How Spanning Tree Protocol detects Loops

2

For last few days I've been reading about Spanning Tree Protocol ,L2 protocol and understood how it prevents loop in network ,various steps in STP but one thing i wanted to know how STP actually detects the loops in network so that it can prevent it.Somewhere I read STP uses BPDU as probe and detects loops I mean how it happen is when switch send a BPDU with Destination Address as multicast and receive same BPDU again mean there is loop in network .

But is it how STP detects loops in network?

AMIT

Posted 2012-09-06T08:56:59.287

Reputation: 499

Answers

3

For every bridge, it computes the least cost paths to the root bridge, and disable all other root paths by blocking the other ports. So obviously, any path including a loop wouldn't have the least cost, and would thus be discarded.

m4573r

Posted 2012-09-06T08:56:59.287

Reputation: 5 051

2so, somehow, STP doesn't bother detecting loops: it just always prefer loopless paths because they're shorter... – sylvainulg – 2012-09-06T10:05:39.883

Absolutely, that was my point :) – m4573r – 2012-09-06T10:14:19.933

Asked: 2012-09-06T08:56:59.287

Viewed: 799 times

Active: 2012-09-06T09:08:16.593