Subject: [rbridge] Non-Spanning-Tree bridges do exist

From: harald at alvestrand.no (Harald Tveit Alvestrand)
Date: Tue, 18 Oct 2005 23:40:53 +0200

My curiosity got the better of me....

I remembered that the el-cheapo switch I'm using as a junction box in my 
office had 2 spare ports.
So I crawled under my desk and connected a wire between the two.

Sure enough, in a little while the two lamps turned green; a little later 
the lamps started flashing, and just a few moments later, ALL the lamps on 
the box started flashing.

I had created a broadcast storm.

I hurriedly disconnected the link, and the network went back to normal. End 
of experiment.

Conclusion:
Not all bridges implement spanning tree.
Users who have physical access to such a device, and connect wires without 
thinking, can create broadcast storms.
But as long as the physical topology is a tree, they do no harm.

Not sure what implications this has for this group.

(note: Either this device is in category BLOCK, or it's TRANSPARENT, and 
ALL the switches in my house, which are of about 4 different makes, all of 
them cheap, fail to implement any form of ST - because I don't see any 
BPDUs on the wire).

                  Harald
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