The switch is a Cisco Small Business SG350-48x. We have four Meraki APs connected to individual ports on it. The site has been complaining about periodic slowdowns on the network, though not restricted to clients connected to the MR18; we haven't managed to ID a specific problem so far but found this issue while analyzing.
On one of the ports with an MR18 as the only connected device, we are getting a continuously escalating PAUSE frame counter. There is no indication of overutilization, no loops, drops, STP errors etc on the switch and on its initial check the Meraki tech said they saw no indication the AP was overutilized. The PAUSE counter increases continuously whether or not clients are connected to the MR18 and we are sure there are no double-connected devices (wireless and wired), though since they are on different subnets and VLANs that shouldn't be an issue.
We've also run a wire test with our Fluke gear and its good. Have not had time to do an AP swap.
We set up a SPAN monitor port and have run captures (we do have an open ticket with Meraki but they haven't gotten back to us recently so asking here). The PAUSE frames are seen between 8 and ~60 times per 10 second interval, and continuously, not just during periods of perceived slowdown (so possibly unrelated). They come in pairs, with one giving pause time of 65535 quanta and the next a pause time of 0 quanta, repeated endlessly.
The MAC address being reported as the source for the pause frames doesn't show up anywhere else. It isn't the MR18's MAC, nor any of the attached clients, doesn't show up in ARP tables anywhere on the client network, including the switch we're recording the pause frames on, and also doesn't show up in any MAC vendor database that I've been able to find
3 15:19:46.907701 c5:20:7f:0a:18:00 Spanning-tree-(for-bridges)_01 MAC CTRL 60 Pause: pause_time: 65535 quanta
4 15:19:46.907701 c5:20:7f:0a:18:00 Spanning-tree-(for-bridges)_01 MAC CTRL 60 Pause: pause_time: 0 quanta
I believe these are BPDU frames (Bridge Protocol Data Unit), but the MAC doesn't correlate to the multicast MAC I read about online, and I haven't been able to figure out why we are seeing these on the one port with an AP connected and no others.
Any thoughts? I may be imposing a bit on Meraki since its not a Meraki switch, but the AP is Meraki, and as the only device connected to that port, it presumably has to be the source of the PAUSE frames.