ok so i have this port configure as an access port for vlan 10. I connected a cisco wireless access WAP321 configure to send untagged traffic to expand this vlan for wireless access. I have two of these in the same /24 network with different SSID. however when I plug it into the switch it triggers BPDU guard and shuts the port down. this only happens with one access point the other didnt give me this issue.below the configuration for both interfaces. should the access point send bpdu??

interface gigabitethernet1/38
 spanning-tree portfast
 spanning-tree bpduguard enable
 switchport mode access
 switchport access vlan 10
  • 1) do you understand what bpduguard does? (shutdown the port to prevent untrusted devices from interacting with your STP) 2) is the AP generating the BPDU or is some wireless client sending them?
    – Ricky
    Commented Oct 29, 2015 at 19:50

2 Answers 2


It has to do the the WAP configuration. I was just discussing something similar here at work. A Cisco WAP can actually convert an access port into a trunk without changing the visible switch configuration; apparently, it negotiates this via CDP. You have something in, or missing from, the WAP configuration which causes it to send BPDUs, but you didn't include the WAP configuration in your question.

Side note:

Rather than placing portfast and bpduguard on the individual switch ports, you can globally enable them as port defaults. When you do this, it only affects access ports unless you also add the trunk option to the command. We do this to save configuration steps.


Somehow STP got enabled on those two, which is strange because it's disabled by default...

To resolve, whether you configured this or not do one of these: Disable spanning-tree on the bridge group ( bridge-group # spanning-disable), turn off BPDUGuard on these ports, also since technically an AP is a switch or make sure the 'bridge protocol ieee' isn't on the bridge group of the 2 as well.

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