Cisco Aironet 1100 Series

Cisco Aironet AP1100 Series: Broadcast Storm May Occur When Unpowered and Connected to Unmanaged Switch

August 11, 2003

Products Affected


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Problem Description

When connected to many unmanaged switches, an unpowered, not attached to a power source, 1100 series access point, AP1100, exhibits a loopback effect. As a result, the port to which it's attached will remain active, as shown by the port activity light blinking rapidly. In some cases, particularly on switches that do not support the Spanning Tree Protocol, a broadcast storm may occur.


For most unmanaged switches, a broadcast storm may occur that is limited to the switch port that the access point is connected to. It does not propagate through the rest of the switch and the rest of the network. A few unmanaged switches cannot distinguish between a looped-back packet and a legitimate packet. A broadcast storm may occur due to the lack of Spanning Tree Protocol support.

Problem Symptoms

When an unpowered AP1100 is connected to an unmanaged switch, a broadcast storm may occur and interrupt the network traffic. Clients connected to the switch will not be able to communicate with the rest of the network. The AP1100 will not have any Light Emitting Diode (LED) activity.


The following workarounds can be implemented.

Since most, if not all, managed switches can distinguish between a looped-back packet and a legitimate packet, connect the AP1100 directly to a managed switch. An additional workaround would be to power the AP1100 with a power injector (AIR-PWRINJ2) that is on the same alternating current (AC) power circuit as the switch to which the AP1100 is connected. If the power fails and the AP1100 is unpowered, no broadcast storm can occur because the power to the switch is out and the switch is down as well.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: