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Date:   Sun, 4 Jun 2023 12:23:04 +0300
From:   Vladimir Oltean <olteanv@gmail.com>
To:     =?utf-8?B?QXLEsW7DpyDDnE5BTA==?= <arinc.unal@arinc9.com>
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Subject: Re: [PATCH net-next 27/30] net: dsa: mt7530: introduce BPDU trapping
 for MT7530 switch
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On Sun, Jun 04, 2023 at 11:51:33AM +0300, Arınç ÜNAL wrote:
> > If the switch doesn't currently trap BPDUs, isn't STP broken?
> 
> No, the BPDU_PORT_FW bits are 0 after reset. The MT7620 programming guide
> states that frames with 01:80:C2:00:00:00 MAC DA (which is how the BPDU
> distinction is being made) will follow the system default which means the
> BPDUs will be treated as normal multicast frames.
> 
> Only if all 3 bits are set will the BPDUs be dropped.

Right, if you don't trap BPDUs just to the CPU but flood them, I believe
the STP protocol won't behave properly with switching loops. Worth testing.