Want to Creat Loop

Unanswered Question


There had been instances where in my live network (where STP is enabled)if someone plugs in a hub my network goes down.Now i want to replicate same scene in the Lab and i unable to create loop as STP automatically blocks that port( which it should do idealy on a live LAN) If anyone could help me , i have tried everything from

1) using cross cable to connect switches

2) connecting hub to both switches

3) and connecting a cross cable on hub

but still no loop.If anyone could help me on this.



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mheusinger Wed, 03/07/2007 - 03:54
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if everything is as it should be, spanning tree will create a loop free topology.

So one way to intentionally create a loop will be to turn off spanning tree and create a physical loop in the lab topology.

Another option is to create an unidirectional link, i.e. only ONE fiber connecting tx from one prot to rx on another port. This can also generate loops with STP enabled.

You could also configure a port to completely block BPDUs (BPDU filter).

Or you use hubs (without STP) to create the loop.

If you only want a transient loop, then portfast on a port interconnecting switches (no trunk) can achieve this. But it should only last a couple of seconds.

Hope this helps!

Regards, Martin


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