Wired Intelligent Edge

last person joined: 17 hours ago 

Bring performance and reliability to your network with the HPE Aruba Networking Core, Aggregation, and Access layer switches. Discuss the latest features and functionality of your switching devices, and find ways to improve security across your network to bring together a mobile-first solution
Back to discussions
Expand all | Collapse all

POE Problems

This thread has been viewed 18 times

  • 1.  POE Problems

    Posted Jul 25, 2018 10:18 AM

    Scenario

    I spent a long time onsite today working through some messy POE/POE+ issues. The problem statement in a nutshell "2930M switch does not power camera".

     

    The camera doesn't actually have a POE/POE+ input port, but instead has an ethernet port and 12V connector. An additional external box splits the POE+ connection from the switch into data (ethernet) and a separate power feed.

     

    Symptoms

    • Directly connecting the power splitter + camera to the 2930M POE+ port didn't power on the camera without configuration changes (see "Useful Commands" below).
    • port would sometimes flap - power on/power off
    • switch logfile indicated several POE related errors
    • additional problems seemed to arise when three or mode cameras were connected
    • multiple switch brands and models experienced similar or identical symptoms

    Sample logfile entries

     

    W 07/25/18 13:54:39 00564 ports: port 5 PD Invalid Signature indication.
W 07/25/18 13:54:37 00562 ports: port 5 PD Over Current indication.
I 07/25/18 13:54:37 00077 ports: port 5 is now off-line
I 07/25/18 13:54:36 00565 ports: port 5 PD Removed.
W 07/25/18 13:54:36 00562 ports: port 5 PD Over Current indication.

     Example of excess power draw

    5     Yes  critical on      value value  30.0 W  31.8 W  Delivering   4   2
6     Yes  critical on      value value  30.0 W  18.4 W  Delivering   4   2

     

    Answer

    In fact the 2930M switch is fully compliant with 802.3at - POE+, with support for a maximum of 30W. On several occasions, the switch reported 31.8W on the port - and shut down. This is exactly what it is supposed to do.

     

    Even though the splitter specified 802.3at POE+ compliance, that seemed doubtful. The switch log entries were conclusive in pointing to a non-compliant endpoint.

     

    External third-party POE injectors that supplied 35W have been used as the fallback solution.

     

    Useful Commands

    The interface has some POE options; these ones helped:

    poe-allocate-by value
poe-value 30

    In addition, this command run at the global level (ie not from the interface perspective) alloed the camera to power on:

    power-over-ethernet pre-std-detect ports <port IDs>

    Both should be used with caution.