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iMac computer being blocked by spanning-tree

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  • 1.  iMac computer being blocked by spanning-tree

    Posted Feb 10, 2023 11:02 AM

    Hi All,

    I have noticed some odd behaviour on my Aruba switches regarding spanning-tree. 

    At all of my sites, when an Macintosh computer is plugged in through Ethernet, I get ports blocked due to spanning tree. I have tried settings these ports as admin-edge ports, but this did not help. Here is an example of the STP messages I'm getting in my logs.

    I have checked these ports, and none of them do have loops, they all just have iMacs plugged into them. Has anyone else encountered this issue before, and if so, are there any steps to mitigate this.

    Thank you,

    wnygard



  • 2.  RE: iMac computer being blocked by spanning-tree

    Posted Feb 13, 2023 11:55 AM

    admin-edge enables immediate forwarding state in STP ports, skipping the usual blocking state. That helps with DHCP issues but not when a port remains blocked.

    You should check the log for what's really happening. If bpdu-protection is used that might result in port blocking but normally it disables the port.

    Also run show spanning-tree to see the port state in more detail. "Designated bridge" tells you where received BPDUs originated from - if it's the switch itself then the connected Mac seems to reflect the switch BPDUs. You could bpdu-filter (effectively disabling STP on that port) or, preferably, disable whatever is causing the problem on the Mac.