STP - Do all frames go through the root bridge

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Istvan_Rabai Fri, 10/17/2008 - 13:52
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Hi Michael,

That would go direct.

Frames follow the outgoing port where the destination mac-address is learned.



Jon Marshall Fri, 10/17/2008 - 13:54
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Short answer is no they don't. A lot depends on whether the frames are destined for another device within the same vlan. If they are in a different vlan then the packets have to be sent to the HSRP active gateway which is quite often also the root bridge - doesn't have to be but often is.

If a switch knows that the destination for a mac-address is on a another switch and it has a connection to that switch which is not blocking it will forward that frame down the link.


Joseph W. Doherty Fri, 10/17/2008 - 16:25
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As other posters have noted, frames do not have to tranverse root, but they may. If source and destination are within same subtree off root, frame would not transverse root.

If you look at this Wiki article,, consider in the example diagrams 5 and 6, which switches can pass traffic to other swithces without needing to transverse the root switch.


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