-cisco devices.

However, when I look at the power info, it appears that there should be enough power left to power up a 15.4 Watt AP.

Power Summary                      Maximum

(in Watts)              Used     Available

----------------------   ----     ---------

System Power (12V)        590         617

Inline Power (-50V)       683         710

Backplane Power (3.3V)      0           0

----------------------   ----     ---------

Total                    1273 (not to exceed Total Maximum Available = 1300)

It appears that I have 15 watts available.

Available:710(w)  Used:683(w)  Remaining:27(w)

Interface Admin  Oper            Power(Watts)     Device              Class
                            From PS    To Device
--------- ------ ---------- ---------- ---------- ------------------- -----

Gi5/36    auto   off        0.0        0.0        n/a                 n/a

Interface  AdminPowerMax   AdminConsumption
             (Watts)           (Watts)
---------- --------------- --------------------

Gi5/36                15.4                 15.4

So, I am just trying to figure out why the switch won't power up this AP.  Now, I do have an injector so, I have a work around but I am wanting to understand whey the switch appears to be giving me conflicting information.  Either that, or I am not understand the output of the sh power commands correctly.

[paolo bevilacqua]

There could be a safey marging to pfrever overloading the system,

. In any case you need a biiger PoW PS, check table 2.

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps4324/product_data_sheet09186a00801f3dd9.html

[jlhainy]

yeah, I knew I was getting close.  I just threw in an external injector.  What I was trying to figure out was the "safety measure" that you referred to.  I really didn't see any documentation on it and was just looking for a verification.

In the meantime, I was trying to squeeze out 15 watts and couldn't do it.  I put two 1300s into combined mode and still got no power, which kind of suprised me because I was expecting or hoping that doing so would give me the needed extra 15 watts.