Controller Based WLANs

Why do APs on a Cisco 3550 PoE switch fail to boot up after the controller upgrades to ArubaOS?

Aruba Employee

Product and Software: This article applies to all Aruba controllers and ArubaOS 3.3 and later.

 

About the Cisco 3500 Switch

The Cisco Catalyst 3550-24PWR switches automatically supply inline power to connected Cisco IP Phones, Cisco Aironet Access Points, and IEEE power devices if it senses no power on the circuit. Using a Cisco inline power capable switch or Power Sourcing Equipment (PSE), the switch port sends discovery signals on active and inactive Ethernet ports to detect whether a powered device is present or not. Remember that if a powered device is not powered at this time, the link cannot be brought up. Therefore, it is necessary to transmit the discovery signal on a continuous basis because a powered device may be plugged into the port at anytime.

 

Cisco pre-standard Power over Ethernet (PoE) ports have a power disconnect mechanism that will remove power from the port if the Ethernet link status is down. For certain IEEE power devices, such as Aruba APs, that require multiple reloads during initialization, the delay shutdown time has to be set manually on the Cisco Catalyst 3550 to continue providing power during initialization.

 

Symptom

APs that are powered by a Cisco 3550 PoE switch cannot boot up after the controller is upgraded to ArubaOS 3.3.1.x or newer code. All the APs are rebooted every 30 seconds.

 

Root Cause

The ArubaOS 3.3 image is much bigger than the old image, so the APs take a longer time to boot up. When an AP is booting up, the link is not up. The Cisco 3550 thinks the device connected is somehow stuck and it resets the POE port.

 

Solution

You must reconfigure the Cisco 3550 to wait longer before resetting the power if the link is down. Reconfigure the "power inline delay" on the Cisco POE port to a longer time. Issue this command on the Cisco switch:

 

(Cisco Switch) (config)# interface FastEthernet0/1

 

(Cisco Switch) (config-if)# power inline delay shutdown 15 initial 25

 

Note: The 'power inline delay shutdown 15 initial 25' command tells the switch to continue supplying power for 15 seconds after a link-down event. The "initial" parameter tells the switch for how long the delay is active after the device is detected. For more details on this command, refer to Cisco documentation of the Cisco 3500 PoE switch.

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‎07-01-2014 04:01 PM
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