I've just encountered similar loop-related problems in a small network with just two MS120 and one MS220, running 9.37 code. As soon as I started connecting redundant links between devices we started seeing loops and broadcast storms every so often. I initially allowed all VLANs on all trunk ports between devices. There are also two MX84's in the network. Things might have gotten a little bit better after I disabled one possible loop by configuring the connection I have setup directly between the MX84's on its own unique VLAN and I permitted only the relevant VLANs on all trunk ports in the network. But the problem is not completely gone. Have either of you tried v10 Beta code yet? I'm interested both in the Storm Control (not available on MS120 unfortunately) but especially in the improved STP Anomaly Detection and Loop Guard features and how they might improve the situation.
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