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This weekend I have not time to relax and enjoy my beer. Instead I was spent time in Server room with my lovely "roommates" 2x S3300 and 4x GS752TP.
I spent few long hours before I found, that I old lady plug one VoIP-phone two times in my switch (using wall plugs in her office). So it was funny time, but I do not want it to happen again! 🙂
Image to clarify:
I have activated RSTP at these switches, but this is not helped my to prevent this loop.
So, when I got call from stuff about the problem, the broadcast storm had fully frezed all processes in the networks (servers, switches, wlan, routers, all). So I even have not had any syslog. Anyway, after the time, I found this port and disabled it.
But, the question - Is there any mechanismes to prevent such loops and/or to notify my about such even? Could you please share you experience and advise me please!
Just turning on RSTP on its own is likely not hepling because the phone does not support spanning tree. That is pretty common that phones don't. When the switch ports (those the phone is connected to) are in "main STP mode" the spanning tree negotiation can't happen as the phone does not understand/support that. Main STP mode should be used between devices that understand and support spanning tree.
Leave RSTP enabled overall and can you then also please try to enable "Egde Mode" on those ports where the phone is connected? Go to: "STP" --> "CST Port Configuration"
Just turning on RSTP on its own is likely not hepling because the phone does not support spanning tree. That is pretty common that phones don't. When the switch ports (those the phone is connected to) are in "main STP mode" the spanning tree negotiation can't happen as the phone does not understand/support that. Main STP mode should be used between devices that understand and support spanning tree.
Leave RSTP enabled overall and can you then also please try to enable "Egde Mode" on those ports where the phone is connected? Go to: "STP" --> "CST Port Configuration"
I forgot to mention, that Eth port and PC port have different vlan. Thats why broadcast storm is performing.
Since, S3300 is working on production, so I cannot apply any changes without testing at the lab, so I took GS752TP and simulate my production network, I activated RSTP (that was enabled before on my S3300) and also I enabled "Fast link" (that was not configured before). After test - nothing changes.... few seconds and all ports are begining to receive 7-8Mbps of traffic.
Anyway, at S3300 is little bit different firmware, and it gives me possibily to active one more option - Auto Edge. Is that function, that you advice my to configure?
Okay, so if "Auto Edge" is on then that is fine. The switch will detech itself edge devices. Fast link should be OK as well. The VLANs doesn't matter as RSTP does not care about the VLAN config.
As I previously mentioned, any changes after activation / de-activation Fast Link. Even when I changed it to Auto, in STP - CST Status - Edge Port status changes to True, but anyway storm is performing. So this feature does not help me till now.
But also I found one interesting regularity: when I plug phone`s eth port in switch port (lower port number, e.g. g4), and after I plug phone`s PC port in any higher port number (e.g. g5-g48) storm is not performing. Otherwise, if PC port has lower port number that eth port, storming as in Pirates of the Caribbean!!!
Yalink gives 80-90 Mbps storm.
Fanvil gives 7-8 Mbps storm.
I would like also note results of my research in this case:
1. When I plug eth port, and after plug pc port in lower port number - port up to 7 seconds stays at learning state.
2. After 5-7 seconds port is chaning at Forwarding state, Address tables is removing and storm is beginning (so I mean that ports are in state Forwarding both) - I cannot change it, since I have not BPDU Guard or BPDU filter functionality.
I`m not sure, that even BPDU guard will help me. I will try to find M-series switch to proove it.
If the datasheet specifies that it has BPDU Guard, then it probably does. I assume it is just enabled and non-configurable (therefore not visible to you). I would not know enough about spanning tree to determine whether the issue of your phones really is down to BPDU Guard or not.
I suggest you reach out to support in this one, to see what they say.
