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Our network switches have STP enabled, and I see that my APs have an option to enable STP as well. The purpose of STP is to prevent network path loops, but the AP only has one connection back to the switch, and only one connection to each client. Why would I want to enable STP on an AP, or would enabling it be moot?

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    If the APs support bridging or routing (especially with vLANs) I could see a use; otherwise you're right, useless.
    – Chris S
    Apr 26, 2012 at 17:02
  • Yeah - I can imagine use cases for spanning tree if you've got a mesh network of access points, or you're using a switch built into the AP as an actual switch - but in normal deployments, it's not useful. Apr 26, 2012 at 17:09

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In most deployments it is not necessary to configure STP on an access point. However, there are several deployment scenarios where it is advisable.

One such scenario I encountered in production when it was biting the network in the proverbial posterior.

Instead of running a physical cable to connect a printer on a shop floor, an access point radio was configured in what is called "workgroup bridge" role. In this case the radio interface plays the role of uplink to the LAN (associating to another access point that is actually plugged into the LAN) while the physical Ethernet interface connects to the printer. The printer worked great for a year until the business needs changed.

At some point additional printers were needed and a few physical cable runs and a switch (as part of an intermediate distribution frame) were installed at the shop floor location. The printers were plugged into the new switch -- which was plugged/uplinked into the LAN from the new runs. The access point physical Ethernet interface that was once plugged into a printer was also plugged into the new switch.

With both the access point physical Ethernet interface and the radio interface connected to the same broadcast domains -- a loop was formed. Storm-control was in place and caught the broadcast storm in both places. However, if it was not in place that would have been a very tricky loop indeed.

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